I

JOURNAL

OF THE

Association of Entering Societies.

Boston. Cleveland. Minneapolis. St. Louis.

Montana. St. Paul. Detroit. Pacific Coast.

Buffalo. Louisiana. Cincinnati.

CONTENTS AND INDEX.

VOLUME XXIV. January to June, 1900.

PUBLISHED BY

THE BOARD OF MANAGERS OF THE ASSOCIATION OF ENGINEERING SOCIETIES.

John C Trautvvtne, Jr., Secretary, 257 S. Fourth Street, Philadelphia.

75513

€

CONTENTS.

VOL. XXIV, January-June, 1900.

For alphabetical index, see page v. No. i. JANUARY.

PAGE

Dock Equipment for the Rapid Handling of Coal and Ore on the

Great American Lakes. Arthur C. Johnston i

The Present Status of Engineering Knowledge Respecting Masonry

Construction. David Molitor 25

Temporary Bridge across the Mississippi River at St. Paul, Minnesota.

Moving of Three 140-Foot Spans. A. W. Minister 58

Progress of Drainage in New Orleans. Alfred Francis T heard 62

Thomas Doane. — A Memoir. Desmond FitzGcrald, C. Frank Allen,

Chas. A. Pearson jt,

Clarence Allan Carpenter. — A Memoir. E. A. Handy, August Mordecai,

F. C. Osbom 81

Association of Engineering Societies 83

Proceedings.

No. 2. FEBRUARY.

English Experiments on the Bacterial Treatment of Sewage, with an Account of the Work Done at Manchester, England, during the Past Year. Prof. Leonard P. Kinnicutt 107

Pollution of Streams, with Special Reference to the Chicago Drainage

Channel. B. H. Colby 137

Paints and Varnishes. Prof. A. H. Sabin 146

The Engineers' Club of St. Louis ; its History and Work. William II.

Bryan 158

Obituary. — Archibald Johnson 175

Proceedings.

No. 3. MARCH.

The Outlook for Engineers. C. Frank Allen 185

Engineering Work in Louisiana. Thomas L. Raymond 198

Address before the Thirteenth Annual Meeting of the Montana Society

of Engineers. Eugene Carroll 210

Obituary. — Samuel Nott, William Scollay Whitwell, Sumner Hol-

lingsworth, Harry Herbert Hirst 227

Proceedings.

iv ASSOCIATION OF ENGINEERING SOCIETIES.

No. 4. APRIL.

PAGE

The Reconstruction of the Big Hole Dam. Jos. H. Harper 239

Discussion. Messrs. Keerl, Harper, Carroll, Harrison, Hollins-

licad, Vail 252

Drainage of the Valley and City of Mexico. Willis B. Wright 256

The Cement Age. G. W . Percy 264

Proceedings.

No. 5- MAY.

Difficulties Encountered in Building the Storage Well for the Sewerage

System of Concord, Massachusetts. Leonard Mctcalf 277

Discussion. Messrs. Taylor and Richardson 290

Experiences in the Operation and Repair of the Hydraulic Dredges on

the Mississippi River. F. B. Maltby 299

The Water Supply of New Orleans. Prof. John M. Ordzvay 311

Notes on the Relation between the Geology of the Sources of Water

Supply and Disease. Marsdcn Manson 321

Sea Level Canal across the Isthmus of San Bias. Wm. W. Rcdficld. . 327

Discussion. John C. Trautwine, Jr 336

Proceedings.

No. 6. JUNE. .

Siphons. Thomas McKeown 339

Discussion. Messrs. Richer, McKeown, Symons, Knapp,

Guthrie, Knighton, Tutton, Morse, Bardol, Haven 341

Trusts and Their Relation to the Engineer. Charles H. Wright: 345

The Use of Acetylene in Railway Station and Train Lighting. A. Lip-

schuts 355

Sewer Maintenance. W. C. Parmley. ■. 370

Discussion. Messrs. Razvson, Parmley, Bcardsley, Cozulcs 381

Proceedings.

INDEX. VOL. XXIV, January-June, 1900.

The six numbers were dated as follows :

No. 1, January. No. 3, March. No. 5, May.

No. 2, February. No. 4, April. No. 6, June.

Abbreviations. — P = Paper; D = Discussion; I = Illustrated. Names of authors of papers, etc., are printed in italics.

PAGE

/\cetylene, Use of in Railway Station and Train Lighting. A. Lip-

schuts P., June-, 355

Address before the Thirteenth Annual Meeting" of the Montana So- ciety of Engineers. Eugene Carroll March, 210

Allen, C. Frank. The Outlook for Engineers P., March, 185

Ijacterial Treatment of Sewage, English Experiments on the ,

with an Account of the Work Done at Manchester, England, during the Past Year. Prof. Leonard P. Kinnicutt.

P., I., February, 107

Big Hole Dam, Reconstruction of . Jos. H. Harper.

P., D., I., April, 239 Bridge, Temporary across the Mississippi River at St. Paul, Minne- sota. Moving of Three 140-Foot Spans. A. W . Munster.

P., I., January, 58 Bryan, William H. The Engineers' Club of St. Louis; its History and

Work P., February, 158

l^anal, Sea Level across the Isthmus of San Bias. Win. W. Red- field P., D., I., May, 327

Carpenter, Clarence Allan . A Memoir. E. A. Handy, August

Murdecai, F. C. Osborn January, 81

Carroll, Eugene. Address before the Thirteenth Annual Meeting of

the Montana Society of Engineers March, 210

Cement Age. G. W. Percy P., April, 264

Chicago Drainage Channel, Pollution of Streams, with Special Refer- ence to the . B. H. Colby P., February, 137

Coal and Ore, Dock Equipment for the Rapid Handling of on the

Great American Lakes. Arthur C. Johnston P., I., January, 1

Colby, B. H. Pollution of Streams, with Special Reference to the Chi- cago Drainage Channel P., February, 137

Concord, Mass., Difficulties Encountered in Building the Storage Well

for the Sewerage System of . Leonard Metcalf.

P., D., I., May, 277 (V)

vi ASSOCIATION OF ENGINEERING SOCIETIES.

JJam, Big Hole, Reconstruction of the . Jos. H. Harper.

P., D., I., April, 239

Difficulties Encountered in Building the Storage Well for the Sewer- age System of Concord, Mass. Leonard Mctcalf. .P., D., I., May, 277

Disease, Notes on the Relation between the Geology of the Sources of

Water Supply and . Marsden Manson .P., May, 321

Doane, Thomas . A Memoir. Desmond FitzGerald, C. Frank

Allen, Chas. A. Pearson I., January, 73'

Dock Equipment for the Rapid Handling of Coal and Ore on the Great

American Lakes. Arthur C. Johnston P., I., January, 1

Drainage, Progress of in New Orleans. Alfred Francis Theard.

P., I., January, 62

Drainage of the Valley and City of Mexico. Willis B. Wright.

P., I., April, 256

Dredges, Hydraulic, Experiences in the Operation and Repair of the

in the Mississippi River. F. B. Maltby P., I., May, 299

H,ngineering Work in Louisiana. Thomas L. Raymond ... .P., March, 198 Engineer, Trusts and Their Relation to the^ — . Charles H. Wright.

P., June, 345

Engineers, The Outlook for . C. Frank Allen P.. March 185

Engineers' Club of St. Louis; its History and Work. William LI.

Bryan P., February, 158

English Experiments on the Bacterial Treatment of Sewage, with an

Account of the Work Done at Manchester, England, during the

Past Year. Prof. Leonard P. Kinnicutt P., I., February, 107

Experiences in the Operation and Repair of the Hydraulic Dredges in

the Mississippi River. F. B. Maltby P., I., May, 299

(jeology of the Sources of Water Supply, Notes on the Relation be- tween the and Disease. Marsden Manson P., May, 321

Warper, Jos. H. Reconstruction of the Big Hole Dam.

P., D., I., April, 239

Hirst, Harry Herbert . A Memoir. H. I. Randall and Frank

Soule March, 236

Hollingsworth, Sumner . A Memoir. John R. Freeman and Chas.

T. Main March, 234

Hydraulic Dredges in the Mississippi River, Experiences in the Opera- tion and Repair of the . F. B. Maltby P., I., May, 299

Johnson, Archibald . A Memoir. W. A. Truesdell February, 175

Johnston, Arthur C. Dock Equipment for the Rapid Handling of Coal

and Ore on the Great American Lakes P., I., January, 1

\\innicutt, Prof. Leonard P. English Experiments on the Bacterial Treatment of Sewage, with an Account of the Work Done at Manchester, England, during the Past Year P., I., February, 107

JL/akes, Great American , Dock Equipment for the Rapid Handling

of Coal and Ore on the . Arthur C. Jolinston . P., I., January, 1

Lighting, Railway Station and Train— — . Use of Acetylene in .

A. Lipschutz P., June, 355

Lipschutz, A. Use of Acetylene in Railway Station and Train Light- ing P., June, 355

Louisiana, Engineering Work in . Thos. L. Raymond. .P., March, 198

I

INDEX. vii

/

PACF 370

Maintenance, Sewer . W. C. Parmley .J. .P., June,

Maltby, F. B. Experiences in the Operation and Repa,^ of the Hy- draulic Dredges on the Mississippi River P., I., May, 299

Manson, Marsden. Notes on the Relation between the Geology of the

Sources of Water Supply and Disease P., May, 321

Masonry Construction, Present Status of Engineering Knowledge Re- specting . David Molitor i P., I., January, 1

McKeown, Thomas. Siphons .' P., June, 339

Memoir. See Obitiiary.

Metcalf, Leonard. Difficulties Encountered in Building the Storage

Well for the Sewerage System of Concord, Mass. .P., D., I., May, 277

Mexico, Drainage of the Valley and City of . Willis B. Wright.

P., I., April, 256 Mississippi River, Experiences in the Operation and Repair of the

Hydraulic Dredges on the . F. B. Maltby P., I., May, 299

Mississippi River, Temporary Bridge across the at St. Paul, Minn.

Moving of Three 140-Foot Spans. A. W. Munster.

P., I., January, 58 Molitor, David. Present Status of Engineering Knowledge Respect- ing Masonry Construction P., I., January, 25

Montana Society of Engineers, Address before the Thirteenth Annual

Meeting of the . Eugene Carroll March, 210

Munster, A. W. Temporary Bridge across the Mississippi River at St. Paul, Minn. Moving of Three 140-Foot Spans.

P., I., January, 58

l\ew Orleans, Progress of Drainage in . Alfred Francis Theard.

P., I., January, 62

New Orleans, Water Supply of . Prof. John M. Ordway.

P., I., May, 311 Notes on the Relation between the Geology of the Sources of Water

Supply and Disease. Marsden Manson P., May, 321

Nott, Samuel . A Memoir. L. B. Bidwell and Edward Sawyer.

March, 227 (Jbituary —

Carpenter, Clarence Allan January, 81

Doane, Thomas January, y^

Hirst, Harry Herbert March, 236

Hollingsworth, Sumner March, 234

Johnson, Archibald February, 175

Nott, Samuel March, 227

Whitwell, William Scollay March, 232

Ordway, Prof. John M. Water Supply of New Orleans. .. .P., I., May, 311

Ore, Coal and , Dock Equipment for the Rapid Handling of on

the Great American Lakes. Arthur C. Johnston. .P., I., January, 1 Outlook for Engineers. C. Frank Allen P., March, 185

I aints and Varnishes. Prof. A. H. Sabin P., February, 146

Parmley, W. C. Sewer Maintenance P., June, 370

Percy, G. W . The Cement Age P., April, 264

Pollution of Streams, with Special Reference to the Chicago Drainage

Channel. B. II. Colby P., February, 137

vm A SSOCIATION OF ENGINEERING SOCIETIES.

pr.E

Present Status. Q£ Engineering Knowledge Respecting Masonry Con- struction. :r>avid Molitor P., I., January,

Progress of Draina^ in New 0r]eans Alfred Francis Thcard. p. P., I., January, 62

Raymond, Thomas L. ^ ineering Work in Louisiana . .P., March, 198 Reconstruction of the Big Ho. Dam_ Jo H. Harper. .P., D., I., April 239 Redfield, Wm. W. Sea Level U„al across the Isthmus of San Blas.

c P,D„I, May, 327

^abin, Prof. A. H. Paints and Varnish^ p -. ' irV , a,

St. Louis, Engineers' Club of ; its History ^d/^ork' William H.

Bry™ P., February, 158

St. Paul, Minn., Moving of Three 140-Foot Spans of Temporary Bridge

across the Mississippi River at . A. W. Munster.

P., I., January, 58 San Bias, Sea Level Canal across the Isthmus of . Win. IV. Red- field P., D., I., May, 327

Sewage, Bacterial Treatment of, English Experiments on the .

Prof. Leonard P. Kinnicutt P., I., February, 107

Sewer Maintenance. IV. C. Parmley P., June, 370

Sewerage System of Concord, Mass., Difficulties Encountered in Build- ing the Storage Well for the . Leonard Metcalf.

P., D., I., May, 277

Siphons. Thomas McKcozun P., June, 339

Storage Well, Difficulties Encountered in Building the for the

Sewerage System of Concord, Mass. Leonard Metcalf.

P., D., I., May, 277

Streams, Pollution of , with Special Reference to the Chicago

Drainage Channel. B. H. Colby P., February, 137

1 emporary Bridge across the Mississippi River at St. Paul, Minnesota. Moving of Three 140-Foot Spans. A. W. Munster.

P., I., January, 58 Theard, Alfred Francis. Progress of Drainage in New Orleans.

P., I , January, 62 Trusts and Their Relation to the Engineer. Charles II. Wright.

P., June, 345

[J se of Acetylene in Railway Station and Train Lighting. A. Lip-

schutz P., June, 355

V arnishes, Paints and . Prof. A. H. Sabin P., February, 146

Water Supply of New Orleans. Prof. John M. Ordway. .P., I., May, 311 Water Supply, Notes on the Relation of the Geology of the Sources

of and Disease. Marsden Manson P., May, 321

Well, Storage at Concord, Mass. Leonard Metcalf. .P., D., I., May, 277

Whitwell, William Scollay . A Memoir. Francis Blake and

Ernest W. Bozvditch March, 232

Wright, Charles II. Trusts and Their Relation to the Engineer.

P., June, 345 Wright, Willis B. Drainage of the Valley and City of Mexico.

P., I., April, 256

THOMAS DOANE.

President Boston Society of Civil Engineers, 1874-80 and 1880-

Editors reprinting articles from this journal are requested to credit both the Journal and the Society before which such articles were read.

As

SOCIATION

OF

Engineering Societies.

Organized 1881.

Vol. XXIV. JANUARY, 1900. No. i.

This Association is not responsible for the subject-matter contributed by any Society or for the statements or opinions of members of the Societies.

DOCK EQUIPMENT FOR THE RAPID HANDLING OF COAL AND ORE ON THE GREAT AMERICAN LAKES.

By Arthur C. Johnston, Member Civil Engineers' Club of Cleveland.

[Read before the Club January, 1900.*]

Sir William H. White, director of naval construction in the British navy, in a recent review before the Institution of Mechanical Engineers, says : "One of the most marked tendencies in recent construction has been the increase in size and carrying power of ships. Unless there had been a corresponding development in the means of dealing with cargo this increase in size could hardly have occurred, and the advantages resulting from that increase would not have been realized." And further he says : "It is well recog- nized that unless there is 'quick dispatch' in loading and unloading cargoes very serious diminutions of earnings must result from the longer detention in port. Hence it follows that for the complete commercial success of the larger classes of cargo carriers lifting appliances of the most efficient character and of ample capacity are of the greatest importance." If this is true of ocean-going vessels, where voyages are, on the average, comparatively long and ex- tended, to a much greater extent is it true of vessels carrying cargo on the Great Lakes, where, even with rapid loading and discharg- ing of cargoes, the ratio of time spent in port to that spent in transit is very great, amounting to one-sixth under the most favor- able circumstances. The object of this paper is to deal with the special types of machinery built for the purpose of insuring "quick dispatch" in loading and unloading the enormous tonnage of ore and coal that is shipped annually on the Great Lakes, the founda-

*Manuscript received January 12, 1900. — Secretary, Ass'n of Eng. Socs.

1

ASSOCIATION OF ENGINEERING SOCIETIES.

N I Uj

DOCK EQUIPMENT ON THE GREAT AMERICAN LAKES. 3

tion of the gigantic steel industry that has made the United States a competitor in the markets of the world.

The shipments of ore from Lake Superior iron ranges repre- sent roughly one-third of the entire freight traffic on the lakes, and for this reason a large fleet of modern cargo vessels has been built specially for this trade, represented as a type by the tow barge shown in Fig. 2, the steam barges being of the same general type. The largest of these are 500 feet long and 50-foot beam, the dis- tinctive feature of these boats being the large size and number of hatches — 30 to 34 feet long by 8 feet wide, spaced 24 feet center to center along the entire available deck length. This greatly facili- tates loading and unloading operations, at the expense, however, of the strength of the deck plating, since the ship is almost cut in two crosswise of her deck.

3124

"Magna." Gross Tonnage 3259. Net Tonnage . Keel 352 Feet. Beam 44 Feet.

In Fig. 3 is shown the cross-section of a typical ore-loading dock and the method of loading vessels. The ore is dropped into the pockets from drop-bottom "Jumbo" cars running on the tracks above, and from the pockets the chutes discharge the ore into the vessels lying alongside the dock. At the end of the season of 1898 there was, at the different points, a total of 4354 pockets, having a

4 ASSOCIATION OF ENGINEERING SOCIETIES.

total storage capacity of 623,612 gross tons of ore, constructed at a cost of about $7,000,000. The following table gives a list of docks, with principal dimensions and location, and the names of the rail- way companies owning them :

			Length	Width	n eigne of Dock		Storage
		Dock	of	of	No. of '	Capac-
Railway.	Location.	No.	Dock	Dock	Water	Pockets	ity. ' Gross
			in	in	to Deck.
			Feet.	Feet.		Tons.
Dulut'h and Iron	Two Harbors,	1	1,056	4i'o"	45'6"	141	18,000
Range R. R. Co.	Minn.	2	1,248		57'°"	208	41,600
		3	540	49'o"	5i'6"	90	16.000
		4	1,008	49'o"	51 '6"	168	30,000
		5	1,008	49'o"	54'o"	168	33.ooo
Duluth, Masaba and	Duluth, Minn.	1	2,340	52'0"	53'6"	384	57.6oo
Northern.		2	1.738	52'o"	57'4"	288	42,400
Duluth, Superior and	Allouez Bay	1	1 a- 300	49'8"	52 0"	40	12,000
Western Ry.	Superior, Minn.		[b-1,200	49'8"	57'o"	190	25.500
Chicago and	Ashland, Wis.	1	1,404	46'8"	54'o"	234	36,036
Northwestern R. R.		2	1,404	46'o"	58'8"	234	24,156
	Escabana, Mich.	1	1,404	37'o"	46'o"	184	24,104
		3	1.356	37'o"	39'o"	226	30,284
		4	1,500	37'o"	59V	250	37.500
		5	i,392	37'o"	5i'io"	232	43.152
Duluth, South Shore	Marquette, Mich.	1	1,700	4o'o"	45'o"	270	27,000
and Atlantic R. R.		3	1,200	53'6"	37V	213	12,780
		4	1,200	36'8"	47'3"	200	28,000
Lake Superior and
Ishpeming.	Marquette, Mich.	1	1^00	52'o"	54'o"	203	36,000
Minneapolis. St. Paul
and Sault Ste. Marie
R. R.	Gladstone, Mich.	1	76S	37'o"	47'o"	120	15,000
Wisconsin Central
Lines.	Ashland, Wis.	1	1,908	36'o"	54'6"	3H	33.500

The Duluth, Masaba and Northern Railway has now under construction a new dock which is 66 feet 6 inches in height, 62 feet in width, the heel of the spout being 40 feet above the water line. There will be 192 pockets, with a capacity of 210 tons each. The additional width permits the placing of a track along the center of the dock for storing empty cars and minimizing the work of the switching engines. The dock proper will require 6,500,000 feet of sawed timber and 4780 pieces of piling.

The pockets of these docks can be filled with the different grades of ore ready to be discharged into the vessels as they arrive, and it is not an uncommon thing for a vessel to come alongside of one of these docks, take on a cargo of 5000 tons of ore and depart within two or three hours from the time it reached port. In the busy seasons, however, the vessels are loaded directly from the cars by dropping the ore through the pockets. Timbers are placed across the lower batch to break the fall of the ore, and, with proper manipulation of the chutes, an entire cargo can be loaded with little or no trimming.

The following table gives the output of the Lake Superior ranges from 1896 to 1899, inclusive:

DOCK EQUIPMENT ON THE GREAT AMERICAN LAKES. 5

6 ASSOCIATION OF ENGINEERING SOCIETIES.

OUTPUT OF IRON ORE FROM ALL MINES OF THE LAKE SUPERIOR ORE REGION, 1895

TO 1899, INCLUSIVE.

Ports. 1899. 189S. 1897. 1896. 1895.

Escanaba 3,720,21s 2,803,513 2,302,121 2,321,931 2,860,172

Marquette 2,733.596 2,245,965 1,945,519 1,564.813 1.079.485

Ashland 2, 703,4/17 2,391,088 2,067,637 1,566,236 2,350,219

Two Harbors 3.973733 2,693,246 2,651,465 1,813,992 2,118,156

Gladstone 381,457 335,955 341,014 220.887 109,211

Superior 878,9-12 55°.4°3 531,825 167,245 117,884

Duluth 3,509,965 2,635.262 2,376,064 1,988.932 1,598,783

Total by lake 17,901,358 13,655,432 12,215,645 9,644,036 10,233,910

Total by rail 369.241 253,993 290,792 I95,i27

Total shipments 17,901,358 14,024,673 12,469,638 9,934,828 10,429,037

Practically all this ore is unloaded at South Chicago for con- sumption there, or at some of the Lake Erie ports for consumption in the Pittsburg district. The relative locations of these places will be seen on the map in Fig. i. One of the most recent and largest installations of ore-unloading equipments is the plant on the docks of the Lorain Steel Company, built by the McMyler Manufacturing Company, and shown in Fig. 4. The plant con- sists of four machines of three bridges each, the distinctive feature being the long cantilever of 127 feet overhanging the boat and the great length of bridge. On a return trip from the bottom of the boat to the extreme end of the rear cantilever the bucket travels 940 feet. As will be seen, the ore can be dumped on the stock piles, or through the suspended hoppers into cars, which carry it to the furnaces situated directly behind the hoists. In Fig. 5 is shown the wagon and front stop used on these machines, and Fig. 6 is a detail of the 20-cubic-foot bucket used. The most economical size of bucket for use in connection with ore hoists has been found to be from 17 to 20 cubic feet capacity, as a larger bucket is so heavy for the shovelmen to handle that much time is lost. Seventeen cubic feet contain one gross ton of light soft ore or 2500 pounds of hard ore. Each bridge of the conveyors shown in Fig. 4 is equipped with a pair of 12 x 12-inch non-reversing engines carry- ing a 40-inch drum directly on the crank-shaft for the main hoist- ing rope. As will be seen from Fig. 5, the wagon is arranged with a "three-part" hoist, but in traveling along the bridge the full cir- cumferential speed of the drum is effective on the wagon ; so that a single revolution of the engine carries the wagon 10 feet 5 inches along the bridge in trolleying, or lifts the bucket 3 feet 5f inches in hoisting, thus making the machines very quick in action. In re- turning the wagon, the incline of the bridge is aided by a counter- weight in the rear tower. The main hoisting ropes are f inch in diameter (-|-inch ropes having been found too light for the severe service), running on 24-inch sheaves, except in the wagon, where

DOCK EQUIPMENT ON THE GREAT AMERICAN LAKES. 7

8 ASSOCIATION OF ENGINEERING SOCIETIES.

they are 17 inches, and in the hanging block, where they are 14^ inches in diameter. The engines have auxiliary drums for hoisting the boom or apron that overhangs the boat, and they are also ar- ranged to move the front end of the bridges in or out from the center bridge in order to accommodate any spacing of hatches and to propel the front tower along the track parallel to the dock face. The rear towers are moved by a locomotive on a parallel track. The returning wagon is controlled by a band brake on the drum, worked by the foot of the operator. These machines have made some remarkable records in point of speed, as an individual wagon has made fifty return trips per hour, carrying the bucket from the

Fig. 5.

bottom of the boat to a point halfway between the towers. The best cargo record was 3241 gross tons taken out in twelve and one- half hours by six bridges. The operator is located in the front tower in these machines, in full view of the hatch, which makes the matter of getting the bucket up and down through the hatch much easier and quicker than when he is further removed from the boat. In Fig. 7 is shown the type of unloader built by the Brown Hoisting and Conveying Machine Company, the pioneers in the building of dock machinery on the lakes. It differs from the McMyler hoists, already described, in the type of towers employed and in the arrangement of the towers. The engines also' have a single reduction gearing between the crank-shaft and drum, thus

DOCK EQUIPMENT ON THE4 GREAT AMERICAN LAKES. 9

using a smaller engine with higher piston speed. The machines are generally arranged in groups of two, with the engines and boilers and operators in the rear tower. Both towers are generally moved along the dock by hand. There are over 175 bridges of the Brown type of conveyor at the different Lake Erie ports.

In Fig. 8 is shown yet another type of ore unloader, built by the King Bridge Company. Its distinctive feature is the great free- dom of motion of the bucket. In both the Brown and the McMyler type the hanging block is locked in the wagon, and cannot be re- leased without striking a stop which is bolted between the tracks. Thus, when unloading very narrow boats, the front stop on the apron must be moved in till it is vertically over the center of the

Fig. 6.

hatch, and, similarly, for loading into a car on a track under the rear cantilever a stop must be placed over the center of the track to allow the bucket to be lowered in order to reduce the drop of the ore. In the King machines, however, the bucket can be raised or lowered to any desired height simultaneously with its travel along the bridge. The dock records of Conneaut Harbor show that noth- ing is lost in point of speed of operation, and, considering its advan- tages, it is surprising that the system has not been used to a much greater extent ; its only disadvantage being that three drums and reversing engines are required for its operation.

When railway cars are always available "direct unloaders" are used to transfer the ore directly to cars. The latest plant of this kind is that shown in Figs. 9 and 10, built by the McMyler Manu- facturing Company for the Pittsburg and Conneaut Dock Company,

io ASSOCIATION OF ENGINEERING SOCIETIES.

at Conneaut, Ohio. These machines have attracted a great deal of attention, and a description of their equipment will be of interest. Each machine, complete in itself, carries three bridges, which can be racked in and out to suit any spacing of hatches from 21 to 36 feet centers. The bridges cover five loading tracks, and are high enough to acommodate the largest lake vessels. An 80 H. P. locomotive-type boiler supplies steam to three pairs of 10^ x 14- inch reversing engines. Each pair of engines has 40-inch drums for both hoisting and trolleying, mounted on the crank-shaft, the

Fig. 7. Brown Type Ore Hoist.

wagon having a three-part hoist. A feature of the arrangement of the engine is the method of controlling the clutch and brake for the trolleying drum, by using a steam cylinder, which, when it sets the brake, at the same time releases the clutch, and vice versa. Nine- sixteenths-inch cables are used for hoisting, running on 24-inch sheaves, except in the wagon, where they are 17-inch, and in the hanging block 15 inches in diameter. It is made impossible for a rope to leave the sheave by the use of the very simple guard shown in Fig. 1 1 . The machines can travel along the dock by steam, and

Fig. 8.

the racking of bridges is also effected by the engines. All move- ments other than hoisting and trolleying of the bucket are accom- plished by means of a jack-shaft driven by a pinion on the crank- shaft of the main engines. Under actual working conditions the capacity of the plant of twelve bridges at Conneaut is 6000 gross tons per day.

In a similar direct unloading plant built by the Brown Hoisting and Conveying Machine Company on the C. and P. docks at Cleve-

DOCK EQUIPMENT OX THE GREAT AMERICAN LAKES, n

land the drum is geared to the crank-shaft, and the "suspended hook" is used. In neither the Brown nor the McMyler direct un- loaders is the hanging block locked in the wagon, except to obtain the maximum clearance under the bucket. The lock on the wagon is very handy, however, to hang empty buckets from when the machine is idle.

With all these machines, in which the buckets are filled by hand, the actual cost of handling the buckets is very small, varying accord- ing to how nearly up to its full capacity a machine is worked ; but under actual working conditions, from figures prepared by Mr.

Eir;. 9. McMyler Direct Ore Unloaders. Pittsburg and Conneaut Dock Co., Conneaut, Ohio.

A. E. Brown, the cost per gross ton of ore handled by his machines varies from 0.7 cent to 1.37 cents. But the greatest expense is incurred in filling the buckets. The shovelmen are paid from 10^ cents to 13 cents per gross ton, so that, at an average rate of 1 1 cents per ton, it cost $1,980,000 for shoveling to unload the 18,000,000 tons of ore shipped this year. It was to reduce this cost that the Hulett ore unloader, shown in Figs. 12, 13 and 14, was designed and built by the Webster, Camp & Lane Machine Company for the Pittsburg and Conneaut Dock Company at Conneaut. Up to the present not enough has been done with this machine to obtain any

ASSOCIATION OF ENGINEERING SOCIETIES.

DOCK EQUIPMENT ON THE GREAT AMERICAN LAKES. 13

data in regard to its performance. Its method of operation will be evident, however. The bucket is designed to lift 10 tons of ore at one scoop and dump it into the railway cars, or into a skip which can deliver it to the stock piles. All the motions on the trolley carrying the tilting girder are effected by hydraulic power, the pumps and tank being carried on the trolley itself, and the steam- loaded accumulator is used to partly balance the weight of the bucket. The operator is located just above the bucket, and descends into the hatch with it. The bucket can rotate in either direction about the axis of the vertical ram, thus enabling the ore lying in between hatches to be reached. It is expected that very little of the ore will have to be shoveled bv hand with this machine.

SSS353KS3SS

^ssssssssa

Fig. 11. Rope Guard for Sheaves.

The large vessels returning from the lower lake ports go up in water ballast or take a return cargo of coal ; and to facilitate the loading of the enormous tonnage that is carried to the upper lake ports each year the car dumper has been developed, — a machine which picks up bodily a car weighing 17^ tons and carrying 40 tons of coal and empties the contents into the hold of a vessel at the rate of as high as thirty cars per hour. Fig. 15 shows the first type of McMyler "side dump" machine built on the lakes. The first successful machines were of the "end dump" type, but they require special cars. They are still in operation, one at Ashtabula and one at Fairport. The machine shown in Fig. 15 is very flexi- ble in operation, as the hinge of the aprons may be raised or lowered vertically to suit any class of vessel, and the car and cradle in ascending begin to turn over on striking the hinge point of the apron. This machine has been built with several types of chutes, but perhaps the most successful is the telescopic chute shown, as by

14 ASSOCIATION OF ENGINEERING SOCIETIES.

Fig. 12. Hulett Ore Unloader built by the Webster, Camp & Lane Machine Co. for the Pittsburg and Conneaut Dock Co.

Fig. ii. Hulett Ore Unloader.

DOCK EQUIPMENT ON THE GREAT AMERICAN LAKES. i>

/	/ V / /
// / /	/ / /
/ /	/ 1 ,
	i rf-4...

i6

ASSOCIATION OF ENGINEERING SOCIETIES.

its use much trimming of cargo is avoided. The car-clamping mechanism is beautifully simple, being merely four chains with counterweights suspended, the chains wrapping round the car as it is overturned. The cable is hoisted by four i|-inch cables arranged

as a "two-part" hoist on 45-inch drums, driven through double reduction gearing by a pair of 14 x 18-inch engines. The load is lowered by using the engines as air pumps and throttling the exhaust, or with a foot brake, as desired. In operation the machine,

DOCK EQUIPMENT ON THE GREAT AMERICAN LAKES. 17

though so powerful, is extremely simple, considering the work it accomplishes, and has a record of thirty-two cars an hour ; but of course this speed cannot be maintained, on account of delays in switching cars and shifting the boat to reach different hatches. There are three machines of this type in operation : one on the docks of the Cuddy-Mullen Coal Company at Cleveland, one on the docks of the Cleveland Terminal and Valley Railway at Cleveland and one at Erie, Pa., on the docks of the Erie and Pittsburg Rail- way.

Fig. 1 6 shows the latest type of McMyler car dumper ; designed to handle the coal more gently, in order to reduce the breakage to as small a percentage as possible. There are also' three of these

C.T. 1.V Ry. CLt«nm.n o

O 5 10 15 20 25 30 35 40 45 50 FEET

llllil I I I I I I I

Fig. i6.

machines in operation ; one operated by the Pittsburg and Conneaut Dock Company at Conneaut, Ohio, another by the Cleveland, Lorain and Wheeling Railway at Lorain "and a third at Ashtabula. As will be seen, the coal is first dumped into a pan, which is partly overturned to receive the coal as it rolls out of the car. The pan is then hoisted — the car being: lowered meanwhile — until the chute

18 ASSOCIATION OF ENGINEERING SOCIETIES.

is reached, when a door in the pan opens automatically and dis- charges the coal into the chute. This machine is also very fast, and handles regularly, under working conditions, iooo tons of coal per hour. All the motions, with the exception of hauling the cars onto the cradle, are performed by a single pair of 16 x 1 8-inch engines. The car and cradle are hoisted by eight i^-inch cables on 6o-inch drums, geared to the crank-shaft by single reduction gear- ing. The operations of hoisting and tipping the pan are accom- plished with sixteen i-inch ropes on four drums 40 inches in diameter. The unit stresses specified by the P. and C. Dock Com- pany's specifications covering this machine were as follows :

UNIT STRESSES.

Direct tension machinery steel in structural work, 10,000 (i-f )

\ 2 max./

Tension flanges of built girders, 8,000 ( 1 + \

\ 2 max./

Tension flanges of symmetrical rolled sections, 10,000 ( 1 + )

V 2 max./

Direct compression, (10,000 — 30 — ) (1 + -1

V r / \ 2 max./

Maximum limiting value for direct compression, — === 120.

r

1 = length of member in inches.

r = least radius of gyration in inches.

Unstayed length of flanges for built beams, — = 16.

w

Unstayed length of flanges for rolled beams, — = 20.

w

1 = length of unstayed flange in inches.

w = width of flange in inches.

Allowance for impact of moving loads, 50 to 100 per cent.

MACHINERY SPECIFICATIONS.

Babbitted bearing pressures. For steady pressures — pressure per square inch X velocity of journal

in feet per minute must not exceed 60,000. For intermittent pressures, use 120,000.

For slow moving bearings (not over 100 feet per minute), use 600 pounds per square inch. Chain and rope sheaves and drums.

For link chains, diam, of sheave nQt less than lg diam. of chain diam. of drum not less than 24.

diam. of chain

Ropes, diam. of rope nQt greater than _2_

diam. of sheave

diam. of rope nQt greater than ^ diam. of drum

For all sheaves, diam' of Pm not greater than I. diam. of sheave

DOCK EQUIPMENT ON THE GREAT AMERICAN LAKES. 19

The Brown Hoisting and Conveying Machine Company has built five car dumpers that handle the coal still more gently, but on that account they are necessarily slower in operation. With these machines the coal is dumped from the cars into six buckets carried on a transfer car. Each of these buckets is then lifted by either of two traveling cranes, which carries it out over the boat and lowers it into the hatch, when the bottom is opened and the bucket drawn away, thus placing the coal very gently and just where wanted. The mechanical arrangements are very ingenious and well executed in securing the complicated motions necessary.

The Hulett car dumper, built by the Webster, Camp & Lane Machine Company for the Rochester and Pittsburg Coal and Iron Company at Buffalo, works somewhat on the principle of the Brown car dumper, but it is much simplified by using only two buckets ; in fact, the whole machine is comparatively simple. The clamping mechanism is of the same type as that of the McMyler machine. The engines for tipping the cradle are located underneath same, while those for controlling the buckets are located on the platform on top of the machine. The tracks on which the trolleys carrying the buckets run can both be swiveled about a pivotal point by hand to suit any spacing of hatches. The machine can handle regularly twenty cars an hour, but the switching room at Buffalo is so limited that a sufficient supply of cars cannot readily be made accessible to the machine.

A novel design of car dumper is shown in Figs. 17 and 18, built by the Excelsior Iron Works Company for the Erie Coal Transfer Company at Cleveland. This is an exceedingly fast machine, and its operation is very simple. The loaded car is pushed into the cylinder by a locomotive, and the cylinder and car are turned over by a steam cylinder of long stroke operating through a "two-part" rope. In turning over the car is supported on its side by a hydraulic cylinder and clamped on top by a simple device. The machine is well adapted to its peculiar location, where the bank of the river is very high, but the fall of the coal is considerable.

In all the car dumpers the speed depends largely on the switch- ing arrangements and on the storage capacity for loaded and empty cars. The three methods in use for bringing the loaded cars into the machine are :

First. By means of a locomotive.

Second. By storing the loaded cars on tracks having a down grade into the machine.

Third. By the use of a haulage mule similar to that shown on

Fig- 19-

ASSOCIATION OF ENGINEERING SOCIETIES.

Fig. 17. Car Dumper built by the Excelsior Iron Works Co. Erie Coal Transfer Co., Cleveland, Ohio.

Fig. 18. Car Dumper built by the Excelsior Iron Works Co.

DOCK EQUIPMENT ON THE GREAT AMERICAN LAKE5. 21

In the last case there is a grade up into the machine. The loaded car pushes the empty car out in all cases.

Car dumpers are also used for fueling vessels, although some of the fuel hatches cannot be reached by the chutes ; but most docks handling fuel alone are equipped with coal pockets at a sufficient elevation to discharge the coal through chutes into the coal bunkers, the pockets themselves being filled by drop-bottom cars from a track carried on top. Fig. 19 shows the equipment of a large fuel- ing block operated by the Cuddy-Mullen Coal Company at Cleve- land, built specially for fueling the passenger steamers "Northwest" and "Northland." The chutes in this case are round, in order to inclose the dust. The method of hauling the coal cars up the steep grade is shown ; also the ingenious method of holding the mule down to its track, thus preventing it from climbing, due to the fric- tion between the coupler and the front of the mule.

For unloading coal at the Northern ports there are many special machines of the Brown type and others adapted to the special condi- tions, such as storage for railroad reshipment and wagon delivery in large cities. Many of the large mining companies also have extensive coal storage docks to tide them over the four months of closed navigation. A notable storage plant is that of the Lehigh Valley Coal Company at West Superior, Wis., in which there is storage capacity for 100,000 tons of anthracite coal under cover by the Dodge system, and for 90,000 tons of bituminous coal exposed, in piles not over thirty feet high as a precaution against spontaneous combustion. At this plant all the operations of unloading from the boats, storing and reloading into the cars are performed by machinery.

The most surprising feature in connection with the equipment of docks generally on the lakes — using the word dock in the Ameri- can sense of pier or landing to which a boat ties —is that such highly improved and expensive machinery should be placed on such poor and entirely inadequate foundations ; often merely a few piles driven in soft mud many feet below the water line, with little or no cross-bracing to give them some rigidity. This is probably due to the nervous speed with which a great many dock improvements and extensions have been made.

There is a growing feeling, however, in favor of great im- provements in this direction, and as examples of recent construc- tion Figs. 20 and 21 are introduced. Fig. 20 is the cross-section of a dock built by the Illinois Steel Company at their South Chicago works which has attracted a great deal of attention from engineers in this country. This dock, which is 1608 feet long, was built at the rate of about 15 feet per day. Fig. 21 is a cross-section through

ASSOCIATION OF ENGINEERING SOCIETIES.

1 fe

DOCK EQUIPMENT ON THE GREAT AMERICAN LAKES. 23

the foundation for the McMyler car dumper on the dock of the Pittsburg and Conneaut Dock Company at Conneaut, Ohio. This foundation has proved itself to be immovable.

It will be of interest here to quote from the "Blue Book of

9

American Shipping," issued by the Marine Review, that on the Great Lakes there are "the greatest iron mining resources, most rapid cargo-handling facilities and the most efficient iron-producing plants in the world," together with the statement that "it is possible to take ore from the mountain iron mine and convert it into steel ship plate within ten days." While not becoming responsible for the accuracy of the last statement, quoting from the same source, the explanation is as follows :

"Suppose that on the first day and night of a month 9000 tons

24

ASSOCIATION OF ENGINEERING SOCIETIES.

were mined and loaded. The second day at noon this ore could be run onto the Duluth, Mesaba and Northern Railway docks at Duluth, 80 miles from the mine, and dumped into pockets. Each of the two docks lacks 600 feet of being one-half mile long, and both have capacity for 100,000 tons of ore. In one hour the 9000 tons could be loaded into a Bessemer steamer and barge, 424 and 366 feet long respectively. The Bessemer fleet consists of ten steamers and eleven barges, and the carrying capacity of the fleet for one season, between eight and nine months, is over 1,500,000 tons. At one o'clock on the second day the steamer and consort would start on their 890-mile trip. On the sixth day at one o'clock they would arrive at Conneaut, Ohio, the steamer, we will say, going to the McMyler rapid direct-unloading plant and the consort to the Brown

Fig. 21.

plant. The seventh day at one o'clock the 9000 tons of ore would have been taken from the holds of the vessels and loaded into 180 of the 50-ton steel cars, of which the Pittsburg, Bessemer and Lake Erie has 600 and is building 400 more. On the morning of the eighth day these cars would be delivered to the furnace at Bessemer or Duquesne, the four-stack furnace, having annual capacity of 800,000 gross tons of pig iron, at the latter point. The distance from Conneaut to this furnace is about 150 miles. On the ninth day, at seven o'clock in the morning, the ore would have run through the cupola and could be transferred to the Bessemer converter or mixer, and in less than an hour be turned into steel ingots. These ingots could be taken hot to the plate mill and made into ship plate in one hour; or if from the furnace the iron was made into pigs, some eight hours more would be required to make ingots of the pig. By the evening of the ninth day this plate would be ready for ship- ment. Even if twenty-four hours for delays are added, it is shown that in ten days ore from Lake Superior can be made into plate on a larger scale than in any other country in the world, and at con- siderably less cost."

MASONRY CONSTRUCTION. 25

THE PRESENT STATUS OF ENGINEERING KNOWL- EDGE RESPECTING MASONRY CONSTRUCTION.*

By David Molitor, Mem. Am. Soc. C E., Mem. Detroit Engineering

Society.

I. INTRODUCTORY.

Masonry construction, in its relation to engineering, may be regarded as the origin from which the present science was evolved by a gradual progress of human research and experience. In the history of the world's advancement it constitutes a measure of the degree of civilization. It is older than the written history of any people ; it ranks as the foremost instance in the adaptation of nature's forces and products to the uses and convenience of man ; and, as an engineering subject it deserves the highest considerations, and gives birth to monumental works which, by their natural beauty and lasting qualities, stand as wonders of the world.

The volumes treating of the mechanics of engineering con- struction, or more particularly the subjects of earth pressure, retain- ing walls and masonry arches, constitute a very voluminous library. It would require many years of patient reading to review only the most important German, French, English and American produc- tions. However, to infer from this, that our knowledge of the theories of masonry structures has advanced to a state commen- surate to modern engineering science, is entirely erroneous. On the contrary, this vast mass of literature represents in reality an unceasing effort to determine a few complex natural laws by an endless series of mathematical speculations, based on a meager assortment of experimental data.

The truth of this assertion must be conceded when it is remem- bered that all of our theories on earth pressure are derived from miniature laboratory experiments, generally made with sand or grain, and under conditions vastly different from those found in nature. To within four years ago experiments relating to masonry arches were limited to a very few of almost insignificant character. As problems of this nature can be solved only by empirical methods, it is natural to conclude that the empirical laws found apply only within the scope of the experiments. Hence earth pressure and arch theories based on small laboratory tests are quite worthless when applied to full-size structures. Modern writers frequently treat of these subjects, but they advance nothing essentially new. Starting from the same erroneous assumptions employed by the old pioneers, they arrive at the same old conclusions, though the inter-

*Entered for copyright February 12, 1900.

26 ASSOCIATION OF ENGINEERING SOCIETIES.

mediate steps may be new and original. Hence such efforts do not represent real progress.

Much credit is due to the old theorists, among whom may be mentioned Coulomb, Poncelet, Scheffler, Culmann, Redtenbacher, Mohr, Considere, Winkler, Levi, Rankine, Weyrauch and many others. They have practically exhausted the subject as far as the meager experimental data available would warrant, and since the time of their investigations little or no progress has been made toward a satisfactory solution of the perplexing problem of earth pressure upon which the analysis of a large class of masonry struc- tures depends.

Unlike the chaotic condition existing in regard to earth pres- sure theories, our knowledge of constructive details has steadily increased, and many modern masonry structures stand as monu- ments to engineering genius.

Despite the test of time which the numerous engineering stone structures of past ages have endured, it is nevertheless true that our modern high-grade masonry generally excels in quality and appear- ance the famous specimens of mediaeval and ancient production. However, this is not generally true of the esthetic feature of modern designs.

Our modern, practical, improved methods of construction have never been excelled, or even equaled ; and this feature in particular is entitled to even more credit as pertaining to engineering progress than would be a purely theoretical advancement.

While the pyramids of Egypt are still recognized as a "world wonder," yet the conditions under which they were produced, if known to us, would probably permit of their construction now as well as in ages past.

The wonderful improvements made in recent years in the manufacture of cements is undoubtedly responsible for much of the success attending modern achievements in masonry construction.

The elaborate arch tests, made in 1890-95 by the Austrian Society of Engineers and Architects, demonstrate that fixed arches may, within certain limits, be designed and constructed by the methods hitherto employed without incurring more error than is inherent in the nature of the problem, but the inference frequently drawn from these tests regarding the applicability and reliability of past theory and practice respecting long-span fixed masonry arches is somewhat erroneous. In fact, these experiments show conclu- sively that fixed masonry arches invariably fail by flexure, and not necessarily by compression ; as under heavy loading the masonry breaks its continuity at the haunches and later at other points,

MASONRY CONSTRUCTION. 27

creating flexible or hinged joints; and failure finally occurs by a collapse of the masonry at the points so weakened.

In the light of these tests, therefore, it would seem proper to provide artificial hinges, thereby making the masonry arch suscep- tible to rigid analysis, permitting higher unit working stresses and obviating the danger of objectionable and often serious cracks generally occurring in large arches. This idea, after passing through various primitive stages in its development, finally resulted in the production of a perfect three-hinged masonry arch, of which type numerous masonry and concrete bridges have recently been erected in Germany. They have proven a success, and virtually mark a new era in masonry arch construction, as the introduction of hinges has removed the innumerable difficulties attending the computation and construction of large masonry arches.

In the following the subject is considered more in detail under separate headings :

2. EARTH PRESSURE THEORIES.

Theories in Common Use.

Classification of Theories. These may be divided into two principal classes :

First, those in which it is assumed that when the retaining wall of an earth bank fails, a prism of the supported earth severs its con- nection from the bank and slides on a plane surface called the sur- face of rupture. This is called the "theory of the prism of maxi- mum pressure," originated by Coulomb, Poncelet and Scheffler, and was solved graphically by Professors Mohr and Karl von Ott.

The second class is founded on the theory of conjugate pres- sures. The differential equations, representing the equilibrium of a particle of earth in the interior of a mass, are applied to any point in this mass, and by. integration the total resultant earth pressure is found. This theory, proposed by Rankine, Levi, Concidere, St. Venant, Winkler, Mohr and Weyrauch, is called "the theory of earth pressure in the indefinite mass." The graphical solutions of Professors Culmann, Scheffler, Karl von Ott, Winkler and Chas. E. Greene are based on this theory.

Assumptions. These theories are based on certain assump- tions, and when applied to retaining walls give rise to contradictions which cannot be harmonized with facts observed in practice. While this is not surprising, especially when all the phases of the problem are considered together with the very limited experiments upon which the theories are based, yet it is very perplexing and often discouraging to the practicing engineer, who considers himself a

28 ASSOCIATION OF ENGINEERING SOCIETIES.

member of a learned profession, when he begins to realize his inability to solve what appears to be a most simple problem in engi- neering mechanics.

The assumptions are as follows: I. That a certain kind of earth possesses a certain constant angle of repose. 2. That when an earth bank is artificially constructed with a slope exceeding the angle of repose for that material, a certain prism will sever its con- nection from the remaining earth and slide into a new position of equilibrium. This surface of separation, called "the plane of rup- ture," is assumed to be a plane surface. 3. That the resultant earth pressure exerted by such a sliding prism against the back of a retaining wall acts upon that wall in a direction which may vary between the limits of being parallel to the surface of the retained earth to making the angle of repose of the earth with the normal to the back of the wall. 4. That the resultant earth pressure has its point of application at a height above the base of the wall equal to one-third the height of the wall.

Accepting these assumptions, the plane of rupture and the re- sultant earth pressure become definite and determinable when the question of cohesion is neglected.

It will now be shown that these assumptions are all materially erroneous, approaching somewhat the truth for dry sand, but de- parting therefrom for other materials, such as common surface loam, clay, marl and mixtures of these with each other or with sand.

Angle of Repose and Surface of Rupture. To prove the fallacy of assumptions 1 and 2 it will be necessary to review the results of experiments on high embankments given in a paper on "Land- slides," by the writer. (See Journal of the Association of Engineering Societies, Vol. XIII, No. 1, January, 1894.) This subject will be taken up later, and only a passing reference here will suffice for the present purpose.

A sliding embankment, representing the actual conditions which obtain when earth is deposited at a steeper slope than is per- missible, is shown in Fig. 1, where the material was Turneri clay. From this, and from a number of similar experiments for embank- ments of different heights, it was found that the angle of repose for the same material was not by any means a constant, but was an inverse function of the height of the fill. Also that the surface of rupture had no resemblance to a plane, but was practically an hyperbola in section. This fairly represents the disparity existing between results obtained from small laboratory experiments and actual cases as they occur in construction.

Direction of Pressure. The third assumption regarding the direction of the resultant earth pressure is probably nearer to the

MASONRY CONSTRUCTION. 29

facts than any of the others, though the following considerations are offered: According to Rankine and others this direction is parallel to the surface slope, and according to the majority of writers the resultant makes the angle of repose of the material with the normal to the back of the wall. The former theory is not rational, because the direction of motion of the sliding prism is not governed by the direction of the surface of the slope, but is largely dependent on the surface of rupture. The sliding prism glides on the surface of rupture, and the direction of motion will be parallel to that surface until the resistance of the wall changes this direc- tion. When this occurs, then the direction of the resultant pressure must of course make the angle of repose with the normal to the back of the wall, but in the instant after rest is restored the direc- tion of this pressure returns to its former position. It is readily understood that the pressure is a maximum when there is absolutely no motion, and that in the instant when motion occurs by partial giving way of a wall the pressure changes its direction and dimin- ishes in intensity, thus relieving the wall of a portion of its burden and establishing a temporary state of rest.

Hence, in designing a wall the direction of pressure should be taken for the state of rest when the effect will be a maximum, as otherwise a motion is necessary to permit the earth to establish a frictional resistance with which to diminish its direct pressure against the back of the wall.

Point of Application. The fourth assumption, that the point of application of the resultant earth pressure is above the base of the wall by a distance equal to one-third the height of the wall, could be true only for a perfect liquid, in which the pressure in- creases with the depth below the surface and the distribution of pressure is represented by a triangle. Were the earth an inelastic solid, then the point of application of the resultant would be at half the height of the wall, and the pressure would be uniform and be represented by a rectangle. However, neither assumption is cor- rect, but the two cases cited are the extreme limits ; and, since earth is neither liquid nor solid, the point of application must be located somewhere between one-half and one-third the height of the wall above its base. Hence the pressure would be distributed according to some parabolic curve of the second or higher degree, with its vertex at the top of the wall.

The general condition being more nearly solid than liquid, the point is probably about 0.45 of the height of the wall above its base, varying between small limits, dependent on the amount of moisture contained in the earth. This is substantiated by a few experiments

30 ASSOCIATION OF ENGINEERING SOCIETIES.

made by a French engineer, Leygue, published in Annates des Fonts et Chaussces, 1885, II, p. 788.

Various Recent Theories.

Foremost among these may be mentioned the theory proposed in 1885 by the French engineer Leygue, previously referred to in this paper, and one by M. Chaudy, in Memoires et Compte Rendu des Travaux de la Societe des Ingenieurs Civiles, December, 1895, discussed by G. C. Maconchy in London Engineering of August 26, 1898.

Leygue bases his theory on experiments performed by himself

with sand and grain, from which he determines values for the

■ • • • • sh2

empirical variable coefficient in the equation E = c — , in which E

is the horizontal component of the resultant earth pressure, g the weight of one cubic meter of material and h the height of the wall.

The theory of Chaudy results in the same equation, in which the empirical variable c is theoretically deduced.

All the older theories are based on this same equation, and hence the recent contributions just mentioned differ from them merely in the values assigned to this variable coefficient.

If earth, or earthy materials in general, were possessed with properties similar to water, in which friction between the particles is constant and differing only in degree for the case of liquids of different density and viscosity, then the above form of equation might be accepted as rational. However, it is a well-established fact that earthy materials retain their shape by virtue of frictional resistance combined with cohesion between the particles. Hence the law of equilibrium must of necessity differ widely from that observed for liquids, and in all probability the above equation is incorrect in form, which would explain the reason why none of the methods hitherto proposed are general in their application to all retaining wall problems.

Leygue shows experimentally on a small scale that the point of application of the resultant thrust is at a point varying between 0.38b. and 0.5I1 above the base of the wall. To this extent he has revealed a new fact which corresponds well with modern views.

Chaudy still insists on having the point of application at — above

the base of the wall.

A rational theory of retaining walls (so called) was published by R. Iszkowski in Oesterreich. Monatschr. fur den offentlichen Baudicnst of June, 1898. This theory is based on substitution of

MASONRY CONSTRUCTION. 31

a prism of masonry having a resisting moment to overturning equal to the moment of a triangular earth prism included between the slope of repose and a vertical plane through the crest of the slope of a given embankment. This slope of repose is supposed to be such a slope as would result by filling earth behind a vertical wall, which latter is suddenly removed, thus allowing the retained earth to establish a natural slope.

The fallacy of the argument is essentially in assuming that a prism of earth can exert an overturning moment about an edge, which is impossible. This can only be realized by a solid of suffi- cient strength to resist its weight on one edge, and even in the case of masonry such a point is found near one-third the base from the compressed edge. The data for determining the surface of repose is such as may be found in older text-books, and could not ration- ally be applied in the manner indicated by the author. The value of

eh2 E is again a function of — . The paper is interesting, but unfor- tunately does not increase our knowledge of the subject.

A New Theory of Earth Pressure.

General Remarks. The difficulty attending the evolution of a new theory of earth pressure may be appreciated by the fact that so little progress has been accomplished in the past twenty-five years, despite the many efforts made to advance our knowledge on this obscure branch of engineering science.

While the method proposed in the following may be open to criticism, yet it is thought to embody the most recent ideas and experimental data available. The method is not claimed to be per- fect by any means, but, being based on facts which are not much in error, though at variance with previous assumptions, the best results attainable with the present status of our knowledge are expected therefrom.

The subject of earth pressure will not be definitely understood until some government or institution of learning shall spend a few thousand dollars on large experiments, as was done by the Austrian Society of Engineers and Architects in 1890-95 to solve the mystery of fixed arches. A satisfactory solution of this perplexing subject is considered attainable if the proper method is employed, and, viewed in this light, the neglect to undertake its solution must stand as a blemish on the profession. In the meantime the best available data must be utilized to the best advantage.

Before entering on this subject it will be necessary to abstract the results pertaining to the surface of rupture and angle of repose

32 ASSOCIATION OF ENGINEERING SOCIETIES.

as found from experiments by the writer, published in the Journal of Engineering Societies, Vol. XIII, January, 1894. These experiments were incidental to construction work on the German Government railroad Weizen-Immendingen, a section of which was projected and built under the writer's charge in 1887-90.

The material consisted mostly of Opalinus and Turneri clays, of which about a half-million cubic meters were handled in the con- struction of railroad embankments, varying in height up to 18 meters. These banks were all constructed with 1^ to 1 slopes, and in the course of a few months the material assumed a natural slope, which differed for embankments of different heights. In passing from the artificial to the natural slopes the material usually sepa- rated along a distinct plane of rupture, which, together with the final slope of rest, or surface of repose, was carefully measured. These aggravating mishaps, however, make up an extensive series of elaborate experiments, on which the new theory is based.

To increase the value of these experiments a description of the material used is here given.

Opalinus and Turneri clays are almost identical in appearance and in composition, and it would be difficult to distinguish between them were it not for the strata by which they are separated. The Opalinus clay, varying in vertical depth from 45-75 meters, is found in the lower Oolitic and immediately above the upper Liassic epoch. The Turneri clay, with a vertical depth of from 15-21 meters, is located in the middle Liassic, immediately above the strata of the lower Liassic. Both clays contain iron, and, when the atmosphere and water have not come in contact with them, they may be of a steel gray or blue color. The usual color, however, is brown, or that of ferric oxide, and the presence of a slight percentage of finely- divided silica causes them to glisten. In the natural state, whether blue or brown, these clays are very hard, almost slaty, but on being exposed to the atmosphere and water they disintegrate into a fine powder which when wet presents all possible properties objection- able to the engineer. The weight of a cubic meter of this clay in a naturally damp condition is about 1900 kilograms.

The angle of repose was found to be a variable depending on the height of the fill. The actual surface of repose is not a plane, but a curved surface, as shown in Fig. 1. However, for practical purposes an average plane was taken. From the various embank- ments which were constructed in Opalinus and Turneri clays, and from the numerous slides which occurred in this material, the fol- lowing data (which are probably near enough to the facts for all practical purposes) were collected:

MASONRY CONSTRUCTION. 33

TABLE SHOWING RELATION BETWEEN H AND p, FOR OPALINUS AND TURNERI CLAYS.

Height of embankment H o — im 2 — $m 5 — io;« , 10 — 13m 13 — \$m 15 — 20m

Angle of repose p 45°o/ 33°45/ i 26°4o' ' 24W 22°oo/ i8°io'

Corresponding slope 1:1 iV2 : 1 2:1 2% : 1 2^ : 1 3:1

Tangent of p 1.00 0.66 0.50 0.44 0.40 0.33

Hence, for any given H the corresponding value of tang /> may- be taken from the above table.

As far as is known, this law applies to all materials, varying only in degree, being less marked for sand or sandy loam than for clay. However, no experiments on large sand embankments are at hand to verify this supposition.

The surface of rupture is not a plane, but a curved surface whose normal cross-section is an hyperbola, as is seen from the example shown in Fig. 1 .

Fig. 1 represents a cross-section of a slide showing the pro- posed slope or original condition of the embankment, the actual surface of repose after the slide had established permanent condi- tions of equilibrium and the actual surface of rupture corresponding to this surface of repose.

Let A B C be a given embankment, which, by virtue of the steepness of the slope C B, slides into the position represented by the dotted curved line D E K. The sliding takes place on the surface of rupture D K. After complete equilibrium is estab- lished between the embankment and the moving mass, the surface line A B assumes the position D E while the slope line B C takes the irregular curve E K, the actual surface of repose.

The portion A D M , left standing, will have no influence on the sliding mass, and the level of the embankment is practically changed to D E. The depression from A B to D E could of course be filled up, and thus cause the masses to slide farther and to comply with the conditions imposed by the extra loading. The load A B D E wrould also drop to some new position intermediate between A B and D E, and after a number of repetitions of this process the conditions of the equilibrium for an embankment of height O A might be found ; but this would lead to the same general law that obtained by assuming the portion ADM removed.

For practical and theoretical reasons, the actual curved surface of slope is assumed to be replaced by a plane N K. This will pro- duce little or no difference in the results, and will conform with the usual manner of grading. The angle N K O, which the plane N K makes with the horizontal K O, is called <> . This angle is found to vary with -the height O D = H. 3

34

ASSOCIATION OF ENGINEERING SOCIETIES.

It was found from numerous slides that in this material

(Opalinus and Turned clays) the ratio ^ = =>- — J nearly.

Hence the distance

OK=L=m+ rH =Hf £+-M (i.)

1 tan. (j \ 6 ' tan />/ v J

Taking the horizontal line O K through the foot of the slope, and the vertical O D through the point of rupture D at the crown of the fill, as axes of co-ordinates, an equation representing the sur- face of rupture may then be found.

Fife. 1

Assuming the curve to be an hyperbola whose asymtotic axes are parallel to the axes O K and O D, its equation must be of the form

(x + a) (y + b) =c (2.) where a and b are the perpendicular off-sets between the asymtotes and the axes O K and O D, and c is a constant depending on the eccentricity of the curve.

Taking the co-ordinates of the curve D K from the figure, substituting these in the above equation (2), then solving, from each successive three equations, for a, b and c, and averaging these results, values are obtained which may be substituted in equa- tion (2).

It is found, from numerous curves of rupture and for various heights H, that "these constants bear the following approximate

relations to H and j>, or, indirectly, to L, since L = H( £ -f- g— V

a = — , b = — , therefore c = =6ab (3.)

5 5 25

Solving the above equation (2) for y, and substituting from equation (3) for c — ab, its value 5ab,

y =

_5ab — bx __ H(L— x)

a + x

5x

(4->

MASONRY CONSTRUCTION.

35

TABLE OF COMPARISON OF OBSERVED AND COMPUTED VALUES OF V FOR DIAGRAM IN FIG. I.

Assumed x...	0	2	4	6	8	10	12	14	16	18	20	22	24	26	28	3°	31.5
Observed jr....	. 12.2	9.0	6.7	5-3	4.2	3-2	2.7	2.2	i.8	1.4	I.I	0.9	0.7	0.=;	o."*	0.2	0.0
Computed y..	. 12.2	8.7	6.6	5-i	4.1	3-3	2.7	2.1	1.8	1.4	I.I	0.9	0.6	0.4	0.3	0.14	0.0

The curve of rupture may then be plotted for any case in ques- tion, provided H and p are given.

The above conclusions seem to apply to most other materials, except as to the degree of curvature of the surface of rupture, which for sand would approach a plane surface, as is indicated by small experiments, although not much reliance can be placed on any such conclusions unless they are based on the actual behavior of large masses of sand, for which no experiments have as yet been made.

Time is also an important factor in deciding on what actually takes place when a mass of earth is deposited for the purpose of obtaining its angle of repose. It may require six or eight months for a slope to change from its original to its stable condition, and if the difference between the two is but slight it may require years. In the latter case it may take place by gradual settlement without showing sudden motion.

It will be observed that the term "angle of repose" is here used to signify the natural slope which a certain material acquires when exposed to the elements, and hence is dependent on the friction and cohesion existing between particles of earth. The term as com- monly understood applies to friction between particles of loose, dry earth without cohesion.

The conditions of equilibrium for a certain mass of earth, as- determined experimentally, are illustrated in Fig. I. Accordingly,, any load imposed on the top of the embankment along D E or on the slope near E, will disturb the equilibrium of the sliding prism, and will cause the latter to move to a new position of rest. Also any additional mass placed on the slope near the point K will hinder sliding. Hence, in the nature of the case, the sliding prism, as determined in the preceding, represents the limiting case of equi- librium resulting from the balance between gravity forces and internal friction and cohesion of the material.

Therefore, the sliding prism D N K in its limiting condition of rest, exerts a tendency down the surface of rupture D K just equal to the maximum resistance t, which the underlying earth is able to offer against sliding along this surface of rupture ; there- fore, any additional material added to the prism D N K will cause an increased tendency down the surface D K, which cannot be balanced by the resistance t, and motion will ensue.

36 ASSOCIATION OF ENGINEERING SOCIETIES.

This frictional and cohesive resistance t, when determined, will represent the maximum total resistance which can be exerted on any mass of earth between the foot of the slope K and the top of the bank at N ; and any material in excess of the prism D N K will exert a downward tendency on the surface D K, which must be resisted by a wall at K.

To determine the frictional resistance t, necessary to hold in equilibrium the prism D N K, it is necessary to find the resultant tendency of this prism down the surface D K for the limiting case of equilibrium. (See Fig. 2, in which a section of unit thickness is considered.)

If the area of the sliding prism D N K be divided vertically into laminae or sections, then the weight px of each section will have a component tx parallel to the surface of rupture immediately below the section and another component nx normal to this surface. In the limiting condition of equilibrium this parallel or tangential com- ponent tx representing the downward tendency on an inclined plane, Fig. 2 b, must be exactly balanced by the frictional and cohesive resistance existing along the surface of rupture D K. This is true only in the limiting case. Hence the resultant of all the tangential forces along the surface of rupture will represent the downward tendency of the sliding prism. This resultant must be equal and opposite to the resistance t, which latter is found graphically in Fie:. 2 c.

MASONRY CONSTRUCTION.

37

To find the earth pressure on the back of a retaining wall, Fig. 3, it is necessary ohly to determine the downward tendency T of the sliding prism D S V K on the surface D K, in the manner indicated for finding the frictional resistance t, then knowing the direction and magnitude of t and T, they may be made to form a triangle in which the resultant earth pressure E is the unbalanced force, Fig". 3 b.

Fifc.3.

Hence, the direction and magnitude of the resultant earth pres- sure are found directly, and its point of application is taken at 0.45 K V above the point K, in accordance with the previous discussion.

Another problem, without surcharge, is solved in Fig. 4, where the earth pressure is also found graphically by the method given by Professor Karl von Ott, in which the area of the shaded triangle in square meters, multiplied by the weight of one cubic meter of the material (g =. 1900 kilograms), gives the resultant earth pressure

acting at above K. For this solution E1 = 21. yg, agreeing

closely with the result found by the new method except as to point of application.

In all of the above solutions it is advisable to use areas only instead of actual weights ; and in finding the opposing moment

offered by the masonry wall, the area of the wall is multiplied by ^

to reduce to equivalent mass of earth. In the above this ratio was taken at 1.16 by assuming g1 — 2200 kilograms for masonry.

The direction of the earth pressure as found bears no relation to the direction of the back of the wall, and this is as it should be, giving the most unfavorable condition. However, the resultant thrust in being: resisted by the wall must necessarilv be deflected in

38 ASSOCIATION OF ENGINEERING SOCIETIES.

the instant when motion occurs either of the earth or the wall, but whenever a perfect state of rest obtains then the thrust probably returns to its original direction of maximum effect.

A Probable Future Solution.

From the above it is seen that the older theories are based on assumptions which are largely erroneous, and, while the truth may be more closely approximated in the light of recent experiments and ideas, yet no theory has as yet been formulated which may be regarded as perfect. Therefore, the time has come when a less speculative and more accurate method would be highly appreciated.

The simplest problem of a retaining wall, mathematically treated, leads to quite complicated equations, and in general the graphical treatment is far more satisfactory, being more readily adapted to complex cases and affording a better check and insight into the otherwise obscure analytical methods. For this reason more success may in future be expected from a graphical treatment.

However, to reach a satisfactory solution, the nature of the materials involved, the many variable conditions affecting their behavior, and the prime importance of the subject demand far more than mere mathematical investigation. The only promising solu- tion will probably consist in an experimental or deductive deter- mination of the actual pressure found on the back of a wall under various conditions.

It may seem vain to attempt the exact determination of a function depending on such variable material as earth, yet for a given kind of earth in a given state of moisture a definite law cer- tainly exists, and this law once determined for different conditions of the same earth would enable the engineer to treat the problem intelligently and to estimate the probable error of his assumptions. This is by no means possible at the present status of our knowledge.

While the problem is not considered beyond the possibility of solution, the only reason for a failure to accomplish this end has been a lack of funds and a well-developed plan of carrying on experiments. All engineering structures should be so designed as to comply with the most unfavorable conditions which may at any time occur consistent with economical requirements, and this in itself is sufficient reason why experiments and investigations should be made under correspondingly unfavorable circumstances.

Of all the experiments made, or to be made, those only are valuable which are conducted under the actual conditions existing in nature, and of these the extreme cases are most valuable in lead- ing to proper conclusions.

MASONRY CONSTRUCTION. 39

Experiments performed on dry earth or sand are of little or no value, since nature always supplies a certain amount of moisture, which at times may increase to the limits of saturation, thus vastly altering the characteristics of the material.

The effect produced by moisture on earth, or sand, has been ascertained to be about as follows : The specific gravity increases with moisture ; the friction between the particles is a maximum for the dry state and diminishes with increased moisture, becoming almost nil for the state of saturation ; the cohesion is increased for a slight degree of moisture, but is diminished for a further increase and is nearly destroyed for the case of saturation. The earth pres- sure generally increases for increased moisture and becomes a maximum for the saturated condition, which latter may, however, be prevented by supplying proper drainage to the back filling.

It seems proper here to suggest a method for the successful solution of the problem of earth pressure which at present consti- tutes the most deficient branch of engineering science. As was said before, this may be expected only from an elaborate series of experiments to be conducted on a plan something as follows :

A very rigid wall should be constructed about 20 feet high and perhaps 100 feet long, with good foundation, on level ground. In a vertical section near the central portion of this wall a series of pressure gauges should be placed so as to communicate the earth pressure to indicators on the front of the wall. These pressure gauges would require special design in order that they may fulfill all the necessary requirements. The pressure surface might then be covered with a flexible oiled canvas to prevent the earth from squeezing in between the gauges and the masonry.

The pressure exerted by a fill, placed back of this wall, could now be observed for an expended period of time under various con- ditions of moisture, etc., and when all desirable measurements were made the material could be removed and another kind of earth used to continue the experiments. This should be repeated until the variety of material used and the different heights employed would cover the subject in a general way.

The funds for such experiments could probably be obtained through an appropriation from the national or state government, or from the National Society of Civil Engineers, and the work could be best performed under the direction of some large institution of learning. It is needless to mention the value which such an investi- gation would have for the profession at large, and the engineering students participating in the work would gain a very valuable experience.

40

ASSOCIATION OF ENGINEERING SOCIETIES.

3. DESIGN AND CONSTRUCTION OF RETAINING WALLS.

Without attempting to enter into the details of computation involved in ascertaining the stability of retaining walls, and which may be found in books on masonry construction, so far as theory is applicable to the subject, it is intended here to consider more par- ticularly the economic features of design in connection with practi- cal considerations by which safety and durability in construction may be attained.

Economy in Design. In considering a wall of given cross- section the stability is attained by a certain necessary mass of masonry which, by its resistance to overturning, must sustain the pressure of the retained earth. The quantity of masonry necessary to fulfill this requirement is, however, entirely dependent on the manner in which the mass of masonry is distributed over the section. That is, a certain earth pressure may be sustained with equal safety by walls in which the quantity of masonry employed may differ by 100 per cent., representing comparative economy in design.

The important effect of the shape of a wall on economy of material is clearly illustrated by the following table, in which cer- tain relative dimensions have been worked out for different batters according to Rankine's theory by Professor E. Haeseler. In each case the back filling is assumed level with the top of the wall, and the angle of repose of the material is taken as 330. The bottom

N° of section				O" = g on	* <?- 33:	£•■» MSflf ana £ = 33°
Section	b-fOO	A = f(^).	b-f(K)-	A-fin
1			0.350	0.350	0.320	0,320
	>b.	h
2	1		0.327	0.277	0.300	0 250
1	h
^b*
3			0.307	0.222	0.287	0.198
Ai	*
4	ffi	0.238	0.199	0.215	0.174
5			0.472	0.372	0.456	0.356
	\:
	t-b --i

MASONRY CONSTRUCTION. 41

width of the wall, b, as also the area of cross-section, A, are ex- pressed as functions of the height of the wall, h.

This table, which is quite useful in taking off preliminary values, shows that section No. 4 is most economical, while No. 5 is least so. The effect which the shape of the cross-section bears to the economy in amount of masonry required is also illustrated by the two solutions given in Figs. 3 and 4.

From the above it is seen that the most economical form (local conditions permitting) would be one in which the wall is battered towards the retained earth with a batter just sufficient to retain the center of gravity of the section within the base of the wall; this limit being desirable for safety during construction, though if care is exercised the batter may be increased somewhat beyond this limit.

Provisions to Insure Safety and Durability of Retaining Walls. These are applied in accordance with the causes of failure, which will be briefly discussed before treating of necessary remedies for their prevention.

In computing the stability of a wall it is customary to choose a section in which the resultant of the earth pressure and the weight of the wall shall remain within the middle third of the wall, thus striving to prevent any tensile stresses in the masonry. The entire question of stability is, however, based on the assumption that the foundation is perfectly rigid, which it never is except when bed- rock is available. The yielding of the foundation is one of the most frequent causes of failure, hence the apparent necessity of the greatest precautions on these lines. Besides giving rise to local settlement in the alignment, a faulty foundation usually results in failure by partial or complete overturning of the wall.

Overturning may occur even on good foundations, and is then the result of poor drainage of the back filled material or scanly dimensions or poor masonry.

There are few, if any, long retaining walls which are free from vertical cracks, which latter may result from local settlement, exces- sive pressure or wide changes in temperature. The nature of the cracks will generally disclose their cause. A vertical crack of uniform width is usually the result of temperature stresses. A vertical crack, wide near the ground, gradually diminishing in width and disappearing at the top of the wall, is invariably the result of local settlement. Horizontal cracks are of rare occurrence, except in combination with vertical cracks, and generally have little signifi- cance. Changes in alignment always indicate overturning, and usually accompany settlement. It is scarcely necessary to add that any or all of these causes may at times manifest themselves in a single effect, making a diagnosis more or less difficult.

42

ASSOCIATION OF ENGINEERING SOCIETIES.

When a retaining wall is founded on anything other than bed- rock it is advisable to widen the base of the foundation masonry as indicated in Figs. 3 and 4, so as to bring the resultant thrust R well within the central portion of the base. In doubtful cases the base may be widened sufficiently to allow the thrust to pass through its center.

Great care must be exercised in back filling a newly completed wall, since at this time the mortar is less capable of resisting stress than at any future time when the cement has become thoroughly set. Also, loosely deposited earth, possessing little cohesion in this state, exerts a greater pressure than when well compacted. Hence the back filling should not be applied until the mortar is well set, and then the former should be deposited in successive layers, each of which should be well rammed.

As moisture always accumulates in the back filling, it is essen- tial that proper drainage be provided adjacent to the wall, other- wise a condition of saturation mav follow which would increase the

gh2

This is about twice the

earth pressure to its maximum value —

pressure which any wall is usually designed to carry, and will almost invariably prove disastrous.

The best and cheapest way to establish drainage is to provide a masonry gutter along the back of the wall at the lowest level suit- able for draining either through the wall (by leaving openings at intervals) or at the ends of the wall ; preferably the former. From this longitudinal gutter a dry rubble backing of 1 to 3 feet in thick- ness should be carried to near the top of the masonry, thus inter-

MASONRY CONSTRUCTION. 43

cepting all seepage and completely draining the back filling. In severe cases numerous rubble-filled gutters may be extended into the back filling at right angles to the main wall. This is one of the most important precautions necessary in retaining wall construction.

To prevent vertical cracks from temperature effects in long walls it is desirable to insert vertical expansion joints at intervals of 30 to 50 feet. These joints should be so constructed as not to weaken the resisting power of the wall, which is accomplished by making the joints dovetailed in plan. No such provision is com- monly made, and the results are apparent when it is added that the linear coefficient of expansion of masonry ranges between one-fifth to one-third that of steel.

Cracks resulting from temperature effects should never be closed by filling in cement mortar unless it is found that they do not close in summer after long-continued warm weather, in which case they were probably caused by shrinkage in joints, and may then be filled.

A retaining wall which shows signs of overturning may gener- ally be strengthened by the construction of buttresses placed at intervals commensurate with the case in hand, provided there is sufficient clearance in front of the wall to permit of this. A new wall may show indications of trouble, and if supported by timber braces for a time sufficient to allow the back filling to settle and cohere in itself, the wall may become perfectly safe.

What has been said in the above regarding failures in walls applies generally to wing-walls, masonry culverts and abutments.

A neiv style of retaining ivall might be employed with advan- tage, especially where a good foundation is not available.

The writer has frequently considered the advisability of con- structing a wall of concrete and old railroad iron in such a manner as to make the back filling assist in producing the stability against overturning. (See Fig. 5.)

The earth pressure is resisted by the wall A B acting as a beam in cross-bending, being internally stiffened by old iron rails or similar material embedded crosswise in the concrete near the outer or tension face of the wall. Stability is established by the rails G K acting as tie-rods and held by the concrete base C D, which in turn is loaded with the retained earth. To take up the stress exist- ing along BCD, the base C D is connected with the wall by occasional columns of concrete.

So far as known, this idea has never been carried out, and it may deserve consideration in certain cases where local conditions are favorable to its application.

44 ASSOCIATION OF ENGINEERING SOCIETIES.

4. FIXED MASONRY ARCHES.

General Considerations.

The fixed arch, as distinguished from the hinged arch, belongs to the class of indeterminate structures in which the abutment re- actions cannot be expressed in terms of the external forces without involving the elastic properties of the arch material.

In applying the theory of flexure to material like masonry, considerable doubt may justly be expressed as to the reliability of results obtained. However, the extensive arch tests conducted by the Austrian Society of Engineers and Architects from 1890 to 1895, have demonstrated very conclusively that stone, brick and concrete arches follow the laws of elasticity, and the application of the theory of elasticity to such structures would seem perfectly justified in the light of these experiments.

Fig.5, .

Past experience has shown that only very low unit stresses are allowable in fixed masonry arches, a fact which proves beyond doubt that such arches are not adapted to very economical utilization of material. The reason for this is apparent. The initial stresses in portions of an arch, resulting from distortions and abutment dis- placements during and after construction, may often attain danger- ous values, leaving only a small fraction of the breaking strength for a working stress. Fortunately, a partial failure of a portion of an arch under excessive stress caused by distortions has the ten- dency to readjust the distribution of stress by changing the shape

MASONRY CONSTRUCTION. 45

tc one better adapted to the strained condition. This is the reason why such distortions rarely become dangerous, but the fact illus- trates the extent to which any theory is applicable to fixed masonry arches without using' a large factor of safety, varying from ten to twenty. Without this large uncertainty, resulting entirely from the rigid construction, high unit stresses of one-tenth to one-sixth, the ultimate strength of the material, might safely be employed.

Since masonry is not well adapted to withstand tension, no tensile stresses are allowed in arches. To accomplish this the resultant thrust at any normal arch section must lie within the middle third of such section. This follows from Navier's theory for distribution of stress on a voussoir joint.

Hence, for a given span and load, the arch ring must possess a definite shape, requiring a very delicate adjustment of the line of thrust within the middle third of the arch ring.

Metal arches are independent of this requirement, since the actual stresses arising from a certain loading and shape of arch can always be provided for when the dead load has been approximately assumed.

In designing a masonry arch the shape, dimensions and weight must be known, or assumed ; and if the resulting stresses exceed the allowable limits, then any or all of the assumed values must be altered until by a succession of approximations the proper shape and dimensions are found. This is a long and tedious process, especially when the more accurate methods are employed.

According to the recommendations of the Austrian Society of Engineers and Architects, as a result of their elaborate tests, a fixed masonry arch should be constructed only when the following con- ditions can be realized :

1. The abutments must be perfectly rigid.

2. The false work must retain its form during the period of construction of the arch ring.

3. The masonry must be of the best quality.

4. The construction of the arch ring must be most carefully conducted.

5. The false work must not be released until the mortar has thoroughly set.

6. When the false work is released, it must be done gradually and uniformly.

These conditions, except the two first named, can always be fulfilled, though the lack of rigidity of abutments and false work are the two great obstacles in the way of long span, fixed, masonry arches.

46 ASSOCIATION OF ENGINEERING SOCIETIES.

Arch Theories.

Historical. The earliest theoretical treatment of arches is ascribed to de la Hire, who, in 171 2, advanced the theory that an arch acted as a wedge in which the central or crown portion had the tendency to slide between the quarters adjacent to the abutments. Eytelwein, in 1808, applied this theory to individual arch joints, and made allowance for friction.

The combined action of shear and bending was first recognized by Coulomb in 1773, and this theory assumes that an arch may fail either by one portion sliding on another or by a joint opening as the result of bending. Experiments made by Boistard in 1808, proved that failures were to be expected only by cross-breaking, and not as a result of shearing action.

Coulomb's theory was improved by Audoy (1820), Lame and Clapeyron (1823), Navier (1826) and Mery (1827), and was graphically treated by Poncelet in 1835.

The analogy between the arch and suspension bridge, from which the theory of the line of thrust was evolved, was first estab- lished by Gerstner in 183 1. This theory was improved and adapted to practice by Hagen (1844), Bauernfeind (1846), Schwedler (1859), Heinzerling (1869), von Ott (1870), Ritter (1876) and Wittmann (1878).

The theory of elastic deformation was introduced by Navier in 1826, by his analysis of the stresses on an arch section, in which he assumes a combined thrust and bending moment distributed over the section. This theory was supported by experiments of Bausch- inger and Koepke. Winkler (1867) and Belpaire (1877) apply this theory to the elastic arch, and the more recent modifications by Engesser, Ott, Mueller-Breslau, Melan, Weyrauch and others are now generally accepted as the most reliable arch theories. They differ from each other only in methods of solution and degree of approximation. All are based on the same assumptions, and the derivation of the formulae are essentially alike ; but, owing to the extremely complicated equations resulting from the theory, dif- ferent authors have neglected certain terms supposed to be of in- significant value, while others, especially Melan, and Weyrauch, attempt a rigid solution which is very complicated. The treatment of this subject by modern English and American writers is essen- tially according to Ott and Melan.

The graphical solution in general use is based on the most probable position of the line of thrust in a given arch ring for a given case of loading.

MASONRY CONSTRUCTION.

47

The theory of elasticity leading up to a purely analytical solu- tion is more reliable, though far more complicated in its application.

The comparative accuracy and reliability of these two methods will be discussed in the following :

The theories in common use are two in number. First, the line of thrust theory, which is generally employed, and depends on an assumed, most probable position of the line of thrust within the arch ring; and, second, the theory of elastic deformation, by which the statically indeterminate abutment reactions are found by the application of the theory of flexure. The method of solution by the first theory is purely graphical, and by the second theory it is purely analytical, and does not necessitate finding the line of thrust, though this line is definite and determinable by the method. The second method may be made semi-graphical by the introduction of influence lines, which are very serviceable when dealing with con- centrated moving loads.

To give a clearer idea of the distinctive features of these two theories it will be necessary to show the general relations existing between the external or applied forces and the internal stresses in a fixed arch. (See Fig. 6.)

The arch A O B supports the loads P^ P2, etc., producing -tactions RA and RB. The reaction RA can be replaced by a hori- zontal component H and a vertical component V acting at the point A, and a moment RA d = M about A. Also RB can be replaced by H and V1 acting at B, and a moment RB dx = M1. Hence V and V1 are the vertical abutment reactions, H is the constant horizontal thrust and M and M1 are the abutment moments.

By taking center of moments about B and A, the respective values V and V1 can be found thus :

V =

= f[M'-

M

M — M1 - £ Pa

2oP(l-a)]

]

(i.)

(2.)

4? ASSOCIATION OF ENGINEERING SOCIETIES.

For any section M N having- co-ordinates x and y, the shear Vx, bending moment Mx and resultant thrust Rx, are as follows :

VX = V-2X0P (3.)

M, = M + Vx — Hy — 5; P (x — a) (4.)

Rx=l/Vx + H2 (5.)

Nx = Vx sin.cr -j- H cos.cc = thrust normal to the section (6.)

From Nx and M x the stresses on the extreme fibres of the sec- tion M N may be found from

!-*> + ^ (7.)

in which F is the area of the arch section M N, and W is the moment of resistance of this section.

It is readily seen that the determination of unit stresses result- ing from any system of loading involves the terms M, M1 and H, which cannot be determined from purely statical considerations.

According to the theory of elastic deformation, these unknown factors are determined from the elastic properties of the material, while in the older graphical solution they are merely approximated by assigning certain assumed conditions to be fulfilled by the line of thrust.

Hence the theory of elastic deformation fixes the position of the line of thrust in terms of the elasticity of the material, while according to the graphical solution an infinite number of lines of thrust may be constructed for the same arch and same loading, and it becomes a question to decide which of all the possible lines is the most probable.

Hagen (1862), according to his "theory of the most favorable distribution of stress," defines the most probable line of thrust as one for which the vertical projections of the minimum distances, between the line of thrust and the edges of the arch ring, become equal. Culmann (1866) designates this most probable line as the one which approaches most nearly to the arch center line in such a manner that the pressure at the most critical points becomes a minimum. Winkler defines the most probable line as the one for which the areas inclosed between the line of thrust and the arch center line are equally divided according to the method of least squares. Generally a problem is considered solved when, for a given span and load, a line of thrust is found which falls entirely within the middle third of the arch ring. This is, however, very far from constituting an acceptable solution, as will presently be shown. Plausible proofs for all the above assumptions have long been sought, but have never been found.

MASONRY CONSTRUCTION. 49

The graphical method is, at best, nothing more than the appli- cation of the principles of the three-hinged arch to fixed arches, in which the location of the hinged points is arbitrarily assumed at the crown and springing. A line of thrust passed through these three points must remain within the middle third of the arch ring. If these points are assumed on the arch center line, then M and M1 become zero, and H is determined as for a three-hinged arch. While all this is constantly done, there is nothing to justify the procedure.

The derivation of the formulae for M, M1 and H is considered foreign to the purpose of this paper, and is, therefore, omitted.

It is now proposed to show the comparative value of the two methods of solution of fixed arches and their reliability, as found from the experiments of the Austrian Society of Engineers and Architects.

Reliability of the Methods in Common Use. The graphical method, as was just stated, assumes that the real or most probable line of thrust is the one for which the highest pressures at the critical points become a minimum. Hence every line of thrust must either be the most probable line or else it is one which is less favorable than the most probable line. But, if only one line of thrust is possible for a given allowable stress on the extreme fiber at the critical points, then, if the structure is to be regarded safe for all time, this line must continue to exist when the material increases in strength (as by setting of the cement), or when the arch under- goes slight elastic or permanent deformations. For this there is absolutely no assurance, though it is an essential necessity in the general assumption.

It is also a matter of great uncertainty to know when any line of thrust really is the most probable line, since this depends on a more or less arbitrary definition, the requirements of which are ful- filled by a series of approximations.

From these and other considerations it follows that this method ?s neither reliable nor scientific. If arches designed by this method have stood well it is most probably due to the extremely high factor of safety generally employed, and not to the reliability of the method.

The analytical method, based on the theory of elasticity, is cer- tainly scientific, though its value depends largely on experimental, verification.

A sandstone masonry arch, of 23 meters span and 4.6 meters rise, was tested to destruction by the Austrian Society of Engineers and Architects. The breaking load was 3218 kilograms per square

So ASSOCIATION OF ENGINEERING SOCIETIES.

meter on the half arch. For this load the formulae of Professor Weyrauch give a maximum ultimate compressive resistance at failure of 33 atmospheres. The sandstone had a compressive strength of 770 atmospheres, and the cement mortar 311 atmos- pheres. Samples of mortar taken from the arch after destruction broke under a pressure of 80 atmospheres. The compressive strength of the masonry must, therefore, have been about 400 atmospheres, or over twelve times the actual strength developed by the arch.

The results obtained from the tests on a brick arch and a Monier arch, of practically the same dimensions as the sandstone arch, are similar to those just cited.

While it is not fair to expect very reliable results from the application of the theory of elasticity to material stressed to the point of rupture, yet the error incurred would probably not exceed 100 per cent., which would not begin to explain the still existing dis- parity in the above results.

It seems quite likely, however, that a very high initial stress existed in the arch as a consequence of the changes in shape of the arch ring, resulting from the shrinkage of the mortar joints by the setting process of the cement after the mortar had attained sufficient strength to sustain the partial dead load imposed prior to removal of the centers.

If this supposition is justifiable, then it follows that though the theory may be correct and perfectly applicable within the limits of elastic deformation, yet the large factor of uncertainty resulting from permanent distortions, which must always be expected in fixed arches, necessitates a high factor of safety in addition to a very thorough mathematical investigation, if reliable results are expected.

While the theory of elasticity is undoubtedly the only trust- worthy basis for the analysis of fixed arches, and should always be employed in designing structures of any importance, it does not fol- low that the older graphical method of investigation and many of the empirical rules in common use are all worthless. On the con- trary, the preliminary design can be carried out most efficiently by the aid of the simpler methods, and the final design may then be tested by the application of the more accurate method.

It is thus seen that the theory of fixed arches has reached a status of perfection quite in keeping with the nature of the problem, the still existing uncertainty being a function of the material and other circumstances, depending on the rigidity of the abutment foundations, conditions of erection, etc., all of which can never be entirely eliminated.

MASONRY CONSTRUCTION. 51

The above applies only to arches for which the loading is known with considerable accuracy. For arches sustaining high earth banks the loading cannot be determined with any great degree of certainty. Hence the design of such structures is less definite, though the elastic property of the superimposed earth assists greatly in distributing pressure and rendering conditions more favorable to their safety.

The methods employed to obviate excessive stresses in fixed masonry arches will now be discussed.

If it were possible to build an arch ring in such manner that its line of thrust would pass through the center of the ring at the crown and haunches at the time of releasing the false work, a large proportion of the indeterminate stress could be prevented. In other words, the bending moments at the critical points would then be almost zero for symmetrical loading, reserving the strength for the unsymmetrical live load and other contingencies affecting the shape of the arch ring.

In the ordinary process of construction the arch ring is com- menced at the haunches and the load gradually applied to the false work, thus distorting the latter and causing bending stresses in the cconpleted parts of the ring. The final settling of the ring, pro- duced by the contraction of the mortar joints as a result of compres- sion and shrinkage during the setting process of the cement, even when the abutments remain perfectly rigid, is often sufficient to create serious initial stresses, thus destroying to a large extent the usefulness of the structure.

Several methods have been used, with more or less success, to relieve an arch of undue initial stress during construction.

One of the oldest of these is to set the arch stones on the entire false work, spacing the joints by inserting small strips of wood, and lastly filling all the joints simultaneously with mortar. This is still a very good program for erection, but it is not very well adapted to large structures, owing to the excessive stresses pro- duced in the false work, and frequently causing considerable settle- ment in the entire arch ring. This can, however, be prevented by wedging up the false work just previous to filling the joints.

Another method frequently employed in the construction of brick and concrete arches is to close a complete ring adjacent to the false work, and, after allowing the mortar or concrete to set, the remainder of the arch is constructed and the total load is carried by the first ring rather than by the false work. By this means the settlement during construction is very slight, but, as is readily seen, the intrados is excessively stressed, a condition which cannot be averted and which is highly objectionable.

52 ASSOCIATION OF ENGINEERING SOCIETIES.

A program of construction frequently used on large arches necessitates commencing work simultaneously at two, four or six points of the ring and closing at three, five or seven points, respec- tively. The longer the span the greater the number of points of commencement.

The most modern method consists in the introduction of tem- porary flexible or hinged joints at the crown and haunches, and following the previous program of construction. These flexible joints are made of stone with curved, roller-like surfaces ; or iron blocks may be used, forcing the line of thrust through the center of the arch ring at the crown and haunches during the period of con- struction. These open joints are filled with cement mortar either before or after removing the false work. Sheet lead has also been used for this purpose by inserting narrow strips into the crown and springing joints, allowing just sufficient surface of contact on the arch center line to carry the pressure without causing the lead to flow. The open joints are afterwards filled with good mortar.

This last mentioned method gives very good results in pre- venting cracks and excessive settlement during construction, but subsequent changes cannot be compensated for, which is the only obstacle still remaining in this class of structure. Eventual settle- ments in foundation masonry ; contraction of mortar by evaporation of water used in mixing the same; compression of mortar joints from loading ; elastic deformations caused by temperature and load effects ; all these are ever present to create stresses which, in spite of all precautions during construction, may attain dangerous pro- portions and make it utterly impossible to estimate the actual ulti- mate strength of a fixed masonry arch.

It should be remembered that for masonry arches the live load is generally only a small fraction of the dead load, and for this reason an arch which is sufficiently strong to sustain its own weight permanently will carry temporary live loads with perfect safety. When initial stresses attain breaking limits the masonry generally chips near the surface, thus relieving the stress and allowing the line of thrust to return to a more favorable position. In this way an arch which has become distorted may readjust itself to a new condi- tion of stress.

In conclusion, it might be well to recall the recommendations proposed by the Austrian Society of Engineers and Architects, which, if strictly carried out, would limit the adaptation of fixed masonry arches to comparatively short spans and bedrock founda- tions, as these recommendations require the fulfillment of the fol- lowing conditions :

MASONRY CONSTRUCTION. 53

1. The abutments must be perfectly rigid.

2. The false work must retain its. form during the period of construction of the arch ring.

3. The masonry must be of the best quality.

4. The construction of the arch ring must be most carefully conducted.

5. The false work must not be released until the mortar has thoroughly set.

6. When the false work is released, it must be done gradually and uniformly.

The use of sand jacks or sand pots, which was introduced in 1854, during the construction of the Austerlitz Bridge in Paris, offers a very novel and efficient means of releasing the false work supports.

The necessity of these recommendations is clearly understood after what has been said regarding the theory of fixed masonry arches and its application to practice.

The first two conditions can only be realized when rock founda- tions are available, and when the false work is made rigid by very substantial foundations. The other requirements can generally be fulfilled by exercising proper care, and by permitting only good material and workmanship.

5. THREE-HINGED MASONRY ARCHES.

The extent to which theory is applicable to fixed masonry arches has been adequately demonstrated in the previous.

To obviate the difficulties and prevent the uncertainty shown to exist in fixed arches, the introduction of hinged joints at the crown and haunches may be regarded as a most welcome innova- tion; first applied bv Koepke, of Dresden, in 1880, by providing curved, open, voussoir joints in the arch ring at the crown and haunches. In 1885 Karl von Laibbrand, of Stuttgart, substituted sheet lead for the open joints, and in 1893 applied cast iron hinged bearings.

The three-hinged arch is free from initial stresses, otherwise resulting in fixed arches after releasing the false work. Small abutment displacements and changes in temperature do not affect the magnitude or distribution of stress in the arch ring, and hence do not cause cracks.

This form of arch admits of a rigid analytical treatment. For this reason the allowable working stresses may be chosen much higher than for fixed arches; they may range from one-tenth to one-quarter the ultimate strength of the masonry without sacrific-

54 ASSOCIATION OF ENGINEERING SOCIETIES.

ing safety or durability. The strict requirement regarding the rigidity of abutments and false work, so very essential to fixed arches, is a matter of comparative insignificance, provided the abutment foundations are safe.

Therefore, the three-hinged arch is especially well adapted to the economic construction of long-span bridges, and, being free from the numerous objections inherent in the fixed arch, is well adapted to conditions where only moderately good foundations are available.

The introduction of hinges has placed the masonry arch on a high plane of engineering perfection, and has removed its restricted application, thus materially enlarging the field of usefulness so^ justly belonging to this most substantial, economic and esthetic form of bridge construction.

No disadvantages have as yet developed from the use of hinges, and none are likely to develop. Numerous bridges of this type, of spans ranging from 10 to 50 meters, have been constructed in Ger- many and Switzerland within the past fifteen years. All are giving excellent satisfaction.

Therefore, owing to its economy, permanence, low cost of maintenance and esthetic features, the three-hinged masonry arch is destined to become a successful competitor of iron and steel bridges in all cases where the natural conditions of foundations and length of span do not offer unsurmountable difficulties.

This subject has been exhaustively treated in a paper read by the writer before the American Society of Civil Engineers. (See Vol. XL, 1898, Trans. Am. Soc. C. E.)

6. CONCRETE AND IRON ARCHES.

This comparatively new system of construction, introduced about twelve years ago in France and Germany, is fast displacing the solid masonry structures of the past.

The desirability of combining concrete with steel or iron evi- dently arises from the widely different properties of concrete under compressive and tensile stress. The compressive strength being about ten times the tensile strength (so far as our present knowl- edge of concrete would indicate), makes it impossible to use con- crete with economy. In fact, common practice has always been to use concrete and masonry only under compressive stress. By sup- plying tensile strength to those parts of a structure where tensile stress occurs, by the insertion of steel or iron rods, the combined material becomes more widely applicable, and is susceptible to a more economic utilization.

MASONRY CONSTRUCTION. 55

The various systems of concrete and iron arches (mostly patented) may be summarized as follows: The Monier, the Wuensch, the Moeller and the Melan. There may be others, but they probably involve no new principles.

The Monier patent is so broad, embracing in a general way any iron parts enveloped by cement, that it is difficult to understand why not all other systems are infringements. However, this system as generally employed consists of a series of iron rods imbedded in the concrete near the surfaces of the intrados and extrados to supply the required tensile strength. The rods extend longitudinally from one abutment to the other, and are tied together at intervals by wire. Expanded metal has been used in a similar manner.

The Wuensch system employs only longitudinal angle irons or tees, placed near the intrados and extrados of the arch or beam, relying on the concrete to perform the functions of a web system.

System Moeller amounts to nothing more than a very flat con- crete arch with a metal tie-rod to take up the horizontal thrust. The tie-rod is anchored directly in the concrete of the arch abut- ments.

The Melan system inserts concrete arches between iron I beam or latticed arches. It is, therefore, a succession of parallel metal and concrete arches in the same span.

The combinations of concrete with iron or steel offer a great many advantages in practical and economic construction, though the application is perhaps too recent to warrant a definite conclu- sion regarding the lasting qualities of these composite structures. It must also be admitted that the theories of this class of structure are still very primitive.

Monier arches are generally designed for a constant modulus of elasticity,

-['M^

in which E0 = modulus of elasticity of concrete ; Ex = modulus of elasticity of iron ; I = moment of inertia of the combined concrete and iron section, and I1 = moment of inertia of the iron section alone. This is based on the assumption that the two materials in acting together must undergo the same elastic distortions.

Arches built according to Wuensch are designed to carry the total maximum load entirely by the concrete, and the unsymmetrical live load entirely by the metal parts. This is a somewhat arbitrary method.

The Moeller system probably admits of the most exact design,

56 .ASSOCIATION OF ENGINEERING SOCIETIES.

and is especially well adapted to floor arches and light bridges. There is nothing about the design which would require special con- sideration.

The Melan arch being a combination of arches of different materials, makes it difficult to determine the proportion of the total load carried by each material. However, since the elastic deforma- tion of an arch is approximately proportional to the quantity pry,

and two arches if they would work together must undergo the same deflection, it follows that the load must be divided in proportion to the products E I for each material, or that

Load carried by the concrete arch jro jo Load carried by the iron arch ~~ jTy

in which E0 and I0 apply to the concrete section and Ex and It to the iron section. This may be far from the truth, though it has generally given good results compared with tests.

Regarding the durability of concrete and iron structures, we are not in a position to say definitely what the probabilities are. However, with the exception of the Melan system, the iron section is generally quite small, and even a slight corrosion might prove disastrous, because so much depends on the iron parts. It is quite likely that moisture might penetrate some of the hair-like fissures generally found in masonry and concrete, which would do mischief in the course of time. Roebling found such corrosion on some of the outer strands of the anchorage cables of the Niagara and Brooklyn Bridges, where the cables had been imbedded in concrete.

The widely different physical properties of concrete and iron do not seem to offer any serious obstacles, as was at first predicted ; at least, none have developed during past experience. Concrete appears to possess an adhesive strength with iron which is equal to, or even greater, than the tensile strength of the former; the co- efficients of expansion are nearly enough equal in the two materials to offer no serious objections, and by a proper distribution of loads their elastic properties may be so harmonized as to make them work fairly well together.

Meanwhile many new structures of this type are being con- structed, and time alone will suffice to clear up the still existing doubts. So much may, however, be predicted that it is not unlikely that some of the very keen Monier arches, depending so largely on the slender iron network for their strength, are apt to prove un- satisfactory in point of durability. Melan and Moeller arches will probably be longer lived.

MASONRY CONSTRUCTION. 57

7. CONCRETE.

Concrete has become one of our most important materials of construction, and a few remarks may be appropriate in concluding this paper.

This material, universally used in compression, has been won- derfully improved in recent years by the general introduction of high-grade cements, though our knowledge of the properties of concrete under compressive stress is rather meager, and much valuable work still remains to be done towards increasing our present supply of reliable experimental data.

Among the most desirable experiments to be made the follow- ing might be mentioned : The determination of the shrinkage of concrete of different mixtures while setting from time of placing same till it has reached various ages ; the permanent set which con- crete undergoes under various compressive stresses ; the modulus of elasticity at various ages for different mixtures, and, lastly, the compressive strength of cubes corresponding to mixtures used for the above experiments.

Such work would be highly valuable, and interesting as well. Those wishing to take up this subject may find some valuable sug- gestions in a paper by the writer on "The Properties of Concrete under Compressive Stress," published in the Journal of Engi- neering Societies for May, 1898.

58 ASSOCIATION OF ENGINEERING SOCIETIES.

TEMPORARY BRIDGE ACROSS THE MISSISSIPPI RIVER,

AT ST. PAUL, MINNESOTA. MOVING OF

THREE 140-FOOT SPANS.

By A. W. Munster, Member of the Civil Engineer Society of St.

Paul.

[Paper presented to the Society December 4, 1899.*]

The reconstruction of the old part of the Wabasha street bridge across the Mississippi River at St. Paul, Minn., required the build- ing of about 700 linear feet of temporary bridge over the south arm of the river to carry the traffic during the construction period of one vear.

Fig. i.

This temporary structure was located 50 feet downstream from, and parallel to, the bridge line for a length of 420 feet across the river-arm ; the remaining portion being curved land approaches, connecting at the north end with the spans across the main channel of the river (rebuilt in 1889), and at the south end with an embank- ment in continuation of South Wabasha street.

The spans in the old structure, for the length covered by this temporary bridge, consisted of four spans of 140 feet and one of

^Manuscript received January 22, 1900.— Secretary, Ass'n of Eng. Socs.

TEMPORARY BRIDGE ACROSS MISSISSIPPI RIVER. 59

Fig. 2.

Fig. 3.

6o

ASSOCIATION OF ENGINEERING SOCIETIES.

112 feet. The most economical and satisfactory procedure was to utilize three of the four 140- foot spans, by moving them the re- quired distance to timber piers constructed for their support at properly located points in the line of the temporary bridge. This gave an unobstructed waterway; and, by leaving the old piers in position until next summer, the timber piers will be protected from drifting logs and ice.

This work was completed in November last. The approaches at each end are supported on trestle-bents of common type, and the piers for the spans are constructed as braced trestle-towers sup- ported on piles.

Fig. 4.

The accompanying photographs show so clearly their construc- tion, and the manner in which the spans were moved, that very little additional explanation is necessary. The distance between the faces of the old and new piers is about 30 feet, and this space was bridged with four 15-inch I beams bolted together with separators, and supported midway by a trestle-bent on piles. Four beams of the same section, bolted together in a similar manner, formed the support from bridge-seat to bridge-seat on the timber piers, and four 6-inch I beams, on blocking, made a track for the passage of

TEMPORARY BRIDGE ACROSS MISSISSIPPI RIVER.

61

the shoe across the old masonry piers. The ends of the 15-inch I beams rested on the top of masonry and timber piers respectively, and the spans were first lifted vertically to bring the bottom of the shoe above the top of the I beams. Plates § inch in thickness were placed, one under each shoe, and connected together with an angle strut, and loose i-inch rollers were placed between these plates and the I beams. The spans were moved with a 2-inch screw about 6

Fig. 5.

feet in length, connected, through removable iron links, to the f-inch plate under the pilot-shoe, and operated by a system of hand-cranks and cogwheels in a frame fastened to the top of the I beams.

The time used in moving each of these spans was about eight hours, and the work was accomplished without hitch or accident of any kind.

The plans of operation were devised jointly by the contractor, Mr. W. S. Hewitt, of Minneapolis, and the writer.

62 ASSOCIATION OF ENGINEERING SOCIETIES.

PROGRESS OF DRAINAGE IN NEW ORLEANS.

By Alfred Francis Theard, A.M.C.E., Member Louisiana Engineering

Society.

[Read before the Society October 9, 1899.*]

In view of the partial completion of one section of the drainage system in this city, I have thought that a careful study of the general plan as recommended in the report of the Advisory Board of Engi- neers would prove interesting; and the object of this paper is. to explain the general features of this plan as to its several sections, and to show how far it has been carried out as to the section now nearly completed.

The essential factors for solving any drainage problem are :

First. The topography of the territory to be drained.

Second. Hydrography; the quantity of water to be taken care of.

Third. The available means, if any, of removing this water.

These three factors divide the subject into three branches, and can be made to include all of its details.

First. Topography includes conditions of the entire territory ; the permeability of its surface, conditions as to navigation and improvement, existing or future.

Second. Hydrography includes the amount of rainfall to be cared for; the rate of precipitation, its duration, its usual area, its actual run-off; the daily seepage; the daily quantity of water to be disposed of outside of rain water.

Third. The available means of obtaining drainage ; that is, the existing system, if any; the location of the outfalls.

For the information of those who are not familiar with the report of the Advisory Board on the drainage of New Orleans, 1895, in which all of these subjects are fully described, I will try, as briefly as possible, to explain what these factors are in this city.

The territory upon which the city of New Orleans is built has an area of 24,932 acres, on both the left and right banks of the Mississippi River, within levees. It has an elevation of 33 to 20 feet, Cairo Datum; this slope occurring within 6000 to 9000 feet of the river banks, leaving a large surface practically level, with an elevation of about 21 Cairo Datum, or some 18 feet below the high water of the Mississippi River and some 4 feet below that of Lake Pontchartrain ; or, as the mean elevation of the Gulf is 21.26 Cairo Datum, never at any time above the level of the sur- rounding bodies of water. Six thousand acres of this territory are

^Manuscript received January 11, 1900. — Secretary, Ass'n of Eng. Socs.

PROGRESS OF DRAINAGE IN NEW ORLEANS. 63

improved, being paved or covered by buildings ; the remaining por- tion is composed of farms, gardens, suburban lands or swamps. All of this territory is now surrounded by levees, «the elevation of which is 41 Cairo Datum on the river front and 27 Cairo Datum along the upper and lower boundary lines, the lake front and navi- gation canals.

Information as to rainfall was obtained by means of self- registering rain gauges distributed at six different points in the city. These gauges, which are still in operation, give the total rainfall, its duration and its time, and can be checked by actual measurement with a graduated stick. In charge of attentive observers, they have given very satisfactory and valuable results.

From these observations, in my opinion, it can be safely con- cluded that the average annual rainfall is 55 inches ; that it is prin- cipally made up of short showers, lasting from five to twenty minutes, yielding a maximum total precipitation of 1 inch per shower, and that the rate of precipitation has been often as high as 6 inches, and once as high as 7 inches, per hour.

The run-off from these rains has been carefully computed, both as to slope of territory (from 3 feet per thousand, as a maximum in the improved portion, to almost a level in the unimproved sections), as to the natural permeability of the soil (which will become greater as the moisture line is reduced), as to the amount which is collected by the roofs of buildings, cisterns, tanks, etc., in the improved sec- tion and as to the evaporation, in this hot climate, of a percentage of that portion which naturally remains over the undrained and un- improved section.

The result of these computations has been embodied in a diagram of run-off curves annexed to the report above mentioned, and has been found of such interest that all recent publications on the subject of run-off have treated of and reproduced it. Gaugings covering a period of over one year at each of the old draining machines showed the marvelous result that for a rainfall of two hours' duration it took nearly seventy-two hours to pump 52 per cent, of the total precipitation.

The daily flow, or amount of water which will reach the drain- age canals in dry weather, was, from actual observations made dur- ing a dry spell of forty-one days, accurately established. This quantity, of course, can be considered as constant, because, while it will be considerably lessened by the inauguration of a sewerage system, it will be increased by the natural growth of population and the development of the improved section.

As to the outfalls, one can easily decide as to which should be selected between the Mississippi River, Lake Pontchartrain and

64 ASSOCIATION OF ENGINEERING SOCIETIES.

Lake Borgne. Lake Borgne was recommended by the advisory engineers. Its selection avoids the pollution of Lake Pontchartrain by drainage water, and affords an advantage in its proximity to the Gulf. As to the river, it would be far too expensive to raise the water over the levees, and all advantages derived from the natural fall of the surface to be drained would be lost.

The adopted plan provides for a main canal leading through the entire area, and to which the canals and drains of the several sections are tributary. This canal was located in about the lowest part of the city, thus affording the best opportunity for using natural fall. Beginning at the intersection of Nashville avenue and Claiborne street, it runs in a northeasterly direction along Broad street to St. Bernard avenue ; thence in an easterly direction to Lafayette avenue ; thence along Florida avenue to Jordan avenue, where pumping station Xo. 5 is located. The main outfall begins at this point ; runs in a northeasterly direction to Bayou Bienvenu ; this waterway connecting it with Lake Borgne. The plateau or level basin, through which the main canal is located; and the recognized fact that it is unsafe and very expensive to excavate in this soil at a greater depth than 15 feet below the surface, made it necessary to establish stations, at equal distances along the main canal, for the purpose of lifting the water, to give it artificially the slope which cannot be obtained naturally by the topography. It was also desir- able, because of the difference in area of the several sections and of peculiar difference in the intensity of storms over these areas, to provide a separate and distinct service for the several sections.

For the above purposes the five pumping stations were located along the main canal, each giving full service to the section by the number of which it is designated and at the same time lifting the water to obtain a sufficient head for a calculated velocity through the main canal. Thus Melpomene pumping station, No. 1, receives all drainage from Section No. 1, and St. Louis pumping station, No. 2, Bernard pumping station, No. 3, Lafayette pumping sta- tion, No. 4, and Jourdan pumping station, No. 5, give the same service for Sections Nos. 2, 3, 4 and 5 respectively. Algiers pump- ing station, while of a different type, gives the same service to the Algiers section.

The water in the several sections is carried to the pumping stations by branch canals, drains and branch drains ; all of which are located so as to afford immediate relief to the several localities which they are to drain in so far as can be done with the existing grades now used for the surface drainage, and all are so graded as to provide for future connections with an underground system. By this I mean that as a canal is built it is arranged to connect, by

PROGRESS OF DRAINAGE IN NEW ORLEANS. 65

a system of temporary catch-basins at street intersections, with existing gutters, and will in such a way give relief ; but as a street is improved the old system of gutters will be dispensed with and a modern underground system will connect directly with the drainage canal.

The adopted plan divides the city into six drainage sections entirely independent and distinct ; each served by a complete system of its own; all to be connected by a main canal, thereby affording opportunity to build at any one time so much of the system as the means at the disposition of the city will permit. The territorial limits were so fixed as to provide improved drainage adapted to present as well as to future conditions : increased population, more crowded buildings, paving of streets more extended and impervious.

Each section is provided with a complete system located advan- tageously both as to surface slopes, extent, shape and character of the locality. The natural depressions throughout the city deter- mined the location of several canals. For instance, Lake Borgne being conceded as the best outfall, and the natural fall being from the ridge and the river bank towards Broad street, the logical loca- tion of the main canal was along that stretch of territory, the lowest of the entire city, ranging in elevation from 19 to 21.5 feet Cairo Datum.

For a full illustration of the location of the several drainage canals, drains, branch drains, pumping stations, relief canals, out- falls, etc., and the relative position of the several sections, I have prepared the accompanying map, and for further information I beg to refer you to the report on the drainage of New Orleans (1895) already mentioned. In it will be found a full description of the adopted plan.

The following, quoted from the report, gives the order of importance for the extension of the several parts of the work :

"That part of the second section lying between Broad street and the river, on account of the concentration there of improved properties, paved streets and business houses, and of its central position with reference to the most densely inhabited area of the city, is now (1895) mure urgently in need of improved drainage than other localities, and it is evident that the benefits to be derived from the extension of the plan would be of greater immediate public value there than in any other section of the city."

This recommendation includes :

First. The construction of pumping stations Nos. 2 and 7, and the relief branch canal connecting these stations.

Second. The construction of St. Louis canal.

66 ASSOCIATION OF ENGINEERING SOCIETIES.

Third. The Basin street, Canal street, Camp street, Chartres street, Julia street, Constance street, Claiborne street and Galvez street drains.

Fourth. The improvement of street grades and gutters.

Fifth. The improvement of Orleans relief outfall (giving a relief outlet to Lake Pontchartrain).

Sixth. The construction of the Hagan avenue, Carrollton avenue, Murat, Banks, Taylor and Conti streets open canals.

Seventh. The construction of the main canal and its connec- tions with the sections above and below.

Says the report :

"The work in other sections may be prosecuted in any order or at any time as it may be found most convenient. Whatever is done towards carrying out the plan in any section cannot be injuri- ous to the interests of other sections, whether or not they are directly benefited.

"The first section has the largest area, and at present its ten- dency towards increase in population and improvement is probably more apparent than that of the other sections.

"The work in the Algiers section, on account of its compara- tively small size and cost, might be done with less means than would suffice for much effective work in othe/ sections, and hence might be undertaken at an early date.

"In the third, fourth and fifth sections the situation and condi- tions are so similar as to offer at this time no suggestion of priority in date or of limit in which work should be undertaken."

Let us now consider what has been done so far to carry out the recommendations of the advisory engineers and the adopted plan.

Pursuant to an order issued by the State Legislature, request- ing that the Louque cut, which connected the Melpomene outfall with* the New Orleans navigation canal, be closed, the initial step of the Drainage Commission was to award a contract, November 27, 1896, for the digging of a canal to connect the Melpomene canal with the upper protection canal. Thus, compelled by legis- lation to devote their attention to the first section, it was decided, with the advice of the Chief Engineer, that the proposed canal should form part of the ultimate system. Hence its location on Seventeenth or Palmetto and North Line streets to the upper pro- tection canal. It forms part of the relief canal between pumping stations Nos. 1 and 6, is 6300 feet long, 56 to 80 feet wide and about 14 feet deep, with side slopes of 1^ to 1, and has a level bottom at elevation 8 feet Cairo Datum. Total cost, $53,000.

Upon organizing, and assuming charge of all funds available,

PROGRESS OF DRAINAGE IN NEW ORLEANS. 67

the Drainage Commission decided, upon the advice of the Chief Engineer, to carry out as much of the recommendation of the Advisory Board as the funds at hand would permit. The question whether electricity or steam should be used as a motive power to operate the several stations to be eventually constructed was then discussed, and it was decided to refer this to an expert electrician, who would, in conjunction with the Chief Engineer, examine into the relative cost of building and operating an electric power plant. It was decided, pending this decision, to take alternate bids to afford comparison as to the cost of steam and electric operation.

On July 8, 1897, bids were opened for the construction of the following :

Contract "A." Central electric power station, St. Louis pumping station, No. 2, Orleans pumping station, No. 7, and (because of the construction of the Seventeenth street canal ) Metairie pumping station, No. 6.

Contract "B" (alternate for Contract "A" without central electric station). Pumping stations Nos. 2, 6 and 7 for steam operation.

Contract "C." Lined and covered canals, — viz, St. Louis canal, Basin street canal, Julia street canal, Constance street canal, Canal street canal, Chartres street canal, Camp street canal, Clai- borne street canal and Galvez street canal.

Contract "D." Open and unlined canals, — viz, Orleans relief canal, Orleans relief outfall and Metairie outfall.

The report of the expert and of the Chief Engineer, based upon information gathered from a tour of inspection through the prin- cipal Northern cities, and also upon a comparison of the bids sub- mitted for the construction of an electric plant for the operation of the several stations, proved decidedly favorable to electricity as a motive power. Thus the bids for Contracts "A," "C" and "D" were accepted ; the contract for this work was signed on August 9, 1897, and work was immediately started.

Considering the nature of this work, now nearly completed, the ability with which it was planned and executed speaks for itself. Allow me, however, to state here that it is a most extraordinary occurrence, and a most unnatural one in our city, that work of such magnitude could have been carried on to completion without a single appreciable interruption caused by complaints of residents, interference from courts, injunctions, etc., and without any serious accidents. This has been a source of gratification for those con- nected with this work, and I think speaks very highly of the work itself.

68 ASSOCIATION OF ENGINEERING SOCIETIES.

LINED AND COVERED CANALS.

The several canals which I shall briefly describe, and which are included in Contract "C," just above mentioned, are lined with sides of masonry. These retaining walls have a thickness of i^ to 2\ brick at the flood line, 3^ to 6^ brick at the bottom ; the thickness of the walls being regulated by the depth and width of the canals, and vary in height from 3 feet 6 inches to 6 feet o inches. They are on concrete bottoms 1 foot 3 inches to 2 feet 6 inches in thickness, and for all the larger canals on a double row of 40-foot piles, 4x8- foot centers, with 12 x 12-inch caps. All the lined canals are covered with brick arches supported by I beams, 7 to 20 inches in depth, all 4 feet o inches centers, with a cover of a thick layer of concrete having a thickness over center of arches of 1 to 4 inches.

The St. Louis canal extends from Basin to Broad street, along St. Louis street. It is 5600 feet long, 20 to 25 feet wide at the flood line, 8.2 to 8.7 feet deep and has a fall of 3.6 feet in the total distance. Cost, including $60,000 of asphalt pavement, $407,000.

The Basin street canal extends along Basin street from Julia to St. Louis street, is 4950 feet long, 13 to 20 feet wide, 6.6 to 8.2 feet deep and has a fall of 4.1 feet in the total distance. Cost, $181,000.

The Julia street canal extends from Constance to Basin street, along the upper side of Julia street; is 2800 feet long, 8 feet 4 inches to 11 feet wide, 5.4 to 6.2 feet deep and has a fall of 4.7 feet in the total distance. Cost, $75,000.

The Constance street canal extends from Howard to Julia street, on the river side of Constance street ; is 960 feet long, 6 feet o inches to 8 feet 4 inches wide, 4 to 4.9 feet deep and has a total fall of 2.6 feet. Cost, $17,000.

The Canal street canal extends from Chartres to Basin street, on the north side of Canal street; is 2100 feet long, 9 feet to 9 feet 8 inches wide, 6 to 7.5 feet deep and has a total fall of 4.5 feet. Cost, $68,000.

The Chartres street canal extends on the lake side of Chartres street from St. Louis street to Canal street; is 1450 feet long, 5 to 6 feet wide, 3.5 to 4.8 feet deep and has a total fall of 4.3 feet. Cost, $26,000.

The Lower Camp street canal extends from Poydras to Canal street, along the river side of Camp street; is 1296 feet long, 5 to 6 feet wide, 3.5 to 5.3 feet deep and has a fall of 4.1 feet. Cost, $16,000.

The Upper Camp street canal extends from Girod to Julia

PROGRESS OF DRAINAGE IN NEW ORLEANS. 69

street; is 560 feet long, 5 feet wide, 3.1 to 3.9 feet deep and has a fall of 1.9 feet. This canal is on the river side of Camp street. Cost, $8000.

The Claiborne street canal extends along the center of Clai- borne street, from Julia to St. Louis street; is 5016 feet long, 5 feet to 10 feet 6 inches wide, 3.8 to 7.9 feet deep and has a fall of 6.3 feet. Cost (estimated), $90,000.

The Galvez street canal extends along the center of Galvez street, from Julia to St. Louis street; is 5000 feet long, 5 feet to 12 feet 6 inches wide, 5 to 6 feet deep and has a fall of 2.7 feet. Cost (estimated), $110,000.

PUMPING STATIONS.

St. Louis pumping station, No. 2, is located at the intersection of Broad and St. Louis streets. The building covers an area of 5000 square feet. It receives all the water collected by the system of canals on the river side of Broad street, in the second drainage section, and pumps it, for the present, by way of Orleans relief canal towards pumping station No. 7. In addition to this, upon the completion of the main canal, it will receive all the drainage from the first drainage section and pump it down Broad street towards pumping station No. 3. In the future, in times of exces- sive storms, its discharge by way of the Orleans relief canal can be used. Total cost, including suction and discharge basins, $135,000.

Orleans pumping station, No. 7, is located at the intersection of Taylor avenue and Orleans street, near the New Orleans and Western Railroad crossing. It covers an area of 5000 square feet, exclusive of the suction and discharge basins. Its duties are, for the present, to pump all the drainage water of the second section, delivered from pumping station No. 2, by way of the Orleans relief canal., to Lake Pontchartrain, through the Orleans outfall. In the future, during heavy storms, after the first wash from the streets has been directed towards the ultimate outfall, it will give additional relief by discharging some of the accumulated storm water, by way of the Orleans relief outfall, into Lake Pontchar- train. Total cost, including basins, $175,000.

Metairie pumping station, No. 6, is located at the intersection of the New Orleans and Western Railroad and the upper protec- tion canal. Its model and dimensions are similar to those of pump- ing station No. 7, and its duties are the same for the first drainage section as are those of pumping station No. 7 for the second section. Total cost, including basins, $175,000.

The Central electric power station is built at the intersection of

70 ASSOCIATION OF ENGINEERING SOCIETIES.

the New Orleans and Western Railroad and the New Orleans and Northeastern Railroad, fronting on Florida' avenue, and very near the corner of Lafayette avenue. The building covers an area of 25,000 square feet. It has a separate boiler room and an electric plant. It was so arranged as to allow a partial equipment of boilers and electric plant for the present requirements of the drainage system, reserving additional room for a complete installation when the system is completed. The electric plant is of the most improved design, and one of the finest in the South. Total cost, including installation for present requirements and line for transmission of power to pumping stations Nos. 2, 6 and 7, $350,000.

In speaking of the power plant and pumping stations I have restricted myself to generalities, as a full description of their machinery, foundations and of all details of their construction and operation could not be comprehensively included in this paper.

I should very much desire, at some future meeting of this Society, to listen to a paper on this subject, which could no doubt be made very interesting when explained by one more competent than myself.

OPEN AND UNLINED CANALS.

The Orleans relief canal extends along the line of the old out- fall, from pumping station No. 2 to pumping station No. 7.. It is an earth canal, 12,000 feet long. 34 to 80 feet wide at the surface, with side slopes of from i^ to 1^ to 1 and a level bottom throughout at 8 feet Cairo Datum. Cost, $70,000.

The Orleans relief outfall is the old Orleans canal. It is 10,000 feet long, about 60 feet wide and 10 feet deep. Cost of cleaning and widening, $10,000.

The Metairie relief, or upper protection outfall, extends from pumping station No. 6 to the lake shore. It is 50 to 65 feet wide, 12 feet deep and 13,000 feet long. Cost of cleaning and widening, $4000.

The Metairie relief canal, or rather that portion of it which connects the Seventeenth street canal with pumping station No. 6, is 3700 feet long, with side slopes of 1^ to 1, and a level bottom at elevation 8 Cairo Datum. Cost, $11,000.

The Dublin and Claiborne canals, from Seventeenth street along Dublin to Claiborne street, and along Claiborne or Mobile street to Nashville avenue, were also cleaned and reshaped. Cost, $13,000.

The above-named work on open canals was made by means of floating dredge.

On October 21, 1897, four months after letting the above-

' .. .

2i

PROGRESS OF DRAINAGE IN NEW ORLEANS. 71

mentioned contracts, the Drainage Commission decided to give some relief to the section in the vicinity of the Jourdan avenue pumping station, thereby claiming from overflow a large tract forming the rear of the fifth drainage section. The Jourdan avenue canal was ordered built. It extends from St. Claude street to Florida avenue ; is 6266 feet long, 33 to 42 feet wide, with side slopes of i\ to 1, 12.4 to 13.5 feet deep and has a fall of 2.3 feet. Total cost, $30,000.

On July 21, 1898, owing to the benefit derived by the residents of the district from the inauguration of the Jourdan avenue canal, and the presence of the dredge in the vicinity offering an induce- ment to secure additional work at reduced prices, the Florida and Lafayette avenue canals were put under contract.

Florida avenue canal forms part of the main canal. It extends from Elysian Fields avenue to the Lafayette avenue pumping station: is 4300 feet long, 50 feet wide and 11 to 12 feet deep, with side slopes of 1^ to 1.

Lafayette avenue canal extends from Claiborne street to Florida avenue on Lafayette avenue ; is 4342 feet long, 35 feet wide and 8 to 12 feet deep, and has a fall of 4 feet. Cost of the two canals last named, $19,000.

Thus the fourth and fifth drainage sections were benefited, but this at the detriment of the farmers along the Louisville and Nash- ville Railroad between Peoples avenue and Lee Station, because the water collected by the Jourdan avenue system was, at the Jourdan avenue pump, lifted over the rear levee and there left to find its own way into the lake. This caused the letting of the main outfall. It extends from Jourdan avenue pumping station, No. 5, to Bayou Bienvenu ; is 11,000 feet long (including that part of the bayou which is widened), 60 feet wide and 10 feet deep. Estimated total cost, including levees, $25,000.

In addition to all of the work above named, a contract was given for the cleaning of the Eliza and Lapeyrouse canals, in the Algiers section, and of several earth canals in the central, fourth and fifth sections. This was intended to give relief until such time as more permanent work should replace these earth canals. The total cost of this work was $14,000.

The following contracts were awarded during July, 1899:

Contract "E." Melpomene pumping station, No. 1, at Broad and Melpomene streets. It will give the first section the same ser- vice as pumping station No. 2 gives to the second section.

Contract "F." Third street canal, from St. Charles avenue to Claiborne street ; and St. Charles street branches, from Toledano to Felicitv street. These canals will be lined and covered.

72 ASSOCIATION OF ENGINEERING SOCIETIES.

Contract "G." The Claiborne and Melpomene canals, from Third street to pumping station No. I, thence to Carrollton avenue and Seventeenth street, thus completing the connection between pumping stations Nos. I and 6.

Contract "H." Algiers pumping station building, removing one set of boilers from Jourdan avenue station, furnishing one pump at Algiers station and installing necessary pole line and motors, etc., to operate Jourdan avenue pump by electricity fur- nished by the central plant.

Work on the last five contracts has merely been started, and should be completed within one year.

From the preceding resume of what has been accomplished with the limited resources of the Drainage Commission it is evident that all work so far completed or contracted for has been a step forward in the right direction for the construction of a complete drainage system in accordance with the plan recommended by the Advisory Board of Engineers in 1895.

It was a happy occurrence for our city, and most eminently proper, that the two distinguished engineers selected to design and execute this great work, one as the Chief Engineer of the Drainage Commission and the other as the engineer of the contracting com- pany that secured the bulk of the work, had participated so actively in preparing this plan during their connection with the Advisory Board. This insured a thorough familiarity with all of its details and purposes, and a most perfect design and execution.

I have refrained from further description of the canals and stations for the obvious reason that each, in my opinion, could be made the subject of an interesting study, and any attempt to go into details would have been an imposition on your kind attention.

I have gathered the information imparted herein largely from the report of the advisory engineers, which I have often quoted, and from the records of the Drainage Commission, to which I, as an humble assistant, have personally contributed.

Through the courtesy of the Chief Engineer of the Drainage Commission, and with his permission, I have prepared the follow- ing drawings here exhibited :

First. Contour map and profile.

Second. General map showing work so far completed or under contract.

Third. Section of St. Louis canal (24 feet 4 inches width and piling).

Fourth. Section of smaller drainage canal (8 feet width and no piling).

THOMAS DOANE.— A MEMOIR. 73

THOMAS DOANE.— A MEMOIR.

By Desmond FitzGerald, C. Frank Allen and Chas. A. Pearson, Com- mittee of the Boston Society of Civil Engineers.

[Read September 20, 1899.*]

Thomas Doane was born September 20, 1821, at Orleans, Mass., and died October 22, 1897, at West Townsend, Vt, during a visit to that place from his home, in Charlestown. He could readily trace his ancestry to the early settlers in Massachusetts, he being a direct descendant, in the seventh generation, from John Doane, who came to Plymouth probably about the year 1630, and who seems to have been of much prominence in his time The earliest authentic records of Plymouth Colony in 1633 show John Doane to have been a member of the council to the Governor of Plymouth Colony, and, what was perhaps a greater distinction, that he was elected deacon during that year. Deacon John Doane was one of the seven heads of families who sailed from Plymouth in 1644 and first settled Eastham (then Nauset), which was incor- porated in 1646, and from which Orleans was set off in 1797. It appears that he ranked among the seven as second in dignity only to Governor Thomas Prince. He represented his town as select- man, and also as deputy to the general court. He died in 1686, at the advanced age of ninety-six years.

John Doane, the father of the subject of this memoir, was also a man of note, having served as county commissioner, representa- tive to the general court, State Senator, a member of the Governor's Council and a delegate to the convention of 1820 to revise the con- stitution of Massachusetts. "Squire" Doane, as he was known, was a lawyer of the type to which the word counselor best applies, and had the reputation for discouraging, rather than provoking, litigation. He was one of the company which built the Orleans Academy, and was among the first, if not the earliest, in this coun- try to engage in arboriculture, planting many acres in pine and oak trees.

The mother of our Thomas Doane was Polly Eldridge, and there were eight children, only one of whom, Charles, is now living. Thomas, the eldest, attended the Orleans Academy, and later the English Academy at Andover, Mass. His school education ended when he was about twenty-one years old, and he then entered as "student" the office of Samuel M. Felton, a noted civil engineer,

^Manuscript received November 14, 1899. — Secretary, Ass'n of Eng. Socs.

74 ASSOCIATION OF ENGINEERING SOCIETIES.

then practicing in Charlestown. Mr. Felton was a member of this Society until his death, and Mr. Doane served there what might be called his apprenticeship of three years. Immediately after this he was placed in charge, under Mr. Felton, of the Windsor White River division of the Vermont Central Railroad, and later was for two years resident engineer of the Cheshire Railroad, with head- quarters at Walpole, N. H.

In December, 1849, ^r- Doane returned to Charlestown and, in company with his brother, John Doane, Jr., opened an office under the firm name of T. & J. Doane, Jr., for the general practice of civil engineering and surveying, an office whicn was maintained until his death. During his extended absences from Charlestown the conduct of the business was in the hands of trusted assistants. The firm also maintained for many years, ending in 1870, a Boston office ; first at 4 Cornhill Court, and later in Barrister's Hall, Court Square, a building which was then occupied by several others of the best known and successful engineers of a generation or more ago, a number of whom are still living.

During the early fifties Simeon Borden, who made the trigo- nometrical survey of Massachusetts, spent much of his time in the Doane office in Cornhill Court. In the Charlestown office were retained many old plans and notebooks of value, including those formerly belonging to Mr. Felton which had come into the pos- session of Mr. Doane.

In October of 1863, after the commonwealth had undertaken the work of continuing the construction of the Hoosac tunnel, Mr. Doane was appointed chief engineer under a State commission consisting of John W. Brooks, Samuel M. Felton and Alexander Holmes. Upon assuming control he revised the line of tunnel loca- tion, "boldly locating on a tangent throughout." He did away with the slight angle at the center adopted by the engineers previously in charge, and on his location the tunnel was finally constructed. Under his direction were carried on the very careful preliminary operations for determining the final line over the mountains ; work done with a degree of precision which rendered possible the meet- ing of the lines with an error in alignment of nine-sixteenths of an inch in one case and five-sixteenths of an inch in the other, although the points were, in the first case, 2056 feet from the shaft and 10,138 feet from the portal, and in the other 1563 feet and 11,274 feet respectively. It was Mr. Doane who ordered the large Temple transits which were an important factor in securing the exact alignment. His measurements for distance and level were also made over the mountain with painstaking accuracy, and with almost equally satisfactory results.

THOMAS DOANE.— A MEMOIR. 75

It was, however, in the construction work of the tunnel, or, more definitely, in introducing and developing better methods of rock drilling and blasting, that Mr. Doane's most valuable services were rendered and his greatest distinction as an engineer achieved. Experimental studies were made, and critical attention was given by him touching the use of nitro-glycerine for blasting, of com- pressed air for rock drills, to the form and details of rock drills and carriages and to the electrical firing of charges. In 1866 he intro- duced into this country the frictional ebonite battery for electrical firing, by which he was able to fire simultaneously thirty-one charges, as compared with five charges, which he found the limit with Shaffner's electro-magnetic system.

Of his work in connection with rock drilling and explosives, Drinker, in his great work on "Tunneling," says: "In fact, it is to the Hoosac tunnel that we owe the development of rock drilling machinery in America." "Experiments were made by the Massa- chusetts State Commission." "They were supported by Mr. J. W. Brooks, chairman of the commission, but they were chiefly carried on under the direction of Mr. Thomas Doane, then chief engineer of the tunnel.

"Air compressors were first applied for purposes of rock drill- ing at the Hoosac tunnel." "Mr. Thomas Doane had the experi- ments in charge." "To Mr. Doane is chiefly due the larger share of the credit for the persistent efforts made by the commission to develop practical rock-drilling machinery. He originally invented many points connected with such machinery, for some of which he holds patents ; others were allowed to pass without patenting." "Among the first men in America to encourage the introduction of nitro-glycerine was Mr. Thomas Doane, who, when acting as chief engineer of the Hoosac tunnel in 1866, caused Shaffner to make a number of trials with the (then) new blasting agent. These trials were eminently successful, and ultimately led to the permanent adoption of nitro-glycerine in place of black powder in the tunnel.

"So many able and distinguished engineers and contractors have, during the progress of the Hoosac tunnel, contributed in a greater or less degree to its final success that it would be out of place in a record such as this purports to be for the author to attempt to give especial credit to any, where so much was done by all, in the work of the tunnel proper. But Mr. Doane's connection with the Hoosac tunnel in the early days of that great work is not a matter of especial, but of universal, interest to the engineering pro- fession in America ; for to his persistent energy, his far-seeing sagacity and his able management we in a large measure, and in

76 ASSOCIATION OF ENGINEERING SOCIETIES.

fact chiefly, owe the development and introduction into this coun- try of the present advanced system of tunneling with machinery and high explosives. It was under his direction, as engineer of the commission, that the State experiments were made, and the long and disheartening fight carried through which terminated in favor of the new system ; the system which has since given us the Bur- leigh, Ingersoll and Wood drills, and which also first showed Americans practically what the potent agency of nitro-glycerine first applied by Nobel in Europe in reality was."

In connection with the tunnel work he constructed the dam across the Deerfield River, 250 feet long and 20 feet high, a work of some importance at that time. It was built to furnish power for a machine shop and to operate the machine drills, and also to furnish ventilation for the tunnel. This work was in charge of Hiram F. Mills, as assistant engineer. Charles S. Storrow was consulting engineer. James B. Francis was also consulted, and gave his approval to the location and plan.

Mr. Doane resigned his position as chief engineer of the Hoosac tunnel in 1867, but was afterwards employed as an expert, with others, to determine the amount of lining necessary for the tunnel, and was given charge of doing this work under the title of consulting engineer. In 1875, at the opening of the tunnel, Mr. Doane ran the first engine, the "N. C. Munson," through it. Even after resigning his position as chief engineer he maintained his interest in the question of the use of compressed air and the per- fecting of machinery for its production and use, in which he was an advanced thinker; and in 1873 published an article in which he advocated some of the methods which are coming into favor at the present time.

In 1869 Mr. Doane became the chief engineer of the Burling- ton and Missouri River Railroad in Nebraska, a part of the Chicago, Burlington and Quincy Railroad, extending west from Plattsmouth, at which point he established a -steam ferryboat service as a neces- sary part of the system. As would be expected by any one familiar with Mr. Doane's views on the subject, special effort was made to secure as low grades as possible in order to secure economy in operation, and at the few points where higher grades seemed un- avoidable arrangements were made to use auxiliary power. This railroad was built with a thoroughness unusual in that section of the country. Howe trusses on masonry abutments were used in crossing streams, in accordance with New England custom. In two cases on Salt River the rather unusual device of piers of screw piles was adopted. Hardwood ties of oak were used under the

THOMAS DOANE.— A MEMOIR. 77

rails, and careful attention was given to the drainage of the roadbed. In fact, the expense of the work, due to securing low grades and more permanent work than was there customary, led to unfavor- able criticism. However, after the railroad had been in operation about a year Mr. John W. Brooks, president of the railroad, and himself a civil engineer, in a report to the directors said : "Your road was built by an engineer who did not know how to build a poor one. We have an opportunity to judge of the value of light gradients, for as our business increases, instead of multiplying trains, we have but to add cars to trains already scheduled." It is said that one train from the West arriving at Plattsmouth would have made three in its further journey across Iowa.

Upon completion of the railroad in 1873 Mr. Doane returned to the East. In addition to the work on the Hoosac tunnel, he was given charge of the relocation and construction of the Troy and Greenfield Railroad, on which there was a large amount of heavy work in the way of abutments, piers, culverts and retaining walls, as well as in excavation of earth and rock in large quantities. Much of it was mountain side-hill work, in which there was danger from washouts on one side and from landslides on the other.

In 1879 Mf- Doane again went West, having received the ap- pointment of consulting and acting chief engineer of the Northern Pacific Railroad. He served in that capacity for one year, re- organizing the engineering force and giving his attention largely to locating what was known as the Pend d'Oreille division, cross- ing the Columbia Plains in Washington Territory. In Dakota, part of the Missouri division was located under his direction dur- ing that time. While with this railroad he found that the move- ment of railroad materials would be greatly facilitated if a track could be carried across the Missouri River, and he therefore built during the winter a railroad across the ice which was of consider- able value for this purpose.

In 1880 he made a railroad reconnoissance in West Virginia, and prepared a profile by the aid of an aneroid barometer only ; the line being 150 to 200 miles in length, and the exploration being accomplished on horseback with a single guide in the brief period of about ten or twelve days. A year later the line was chartered as the Atlantic and Ohio Railroad, with Mr. Doane as chief engineer. Some work of location was done, but financial troubles soon put a stop to further work. As an example of Mr. Doane's standard of honor, it is related by Mr. C. W. Folsom, of this Society, that "about two months' pay was due the engineers, and Mr. Doane, with rare chivalry of character, assumed the liabilities of the com-

78 ASSOCIATION OF ENGINEERING SOCIETIES.

pany and paid us out of his own pocket. He had made himself in no way legally responsible, but, we having come out to that inhospi- table wilderness on his invitation, he seemed to consider himself in honor bound to see us through. He was never remunerated for this outlay by any of the projectors."

For a number of years past Mr. Doane had often been con- sulted by many of the railroads centering in Boston on important matters connected with their plans, and had frequently been called upon to give expert testimony in the courts. He had also given similar service to the Railroad Commission ; one of the most impor- tant reports in this connection being the report on the proposed Northern Union Station, which was, however, finally built upon a plan different from that advocated by him.

He reported upon the condition of many of the street railways of the State, and was employed as consulting engineer of the West End Street Railway when Henry M. Whitney was president and the question of motive power was under consideration. In the winter of 1887-88, in company with other officials of the railway, he visited a number of Western cities for the purpose of examining cable systems. He also went to Nova Scotia to examine and report on a route for a railroad to transport coal from the mines of the Dominion Coal Company to the coast.

A large part of the engineering for the city of Charlestown was done by Mr. Doane previous to that city becoming a part of Boston in 1874. In fact, it is stated that there is hardly a lot in Charles- town which he had not at some time surveyed. Mr. Doane was doubtless the first surveyor in this section who referred his surveys to a meridian passed through any definite permanent point. His survey of Charlestown, made many years ago, showed all the base line points, as well as many others, by their co-ordinates with refer- ence to the State House.

For more than twenty years, and until the time of his death, Mr. Doane was an active member of this Society. He was elected President shortly after its reorganization in 1874, and was nine times re-elected to serve in that honorable position. He always took a great interest in its affairs, and was very regular in his attendance at its meetings. He served on important committees, notably those on finance and on permanent headquarters. His interest in the Society was maintained to the last. He became a member of the American Society of Civil Engineers in 1882.

From 1869 to 1873, while a resident of Nebraska, Mr. Doane was instrumental in founding "Doane College," situated at Crete, on the "Big Blue" River, twenty miles west of Lincoln, and one of

THOMAS DOANE.— A MEMOIR. 79

the leading institutions of education in the State. Offers by the railroad company of six hundred acres of choice land adjoining- the town site, and of fifty lots in the town of Crete, by the Eastern Land Association, of which Mr. Doane was a member, were made on condition that other valuable property be secured. Through Mr. Doane's influence and his own liberal financial contributions these conditions were fulfilled, and in appreciation of his efforts his name was given to the college. It contains four substantial brick build- ings, a spacious campus, well-equipped laboratories and dormitories for both sexes. It maintains classical and scientific collegiate courses, a military department and a conservatory of music. Mr. Doane rarely failed to attend the commencement exercises, making yearly a trip to Nebraska for this purpose. He was one of the trustees at the time of his death. He had prospered financially, and by his will the bulk of his estate will eventually go to Doane College as an endowment.

Mr. Doane was twice married : on November 5, 1850, to Miss Sophia D. Clarke, who died December 1, 1868, and again November 19, 1870, to Miss Louisa A. Barber, who now survives him, as do also four children by his first marriage.

Mr. Doane possessed something of the religious spirit, which was his rightful inheritance through a long line of ancestors, several of whom were deacons ; and he early associated with the church, being for many years a member and for fourteen years himself a deacon of the Winthrop Congregational Church of Charlestown. He was also the first president of the Charlestown branch of the Young Men's Christian Association, and was a member of the Con- gregational Club of Boston. His religion was of the sort that associates good deeds with the devotional spirit, for he was enthu- siastic and generous in his support of charitable and philanthropic work. He was a director of the Associated Charities of Boston, and president of its Charlestown branch. He was a vice-president of the Hunt Asylum for Destitute Children, and a member of the Bunker Hill Boys' Club.

His interest in good citizenship was manifested by his mem- bership in the Municipal League of Boston, and his frequent at- tendance at their meetings. He was a member of the New England Historic Genealogical Society and of the American College and Educational Society, and was for more than thirty years a justice of the peace.

Success in his profession was the legitimate result of his char- acter and personal qualities. He was possessed of a high sense of honor, both personally and professionally, and was firm, even tena-

8o ASSOCIATION OF ENGINEERING SOCIETIES.

cious, in his convictions and of unflinching integrity. His sound judgment, breadth of treatment, energy and love of accuracy, led to the success of the enterprises entrusted to his charge. No diffi- culty daunted his courage. Work done by him must be good work or none. He would resign rather than imperil life by imperfect construction. He was not content to build for the present only, but constructed for the future as well. From a long line of ancestry he inherited the responsibility of maintaining the family standard, which was high both in ability and in character ; and, in view of his professional services in engineering and their great value to- civili- zation in advancing the general welfare of mankind, of his splendid contribution to the cause of education, his general philanthropic work, as well as of his personal character, it can be truly said that the talent received from his Master he returned increased many fold.

CLARENCE ALLAN CARPENTER.— A MEMOIR. 81

CLARENCE ALLAN CARPENTER.— A MEMOIR.

By E. A. Handy, August Mordecai and F. C. Osborn, Committee of the Civil Engineers' Club of Cleveland.

Never before in the history of this Club have we been called upon to mourn so sudden and so sad a death as was that of our esteemed fellow-member, Clarence Allan Carpenter, who, on the 7th of November, was struck down, near Geneva, Ohio, in the active performance of his duties as engineer of the Lake Shore division of the Lake Shore and Michigan Southern Railway. He had parted from his family but a few short hours before in good health and spirits, only to be brought back to them fatally injured. For two days he lingered between life and death, and for some time it was earnestly hoped that his life might be saved. But he had been too terribly hurt to survive, and on the 9th of November he died.

Mr. Carpenter was born at Dedham, Mass., in 1846. He was the only son of John Allan Carpenter, a well-known contractor, whose works in the construction of the Fitchburg Railroad, the Old Colony Railroad, the Lawrence Dam and many other important enterprises will long survive.

He was educated as a civil engineer at Union College, at Schenectady, N. Y., and began his professional career on the Adirondack Railroad, in Northern New York State. He consecu- tively followed his profession in positions of responsibility on the Missouri, Kansas and Texas Railroad, the New York and Canada line of the Delaware and Hudson Canal Company and the Little Rock and Fort Smith, the Union Pacific and the Chicago, Mil- waukee and St. Paul Railroads. With the last-named road he spent eleven years, attaining the position of first assistant engineer. Later he was engaged in surveys for the Atchison, Topeka and Santa Fe system in California, soon returning, however, to take the position of division engineer on the Northern Pacific Railroad at Helena, Mont. In the fall of 1891 he accepted the post of division engineer of the Lake Shore and Michigan Southern Railroad, which he held till his untimely death.

Mr. Carpenter's reputation for care and accuracy was wide- spread, and his rare capacity for detail rendered him peculiarly fitted for the positions he held. Nothing connected with his depart- ment was of too little importance to claim his careful personal atten- tion and skillful execution, while the effect of his broad and com- 6

82 ASSOCIATION OF ENGINEERING SOCIETIES.

prehensive grasp of the greater problems always won the confidence of his employers.

He had been a member of our Club since January, 1894, and was frequently among us at our meetings, always interested in the proceedings and in the welfare of the Club.

Although quiet, unassuming, even retiring, in disposition, he was, nevertheless, universally beloved among his many friends and acquaintances. There was not a man on this division of the Lake Shore Railway, from the highest officials to the section hands, who did not know him and respect him for his sterling character and generous heart.

It is particularly sad that so able a member, and one so univer- sally beloved and respected, should be thus suddenly cut off in the midst of his career among us. His memory will be always with us, and it is meet that the following resolutions be adopted in his memory :

Whereas, An all-wise Providence has seen fit to remove from our midst another of our esteemed brethren ; and

Whereas, It is fitting that the memory of his life and character be pre- served to us; be it therefore

Resolved, That in the sad and untimely death of Mr. Clarence Allan Car- penter, the Civil Engineers' Club of Cleveland has lost one of its ablest and most respected members; and be it further

Resolved, That the sincere sympathy of the Club be extended to his fam- ily in their bereavement ; and be it further

Resolved, That the Secretary be instructed to spread these resolutions and the accompanying memoir upon the records of the Club and to transmit a copy of these resolutions to the family of our deceased brother.

ARTICLES OF ASSOCIATION.

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