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LIBRARY

OF THE

UNIVERSITY OF CALIFORNIA.
Class

' • — " - - *"• "™" ' - •

Architects' arid Engineers'
Hand-Book of

1%je*Inforced Concrete
Constructions

J. MENSCH, C. £.

Price, $2.OO

Cement and Engineering' News
CHICAGO, ILL.

.. - . . ...... . .

ARCHITECTS' AND ENGINEERS'
HAND-BOOK OF

RE-INFORCED CONCRETE
CONSTRUCTIONS.

Giving in plain and simple language the leading principles
and applications of this modern construction.

WITH NUMEROUS ILLUSTRATIONS AND TABLES.

L. J. MENSCH,
CIVIL ENGINEER AND CONTRACTOR.

Published by the
CEMENT & ENGINEERING NEWS,
162 La Salle Street,
CHICAGO, ILL.

GENERAL

by
WILLIAM SEAFERT.

INTRODUCTION.

The information given in this Hand Book is drawn
largely from the writer's own experience as Designer,
Consulting Engineer and Contractor for re-inforced
concrete constructions.

In the practice of his profession in various parts of
the country, he has been brought in contact with archi-
tects, engineers, contractors and capitalists, interested
in this new method of construction. These clients and
others have from time to time propounded numerous
pertinent and carefully considered questions, relating to
the essential features of re-inforced concrete construc-
tion, especially as compared with other materials and
forms of construction. These questions and the
writer's answers were uniformly reduced to writing,
classified and preserved and now form a portion of this
Hand Book, together with other matter bearing directly
on the subject.

The writer has aimed to treat the subject in plain,
simple language, entirely free from higher mathe-
matical calculations.

The mathematical side of this subject will be exhaus-
tively treated in the more extensive treatise now under
way by E. Lee Heidenreich, to be published by the
Cement and Engineering News.

Re-inforced concrete is the ideal building material
of the future and must in a great measure displace the
older materials of construction upon its intrinsic merits.

124959

Re-inforced concrete construction is at the present
time little understood by our most competent engineers
and architects, due simply to the absence of suitable
literature in the English language on the subject.

If this Hand Book becomes the medium of convey-
ing the desired information to the architects and en-
gineers and thereby promoting the more general use of
this new method of construction by the public, the
writer's aim will have been accomplished.

INDEX.

Arched Bridges 180

Arched Culverts 169

Arches for Halls 177

Basement Walls 91

Beams 14

Bins 151

Bridges 182

Coal bins -. 145

Cement finish 46

Cement specifications. 212
Centering for beams. . 17
Centering for columns 55

Cisterns 137

Columns 53

Considere columns . . 62
Concreting in hot or

cold weather 45

Chimneys 170

Cost of skeleton build-
ings 112

Culverts 169

Dams 132

Deflection of steel

beams 114, 115

Docks 78

Domes 176

Elevator enclosure-
walls 101

Elevators (Grain and

Storage) 145

Factories 48, 50

Finish of floors 45

Finish of walls 88

Finish of tanks . , 137

Fire tests 118

Flumes 162

Floors 35

Floor slabs 35

Floor' loads 50

Footings 67

Foundations 67

Foundries 48, 50

Girders 14

Girder Bridges 186

Grain elevators 145

Granolithic finish .... 46

Halls 177

Hollow floors 38

Harbor work 78

Ingalls Building 109

Jetties 78

Lintels 100

Mattress 71

Marine work 78

Patent bars 206

Piers 78

Piles 75

Pipes 156

Prismatic side-walk

lights 179

Properties of combina-
tion of concrete and

steel 124

Rafts 71

Railroad ties 181

Retaining walls 128

Reservoirs 137

Roofs 4S

Safety of Armored

INDEX.

Concrete Bldgs 126

Sewers 165

Sheet piles 77

Skeleton buildings... 98

Slabs 35

Specifications for rein-
forced concrete work 208
Specifications for ce-
ment 212

Standpipes 137

Stairs 91

Steps 93

Tanks 1 137

Table of loads on floor
slabs 35, 38

Test of reinforced con-
crete beams 19

Test of reinforced con-
crete columns 55

Vibrations of Rein-
forced Concrete floors IIS

Walls, reinforced con-
crete 81

Walls of concrete
blocks 100

Ware-houses 112

Water mains 156

Weight of • concrete
floors 49

Wharves 78

INDEX TO ILLUSTRATIONS.

Fig. 7 Test of girder, Salvation Army Bldg., Cleve-
land, 0 20

Fig. 9 Test of Girder, Davis Sewing Machine Co/s

Bldg 22

Fig. 11 Balcony Girders, College of Music, Cincin-
nati, 0 25

Fig. 12 Eoof and Balcony, College of Music, Cincin-
nati, 0 I 24

Fig. 13 Test Load of 77,000 pounds, J. H. Day &

Co.'s Foundry, Cincinnati, 0 26

Fig. 14 Lintel of 33 ft. span, Cincinnati, 0 27

Fig. 17 Test, Champion Ice Co/s Bldg., Covington,

Ky 31, 32

Fig. 19 Test, McKinley High School, St. Louis 33

Fig. 20 Eoof and Balcony Girders, McKinley High

School, St. Louis 34

Fig. 24 Test of hollow floors, Sheldon residence, New

York City 39

Fig. 26 Hotel Gallia, Cannes, France 41

Fig. 27 Hansa Haus, Dusseldorf, Germany 42

Fig. 28 Electric Fountain and Cascade, Paris Ex-
position 43

Fig. 31 Shed Eoof 47

Fig. 32 Foundry, Hull, England 48

Fig. 33 Foundry Building 49

Fig. 38 Salvation Army Bldg., Cleveland, 0. . .56, 57, 58

Fig. 41 Concreting of Girders, Floors and Columns. 59

Fig. 45 Sugar Warehouse 64

Fig. 46 Cold storage warehouse and power-house,

Southampton, Eng Go

Fig. 53 Warehouse, New Castle-on-Tyne, 69, 72

Fig. 58 Driving of Eeinforced Concrete piles TJ

8 INDEX OF ILLUSTRATIONS

Fig. 57 Retaining bank, Southampton, England.. 78, 80
Fig. 60 Barge-quay and jetty in course of construc-

ton 81

Fig. 62 Woolston jetty 83

Fig. 63 Dagenham jetty 84

Fig. 66 Apartment and office buildings, Paris 86

Fig. 67 Fire-proof Archive Buildings, Paris 89

Fig. 69 Stairs and cable drive 92

Fig. 70 Fire-escape, Strassburg 93

Fig. 71 Staircase, Salvation Army Bldg., Cleveland 94

Fig. 72 Staircase, Ingalls' Building, Cincinnati, 0.. . 95

Fig. 73 Looking down 10 flights of stairs 93

Fig. 74 Staircase of a department store 97

Fig. 75 Skeleton of a flour mill 98

Fig. 76 MacDonald & Kiley's Shoe-factory, Cincin-
nati 99

Fig. 78 Flour mill, grain elevator' and smoke stack,

Brest, France 102

Fig. 79 Cotton spinning mill, Strassburg, Alsace. . . .

103, 104, 105, 106

Fig, 84 Audit office, Paris, France 109

Fig. 85 IngalFs Building, Cincinnati 110

Fig. 86 Factory building 113

Fig. 88 Grand stand, Cincinnati 119

Fig. 89 Flour mill and grain elevator, Swansea, Eng-
land 121

Fig. 96 Design for the Nile Dam at Assouan 135

Fig. 97 Tank at Bournemouth, England 133

Fig. 98 Tank, Scafati, Italy 140

Fig. 99 Water tank with hollow walls 140

Fig. 100 Water tanks 141

Fig. 102 Reservoir Lausanne, Switzerland 143

Fig. 103 Wine vats 141

Fig. 105 Swansea Elevator 146, 147

Fig. 109 Coal bins 152, 154

Fig. Ill Coal breaker stations 153

Fig. 112 Storage bins, Hecla Portland Cement Co.. . 155
Fig. 117 Manufacture of Pipes in movable works. 15 8, 159

Fig. 124 Flume, Simplon Tunnel 162, 163

Fig. 127 Power canal anl spillway 164

INDEX OF ILLUSTRATIONS 9

Fig. 128 Section through 17 foot tunnel, Paris,

France 165

Fig. 132 Chimney, Los Angeles, Cal 171 to 173

Fig.. 135 Limekiln 174

Fig. .136 Dome, Cairo, Egypt 175

Fig. 137 Hall of 81 ft. span 177

Fig. 138 Railroad guard tower 178

Fig. 139 Reinforced concrete side-walk lights. . .179, 180

Fig. 141 Railroad bridges 183, 184

Fig. 143 Girder bridges 184, 185, 186, 187

Fig. 149 Tubular bridge 188

Fig. 150 Covering of Subway, Paris, France 189

Fig. 151 Bridge at Chattelerault 191, 192, 193

Fig. 156 Bridge at Bilbao, Spain 194

Fig. 157 Cantilever Girders 195

Fig. 158 Arched bridge of 60 ft. span 196

Fig. 159 Arched bridge of 50 ft. span 196

Fig. 161 Foot bridge over railroad, 60 ft. span 19s

Fig. 163 Highway bridge of 50 ft. span 199

Fig. 165 Skew bridge of 72 ft. span 200

Fig. 166 Retaining walls and arched bridge, Paris,

France. .'. . .201, 202

Fig. 168 Monier Bridge, Ybbs, Austria 203

Fig. 169 Highway bridge of 80 ft. span 204

Figs. 170-172 Reinforcing an old steel bridge with

concrete ... .200

^« '^ R A o "

^, 3 K A ft y
or

UNIVERSITY

REINFORCED CONCRETE.

It can not be said that modern steel structures are
perfection. Prominent engineers foretell great disas-
ters in the near future on account of the insufficient
protection of the steelwork in many of our modern
office buildings. To-day railway and highway bridges
of steel are considered temporary structures and
require great expense for maintenance. Steel con-
struction is expensive and not durable. Wood is
cheaper, but less durable, and a good quality of tim-
ber is becoming more expensive from year to year.
Owners, architects and engineers are asking them-
selves what to do. Shall they build at ruinous prices
in steel, or shall they build a fire-trap or a temporary
structure? Here reinforced concrete solves the prob-
lem.

WHAT IS CONCRETE AND WHAT IS REINFORCED
CONCRETE?

Concrete is an artificial stone, produced by thorough
mixture of cement, sand, crushed stone or gravel with
water, placed into forms and tamped. The cement
unites chemically with the water and binds the sand
and crushed stone or gravel so firmly together that
the crushing strength of concrete equals that of the
most durable natural stone.

The use of concrete began with the dawn of
civilization. We find concrete in the oldest buildings

12 RE-INFORCED CONCRETE CONSTRUCTIONS

of Mexico, in the Greek colonies in Italy and Sicily;
the largest dome in existence, that of the Pantheon
in Rome, 142 feet in diameter, is a solid mass of con-
crete, about 2,000 years old. In the Middle Ages we
find concrete used for the walls of many castles and
abbeys.

Concrete fell, eventually, into disuse, during the
dark Ages, and was only revived by the discovery of
Portland Cement in the early part of the last century,
affording a much superior material than that used
prior to this time.

The use of concrete was almost entirely confined to
footings and walls on account of its low tensile
strength, making it a very expensive material in all
cases where crossbending stresses are to be overcome.
This deficiency can, however, be remedied by imbed-
ing steel rods in the concrete in proper sizes and posi-
tions, so that all tensile stresses from bending, change
of temperature or initial set of concrete are taken care
of.

This is known as Reinforced Concrete, Concrete-
Steel, Ferro-Concrete or Armored Concrete.

The first reinforced concrete structure which came
to public notice was exhibited at the World's Fair in
Paris in 1855. It was a small rowboat built by a Mr.
Lamont, of a shell of cement mortar 11-2 inches thick
and reinforced by a wire netting. It is still in service
in a pond in Miraval, France.

In 1867 MrJ Francois Monier obtained the first Let
ters Patent on reinforced concrete construction and
subsequently built many water tanks, water mains,
sewers and even houses of armored concrete. Large
companies are now doing business in the Monier system

RE-INFORCED CONCRETE

in all civilized countries. In 1877 we find Mr. Thad
deus Hyatt actively engaged in reinforced concrete
construction in New York and London. He built vault-
ings, cement and steel side walk lights, and engaged
also in the fireproofing business. He had a great many
tests made on reinforced concrete beams by the well
known Dr. David Kirkaldy of London, which first
demonstrated to the scientific world the great eco-
nomical advantages of this new construction.

During the last twenty years Mr. E. L. Ransome
built in this country a number of important structures
in reinforced concrete. The great impulse to concrete
construction was given in 1892 when Mr. Francois
Hennebique opened a consulting engineer's office in
Paris, and, in conjunction with licensed contractors all
over the world, designed and erected nearly ten thou-
sand structures in Armored concrete, valued at nearly
one hundred million dollars. The structures designed
by him were a success from the very beginning, stood
all the tests prescribed by building ordinances and spec-
ifications of engineers and architects, and soon by their
great strength and durability and their low price found
favor with municipal and state governments, who, after
careful investigation, adopted them for work of the
greatest importance.

We will now explain the various details of armored
concrete construction classified as follows: Girders,
floor slabs, roofs, columns, walls, retaining walls, tanks,
stairs, etc.

THE ARMORED CONCRETE GIRDER.

Fig. i shows the elevation, Fig. 2 the section, Fig.
3 a perspective view of the girder. It consists essen-
tially of a concrete rib reinforced by plain round steel
rods, part of which are straight and part of which are
bent into hog chain form, and a number of "U" bars
or stirrups of hoop steel. In comparison with a steel
girder (see Fig. 2) we see that the lower flange of
the steel girder is replaced by the steel rods, the upper
flange of the steel girder by the concrete floor and the
web by the concrete rib and the "U" bars.

The reader will ask the reason for bending up the
steel rods and for the "U" bars. Experience has dem-
onstrated that concrete ribs, which are reinforced by
a high percentage of steel, which is nearly always the
case, the girders being made as small as possible to
save head-room, weight and forms, do not show the
first signs of failure in the center, but show it near
the supports by diagonal cracks, produced by the com-
bined shearing and tensile stresses which are maximum
near the supports. The inclined portion of the bent
rods take up part of the shear and the "U" bars, which
are set close together near the supports, take up the
tensile stresses which arise from the action of the
remaining part of the shear.

A reinforced concrete girder is much safer with "U"
bars than without them. Should the concrete ribs from
any reason crack vertically or diagonally, it is clear

RE-INFORCED CONCRETE GIRDERS

16 RE-INFORCED CONCRETE CONSTRUCTIONS

that the steel rods would alone hold the girder together
and that there would be a tendency to push the rods
out of the concrete, which cannot happen where the
"U" bars are used.

We have said that the concrete floor takes up the
compression of a concrete-steel girder, and in most
cases the section of the concrete floor suffices; in case

Fig. 3. — Perspective View of Armored Concrete Girder.

of heavy girders of small depth, however, also the
top part of the concrete rib is to be reinforced by steel
rods, which must take up the difference between the
figured compression in the upper part of the girder and
the compression, which it is safe to allow on the con-
crete floor.

In building construction girders are seldom freelv
supported at the ends. They are monolithically con
nected with other girders, they are continuous, and
therefore much stronger than freely supported girders.
The deflection of the girders is considerably reduced,
as we know that continuous girders show deflections,
which are one- half to one-fifth the deflection of freely
supported girders.

RE-INFORCED CONCRETE GIRDERS

Fig. 4. — Connection of a Continuous Girder to a Column.

The economical depth of, armored concrete girders
about equals the depth of steel girders of the same
carrying capacity and should not, as a general rule, be
less than 1-20 of the span. The width of these girders
is :

6 inches for girders corresponding to 12 inch I beams.
8 inches for girders corresponding to 12 inch to 18 inch

I beams.
10 inches for girders corresponding to 20 inch to 24

inch I beams.
12 inches for girders corresponding to rivetted girders

of 30 to 40 inches height.
Up to 24 inches for girders corresponding to very

heavy box girders.

Fig. 5. — Forms for Girders and Floors.

18 RE-INFORCED CONCRETE CONSTRUCTIONS

Concrete girders are manufactured in wooden molds,
called forms, at the site, in place, where they belong,
as shown in Fig. 5. The mold for each beam consists
of a 2 inch bottom plate, and two 2 inch side plates,
screwed or clamped to the bottom piece. These molds
should be supported every five feet by an upright, and
the striking of the centering for the girders should
not be commenced before three or four weeks after
concreting. j

Fig. 6.— This Beam was designed for a super-imposed load
of 4 tons, and was tested by a load of 34 tons. It
cracked in the center and deflected considerably; nev-
ertheless, it carried the load for 4 years without further
sign of weakness.

Reinforced concrete girders can span any distance
used in building construction, and carry any load up

RE-INFORCED CONCRETE GIRDERS 19

to many hundred tons. In the larger spans the
weight becomes excessive and we can lay down a limit
for -the span of these girders in buildings at perhaps
100 ft., for bridges perhaps 150 feet; arched ribs, how-
ever, can be built for much larger spans.

We see thus, that the science of reinforced concrete
girders is well developed; all stresses as tension, com-
pression, and shear, are properly cared for by the ex-
perienced designer, and the result is an indestructible
girder construction, which under tests proves a strength
beyond expectation. We cite the following tests made
on girders designed In Armored Concrete which
tests were made according to contracts when the build-
ings were partly or wholly completed, and which tests
must convince any fair-minded person of the safety o[
this modern construction, which is destined in the near
future, to be the only construction.

Mr. Frederick Baird, Architect, 218 American Trust
Bldg., Cleveland, O., writes:
MR. L. J. MENSCH,

Monon Building, Chicago,

DEAR SIR : Regarding the test made at the Salva-
tion Army building, Dec. 16, 1902, I am pleased to
give you the following data : The floor beams tested
were 8 ins. x 16 ins., 7 ft.-o o. c., with clear span of
23 ft. 6 ins. One end of same connects to a column,
and the other to a girder 8 ins. x 16 ins. near the center
of the same. The girders, floors, columns, footings,
galleries and stairs were all constructed in ar-
mored concrete, to sustain a live load of 125 Ibs. per
sq. ft. floor loads. In the test, the above floor space
over the girder 7 ft. x 23 ft. was loaded gradually to
600 Ibs. per sq. ft, which was approximately 100,000

20 RE-INFORCED CONCRETE CONSTRUCTIONS

Ibs. on the beam. The greatest deflection was about
3-8 in., and the final set was 1-8 in.

The beams and floors showed no signs of cracks or
other defects, and the whole test was eminently satis-
factory. The construction throughout and the materi-
als used were of the best quality, and promise to be

Fig. 7.— Test of Girder, Salvation Army Building, Cleve-
land, O.

as durable as anything yet obtainable or known to
science — and also caused us a saving of 23 per cent
over the cost in steel framing with tile floors.
Yours truly,

(Signed) FREDERICK BAIRD.

RE-INFORCED CONCRETE GIRDERS

/. Sec /to /»

Fig. 8. — Diagram of Girder 24 feet, Ginches span, loaded
with 100,000 pounds, Salvation Army Building, Cleve-
land.

22 RE-INFORCED CONCRETE CONSTRUCTIONS

Mr. F. B. Heathman, Architect, Dayton, O., writes ;
MR. L. J. MENSCH,

Monon, Bldg., Chicago, Illinois.

DEAR SIR : In answer to your letter inquiring about
the tests made on the concrete floors and girders at

Fig. 9. — Test of Girder of 27 feet span at the Davis Sewing
Machine Company's Office and Ware-house. Load,
124,000 pounds.

the Davis Sewing Machine Co., of this city, I ant
pleased to say that they were more than satisfactory,
and that the company and all concerned are praising
the work.

RE-INFORCED CONCRETE GIRDERS « 23

The long girders, 26 ft. span, were the only ones
tested. The floor was weighted to 400 pounds per
square foot, twice the load for which is was designed.

Fig. 10. — Concreting of Floors, Davis Sewing Machine Co.

making 124,800 pounds on one girder. The greatest
deflection was found to be only one-tenth of an inch.
Very truly yours,

(Signed) F. B. HEATHMAN.

Mr. G. W. Drach, Architect, Cincinnati, O., writes .
MR. L. J. MENSCH,

Monon Building, Chicago,

MY DEAR MR. MENSCH : The test of the balcony at
the College of Music was very satisfactory. The bal-

24 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE GIRDERS 2o

cony, with girders of 61 foot span, was. loaded in the
in the center a little over 51,000 pounds. The deflec-
tion was 3-16 of an inch. We propose to allow the load
to remain until to-morrow. The deflection has not in-

Fig. 11. — Balcony Girders of 61 feet span, College of Music.
Cincinnati, O., One girder 2 feet 8 inches deep, one
Girder 3 feet 2 inches deep.

creased any from 4 o'clock p. m. yesterday up to 9
o'clock this morning.

Yours very sincerely,

(Signed) GUSTAVE W. DRACH.
Mr. Paul S. Ward, Mech. Engineer for the J. H.
Day Co., Harrison and Bogen Aves., Cincinnati writes :
MR. L. J. MENSCH,

Chicago, 111.

DEAR SIR : Yours of September 3rd at hand asking
us for report of test of concrete floor in our new foun-

26 RE-INFORCED CONCRETE CONSTRUCTIONS

dry building^ and are sending you herewith a brief
statement of the result of the test as made on the sec-
tion of the building adjacent to the old shop.

Fig. 13. — Test load of 77 000 pounds, J. H. Day & Co.'s Foun
dry, Cincinnati, O.

We first tested a floor beam in the construction,
loaded it with a uniform distributed load over a sur-
face of 10x20 feet. The beam being immediately
under the longitudinal center line of this surface, and
as the contract required this to sustain a load of 375
pounds per sq. ft. with a deflection not: to exceed 1-800
of the length of the span, we distributed 77,000 pounds
of pig iron as uniformly as practicable over the sur-
face mentioned above. The beam showed a deflection
of 1-16 of an inch when 1-3 of the load had been

RE-INFORCED CONCRETE GIRDERS 2?

placed, but this only increased to 2.4. MM, or about
3-32 of an inch with the full load of 77,000 pounds
with no evidence of any weakness, no cracks develop-
ing, or none showing that might have existed before
the load was placed.

We next loaded a girder with as nearly a concen
trated load as was possible, if you will remember the

Fig. 14. — Lintel of 33 feet span, supporting a wall 60 feet
high with several floors. J. H. Day & Co.'s Foundry,
Cincinnati, O.

sections in this construction were 20 feet centers
and square. We placed therefore on this girder 77,000
pounds, on a base as small as was practicable, with the
object of approximating a concentrated load, and as
before found that the girder showed above 75 per cent

28 RE-INFORCED CONCRETE CONSTRUCTIONS

of its ultimate deflection with about 1-3 to 1-2 load. The
whole load of 77,000 rested on a span 6 feet square
Under the entire load, the beam showed a maximum
deflection of 2.6 MM, with no evidence of any greater
deflection after the load had remained 72 hours.

Fig. 15. — Floor of 20 ft. span, and Columns 26 feet high.
J. H. Day & Co., Cincinnati,

Lastly, we selected the largest floor panel in the
construction, viz. : one 12 feet wide by 19 1-2 feet long,
and we loaded this with 38,000 pounds of pig iron on
a base 4 feet wide by 19 1-2 feet long over the middle
of the span. This load on a ^375 pound basis should be
about 43,000 pounds, however, after the placing of the
load the deflection at the middle of the span was 1-8
of an inch.

RE-INFORCED CONCRETE GIRDERS'

30 RE-INFORCED CONCRETE CONSTRUCTIONS

Hoping this report is satisfactory, we are,
Yours very truly,

THE J. H. DAY COMPANY,
(Signed) PAUL S. WARD,

Mech. Engr.

Messrs. Dittoe & Wisenall, Architects, Cincinnati
O., write:
MR. L. J. MENSCH,

Chicago, 111.

DEAR SIR : On May 20, 1903, we witnessed a test
made on armored concrete girders and floor construc-
tion of the Hennebique system in the new warehouse
for the Champion Ice Co., Covington, Ky., and which
work was installed by you under our direction.

The girders were located 7 ft. 6 ins. apart, of 18
feet span and were figured for a superimposed floor
load of 250 pounds per square foot. A floor area of
14x18 feet was loaded with 100,000 pounds, i. e., 400
pounds per square foot, and the maximum deflection
reached i-io of an inch. These girders were supported
by 10 inch columns and 4 inch concrete partitions and
as the owners of the building were afraid of the column
and partition construction, the 100,000 pound load was
left upon the second floor and directly above the same,
on the third floor, an area of 14x18 feet was loaded
with 150,000 pounds, equal to 600 pounds per square
foot, and the greatest deflection reached was 1-8 of an
inch, and not the least sign of cracks or weakness in
the columns or partition work could be discovered
although both of these loads were allowed to remain
in place for several days and upon the removal of the
same, the floors and girders resumed their normal po-
sition.

RE-INFORCED CONCRETE GIRDERS 31

We were very much gratified with the success of
this test. The building has now been loaded for sev-
eral months to its safe capacity with goods which were
kept in cold storage during this season of the year, and
the building is very satisfactory for this purpose.

Fig. 17. — Test of Girders and Floor. Champion Ice Co.'s Cold
Storage House, Covington, Ky. Load, 150,000 pounds;
400 pounds per square foot.

We believe this material and your system to be an
excellent building material for buildings of this class
and we wish you the success which your knowledge
of its use certainly deserves.

- Yours respectfully,
(Signed) DITTOE & WISENALL,

Architects

32 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig< 18._Test of Girders and Floor. Champion Ice Co.'s Cold
Storage House, Covington, Ky. Load, 150,000 pounds;
603 pounds per square foot.

Fig. 19 shows a test of girders of the library floor
of the new McKinley High School, Russell and Ann
Aves., St. Louis, Mo., Wm. B. Ittner, Architect.

The girders tested spanned 32 feet. The entire floor
of 32x36 feet was uniformly loaded with 264,000 Ibs
representing a load of 220 Ibs. per square foot, that
is, three times the figured load.

The deflections1 in the center of the beams were :

At a load of 105 Ibs. per square foot 0.087 inches

At a load of 160 Ibs. per square foot 0.165 inches

At a load of 220 Ibs. per square foot 0.323 inches

RE-INFORCED CONCRETE GIRDERS

Under three times the load the deflection was i-i 190
of the span; after removal of the load, there remained
a permanent deflection of 0.118 inches.

Flg> 19._ Test load, Library floor, McKinley High School
St. Louis, Load, 264,000 pounds; 220 pounds per square
foot.

We also refer to another very convincing test made
on girders of fifty-seven feet span at the new Lyric
Theatre, Cleveland, Ohio. These girders were figured
to carry an uniformly distributed load from the bal-
cony of 65,000 pounds, and were tested by hanging a
load of pig iron of 88,000 pounds from the center.

34 RE-INFORCED CONCRETE CONSTRUCTIONS

frill

which is equivalent to a distributed load of 176,000
pounds. The greatest deflection was 9-16 of an inch
and the permenant deflection was less than 1-8 inch.

CONSTRUCTION OF REINFORCED CON-
CRETE FLOORS.

The floor slabs connecting the beams or walls are
generally from 2 1-2 to 6 inches thick and reinforced
by 1-4 to 3-4 inch steel rods 3 to 12 inches on centers.

These slabs are usually continuous, therefore, tensile
stresses are set up not only at the underside of the slab
in the center of the span, but also over the supports in
the top fibres, and the steel rods have to be bent in hog
chain form, as shown in Figures 2 and 21, to take
care of these tensile stresses. Sometimes it is even
necessary to imbed short extra rods in the upper part
of the slab.

For any given percentage of steel reinforcement,
the carrying capacity of the slabs is proportional to
the square of the height.

The following table gives the maximum live loads
per square foot, which these slabs are able to carry
with a factor of safety of four or five, when' reinforced
by a very high percentage of steel.

Thickness

of slab

Span in feet.

in inches.

Si ^

8j 9| 10

450

300

200

140

600

400

280

200

140

560

390

280

200

160

4/2

690

500

370

270

210

I30

640

470

360

270

170

IOO

690

530

410

260

1 60

IOO

36 RE-INFORCED CONCRETE CONSTRUCTIONS

It is always more economical to use, a greater depth
than those given in the table; this reduces the amount
of steel required and cheapens the cost of the floor.

It is advisable to use these slabs for spans not ex
ceeding 8 feet for heavy load, say 200 Ibs. per square

ts/ee/>Ws

Fig. 21. — Girder, Beam and Slab Construction.

foot and over, and for spans not exceeding 12 feet for
lighter loads, and adopt, where economy is the prin-
ciple consideration, an arrangement of beams, girders
and floor slabs as shown in Fig. 21.

RE-INFORCED CONCRETE FLOORS

Much greater spans can be adopted, when the floor
slabs are nearly square and supported on all four sides
as shown in Fig. 22.

— u_

Fig. 22. — Girder and Square Slab Construction.

In this case the slabs are reinforced by steel rods-in
both directions, and the supporting girders have to
carry orify one quarter of the load of each panel, anc
as two panels usually meet over the beams, they have to
be figured for half of the panel load, which loading is
about a mean between a concentrated and a distrib-
uted load.

38 RE-INFORCED CONCRETE CONSTRUCTIONS

The following table gives the maximum live loads
that nearly square slabs, reinforced by a very high per-
centage of steel in both directions, will carry with a
factor of safety of four to five :

Thickness
of slab
in inches.

Side of square, in feet.

6| 8

io| 12! 14

1 |

3
4

4/2

5
6

800

400
600

250
350
550
800

230
360
480
700

150
250
360
480
730

1 80

250

350
540

190

250
400

300

Here also it is more economical to use greater depth
than given in the table.

This arrangement of square or nearly square slabs
lends itself easily to decoration, and is no more ex-
pensive for light loads, and very little more for heavier
loads, than the ordinary slab and beam construction,
and is a very appropriate arrangement for public build
ings, department stores, etc.

Fig. 23. — Section Through Hollow Concrete Floor.

Where flat ceilings for spans of more than 18 feet
are required, a hollow floor construction, as shown in
Fig. 23, gives very satisfactory results.

RE-INFORCED CONCRETE FLOORS

* "P J

Fig. 24. — Test of Hollow Floors, Sheldon residence, New York

City.

40 RE-INFORCED CONCRETE CONSTRUCTIONS

This floor consists of ribs 4 inches to 6 inches thick
and about three feet apart, which are reinforced by
straight and bent bars and stirrups, a i 1-2 inch ceiling,
strengthened by light steel rods in both directions and
a 2 1-2 to 4 inch reinforced concrete floor. The depth
of these floors is 10 inches for 18 feet spans, and 20
to 24 inches for 40 feet spans.

Fig. 24 shows the diagram of a test load on such
floors of 22 feet span, at the Sheldon House, 38 E.
40th Street, New York City, in presence of the repre-
sentative of Mr. Ernest Flagg, the architect, and
engineers of the New York Building Department.
The floor was tested to 350 Ibs. per square foot, and
the greatest deflection was 1-25 of an inch.

•

- ' " - ' 4'v- .^

1 ' 1 TTjTl '

3 1 it /***$

r^y-^v^vfe;^Eid=a;Ej

TT^

.0.30.

Fig. 25. — Section Through Girder and Floor Construction with
Reinforced Concrete Ceiling.

The ceiling and the ribs are usually concreted first
and the centering for the floor is obtained by wire net-
ting, or arched match boards, or thin concrete plates,

RE-INFORCED CONCRETE FLOORS

® o

42 RE-INFORCED CONCRETE CONSTRUCTIONS

J3 P

o '

8 M

^ CO

P' CT

I "I

RE-INFORCED CONCRETE FLOORS

Fig. 28. — Electric Fountain and Cascade, Paris Exposition.
1900. The most elaborate structure of armored con
crete ever erected. 140 feet high.

44 RE-INFORCED CONCRETE CONSTRUCTIONS

etc. These hollow floors are of great advantage in
cold storage houses, as a less conductive floor constfuc-
tion can hardly be imagined.

The centering for floor slabs may be removed eight
days after concreting, if the weather was moderate
during this time; but when the temperature has been
near the freezing point it is advisable to wait 14 days
with the striking of the forms. Most of the accidents
which happen in concrete construction are due to the
fact that the centering was removed before the concrete
had sufficiently hardened.

Fig. 29.— Front View of the Same.

In warm and dry weather, the upper layer of the
concrete slabs sets up very quickly while the interior
remains soft, resulting in fine cracks in the surface.
To prevent this, the floors must be sprinkled, at least

RE-INFORCED CONCRETE FLOORS 45

every two hours, for a few days after concreting. These
cracks appear very soon where the floors are exposed
to the direct rays of the sun. This* must be guarded
against by covering the concrete with cloth and sprink
ling it very often with water.

Frost retards the setting of the concrete. The water
freezes and the cement cannot enter into the chemical
union with the water. Frozen concrete will be found
green in the inside after months of exposure; the
cement has not been destroyed, however. If the con-
crete is sprinkled with water; once the temperature
is again above freezing, the water will soak into the
concrete, and the cement continue to set. This
sprinkling should be continued for at least a week.
Repeated freezing and thawing will usually destroy
concrete, which is not more than 14 days old. The
water by freezing expands and ruptures the concrete.
Therefore, if concreting has to be carried on in weather
near the freezing point, all exposed surfaces should be
covered with cloth and a layer of sand.

FINISH OF CONCRETE FLOORS.

The most common method of finishing concrete
floors is by laying bevelled 2 in. x 2 in. sleepers, 16 in.
centers, on the concrete floor, and by weighing down
these sleepers by a i 1-2 inch layer of cinder con-
crete and nailing the wood floor on the sleepers as
shown in Fig. 30.

Fig. 30. — Wood Floor on Concrete Slab.

46 RE-INFORCED CONCRETE CONSTRUCTIONS

We secure a half inch air space, which makes the
floor much more sound and heat proof.

The cinder concrete should be mixed in the propor-
tion of 3-4 barrel of Portland cement (though one
barrel of Hydraulic cement also gives good results;
to one yard of cinders with a moderate amount of
water. If too much water be used the sleepers will
absorb the water and warp. Careful builders usually
hold up the sleepers by planks and uprights against the
ceiling to insure a good job.

For factories, storage houses, etc., the concrete floors
are generally finished by a half to 3-4 inch coat ot
cement mortar, cement and sand being mixed in the
proportion of one to two. This wearing surface should
be spread on the concrete while the latter is still soft
and adhesive. If this cannot be done at this time, the
surface of the concrete should be scraped and
thoroughly cleaned and well sprinkled with water and
afterwards with neat cement before the finishing coat
is applied.

Granitoid finish is used for corridors of public build-
ings, and is a wearing surface, generally one inch
thick, composed of one part Portland cement to i 1-2
parts of crushed granite, in size from 3-8 inch down.

Cracks in the cement finish are prevented by divid-
ing the wearing surface along the main girders.

Hotels and apartment buildings where the floors
are covered by heavy carpets need no other finish
whatever, only special care has to be taken to have
the surface of the concrete floor fairly smooth. In this
case nailing strips can be imbedded in the concrete to
fasten the carpets, and eventually some finish provided
on the sides of the rooms or corridors for a margin.

RE-INFORCED CONCRETE FLOORS

48 RE-INFORCED CONCRETE CONSTRUCTIONS

Lime plaster adheres firmly to concrete work and the
illustrations show some highly ornamental plaster work
in this line.

RE-INFORCED CONCRETE ROOFS.

The roof construction is similar to that of floors
only that the construction is generally much lighter.
It is, however, not advisable to reduce the thickness
of the floor slabs below 31-2 inches to avoid cracking.

Fig. 32.*— All-concrete Foundry, Hull, England. Unusually
well lighted. Span of girders, 40 feet.

Roofs are exposed to great and often sudden changes
of temperature and must be guarded against cracking
by imbedding plenty of steel rods in both directions
in the slabs.

Concrete roofs are not water proof by themselves.
They must have a water proof covering. A reliabL

RE-INFORCED CONCRETE FLOORS 49

and inexpensive covering is a tar and gravel roof
which can be laid directly on the concrete surface of
the roof, without any intermediate wood floor. A more
expensive covering, yet a very durable one, is a one
:nch layer of asphalt.

Another method, which is, however, not to be rec-
ommended, is by spreading a one inch coat of cement *
mortar, composed of i part cement and 11-2 parts of
sand on the concrete. Only very experienced work-
men can c1o a good job, and it is safer first to paint
the surface of the concrete floor, with a water proof
asphalt paint, for example, Toch Bros.' R. I. W. painty
and spreading on the thus prepared surface, the cement
finish.

The cement coat preserves the asphalt paint which
soaks into the concrete, and adheres to it with great
force, and makes it water proof, and should the cement
finish crack, the water, which may come through the
crack, cannot soak into the concrete of the roof.

The lowest layer of the roof slabs should be made of
a rather porous concrete in order to absorb the moisture
which arises there from condensation, thus preventing
drops falling from the ceiling.

Concrete roofs built in Cleveland, Cincinnati, and
other places, gave no cause of complaint in this
direction.

WEIGHT OF CONCRETE FLOORS.

The weight of one square foot of concrete one inch
thick is 12 Ibs. Therefore, the weight of a concrete
floor per square foot is found by multiplying the thick-
ness of the concrete in inches by 12 and adding 15 Ibs.
for sleepers, cinder concrete, wood floors and plaster-
ing.

50 RE-INFORCED CONCRETE CONSTRUCTIONS
FLOOR LOADS.

Very careful consideration of the floor loads to be
specified for a building will often save a considerable
amount of expense. Floors for residences do not re-
quire to be figured for more than forty pounds per

Fig. 33. — Foundry Building of Armored Concrete Construc-
tion. The columns support a track for a 30 ton travel-
ing Crane. Note holes in columns for attaching bear-
ings of radial drilling machines.

square foot. Experiments made in Boston demon-
strate that the live loads in office buildings are rarely
more than fifty pounds per square foot and do not
generally exceed more than ten pounds. Therefore, it
will be good practice to figure the floor slabs for 60
Ibs. per square foot; this will allow a good margin

RE-INFORCED CONCRETE FLOORS 51

lor heavy safes or similar loads. A reduction of floor
loads can be made for the girders and a still greater
reduction for the columns — as experience has repeat-
edly demonstrated that floor loads vary only from 10
to 50 pounds. School buildings do not require to be
figured for more than fifty to sixty pounds per square
foot.

Department stores, warehouses, and factories have
floor* loads which vary considerably. It is to be borne in
mind, however, that in all these case3 only a small
part of the floor area is really loaded with the heaviest
class of goods or machinery, and that there are usually
many aisles and cross aisles taking up as much as
twenty to fifty per cent, of the floor area.

If, for example, a live load of 150 pounds per square
foot is specified, it means that all columns, girders,
beams and slabs have to be figured for a load which is
equal to the area carried by these members multiplied
by 150. Very often this load of 150 pounds is speci-
fied for very light manufacturing purposes, which is
only a waste of money, as in a panel 14 feet square, for
example, there will probably never be anything near to
30,000 pounds which this specification would require.

The writer determined the live loads in one of the
heaviest hardware houses in Cleveland, Ohio, and
found that the average load on the top floor was not
more than forty to fifty pounds per square foot; and
on another floor loaded with enamel ware, scales,
shovels in bundles of twelve pieces, which materials
weigh about 150 pounds per square foot, the average
load was not more than 100 pounds.

Floors loaded with axes, picks, barrels of hinges
and barrels of tacks, weighing about 500 pounds per

52 RE-INFORCED CONCRETE CONSTRUCTIONS

square foot had an average distributed floor load of not
more than 250 to 300 pounds. The ground floor,
loaded with butts, tin plates, sixteen boxes high, gas
pipes, etc., weighing 900 pounds per square foot, had
an average floor load of 500 to 600 pounds..

Fig. 34. — >Armored Concrete Columns.

CONSTRUCTION OF REINFORCED CON-
CRETE COLUMNS.

Concrete columns are reinforced by 4, 6, 8, up to 20
or more steel rods in diameters from 3-8 inch to 2 1-2
inches. As seen in Fig. 34, the rods are placed near
the circumference, give therefore the largest radius of
gyration, and are in a position to take up tensile
stresses, which may be produced by excentric loading,
wind pressure, pull of beltings, or lateral shocks. The
strength of these columns is the sum of the strength of
the concrete plus the strength of the steel rods, and as
the concrete is here more carefully rammed than in
other concrete work, we can safely allow 300 to 400
Ibs. per square inch in the concrete. The stress in
the steel rods may be computed by the same rule as for
ordinary steel columns. These columns fail mostly by
the shearing of the concrete under 45 degrees, (see
Fig- 35) and by pushing the steel rods apart, there-
fore, we have to connect the different steel rods by ties
in intervals of not more than the diameter of the
column. The following table gives the maximum loads
which square columns, not exceeding in height 1 5 times
the diameter, will carry with a factor of safety of four
to five :

Side of
square in
inches

Maximum
load in
1000 Ibs

140

215

285

380

480

600

720

850

1350

1800

54 RE-INFORCED CONCRETE CONSTRUCTIONS

It is always more economical to use larger columns
than indicated in this table.

The columns can be made of any shape, rectangular,
octagonal, round, etc.; pipes may be imbedded for
water, gas or electric wire conduits.

Fig. 35.— Sketch Showing the Manner in which Columns
Fail.

Reinforced concrete columns are nearly 30 per cent
cheaper than cast iron columns without fire proofing
and are much more reliable than the latter, proof of
which we cite, the test at the S. A. Citadel where
a girder which was connected on one side to a girder
and on the other side to a column, was loaded to four
times the capacity, i. e., 100,000 Ibs., and transmitted
therefore an excentric load of 50,000 Ibs. on the
column; the test at the office building and warehouse
of the Davis Sewing Machine Co., where a beam of
27 feet span, connected at one side to a ten inch column,
produced an excentric loading of 62,000 Ibs., and the
very severe column tests made at the Palais de Cos-
tume at the last Paris Exhibition.

RE-INFORCED CONCRETE COLUMNS 55

The building was entirely constructed in armored
concrete. The columns were twenty feet apart,
and of such small diameter, that the authorities doubted
their resistance to eccentric loading, and prescribed a
test, consisting in a load of sand weighing 150 tons,
or one and one-half times the load, for which the
columns were designed, to be applied on alternate panels
of the two stories (Fig. 37). The lateral spring of
the columns could hardly be measured and was a
minute fraction of 1-32 of an inch.

The columns are concreted in forms, consisting of
three side pieces, while the fourth side is left open

Fig. 36
Forms for Columns.

so o -'--->

£00

Fig. 37. — Column Test.
Palais de Costume.

(Fig. 36). The concrete is rammed in layers of a few
inches, with special small rammers, and the open side
hoarded up as the concreting progresses. This enables
thorough inspection of the work and facilitates the
placing of the ties in proper distances.

The forms may be struck a few days after the con
crete is placed; in this case the columns should be
sprinkled with water in warm weather to prevent
where no plastering is required, it is well to put tri-
checking of the surface. In factories and warehouses,

56 RE-INFORCED CONCRETE CONSTRUCTIONS

angular strips in the corners of the forms, to obtain
a beveled edge, which prevents the breaking off of the
otherwise sharp corners.

<D g

-< Si

RE-INFORCED CONCRETE COLUMNS

58 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE COLUMNS

60 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE COLUMNS

62 RE-INFORCED CONCRETE CONSTRUCTIONS
CONSIDERE COLUMNS.

By inspecting above table of loads for various sizes
of columns, it will be found that the size of the latter
are in most cases smaller than the size of fireproof eel
steel columns. There exists, however, another method

or f i re-proofing

SZCT/ON.

ig. 44. — Considere Columns.

of reinforcement, by which the size of the columns can
be very considerably reduced. This method was in-
vented by Mr. Considere, Chief Engineer of the
French Government Bureau, for the investigation of
armored concrete construction. He made thousands

RE-INFORCED CONCRETE COLUMNS 63

of tests on round concrete columns,' reinforced, by
jn sizes from 1-4 inch to 3-4 inch, which were wound
in .a spiral with close steps around the surface (Fig.
44). He found if the steps of the spiral is less than
1-7 to i-io of the diameter, that such columns have
without any longitudinal reinforcement, an ultimate
resistance of 12,000 to 15,000 Ibs. per square inch of
sectional area of the concrete.

His tests also indicate that if we reinforce concrete
by spirals and by longitudinal rods, we can safely allow
an average compressive stress of three to four thousand
pounds per square inch on these columns, which would
mean that a 20 inch round column can easily carry a
load of one million pounds. These columns do not
fail by shear, but by bending and show a surprisingly
great ductility, many even very short specimens bend
ing into an "S" shape, when the ultimate load was
reached. They give ample warning before failure,
the surface of the concrete begins to scale long before
the limit of capacity is reached. There is no doubt
that these columns will be extensively used for heavy
loads, where small sized columns are preferred. It is
not advisable to use them for light loads; this would
reduce the size of the columns to such an extent that
their appearance would be very frail. Besides they
are much more expensive for smaller loads than the
square or rectangular columns.

64 RE-INFORCED CONCRETE CONSTRUCTIONS

-£>.
Oi

RE-INFORCED CONCRETE COLUMNS

RE-INFORCED CONCRETE CONSTRUCTIONS

CONSTRUCTION OF REINFORCED CON-
CRETE FOOTINGS.

Fig. 48 shows a typical wall footing. It can be con-
sidered a cantilever to both sides of the wall and
figured on the same principle as floor slabs. The height
of these footings rarely exceeds 1-4 to 1-5 of the
width, thus saving a considerable amount of excava-
tion and the cutting into the hard crust which general!^
overlies the yielding stratum. In connection with

^* Steel rod s>

Fig. 48. — Reinforced Concrete Wall Footing

concrete basement walls, these footings form a huge
girder, which will easily transmit the wall loads to a
considerable length, should one part of the soil be less
resisting than another. In case of newly filled up
ground for considerable depth, this kind of foundation,
if only 1,000 to 1,500 Ibs. pressure per square foot is

68 RE-INFORCED CONCRETE CONSTRUCTIONS

allowed on the ground, will be much cheaper and very
often safer than pile foundations. Fig, 49 shows a
column footing designed on the same principles. It

Fig. 49. — Reinforced Concrete Column Footing.

can be considered a cantilever on four sides and the
steel rods cross each other at right angles.

The largest footing built on this order is a square
of 70 feet length of sides.

Figures 50, 51 and 52 show quite a departure in
concrete foundations. They illustrate an all-concrete
warehouse 'with floor loads up to 800 Ibs. per square
foot, built for the Co-operative Wholesale Society,
Limited, at New Castle-on-Tyne.

The building rises to a height of 120 feet above the
quay level, on which it abuts, and consists of basement.

RE-INFORCED CONCRETE FOOTINGS

ground floor, and six upper floors, being in all eight
stories in height from the foundation level to the roof.
It occupies a frontage of 92 feet to both the Quay side

Fig. 50. — Section through Armored Concrete [Ware-ihouse,
New Castle-on-Tyne.

in the front and Sandgate in the rear, and the depth
from back to front measures 125 feet.

The principal difficulty which the architect of the
Co-operative Wholesale Society had to face was that
the ground at the site of the building was of the worst
description imaginable for foundations. It consisted
of the following : Eighteen feet of made ground, prin-

70 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE FOOTINGS 71

cipally clay; eighteen feet of silt and quicksand, ten
feet of soft clay, five feet of hard clay, ten feet of
silty sand, and finally of gravel. And to add to this
difficulty, the above stratification had a pronounced dip
to the River Tyne. It was obvious from the start
that the foundations would have to be of an abnormal
character to carry with safety the enormous weight

Tig. 5.

i. 52.— Plan of a Raft Panel.

superimposed by the projected building, which at first
it was intended to construct of brick on a foundation
of cylinders seven feet six inches in diameter sunk to .
depth of sixty-two feet below the ground level of the
Quay side and twenty feet below the ground level at the
Sandgate side, carrying a raft of concrete four feet
thick, with rails embedded therein. Another alterna-

72 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 53. — Ware-house, New Castle-on-Tyne, with Floor Loads
of 800 pounds per square foot.

RE-INFORCED CONCRETE PILES 73

tive considered was the driving of piles to the same
depth, but the danger of injury to the neighboring
property caused that method to be abandoned. Finally,
the Co-operative Wholesale Society resolved to adopt
their architect's recommendation to have recourse to a
raft of ferro-concrete over the whole area of the
ground. This raft, as constructed, measures two feet
six inches in its thickest part and only seven inches
in its thinnest part, and the idea of sinking piles or
cylinders was thus abandoned, it being found that the
ferro-concrete system would effect a great saving both
in cost and time.

The construction of the raft is well shown in Figs.
51 and 52. Each column rests on two intersecting
beams 2 ft. 5 ins. by 2 ft. 6 ins. deep, which divide the
area of the building into rectangular panels, and which
beams in conjunction with concrete arches, seven inches
thick in the center, transmit the column loads over the
whole available area. These heavy beams are able to
transmit the loads for several panels, if there is a set
tlement at any particular point. It is clear that b>
making these girders five to six feel deep, we can
without much greater expense carry the column loads
over two to three panels, even if the ground disappears
under a whole panel. In the warehouse mentioned
an unequal settlement took place between the date of
construction of the footings and the date of the con-
struction of first floor, being 31-2 inches in the front
and 3 inches in the rear. Since then, no further settle-
ment has taken place. It is remarkable to note that
in this building some panels of 200 sq. feet area have
been tested to 96 tons, the severity of which test will
be recognized when it is remembered that the heaviest

74 RE-INFORCED CONCRETE CONSTRUCTIONS

class of locomotive with tender could have been sup-
ported on a floor panel 14 feet square.

Fig. 54 shows the support of a brick wall on armored
concrete girders and columns, which is a very econom-
ical arrangement, where the good ground is found at
a reasonable depth below the basement floor.

^ fMord Crroynct

Fig. 54.— Wall carried on Isolated Reinforced Concrete Piers.

CONSTRUCTION OF REINFORCED CON-
CRETE PILES AND SHEET PILES.

Concrete piles have great advantages over wooden
piles. They are neither affected by the rise and, fall of
ground water or by sea water, nor can they be attacked
by torredoes, which in certain parts of the world de-
stroy wooden piles in a very short time.

These piles are manufactured in molds, at least
thirty days before use and the concrete is strengthened
by steel rods of suitable dimensions connected at short
intervals by stirrups (Fig. 55). At its lower end the
pile is armed with a pointed shoe with side plates,
the ends of which are turned in, so as to lock the pile
securely in place. The head of the pile is of less width
than the body, allowing a clearance between the heads
of two adjacent piles. In order to insure uniform
blows from the hammer in process of driving, and to
prevent injury to the pile, the head is protected by a
cap of cast steel and closed at its lower end by a clay
ring held by a plug of hemp or spun yarn. This cap
is previously filled with dried sand. A very regular
cushion is thus formed on and all around the head,
which cushion distrubutes the pressure in an absolute!)
uniform manner. This arrangement renders it permis-
sible for the iron rods to project beyond the head of
the pile, so that, in case of need, they may be connected
with other parts of the structure or bent into hooks
for convenience of handling.

76 RE-INFORCED CONCRETE CONSTRUCTIONS

The sheet piles (Fig. 56) are strengthened by foui
rods, connected by wire clamps, which, in their turn,
are cross-tied by flat irons. At the lower end we have
again a shoe, and the head is again of less width than

Fig. 55. — Details of Reinforced Concrete Piles.

the body, allowing room for the insertion of a cap.
About 6 inches above the shoe on the longer of the
narrow sides a projection is formed, while the remain-
der of both narrow sides is grooved for the entire
length. The projection on one of the piles slides in
the groove of the 'sheet pile last driven .

RE-INFORCED CONCRETE PILES 77

A special arrangement is provided to insure the
desired direction of driving. An iron pipe which fits
the groove of the sheet pile last driven, and that of
the pile which is being driven, connects, by means of
a hose, with a pump or water tank. This pipe serves
as guide, and the water forces out the sand which
might jam the grooves, thus facilitating the driving of
the pile. Once the pile is down to the desired depth,

Fig. 56.— Details of Reinforced Concrete Sheet Piles.

78 RE-INFORCED CONCRETE CONSTRUCTIONS

the pipe is withdrawn, cement is run between the
grooves and a perfect water-tight joint and wall are
established. Tongue and groove joints are also some-
times used.

Fig. 57 — Sheet Piles, retaining bank 6
These are splendid members of construction for
marine work such as wharves, docks, jetties, etc. Of
course, such structures have to withstand blows from
vessels, but owing to the elasticity of reinforced con-
crete, the damage caused is certainly less than in the
case of wooden piles and can be more easily repaired.

Masonry as applied to dock and harbor work pre-
sents numerous drawbacks, amongst those commonly
met with being the settlement of heavy walls owing to
the instability and uncertainty of foundations. In
most cases they rest on alluvial .ground, hence, the

RE-INFORCED CONCRETE PILES

Fig. 58.— Driving of Reinforced Concrete Piles, using a 4,000
pound hammer. Section of piles, 8 by 16 inches;
length; 40 feet.

80 RE-INFORCED CONCRETE CONSTRUCTIONS

CD 01

i ?

d
OP "

RE-INFORCED CONCRETE PILES 81

frequent practice of driving wooden piles under the
walls in order to reach a better and firmer stratum.
The necessity for driving these piles to great depths
largely increases the cost of the work and seriously
impedes the operations without always giving satisfac-
tory results.

Fig. 60. — Barge-Quay and Jetty in course of construction.

Should, however, a masonry wall, as above de-
scribed, remain stable as regards foundation, and the
joints resist the effect of the waves, it nevertheless often
remains exposed to the effects of the scouring of the
ground. To remedy this latter evil it is customary to
enclose the work by wooden sheet piles, but their ex-
posed parts rapidly decay or are destroyed by other
agencies.

82 RE-INFORCED CONCRETE CONSTRUCTIONS

The use of reinforced concrete piles and sheet piles
obviates these evils. The following are the principle
advantages claimed for these piles as applied to sea
work : they can be manufactured in any practical
length and section and they can be driven as a con-

Fig. 61. — Cross-section of Jetty.

tinuous pile to great depths. Sheet piles form a water-
tight barrier without a single horizontal joint, which
can be calculated tCj resist any pressure that is brought
to bear upon it. This water-tight wall is carried down
to the firm stratum, thus preventing any disturbance
that might take place/ below the base of an ordinary
wall; once built its relative lightness is such that it
does not add appreciably to the original density of
the ground.

RE-INFORCED CONCRETE PILES

84 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 63. — Dagenham Jetty in course of construction.

Fig. 64. — Dagenham Jetty in course of construction.

RE-INFORCED CONCRETE WALLS 85

The piles used in jetty construction are braced by
struts and covered by a reinforced concrete floor strong
enough to carry the super-imposed loads, railroad
tracks or cranes, which may be imposed upon them. It
is clear that the cost of such a jetty must be very much
lower than if built of stone or solid concrete.

86 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 66. — Apartment and Office Building, Paris France.

CONSTRUCTION OF REINFORCED CON-
CRETE WALLS.

Reinforced concrete walls are seldom built solid in
imitation of brick walls, where they have to support
several floors. It is more economical to transmit the
floor loads to reinforced concrete columns, which form

•• •"• • • .- -

•

i .... r

' i

:i»

^~4rir^r^i

_
' 1

—

~r~t r~^r

-J-F-

ijiJT-jiT^:

:-!--!-"

— -

' ^LUL_

-14 ^ + i-

. 1 I .

:^^-

I T

_ _ _

~]-\- r

--[--}-

— -

—

i i i i

.;'-••" ;j - - :-. ;• i . ••

:.•.•;

| _u_|

_ i

LJ -

•

Fig. 65. — Reinforced Concrete Wall.

pilasters in the walls, and are therefore only curtain
walls (see Fig. 65). These curtain walls are subject
to very little stress ; in outside walls they have to with
stand the wind pressure, which is generally figured at

88 RE-INFORCED CONCRETE CONSTRUCTIONS

30 Ibs. per sq. foot. To prevent cracking .owing to
the influence of change of temperature we have to make
these walls three and one-halt to four inches thick, and
for the same reason they have to be reinforced by steel
rods in both directions, which reinforcement is more
than sufficient to take care of the wind stresses. These
walls are of great importance for buildings in the
business district of our large cities, where each front
foot has a valuation running into many thousands of
dollars ; by adopting side w^alls 4 inches thick, one and
one-half to two feet in width of building is easily
saved. The same holds true for storage-houses which
are often divided up by a large number of brick par-
tition walls. These walls are also much lighter than
brick walls, having a weight, in fact 1-3 to 1-4 of the
latter, thus reducing the cost of foundation consider-
ably, especially where pile driving is necessary. It is
needless to point out that, by the use of concrete walls,
we obtain a rigidity of the building, which cannot be
had by any other construction.

Fig. 66 shows a highly ornamented reinforced con-
crete front wall; all ornaments are cast in place and
monolithically connected with the wall which is 4
inches in the top story and increases to 7 inches in the
first story.

This is by no means an easy and low priced con-
truction; only specially experienced workmen can do
an acceptable job; and it is much easier to build up
such a front of separate blocks of artificial stone.

If only a simple and neat front is required without
being ornamental, a one inch cement finish is applied
to the wall; this also is not an easy job and requires
men well experienced in this class of work; for ex-

RE-INFORCED CONCRETE STAIRS

90 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE STAIRS 91

ample, see Fig. 67. Sometimes the walls are finished
by rough picking them, by hand, or pneumatic tools,
a week or so after concreting. Fig. 68 shows the
application of armored concrete to basement walls.
These walls are required to withstand the horizontal
pressure from the earth and from the load on the
ground above near the wall. This horizontal pressure
will rarely exceed an average of 300 pounds per square
foot, for the depth of the basement in general use,
and by inspecting the table given for floor
slabs, it will be found that it is rarely necessary
to make these walls more than 6 inches thick, if the
pilasters in the walls are spaced 10 to 15 feet. It is
clear that these pilasters, w^hich are often the outside
wall columns, are subjected to bending, and must be
designed accordingly.

REINFORCED CONCRETE STAIRS.

One of the most essential features of a permanent
building is a substantial, fireproof stairway. For this
purpose there is no material which has so many good
properties as reinforced concrete. Compared with steel
stairs, reinforced concrete stairs has numerous advan-
tages, as follows :

First, the cost can be reduced to one-half of that of
steel construction, with decided improvement in ap-
pearance.

Second, they are absolutely fireproof, as far as any
known material can be made to attain this end.

Third, reinforced concrete, applied to stairs, can be
molded into any shape, and can be given either a plain
or elaborate finish.

Fourth, as seen from below, no unsightly structural
steel members are exposed, the soffit of concrete stairs

92 RE-INFORCED CONCRETE CONSTRUCTIONS

Fifth, the risers, treads, stringers and soffit can be cov-
presenting a clean and even surface ready for plaster-
ing,
ered with marble, scagliola, cement, granolithic, mo

Fig. 69. — Stairs, Cantilever Galleries and Cable Drive in a
Spinning Mill.

saic or wood finish, and in fact concrete stairs may be
treated to any design suitable to harmonize with the
surroundings.

RE-INFORCED CONCRETE STAIRS

At the ordinary market price of cut and polished
marble it is possible to build a concrete stairway cov-
ered with slabs of marble at less cost than steel stairs
with cast iron treads and rises.

Fig. 70.— Fire Escape, Spinning Mill. "La Cite," Strassburg.

Reinforced concrete stairs usually consist of hori-
^.ontal floor slabs in the landings, which are coi.
nected to the inclined slabs of the flights, and a num-
ber of girders supporting these landings and flights.

94 RE INFORCED CONCRETE CONSTRUCTIONS

The risers and treads are monolithically connected with
the slabs, both being concreted simultaneously. Where
the free spans do not exceed ten feet or thereabouts,
the stairs can be constructed without any other visible

Fig. 71. — Staircase, Salvation Army Building, Cleveland, O.

support than the slabs. For larger spans girders must
he provided to support landings, and stringers must
likewise be used and treated as girders.

The stringers may be built either as open or closed
stringer; two to four inches thick will be ample for
ordinary spans, and of any depth to meet the archi-
tectural requirements. Figs. 69 and 70 show stairs

RE-INFORCED CONCRETE STAIRS

built up of concrete slabs without stringers, while
Figs. 71 and 74 show stairs of open stringer construc-
tion, and Figure 72 shows a closed stringer type.

Fig. 72.— Staircase, Ingall's Building, Cincinnati, O.

These stairs can be built to conform to any geomat-
rical form used in existing staircase construction of
other material. For example, for winding and spiral
stairs, as shown in Fig. 98.

96 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 73.— ^Looking down 10 Flights of Stairs, Power Build-
ing, Cincinnati, O.

The cheaper class of concrete stairs may be givea
a cement or granolithic finish, with a nosing in exact
imitation of cut stone steps. These stairs have been
adopted in numerous school bouses and public build-
ings in England and France. Where the stairs are
subject to considerable travel, the treads are some-
times inlaid with cubes of lead, rubber or wood, two
to three inches apart, to give a more secure footing,
as the surface otherwise becomes polished.

The material for railings and newel posts may be
cast or wrought iron or other metal, wood, cut stone
or concrete. The railings are fastened to the top
of the stringers or treads by means of expansion bolts,
screwed into holes, which are provided in the con-

RE-INFORCED CONCRETE SKELETONS 97

struction of the stairs, or by bolts which are imbedded
in the triangular face of the steps, where there are
no stringers, or, as it is often the case, the railing

Fig. 74. — Concrete Staircase, Cantilever Galleries and Ceiling
in a Department Store.

is only fastened to the newel posts. For the latter,
sockets are left in the landings and lower and upper
treads, as required, in identical manner as in wood
construction.

REINFORCED CONCRETE SKELETON BUILD-
INGS

Reinforced concrete skeleton building construction
will scon come into universal use for high office build-
ings, hotels, ware-houses, etc., on account of the great
economy this type of construction offers to the publh

Fig. 75. — Reinforced Concrete Skeleton of a Flour Mill.
Columns, 27 feet on centers.

compared with steel construction, even meeting the
competition of wood construction. We understand by
skeleton construction, a frame composed of columns

RE-INFORCED CONCRETE SKELETONS

Fig. 76.— MacDonald & Kiley's Shoe Factory, Cincinnati, O.
Reinforced concrete skeleton construction. 8 inch
brick fillings.

and girders supporting all the outside walls, from
story to story, making it possible to reduce the thick-
ness of the walls to a minimum in each story. This
arrangement gives increased floor space, and reduces
the weight of the walls as well as the cost of founda-
tion.

The outside walls being reduced to curtain walls,
their thickness in high office and hotel buildings is cfe-
pendent on the architectural treatment, though usually
12 inches thick, while in ware-houses and factories, 8
inch walls are sufficient. In hotel and office buildings

100 RE-INFORCED CONCRETE CONSTRUCTIONS

the columns and lintels are always lined with stone,
brick or terra cotta^and for this purpose anchors are
imbedded in the concrete columns and 3 1-2x2 1-2
x 1-4 inch angles are bolted to the lintels, as shown in
Fig. 77. In ware-houses and factories the column^
and girders can be left exposed to view, and finished

r\ '. . . • - r .

r _!>. ." ' ,'

Fig. 77. — Detail showing Brick Anchoring of Brick Facing
to Concrete Lintels and Columns.

by rough picking or by cement mortar in imitation of
cut stone columns and lintels. The curtain walls are
erected on the upper surface of the lower lintels and
extend from column to column, are carried up to the
lower surface of the upper lintel, thus covering the
entire panel except where openings for windows are
required. Brick curtain walls can be replaced with
economy by walls of hollow concrete blocks, and we
thus obtain an all-concrete construction. There are,
however, only very few concrete blocks which we have
found satisfactory ; most of those on the market rapid-

RE-INFORCED CONCRETE SKELETONS 101

ly absorb water and should not be used. A very satis-
factory block is made by Mr. Charles W. Stevens, of
Harvey, 111.; it is also claimed that the blocks manu-
factured by hydraulic pressure do not absorb water;
there may be other satisfactory blocks on the market,
unknown to the writer.

Four inch reinforced concrete walls can also be us^d
but they are more expensive than 8 inch brick or con-
crete block walls. In an all-concrete building all the
columns, footing of columns, basement walls (see Fig.
68), girders, beams, lintels, floors, roofs and stairs
are built of reinforced concrete, while the walls ma}
be of reinforced concrete or concrete blocks.

Tile or reinforced plaster partitions are less expen-
sive than armored concrete partitions. The latter,
however, can withstand the action of fire, impacts from
streams of water or falling objects much better than
the former, and should be adopted, where it is of
great importance to prevent the spread of fire from
one part of a building to the other. Stair case and ele-
vator walls, as well as fire-proof vaults should be built
of concrete instead of hollow brick, as heretofore
universally used. We find in nearly every great fire,
that the brick walls crack and fall ; it is, however, safe
to say that a vault, built from the foundations up of
6 to 8 inch concrete walls, heavily reinforced by steel
rods, will withstand the severest conflagration and re-
main intact even where the surrounding walls of the
building collapse and cover the vault with the debris.

102 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE SKELETONS 103

104 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 80.— Cotton Spinning Mill, Strassburg, Alsace.

RE-INFORCED CONCRETE SKELETONS

105

106 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE SKELETONS 10?

Fig. 78 shows a flour mill in Brest, France, built
entirely of armored concrete; the building site con-
tained quick sand to a considerable depth and concrete
pile foundations were resorted to as the most feasible
method to obtain a suitable foundation ; nevertheless it
settled considerably, as much as 12 to 18 inches in
parts, causing several beams and floor slabs to crack;
however, it safely carries the heavy live loads imposed
by the use of the building, and this can only be ascribed
to the use of stirrups in the girders.

Figs. 79 to 82 show a- cotton spinning mill in
Strassburg, Alsace, constructed entirely of armored
concrete. This building is 140x140 feet and three
stories high. The columns are 24 feet on centres in
both directions and serve as supports for lines of
shaftings.

Figs. 8 1 and 82 show a novelty in mill construction,
the line of shaftings being supported between the
columns by reinforced concrete hangers, which have
proven to be much more rigid than cast iron hangers.
It must be noticed that this building is unusually well
lighted, which could not have been attained by any
other form of fireproof construction.

108 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 83.— Cotton Spinning Mill, Lille, France.

RE-INFORCED CONCRETE SKELETONS

109

Fig. 84. — Eleven Story Audit Office, Paris, France.

Fig. 84 shows the n -story Audit office of the
French government, having a reinforced concrete skel-
eton. All fireproof vaults in this building are of con
crete ; since this modern construction has been adopted
by a government of one of the first civilized countries
for such an important structure, it must have proved
first class in every respect, and should amply meet the
requirements of private buildings.

The highest reinforced concrete skeleton building is
the 1 6-story Ingalls' building, in Cincinnati, O., erected

110 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 85.— Ingall's Building, Cincinnati, O.

RE-INFORCED CONCRETE SKELETONS HI

in 1903. It is 50x100 feet and 210 feet high above the
curb line. This building was very rapidly erected,
averaging eleven days per story. Each floor formed a
perfect roof, under which all plastering, piping, wir-
ing and interior finish was carried on, whereby much
time was saved over other methods of construction
The idea of constructing a high office building in
armored concrete was considered such a' novelty in this
country that the Cincinnati Inspector of Buildings
withheld the building permit for many months.

A wasteful amount of steel and concrete was eventu-
ally used in the construction, to overcome the objec-
tions of the city authorities; and the Ingalls' building
is probably the strongest high building ever erected in
this country: with nil this waste of material a notable
economy over the ordinary tvpe of steel skeleton con-
struction was obtained, and the time of erection was
also considerablv reduced. Messrs. Flzner & Anderson
were the architects. W. H. "Ellis & Co.. the general con-
tractors, and the Ferro-Concrete Co.. of Cincinnati,
the contractors for the reinforced concrete work.

From every point of view armored concrete buildings
are superior to those of any other type. Thev are
monolithic ; settlement of the ground is properlv trans-
ferred and equalized by their enormous rigidity; they
practically consist of one material and variation of
temperature cannot produce unsightly cracks; they
become stronger with age, concrete forming an artificial
stone better, than the. best stone which ever came out of
a quarry. Considering, moreover, the facility with
which the material can be procured, so that a few
months are needed to erect the largest building, to-
gether with the surprisingly low cost, it must be evi-
dent that the time of steel skeleton buildings with all

112 RE-INFORCED CONCRETE CONSTRUCTIONS

their flimsy lug and bracket connections, their insuffi-
ciently protected columns and their high cost, is rapidly
passing and must shortly give way to a far superior
type, namely, armored concrete construction.

The reader undoubtedly desires to know how the
cost of this modern type of construction compares with
that of skeleton steel construction. It depends, of
course, on the cost of the materials, cement, sand,
crushed stone and steel rods, varying in different lo-
calities. Generally speaking, an all-concrete factory
or ware-house can be built for from 7 to 8 cents a
cubic foot, based upon the cubic contents of the build-
ing, and does not include windows, doors or interior
finish.

For hotel and office buildings, the concrete skel-
eton including all foundations, floors, roof, basement
walls and stairs can be built for from 6 to 7 cents a
cubic foot, which figures will be found to be from 25
to 40 per cent lower than for steel construction, de-
pending upon the price of structural steel.

VIBRATIONS IN ARMORED CONCRETE STRUCTURES.

The monolithic character of an armored concrete
buildings is evidence that vibrations produced by im-
pacts, or working machinery, will be much smaller
than in any other class of buildings. Any particular
point of the structure, which is affected by an impulse,
brings into oscillation every part around it, vibrating
a large mass of great rigidity; therefore, the oscilla-
tions must be far less than in steel or wood structures,
where the beams and arches are only loosely connected,
and can be set in vibration independent of other parts
of the building. We have seen how small the deflection

RE-INFORCED CONCRETE SKELETONS 113

Maximum Elastic Deflection in Inches of 5ym-

with an equally distributed load (W) and strained to 16,000
.01655 - when L=span in feet, d, depth of girders in

Depth of
Girder
in
Inches.

SPAN IN FEET.

.0661

.149

.265

.414

.595

.810

1.06

.0529

.119

.212

.331

.476

.648

.845

1.07

1.32

.0441

,0993

.177

.276

,3fl7

.540

.707

,891

1,10

1.33

.0379

.0851

.152

.237

.340

.465

BOTMM^

.606

,766

.946

1.14

1.36

.0331

.074

.132

.207

.298

.405

.530

.670

.829

1.000

1.19

,0295

.0662

.118

.184

.246

.361

.471

.596

,737

,890

1,06

.060

.106

.165

.240

.326

.425

,540

.667

,807

,960

.054

.096

.150

.216

,295

.385

.486

.600

.725

,862

.050

.088

.138

,198

.270

,353

,447

.550

,668

.781

.046

.081

,127

1,84

.250

.325

,412

,610

,617

,732

.075

.118

.170

.232

.302

.383

.472

,572

.680

.070

.110

.159

.216

.282

,357

.440

.530

,632

.066

.104

.149

.203

.265

.335

,413

,500

,596

.062

.097

.140

.191

.250

.315

.390

,471

,560

.059

.092

.132

.180

,235

,297

,368

.445

.530

.056

.087

.126

.171

.223

,282

.349

.422

.501

.053

.083

,119

.162

.212

,267

.331

,400

.477

.079

.114

.155

.202

,255

.315

.381

.454

.075

.108

.147

.192

.244

,300

,365

.432

.069

.100

.135

.176

.223

.276

.335

.396

.064

.092

.125

.162

.206

.255

.309

.365

.059

.085

.116

.152

,191

,236

.286

.340

.055

.080

.108

,141

.179

.221

.267

.318

.068

.093

.122

.154

.190

.230

,274

.081

.106

.134

,165

,200

.238

,147

,178

,211

.190

Deflections at right of heavy broken will cause plaster
For a concentrated load in center of span reduce figures

For any other fibre stress, 13,000 Ibs., for example

metrical, Freely Supported Steel Girders.

Ibs- per square inch, obtained by the formulaD^oo* ^T =
inches.

SPAN OT FEET.

Depth of
Girder
in
Inches.

1.40

1.24

1.44

1.12

1.30

1.02

1.18

1.35

.930

1.08

1.24

1,40

.860 1.00

1.14

1.30

.800

,92"i

1.06

1.20

1,36

.741

.863

.9QQ

1.12

1.27

.700
.658
.621

.810
.762
.720

.930
.876
.829

1.06
1.00
,940

1.19
1,13

1.34
1,96

K^BW

16
17
18

1.06

1,19

.589

.682

.784

,890

1.00

1,13

1.26

.560

.650

.745

.845

.950

1.07

1.19

T.32

.531
.508

.620
.590

,710
.677

,805
,770

,905
.865

1.02
.970

1.14
1.08

1.26
1,20

L60
1.53

1.R8

21
22

.467

.540

.620

,705

.792

,890

1.000

1,10

1,40

1.72

2.50

.430

.500

,572

,650

,730

.820

,920

1.02

1.29

1.59

2.25

• 26

4.00

.463

.531

,602

,680

.765

.850

.945

1,20

1.48

2.12

.363
.320

.432
.375

.498
.429

,563
,485

.635
.550

,715
,615

,800
.685

.882
.760

1,12
.960

1.38
1.18

1.99
1.70

30
35

.230

.325

.362

.422

.476

,537

.600

.661

.838

1.03

1.49

.248

.287

.330

,376

.422

,477

.530

.590

.745

.920

1.32

.223

.260

.298

,337

.380

,430

,480

,530

,670

.826

1.19

.204

.237

.271

,307

,348

,390

,435

,481

,610

,752

1.08

.248

,281

,317

,355

.397

.440

,558

,688

,99

to crack,
by 1-5.

multiply abcmffigures by

116 RE-INFORCED CONCRETE CONSTRUCTIONS

of armored concrete girders is under static loads and in
comparing this deflection with the deflection given in
the accompanying table for steel beams, it will be
found they are often only 1-5 to i-io of the latter.

We cite a very interesting comparative experiment
made at two stations of the Orleans R. R. in Paris.

A Amr. concrete floor, figured to carry a machinery
load of 280 pounds per square foot, of a span of about
1 6 feet, was subjected, for a length of 17 feet, to a load
of 420 pounds per square foot. The maximum deflec-
tion was 1-8 inch, without any permanent set. In order

Fig. 87. — Vibration Diagrams.

to compare the resistance of this floor to shocks with
that of steel girder floors, this floor and a floor of the
Quay d'Orsay station, built for the same purpose and
of the same span, but consisting of I beams and brick
arches, were subjected to the impact of falling weights.
The dead weight of the Amr. concrete floor was 60
pounds per square foot, that of the other, 96 pounds
per square foot. A weight of no pounds, falling from
a height of 6 1-2 feet, produced in the steel and brick
floor, vibrations of an amplitude of 5-32 inches, lasting
two seconds, while a weight of 220 pounds, falling
from a height of 13 feet on the concrete floor,
caused a maximum vibration of only 1-32 of an inch,

RE-INFORCED CONCRETE SKELETONS

lasting 5-7 of a second. Thus, twice the weight falling
twice the height, caused only one-fifth of the deflection,
with vibrations lasting only a third of the time (See
Fig. 87).

This is of great advantage in bridges, and especially

in factory buildings, not only because the lives of such

structures are threatened by vibration, but also because

- absence of vibration preserves the tools and makes

better work possible.

FIREPROOF QUALITIES OF REINFORCED
CONCRETE.

Concrete is the best fireproof material for building
purposes. This was demonstrated over ten years ago
by comparative tests by the fire departments of the
cities of Vienna and Berlin; more recently by the fire
tests conducted by the British Fire Prevention Com-
mittee, and by the very careful and severe tests on a
score or more reinforced concrete floors by the building
department of the city of New York.

In the latter city for each test a house 10x14 feet in
the clear, and about 12 feet high, was built and covered
by the concrete floor to be tested. The interior of the
house was filled with coal and wood, and for five
hours a temperature of over 2,000 degrees Fahrenheit
was maintained, and then a stream of water from the
nozzle of a steam fire engine was directed for a few
minutes on the ceiling. All the floors stood the tests
remarkably well, supported the uniformly distributed
load of 150 Ibs. per square foot without undue deflec-
tion, and with the exception of a few fine hair cracks,
which disappeared af'ur cooling off, no damage what-
ev^r was done to the floors. On the other hand we
know unprotected steel behaves worse in a severe fire

118

FIREPROOF QUALITIES OF CONCRETE

120 RE-INFORCED CONCRETE CONSTRUCTIONS

than heavy mill construction. It twists and warps
into various shapes after a temperature of 1,000 de-
grees Fahrenheit is reached. This was demonstrated
by the fire at the works of the Pacific Borax Com
pany's plant at Bayonne, N. J., in 1902. Part of the
plant was of all-concrete construction, and the annex
was of unprotected steel construction. The annex
was a distorted mass of iron after the fire, while the
concrete building stood the trial exceedingly well, re-
quiring only plastering to restore it to first class order,
The heat in the latter was great enough to melt copper
and cast iron.

We also cite a fire test made by the Belgian Govern-
ment and Mr. Hennebique on a two-story pavilion
erected for this purpose at Ghent, Belgium.

This pavilion, measuring 20x15 feet, was built en-
tirely of ferro-concrete, and the windows and doors
were provided with Siemens wire glass. In all, two
tests were made. In the first test the second floor was
loaded with 300 pounds per square foot, or one and a
half times the load for which it was designed, and a
deflection of 1-3,000 of the span was produced. On
the Qth of September, about 220 cubic feet of wood
and coal were placed in the lower room. This material
was sprinkled with petroleum and set on fire. The con-
flagration lasted one hour, and produced a temperature
of about 1,3000 degrees Fahrenheit. The walls were
red hot on the inside; yet, notwithstanding that their
thickness was only 4 3-4 inches, the hand could easily
be held on the outside without experiencing any dis-
comfort.

The temperature of the second floor increased only
4 degrees, which means that no mercantile product
whatsoever would have suffered damage. The deflec

FIREPROOF QUALITIES OF CONCRETE 121

c.
Pk

o" 3

-M CO

§1
E §

122 RE-INFORCED CONCRETE CONSTRUCTIONS

tion of the floor increased to 6-10 of an inch, but two
hours after the extinction of the fire, was diminished by
half an inch, so that under a very heavy load the per-
manent deflection resulting from the fire was scarcely
perceptible.

In order to prove that an armored concrete floor,
which had been subjected to fire, was still capable of
bearing the same loads as before, Mr. Hennebique
made a new test on the 28th of September; this time
loading the floor with 400 pounds per square foot, or
double its figured load. When the 300 pound mark
was reached the deflection was found to be precisely
the same as before the first fire test. At 400 pounds
per square foot the deflection was only 1-8 of an inch.

The lower room was completely filled with wood
and coal, the upper room partially filled with the same
materials, and the roof was loaded with 200 pounds
per square! foot. At six minutes past four the fire was
lighted on both piles and lasted until half past six. The
fire played so fiercely against the sides and ceiling that
the plastering of the latter was calcined, and the wire
glass of the windows and doors melted.

The building was momentarily forced out of shape
(expanded), but showed no cracks and only very fine
fissures, which in no case permitted the hot air to
escape. Again the contact of the hard to the outside
of the walls could easily be endured. The deflection
of the second floor reached a maximum of 3-4 inch at
20 minutes to six; after this time no further increase
could be observed.

At half past six, when, after continual firing, no
change in the state of the building could be detected,
the commission agreed to extinguish the fire, which
was done by directing a stream of water from a hose

|TQ ^ fSjJ^X

FIREPROOF QUALITIES t>fCONCRETE 123

against the walls and ceiling and against the hot
coal.

When, on the following day, the fire authorities
examined the building, it was found that the conflagra-
tion had not injured the general structure in any way.
There was no permanent set in the floors and the few
fissures caused by the expansion were completely
closed. A series of pyrometers indicated a temperature
of 2,200 degrees Fahrenheit.

Lime kilns, constructed entirely 'of concrete, have en-
dured for years a tempera'ture of 2,200 to 2,500 degrees
Fahrenheit.

All these fire tests are of little importance in com-
parison with the fire tests which steel skeleton buildings
with terra cotta fire-proofing, and concrete steel skele-
tons had to withstand in the terrible Baltimore con-
flagration on the 7th and 8th of February, 1904,
which continued for 27 hours, and destroyed 2,50x3
buildings.

The steel skeleton buildings failed badly, on very
few columns and girders remaining intact, the terra
cotta floors being destroyed very often, and all ex-
perts who visited the burnt district agree that no build-
ing resisted this fire of 27 hours better than the
Junker's Hotel and the International Bank Build-
ing, built entirely of reinforced concrete, undei
the direction of Messrs. Parker & Thomas, Arch-
itects of Baltimore. The columns, girders, and floors
remained perfectly intact, though the contents were
entirely consumed. The fire around this building was
so intense that even the brick, which elsewhere held
out, were entirely destroyed.

Reinforced concrete buildings will now undoubted-
ly command lower rates of insurance than buildings

124: RE-INFORCED CONCRETE CONSTRUCTIONS

of the same class erected on the old style of steel and
terra cotta construction.

The superior fire resisting properties of armored
concrete as demonstrated in the most terrible conflagar •
ation at Baltimore deserves the careful consideration of
Architects, Engineers, and their clients, who are con-
sidering the investment of capital in fire proof struct-
ures.

PROPERTIES OF THE COMBINATION OF CONCRETE
AND STEEL.

Many eminent scientific men have investigated the
properties of armored concrete and established the fol-
lowing facts explaining the great success of the com-
bination of concrete and steel :

First, the coefficient of expansion of concrete and
steel is for all practical purposes the same, therefore,
no interior stresses can be produced by, change of tem-
perature, either in the steel or surrounding concrete.

Second, there exists a surprisingly large adhesion
between concrete and steel, amounting from 500 to
700 pounds per square inch of surface in contact.
Much doubt has been expressed regarding this ad-
hesion ; it is however confirmed by hundreds of experi-
ments here and abroad. Slight rust on the surface of
'the imbedded bar increases this adhesion by about 10
per cent. Corrugating or twisting of bars also in-
creases it to 10 per cent.

Third, the modulus of elasticity of steel is ten to
twenty times, and if the concrete is highly stressed it
is- about 100 times as great as the modulus of elasticity
of concrete. It will be asked how it is possible to
figure reinforced concrete structures if such differences

FIREPROOF QUALITIES OF CONCRETE 125

exist. We must admit that the modulus of elasticity
varies with the amount of water and cement, the
tamping, etc., but all concretes show the fundamental
fact that the modulus of elasticity decreases the higher
the stress, and is nearly zero at 300 pounds per square
foot — that is at the ultimate resistence of non-rein-
forced concrete. That is to say, in a concrete bar
reinforced by steel and subjected to tension stresses
exist in the concrete and the steel which are in the
relation of i to 10, to i to 20, at moderate stresses,
and when the bar is highly stressed, in the relation i
to loo, whatever the modulus of elasticity be at the
lower stresses.

This means that reinforced concrete stretches con-
siderably at 300 pounds stress by the least increase of
tension, and this elongation can reach the elongation
of steel at the elastic limit and amounts to about I in
1,000. It will now be understood why reinforced con-
crete girders and slabs deflect considerably before
breaking, while we know that non-reinforced concrete
breaks without practically any deflection.

This will also explain why reinforced concrete can
be used for water tanks, sewers and roofs, which must
undergo great changes of lengths through the constant
changes of temperature, the steel giving the concrete
an exceedingly great elasticity whereby it can undergo
these changes without danger of cracking.

Fourth, the steel is completely protected by the con
crete from rust and the disintegrating effect of air
and water, sea water, or even sulphuric or chlorine
gases. We know that iron nails were preserved by the
mortar of Roman walls for 2,000 years, and we have
not even the least reason to doubt that the far superior

126 RE-INFORCED CONCRETE CONSTRUCTIONS

Portland cement will show the same preservative
qualities. In order to remove any doubt on the ques-
tion of the preservation of steel in concrete, engi-
neers induced the city authorities of Grenoble,
France, to take up a water main of armored concrete,
which had been in constant service for a period of 15
years under a head of 75 feet of water. The sec-
tions of the pipe were 6 feet 3 inches long, and the
iron skeleton was formed by 30 longitudinal rods, 1-4
inch in diameter, one interior spiral of 5-32 inch wire
and one exterior spiral of 1-4 inch wire.

On the 2d of February, 1901, 16 feet of this conduit
were taken up. The tubes were found in a perfect
state of preservation ; the steel did not show the slight-
est trace of oxidation; the adhesion of the steel to the
concrete, despite the slight thickness of the pipes, was
such that it could be separated only by heavy blows
from a sledge hammer.

SAFETY OF ARMORED CONCRETE CONSTRUCTION.

Vested interests in the old method of buildings which
feel their existence threatened by the great inroads this
modern building process makes into fields, formerly
exclusively their own, are issuing at a great expense
trade literature, full of exaggerated accounts of failures
of armored concrete floors, declaring reinforced con-
crete a dangerous novelty, full of uncertainties, etc.
Governments have investigated these questions and
have decided in favor of reinforced concrete construc-
tion.

We see the United States Government adopting rein-
forced concrete for many important buildings of the
United States Naval Academy in Annapolis, for coast
and harbor defence, and particularly for gun emplace-

FIREPROOF QUALITIES OF CONCRETE 127

ments, for cisterns and stand-pipes in the different
forts on the Atlantic coast, for fire-proofing the Con-
gressional Library, and the new United States printing
office, etc.

The few failures which are recorded in this country
can always be traced to utter carelessness and utter
incompetency on the part of the contractor or his em
ployees. Reinforced concrete is a science like steel
construction and nobody can expect that a contractor
without any engineering education, and whose only
knowledge of concrete is 'derived from putting in con-
crete footings or sidewalks, is able to design struc-
tures in reinforced concrete.

We find many failures in steel and brick construction
due to the same cause. We wish to recall the
failures of two coliseums and the works of the Western
Electric Company in Chicago, etc.

There are to-day at least 50x3 million square feet of
reinforced concrete floors in use and it is very doubtful
whether 1-2 or 1-3 of this area is covered by tile floors.

It can not, therefore, be said that reinforced concrete
is a novelty or an experiment. The tests made in
this country and in Europe have demonstrated rein-
forced concrete to be, in the hand of the experienced
designer, a material, which can be relied upon more
than the best brick, steel or stone construction.

CONSTRUCTION OF RETAINING WALLS.

Reinforced concrete retaining walls are, especially
for great heights, nearly 50 per cent cheaper and much
safer than solid concrete walls. They consist, as shown
in Fig. 90 of a base plate which has a width equal to
about 5-10 to 8-10 of the height of the wall, a cur-
tain wall, which varies in thickness from 4 inches at
the top to generally not more than 8 inches at the
bottom, and vertical ribs from 6 feet to 8 feet apart,
connecting the curtain wall to the base plate and
making the entire wall an indeformable structure. The
horizontal earth pressure increased by the horizontal
pressure from loads on the ground, has the tendency
to slide the wall on its base, and at the same time, to
overturn it, which forces are resisted by the weight of
the earth on the base plate. It: is clear that the curtain
wall is under bending stresses between the ribs from
the horizontal pressure and should be designed similar
to a floor slab; we have noted the great carrying ca-
pacity of reinforced concrete slabs, and, therefore, it
is perfectly safe and legitimate to make these curtain
walls not thicker than indicated above, however strange
it may appear on first consideration. The ribs with the
curtain walls form a "T" section, which takes up the
bending moments from the earth pressure in regard
to the wall as a whole. The base plate is to be designed
strong enough to sustain the weight of the earth and
superimposed loads, and the reaction of the ground.

128

RE-INFORCED CONCRETE RETAINING WALLS 129

We see that every detail of reinforced concrete re-
taining walls is capable of being figured with certainty
in regard to the stresses which are acting upon them.

f'-H-fl-i-PtH-

j+THjif-'-J-H

J-r,TW^:

Fig. 90. — Reinforced Concrete Retaining Wall.

We are able to provide a base which can be given to
masonary walls only at a ruinous expense; besides,
there is no doubt that we know more of the nature
of stresses in reinforced concrete than of the distribu-

130 RE-INFORCED CONCRETE CONSTRUCTIONS

tion of stresses is a masonary wall, which is affected
by lateral forces.

The factor of safety against overturning reinforced
'concrete walls is thus much greater than that of re-

PI*,

.A3

\'-'~r- }

«'" •*•

.^.* ^

', •***•

f • •

t:^\

.t r-- ,

'A * ; < '

•;

(.' #--•

Fig. 91. — ^Reinforced Concrete Retaining Wall with a plat-
form at Mid-height.

taining walls of any other construction, and from an
engineering point of view and from an economical
point of view, there is not the least reason why these
walls should not be adopted by railroads even for the
greatest heights.

RE-INFORCED CONCRETE RETAINING WALLS 131

Fig. 91 shows a concrete retaining wall of a height
of 1 6 feet with a platform at half the height, which
arrangement may save in certain cases a good deal of
excavation.

CONSTRUCTION OF REINFORCED CON-
CRETE DAMS.

These dams are designed on similar lines to retaining
walls. We have again a base plate, curtain walls and
ribs, making the whole an indeformable structure.

, c
Fig. 92. — Reinforced Concrete Dam.

Figure 92 shows the design of a dam for a head of
water of1 about 1 5 feet. The curtain walls are inclined
at an angle of about 45 degrees to a vertical line to
obtain as uniform a pressure on the ground as possible.
By this arrangement the pressure on the ground is
the sum of the weight of the dam and the vertical com-
ponent of the water pressure, which is perpendicular

132

RE-INFORCED CONCRETE DAMS 133

w vf

• gfc n ^.-y •••••••,- ~ :• • igai^7 ^ ^ -^v : ;".-: —.-)

'ig. 93.— Reinfor<
at Mid-heigl

3ed Concrete Dam with
it.

bracing Platform

Pig. 94. — Section of Dam.

134 RE-INFORCED CONCRETE CONSTRUCTIONS

to the curtain wall, and these two forces have to pro-
duce a friction sufficiently large to prevent sliding of
the dam on its base.

If there be danger of sliding, the weight on the
ground can be increased by filling the inside of the dam
with earth up to the line "ab," or by providing a shoe

Fig. £5.— Section of Dam 50 feet high with two Platforms
built on Rock.

"c," or by extending the base plate towards the water
side. The water pressure will then increase the fric-
tion on the ground.

Fig. 93 shows the design of a dam for a head of
water from 20 to 30 feet. It is good practice as well
as economical in this case to introduce at one half the

RE-INFORCED CONCRETE DAMS

135

height a platform connecting ribs and curtain walls
which platform reduces the free, unsupported lengths
of the ribs and permits a reduction in the thickness
of the ribs.

Fig, 94 shows the cross section of this dam.

Fig. 95 shows a cross section of a dam about 50
feet in height, having two platforms to stiffen the ribs
and curtain walls. It is here assumed that the dam
rests on rock and that the base plate is replaced by
footings under the ribs to distribute the weight on
the rock. The curtain walls are required to withstand
a much greater pressure in clams than in retaining
walls. In a 30 foot dam this presure at the base is
1,900 Ibs, per square foot. It will very rarely be neces-
sary to make the curtain walls more than 12 inches
thick at the base, even under the highest pressure, be-

Fig. 96. — Design for the Nile Dam at Assouan, of Reinforced
Concrete, 100 feet high.

136 RE-INFORCED CONCRETE CONSTRUCTIONS

cause the ribs are only 6 to 8 feet apart. The thickness
of the curtain walls can be reduced to 4 inches at the
top. Rich concrete should be used for the curtain walL
and a i inch to1 2 inch cement finish is to be applied to
the exterior of the wall to insure a water-proof curtain.
Fig. 96 shows the design of the Nile dam at Assouan
for a head of water of 100 feet. This design was
accepted as perfectly reliable from an engineering point
of view, but the difficulty of getting enough men,
familiar with this class of work, in such an out-of-the-
way place, was the single reason that a stone dam of
much greater cost was substituted for it.

TANKS, STANDPIPES, CISTERNS, RESER-
VOIRS.

Tanks and Standpipes are receptacles for liquid
above ground.

Cisterns and reservoirs are partly or entirely in the
ground. Reservoirs are large cisterns. The cylind-
rical form is best adapted for these structures, produc-
ing in the walls direct tensile stresses, which are taken
care of by steel rods, while the concrete is assumed to
transmit the stresses to them. We have to guard
carefully against expansion cracks by imbedding steel
rods also in vertical direction in the walls, and in at
least, two directions in the bottoms. Where cisterns
are situated near rivers, there is sometimes danger, that
by an abnormal rise of water the cistern when only
partly full may be lifted out of the ground or the
bottom fractured. In such cases we have to extend the
bottom beyond the walls to get the benefit of the
weight of the surrounding ground; and we have also
to strengthen the bottom by girders, capable of with-
standing the upward pressure. In tanks and cisterns
the walls rarely need to be made more than 6 inches
thick, even for the largest dimensions, and often 3
inches is quite sufficient. Rich concrete has to be used
to insure a waterproof job, which also requires a ce-
ment finish 1-2 in. to 3-4 in. thick. This cement finish
should be applied as soon as possible after concreting
sides and bottom. These surfaces should be carefull)
cleaned, and a wash of cement applied, before spread-

137

138 RE-INFORCED CONCRETE CONSTRUCTIONS

ing the cement finish in thickness of not more than
1-4 in. at a time. One hour or sd should elapse before
applying the second coat, giving time to the first coat
to get "fat," as the workmen call it.

Fig. 97. — 15,000 Gallon Tank, at Bournemouth, England. To-
tal height, 45 feet. Inside diameter, 21 feet. Height
of tank proper, 10 feet.

Smaller tanks and cisterns up to 30 feet in diameter
are covered by domes; the larger sizes by ordinary

RE-INFORCED CONCRETE TANKS

139

column girder and slab construction, as described for
floors and roofs. Groined arch coverings as often
used -in this country are a simple waste of money and

Fig. 98. — 20,000 Gallon Tower, Scafati, Italy.

cost at' least 50 per cent more. It is of course, possible
to make tanks and cisterns, of any other shape, as rec-
tangular, or octognal, etc. In this case the sides of
the tanks are subjected to bending, and require much
more steel than in round tanks. Cistern walls should

140 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 99—65,000 Gallon Water Tanfc with Hollow Walls. Roof
covered with a layer of earth one foot thick. Concrete
housing for pipes and pump.

RE-INFORCED CONCRETE TANKS

141

be reinforced on both sides, because when the cistern
is empty the walls or sides are acted upon by the out-
side, horizontal earth pressure, subjecting the inside

Fig. 100.— 80,000 Gallon Water Tanks used by the Govern-
ment Railroads in France.

of the walls to tension, and when the cistern is filled
with water the water pressure will often exceed the
earth pressure subjecting the outside of the walls to
tension.

142 RE-INFORCED CONCRETE CONSTRUCTIONS

- ! \

• //i/ctoa*s*£ eswfjr 7-#/r/r

Fig. 101.— Section through such a Tank.

RE-INFORCED CONCRETE TANKS

Fig. 102.— 3,000,OCO Gallon Reservoir for the Watei Supply oc
the City of Lausanne, Switzerland.

The illustrations show some very artistic designs
of tanks. They add beauty to buildings or localities
when so erected. They are besides much more dur-
able than steel or wooden tanks. They do not incur
cost for maintenance and will last for an indefinite
time. There are reinforced concrete tanks used by
railroads in France, which are over thirty-five years
old.

Concrete tanks can be used for storing wine, mineral
oils, tar, ammoniac, lyes, salt-water, etc.

144 RE-INFORCED CONCRETE CONSTRUCTIONS

o
o
o

t
I

GRAIN ELEVATORS, COAL AND ORE BINS,
LIME AND SALT BINS.

These structures are designed and constructed on
lines similar to tanks. The circular form is here also
the most economical arrangement ; it is, however, often
desirable to build elevators and bins in clusters, and
in this case, square, rectangular, or hexagonal bins are
preferable to round bins. Round bins built in clusters
leave a nearly triangular space between them, which
is practically lost; where these spaces are filled with
grain great bending moments in the adjoining cylin-
ders are produced, which sometimes caused failure of
the structure. The horizontal pressure from grain or
coal is considerably less than water pressure, and ex-
perience proves, if a certain height of bin is exceeded,
this pressure is nearly constant on the sides of the
bin below this certain height. The sides of rectangu-
lar bins if arranged in clusters, must be reinforced on
both faces, because one bin may be filled and the ad-
joining empty and vica versa. The bottoms of the
bins are generally suspended from the sides ; they sup-

145

146 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE BINS

147

•4-

148 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE BINS

149

150 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE BINS 151

port a relatively small part of the weight of the ma-
terial in a bin, especially, when the height of material
is a multiple of the width. A man can easily inter
rupt the stream of grain out of a six inch hole at the
bottom with his hands, even in the case of high bins,
while in a tank the pressure at a six inch opening
would be very great.

The thickness of sides and bottoms rarely exceeds
six inches, if stiffened by horizontal girders at proper
intervals. The bins are generally supported by col-
umns at the intersection of two side walls; and as
the bins are very often built near rivers or harbors,
where foundations are very bad, a raft over the whole
area is generally applied.

Figs. 104 and 105 show a grain elevator at Swan-
sea, England with bins, five feet by ten feet and sixty-
six feet high. Fig. 106 shows a one million bushel
grain elevator, in Genoa, Italy, with bins 10x14 feet
and 57 feet high.

Figs. 107 and 108 show a grain elevator at Dun-
ston-on-Tyne, England, with bins 14x14 feet, and 60
feet high.

Reinforced concrete grain elevators have been used
in Europe for more than 20 years. They give perfect
satisfaction, do not cause sweating, and are the only
type of fire-proof elevators known there.

Fig. no shows a coal bin at Lens, Belgium. One of
the columns was knocked off by a derailed loco-
motive, and though the bins were filled, the sides
were strong enough to hold up the tremendous weight
without cracking.

Fig. in shows a coal bin of considerable height.
No damage to the sides or bottom is experienced by

152 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 109.— Coal Bins, Foot Bridge and Factory of Reinforced
Concrete. The bottom of the bin is 28 feet above the
ground. <

RE-INFORCED CONCRETE BINS

153

154 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 110.— Coal Bins.

the dropping of a ton of coal at a time through the
opening at the top.

Fig. 112 shows a storage bin, without any inside
partitions, built by the Hecla Portland Cenrent Co., at
their works at Edwards Lake, Mich.

This class of reinforced concrete structures i»
considerably cheaper than steel construction, and un-
doubtedly will have a great future, also in this coun-
try once their great advantages in regard to strength,
durability and fireproof qualities are fully understood.

RE-INFORCED CONCRETE BINS

155

Kig. 112. — Storage Bins, Hecla Portland Cement Co.

Fig. 113. — Detail of Splicing Reinforcing Rods
for Tanks and Water pipes.

REINFORCED CONCRETE WATER PIPES,
SEWERS AND CULVERTS.

This branch of reinforced concrete construction be-
longs to the oldest application of armored concrete.

Water mains are built from 6 inches up to more than
200 inches in diameter, and the thickness of the con-
crete shell is rarely made less than i 1-4 inches, nor
more than 4 inches. The material used is rich cement
mortar in the proportion of not less than i part cement
to 3 parts sand.

All tensile stresses arising from interior pressure
are taken care of by steel rods, which are placed closely
together in both circumferential and longitudinal di-
rections, so that the cement mortar acts only as a
filling to transmit the stresses to the steel rods and
to make the pipes water-tight.

It is good practice to introduce at intervals of from
150 to 200 feet a sliding joint on account of expansion
and contraction due to changes of temperature, simi-
lar to the expansion joints used in cast iron pipes.

During the first week, after water has been turned
on, more or less seepage takes place due to the slight
porosity of the cement mortar, which decreases very
rapidly by the pores gradually being filled up by the
sediment in the water as it passes through the shell,
and it is not perceptible after a period of about three
months, where the head of water is less than 50 to
70 feet. For higher pressures water-tightness should

156

RE-INFORCED CONCRETE PIPES

158 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE PIPES

159

be secured by thin sheet steel tubes about 1-16 of an
inch thick, which shell for pressures of 250 feet and
more is to be increased in thickness to 1-8 or 1-4 of
an inch.

The smaller pipes are manufactured in a factory
or in movable works, near the place where they are
to be used, in lengths from 3 to 15 feet, and have
either hub and flat eend connction as shown in Fig.
1 14, or sleeve connections, as shown in Fig. 115.

Fig. 118. — Manufacture of Pipes in Movable Works.

The water-tight joint is made by pouring rich ce-
met mortar into the space between the pipe and the hub
or the sleeve.

160 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 121. — Pipe of 5 feet 9 inches diameter. Paris Sewage
Disposal System.

Fig. 122. — Manufacture of Reinforced Skeletons.

RE-INFORCED CONCRETE PIPES

1G1

162 RE-INFORCED CONCRETE CONSTRUCTIONS

Larger pipes are built up in the trench by the aid
of movable centerings, making the whole pipe line one
monolith.

There is very little danger of the sheet steel lining
corroding, because the enclosed air is under high
pressure and does not attack the steel. In some cases
it might be advisable to protect the inside of the lin-
ing by an inner reinforced concrete pipe.

Fig. 117 to 123 show the manufacture of rein-
forced concrete pipes of medium diameters.

Fig. 124. — Reinforced Concrete Flume on Reinforced Concrete
Trestle conveying the Water of the River Rhone to the
new Simplon Tunnel.

Fig.- 124 to 126 show a flume built of reinforced
concrete to supply water from the River Rhone to the
2,000 H. P. turbines at the mouth) of the new Simplon
tunnel. It has a square section, 6 feet 4 inches inside,
the walls being 4 inches thick. It is 9,800 feet long
and runs partly in the ground and partly on a rein-

RE-INFORCED CONCRETE PIPES

103

164 RE-INFORCED CONCRETE CONSTRUCTIONS

forced concrete trestles, in some places 30 feet high,
and it also crosses two streets on canal bridges of 35
feet span.

The cost of a wooden flume would have been 85
francs per lineal meter, while the reinforced concrete
flume was built for 100 francs per meter. Considering
that the water power is to be a permanent feature of the
tunnel to supply electrical power required for moving
the trains through the tunnel, it is clear that reinforced
concrete in this case was the most economical form
of construction.

Fig. 127.— Power Canal and Spillway.

RE-INFORCED CONCRETE SEWERS
REINFORCED CONCRETE SEWERS.

165

Reinforced concrete sewers are built on lines sim-
ilar to water mains. The most favorable section in
this case is not a round, but a parabolic shape. The
steel reinforcement is not required to be as high as in

Fig. 128. — Section through Tunnel 17 feet wide, and Rein-
forced Concrete Sewer for Sewage Disposal System of
the City of Paris.

water mains. There is little danger of a sewer being
injured by super-imposed loads, as a parabolic arch
of a thickness of only 3 to 4 inches has an enormous
carrying capacity, as shown, for example, in Fig. 128,
representing a 17 feet tunnel covered by 17 feet of
earth, which \vas built of a shell of armored concrete
less than 3 inches thick, and was tested by a movable
load of ii tons without any sign of weakness, deflect-
ing under this concentrated load not more than 1-25
of an inch.

1GG RE-INFORCED CONCRETE CONSTRUCTIONS

Filling of the trench on one side only will be a
source of great danger to the concrete shell, if this
unsymmetrical load has not been provided for in the
original design.

Fig. 129. — Sewer Sections of small Diameters.

Inasmuch as the greatest portion of the weight of
the earth is above the crown of the sewer, the designer
is liable to fall into the error of not duly providing for
the strains to which the sewer is subjected during the
filling of the trench. It is apparent that the invert of
the sewer must be amply reinforced to withstand the
upward pressure of the ground, due to the weight of
the sewer and the super-imposed loads.

There are many sewers built in the United States
of diameters of 10 to 15 feet, having a thickness at
the crown of i 1-2 to 2 feet. This is often an extrava-
gant waste of money and material.

RE-1NFORCED CONCRETE SEWERS 167

Where sewers must be built on treacherous soil it
may be of advantage to drive piles every 10 feet, and
to make the shell of the sewer to act as a girder be-
tween the piles, able to carry itself, its contents, and
the super-imposed loads.

Nearly all of the cities in Europe have abandoned
brick sewer construction, and substituted reinforced
concrete.

.5-Scm -

Fig. 130. — German Sewer Sections, of Reinforced Concrete
Construction.

Fig.. 130 shows a section of a sewer as it is adopted
in most cities in Germany.

The City of Paris in the construction of its sewage
disposal system adopted reinforced concrete exclusively
and has about 17 miles of conduits up to 10 feet in
diameter, in successful operation. See Figs. 121 to
123.

Large factories exist all over Europe, producing
pipes and conduits of various shapes, sizes and di-
ameters, notably the Dykerhoff & Widemann factories,
which employed in 1900 two thousand five hundred
men.

Fig. 131 is a view of one of these factories. .

168 RE-INFORCED CONCRETE CONSTRUCTIONS

RE-INFORCED CONCRETE SEWERS 169

REINFORCED CONCRETE CULVERTS.

American railways are improving their right of
way by permanent concrete culverts, and while they
used up to a very recent date only massive concrete
construction, they are now beginning to appreciate the
great economical advantages of a well designed rein-
forced concrete culvert. The most economical form is
of a parabolic section and almost any thickness of shell
will be capable of supporting the heaviest super-im
posed loads provided that 'due precautions are taken
to avoid eccentric stresses during the process of filling
the earth around it.

Where the high parabolic section is not exactly suit-
able, a culvert, consisting of vertical side-walls and
of a parabolic or flat covering, may be substituted.

The side-walls must be figured for the lateral earth
pressure as well as for the horizontal pressure due to
the live train loads on similar lines as described for
basement and retaining walls. The flat cover may be
a reinforced concrete slab for spans less than ten feet
or of girder and slab construction for larger spans.

MISCELLANEOUS APPLICATIONS.

To enumerate or even specialize the almost universal
application of reinforced concrete is a task far beyond
the scope of this handbook.

Therefore we will describe only a few of the most
important uses.

REINFORCED CONCRETE SMOKE STACKS.

Many reinforced concrete smoke stacks have been
built in this country and Europe during the past 15
years. These stacks are much stronger than solid or
hollow brick chimneys, and can be erected, not only
in a much shorter time, but also at very great reduction
in cost.

Figs. 132 and 133 show a concrete chimney erected
by Mr. C. Leonardt, Los Angeles, California, for the
Los Angeles Electric Railway Power S cation. It has
an inside diameter of n feet and is 155 feet high above
grade. It consists of solid concrete masonry up to
36 feet above the ground ; from there up of an outside
and an inside shell of reinforced concrete, which latter
can expand independent of the outside wall.

Fig. 134 shows the movable mold used for con-
creting the shells.

In Fig. 78 is shown a chimney 130 feet high buih
of a solid shell of reinforced concrete.

Fig. 135 shows a lime kiln built of a shell of rein-
forced concrete lined with fire brick, which stood for

170

MISCELLANEOUS APPLICATIONS

Fig. 132.— Reirforced Concrete Chimney, in course of erec-
tion, Los Angeles.

172 RE-INFORCED CONCRETE CONSTRUCTIONS

fig. 133. — Completed Chimney for Los Angeles Power Co.

I UNivens

MISCELLANEOUS APPLICATIONS

17:5

Fig. 134. — Movable Centerings for this Chimney.

174 RE-INFORCED CONCRETE CONSTRUCTIONS

MISCELLANEOUS APPLICATIONS

175

176 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 136b.— Dome of 40 feet diameter. Bank Brunner, Brus-
sels, Belgium.

years has withstood temperatures of 2,000 to 2,200 de
grees Fahrenheit.

Fig. 136 shows reinforced concrete domes of dar-
ing design. There is no material which is better
adapted for this class of structures than reinforced
concrete. Even for the largest diameters a thickness

MISCELLANEOUS APPLICATIONS IT?

Fig. 137. — Printing Establishment, Rennes, France. Arches
of 80 feet span.

of three inches at the crown and five to six inches at
the springing is quite sufficient.

Fig. 137 shows a hall for a printing establish-
ment at Rennes, France, consisting of concrete arches
of 8 1 feet span, concrete purlins and a concrete roof
with skylights. Reinforced concrete arches can be
built at very reasonable expense up to 200 feet in span
and over for railroad stations, public halls, factories,
etc., and possess many advantages over steel arches.
They are fireproof and indestructible, cost much less,
can be maintained at very little expense, have a fine
architectural appearance and afford better light for the
interiors.

Fig. 138 shows a railroad tower built of reinforced
concrete. The French railroads build small guard

178 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 138. — Railroad Guard Tower used by French Railroads
Foundations are .enlarged for greater stability.

MISCELLANEOUS APPLICATIONS 179

houses of reinforced concrete and ship them com-
pletely finished on cars to the places where they are to
be used.

Fig. 139. — Reinforced concrete side-walk lights, Power
Building, Cincinnati, built by the Ferro-Concrete Con-
struction Co. Cincinnati.

Figs. 139 and 140 show prismatic sidewalk lights
with reinforced concrete framing. The glass inserts
are two and three-fourths inches in diameter and three
and three-fourths inches on centers, while the concrete
frame is one and three-fourths inches thick, strength-
ened by small steel rods in both directions. Nearly
all the subway stations of the New York Rapid Transit
Railway have reinforced concrete sidewalk lights.

Leading American railways are now experimenting
with reinforced concrete ties, with a view of displacing

180 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 14i>.— View of Reinforced Concrete Side-walk Lights from
below.

MISCELLANEOUS APPLICATIONS 181

the ordinary wooden ties which are yearly becoming
more expensive.

The .Italian government, after experimenting several
years with reinforced concrete ties, has adopted a stand •
ard concrete tie on all the government railways.

The French railroads in China on their right-of-way
of over 300 miles, use reinforced concrete ties ex-
clusively, having an inverted "T" section, with an en-
largement of the stem, where the rails cross, which ties
cost about two and a half dollars each.

These ties are much more ' expensive, in the first in-
stance. Their greater life, however, after 10 years'
use, will result in decided saving.

Reinforced concrete fence posts are rapidly coming
into use in the United States, by railroads along their
right-of-way, especially, in prairie countries where fire
hazards are great. Statistics show that 60 per cent, of
the fence posts of the right of way are destroyed by
fire against 40 per cent, by decay.

Reinforced concrete is likewise coming into extensive
use for agricultural purposes, as, for example, for
small water and feed tanks, silos, for irrigation ditches
etc.

REINFORCED CONCRETE BRIDGES.

Reinforced concrete combining- the massive effect
of brick and stone and the great strength of steel has
found a great field of application in bridge building.

The rapid progress accomplished in bridge con-
struction during the last 30 years is due to the use
of steel, which, being of relatively small weight, en-
abled engineers to erect large spans without the use
of costly scaffolding. Both iron and steel are liable to
deterioration by rust, and as some parts cannot easily
be inspected or painted, the life of a steel bridge is
very limited, and steel bridges are to-day considered as
temporary structures.

Consequently the first class railways in this country
are again returning to stone or solid concrete bridges
which offer the advantage of great stiffness and dura-
bility.

The use of steel reduced the cost of bridges to a
considerable extent ; engineers continually increased the
working stresses to be allowed in the calculation of thj
bridge members, and the result is light bridges, which
are liable to be wrecked in a short time by the con-
tinuous traffic of ever increasing loads. Reinforced
concrete bridges can be expected to last for ever ; just
as the old Roman concrete walls outlasted their stone
linings, even so can we expect concrete bridges to
outlast stone bridges. Repairs and cost of maintenance
are reduced to a minimum ; they can be built at a rea-
sonable cost, very often for less money than steel

182

RE-INFORCED CONCRETE BRIDGES 183

bridges; they are 10 to 20 times more rigid than the
latter.

The first application of reinforced concrete in bridge
construction was in concrete floors of steel bridges,
especially in city bridges where a permanent floor was
required.

The usual distance of stringers in steel bridges is 3
to 5 feet, and it is perfectly feasible to cover them by
a concrete floor i 1-2 to 2 inches thick, capable of sup-
porting any concentrated or distributed load, which
may come on the bridge. Reinforced concrete now
replaces the very expensive floorings, which were N for-
merly made of buckle plates, suspension plates, or
various kinds of trough floors with a covering of
concrete.

These concrete floors are not only more durable
but also much lighter, saving a great amount of dead
weight and, therefore, steel in the bridge and costing
less than the old floorings.

The next application of reinforced concrete in
bridges was due to the demand of railroads for viaducts
of very limited depth for street and railroad crossings.
For railroad crossings it was possible to span distances
up to 20 feet by a reinforced concrete slab, only six
inches thick, while for street crossings a thickness of
12 inches for a span of 10 feet has proved very satis-
factory.

Fig. 141 shows a cross section of such a flat bridge
of 10 feet span, carrying a railroad track of the Jura

: • *..< *.».*. r .....*..* . » «

-t

Fig.. 141. — Railroad Bridge of 10 ft. span, Reinforced Slab
Construction.

184 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 142. — Reinforced Concrete Girder Railroad Bridge.

Fig. 143.— Girder Bridge of 50 ft. span.

RE-INFORCED CONCRETE BRIDGES

185

Simplon R. R. Greater spans than 10 feet for rail-
road bridges should be of girder and slab construction.
Fig. 142 shows the first viaduct of this kind, built
at Creux du Mas, Switzerland. It consists of 10x12
inch beams, six feet apart, spanning 21 feet 4 inches,
on a skew of 24 degrees. Tests made by the Rail-
road Co. before acceptance of this structure showed
deflections of 0.13 inch, when the heaviest locomotive
passed at a speed of 40 miles an hour. Tests made
two years later showed that this deflection had dimin-
ished 1-3, proving, without doubt, that the adhesion
of plain round steel rods to concrete is sufficient and
not weakened by vibrations caused by passing trains
and that a reinforced concrete bridge becomes stronger
with age.

Fig. 144. — Girder Bridge tested by a 20 ton Steam Roller.
Maximum deflection 1-12,000 of the span.

186 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 145.— Reinforced Concrete Girder Bridge of 52 ft. span.i
Rubblestone abutments, girders slightly arched.

A very economical type of highway bridges is shown
by Figs. 143 to 145. Reinforced concrete girders,
six to fourteen feet apart, support the roadway, con-
sisting of a concrete slab, stiffened by girders, while
the side-walks are built in cantilever, as shown in
Fig. 146. The roadway can be formed of macadam or

Fig. 146.— Section through Reinforced Girder Bridge.

RE-INFORCED CONCRETE BRIDGES 187

Fig. 147. — Bridge at Fort De Bron, designed to carry a load
of extremely heavy pieces of artillery for the fort.

Fig. 148. — Continuous Girder, Bridge on Concrete Pier Foun-
dation.

188 RE-INFORCED CONCRETE CONSTRUCTIONS

of a layer of asphalt or of a two inch cement finish
The abutments for such bridges can be built of rubble
stone or reinforced concrete or concrete sheet piles
where the ground is very bad and a low priced bridg
is desired.

These bridges are very rigid and the tests on above
bridges of 50 feet span showed under a moving load
of twenty tons a maximum deflection of 1-12,000 of
the span.

Fig. 147 shows a continuous girder bridge with
reinforced concrete trestle supports, while Fig. 148
shows a continuous girder bridge on concrete piers of
small diameters,' which piers reduce as little as possible
the profile of the river. This class of bridges can be
built with advantage for unsupported spans up to 70

Fig. 149. — Tubular Bridge connecting two Refrigerators.

RE-INFORCED CONCRETE BRIDGES

189

feet ; for larger spans they become more expensive than
arched bridges. Fig. 149 shows a tubular bridge con-
necting two refrigerating plants of a brewery.

Arched bridges of reinforced concrete can be built
up to 500 feet span. The great success of armored con
crete in building arched bridges is based on the adop-
tion of arched ribs similar to steel bridges and by
supporting the roadway by columns resting on the
arched ribs. This reduces the dead weight and the
cost of the bridge. Other systems of reinforced con-
crete construction usually adopt an arched floor 6
inches to 3 feet thick with spandrel walls, filling in the
space between arches and the road grade with earth,
and paving the surface. This, of course,' gives a much

Fig. 150. — Covering of a Subway of the Metropolitan Electric
Railway, Paris, France. Girders, 52 ft. span; live load,
200 pounds per square foot.

190 RE-INFORCED CONCRETE CONSTRUCTIONS

heavier bridge, similar to a solid stone bridge, and con-
siderably increases the weight on the foundations and
arched floors. Reinforced concrete should not imitate
stone, but should create its own particular style of
architecture, which is light and graceful ; in case of
arched bridges this approaches more the design of steel
bridges than stone bridges. Fig. [51 shows a splen-
did example of an arched concrete bridge. It was
built in 1898, at Chaterellault, France, and is 26 feet
wide by 450 feet long. The central arch has a spaii
of 164 feet and the side arches of 135 feet. All arches
haye a rise of i-io of the span. There are 4 concrete
ribs 6 feet 3 inches apart, being only 20 inches deep in
the centre, which are connected throughout by a five
inch concrete floor for wind bracing. The road bed
consists of a concrete floor 5 inches thick at the curb
and 10 inches thick at the centre, which is covered by
a coat of asphalt and supported by girders 6 feet
3 inches apart corresponding to the arches below, which
girders are carried by 8 inch square colums, rest-
ing on the ribs. The piers are built of a shell of con-
crete 4 inches to 12 inches thick, connected by partitions
in the same vertical plan as the arched ribs and the
whole is filled with a low grade concrete. The piers
rest on the rock which was found at a small depth
below the river bottom. The side-walks, which are
5 feet wide, overhang for a distance of 3 feet 5 inches.
The bridge was built in the short time of 3 months,
and cost slightly less than $35,000.

The tests by a Commission of Engineers and repre-
sentatives of the government and the municipality of
Chatellerault were made in the following manner :

First, each span was loaded over its total length, then
on each half, then on its central part, with moist sand

RE-INFORCED CONCRETE BRIDGES

191

Fig. 151.— Bridge at Chatellerault, 26 feet by 450 feet long,
central arch of 4^9 ft. span, side arches 135 ft. span,
rise 1-10 of the span.

Fig. 152.— Bridge at Chatellerault

192 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 153.— Bridge at Chatellerault with soldiers passing over.

1,50 2.5P 2.50 1,50

Fig. 154. — Section through Pier of Chatellerault Bridge.

RE-INFORCED CONCRETE BRIDGES

193

194 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 156. — Highway and Electric Railway Bridge at Bilbao,
Spain. Consists of five arches, of 120 ft. span, of which
only three are visible in the illustration. This bridge
has a much lighter appearance than a steel bridge.

at the rate of 165 pounds per square foot on the road-
way and 123 pounds on the side- walks.

The official report of the test is as follows :

The maximums of deflections weree 1-4 inch for the
arch at the left bank, 7-32 inch for the. arch at the
right bank, and 13-32 inch for the central arch, that is
1-7300 and 1-5000 of the spans, respectively. The
specifications allow deflections of 9-16 inch for the
135-foot span and 2 inches for the 1 64-foot span.
After removing the loads no permanent deflection
could be detected.

The moving test load consisted of \

First. One 1 6-ton steam roller.

RE-INFORCED CONCRETE BRIDGES

195

Fig. 157. — Cantilevers of 27 feet carrying a Railroad track.

Second. Two four-wheeled wagons weighing 16
tons in all.

Third. Six two-wheeled wagons weighing 8 tons in
all; making a total of forty tons moving simultane-
ously over the bridge, while the sidewalks were loaded
to 80 pounds per square foot. Strips of wood were
strewn over the roadway in order to produce shocks
when the steam roller passed over them. The maxi-
mum deflection under these loads was less than 1-9000
of the span.

Furthermore, a troop of 250 infantrymen crossed -the
bridge, first in ordinary marching order, then in double
quick time.

The most remarkable feature shown by these tests
was that a load on one arch caused a perceptible rise
in the two adjacent arches, an evident proof that ferro-
concrete structures are monoliths.

196 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 158. — Arched Bridge of 60 ft. span. Ribs support by
means of spandrel columns, the reinforced concrete
roadwiay; railings consist of reinforced concrete posts
and arches.

Fig. 159. — Arched Bridge of 50 ft. span.

RE-INFORCED CONCRETE BRIDGES 197

Figs. 158 and 159 show smaller arched bridges de-
signed on similar lines with the difference, that the
arched ribs are not connected by a concrete floor for
wind bracing, but only by 8x8 inch ties. In this case
the wind stresses must, of course, be taken care of by
the concrete floor of the roadway and transmitted from
the arched ribs by the spandrel columns to this road-
way. This makes a very neat and low priced design,
and bridges of this type will be found to be less ex-
pensive than steel bridges with wooden floors.

Fig. 160. — 'Arched Bridge carrying a canal.

Figs. 1 60 to 167 show arched bridges where the ribs
are solid from the roadway down. This is in imita-
tion of arched stone bridges, the difference being that
these bridges consist of ribs from 6 to 10 feet apart
with a concrete floor for the roadway and therefore of

198 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 161. — Foot Bridge over Railroad, 60 ft. span.

hollow construction and much lighter than stone
bridges, while they resemble them in appearance. Fig.
1 60 shows a concrete bridge carrying a conduit; con-
sists of two arches each of 42 feet span, and a cantilever
sidewalk. . Figs. 161 and 162 show veary neat de-
signs for foot bridges over railroad tracks. The cost
of these bridges was about 25 per cent, less than of
structural steel. Fig. 168 shows an arched bridg-
designed on the Monier system with an arched floor
and concrete walls to support the roadway.

RE-INFORCED CONCRETE BRIDGES 199

Fig. 162. — Foot Bridge of 100 ft. span.

Fig. 163. — Reinforced Arched Highway Bridge of 50 ft. span.

200 RE-INFORCED CONCRETE CONSTRUCTIONS

Fig. 164.— Highway Bridge with Stone Lining.

Fig. 165.^Skew Bridge of 72 ft. span.

RE-INFORCED CONCRETE BRIDGES

201

202 RE-INFORCED CONCRETE CONSTRUCTIONS

iS; :'"-'

:ffi

RE-INFORCED CONCRETE BRIDGES

203

204 RE-INFORCED CONCRETE CONSTRUCTIONS

REINFORCING EXISTING STEEL BRIDGES
BY CONCRETE.

Existing steel bridges which show signs of deterior-
ation or are too weak for the increased loads passing
over them, can be reinforced by concrete at often nom-
inal expense. Plate girder bridges can be lined with
concrete and additional steel rods added to bottom and
top chords. Also cross girders and stringers can be
embedded in concrete, and a new concrete floor placed ;
in this wray a new bridge is obtained, which will be
more sightly and substantial than the old steel bridge.
A good example of such a reinforcement of a bridge is
shown in Fig. 170. The lattice work of the main gird-
ers and the webs of the cross girders were utterly cor-
roded by sulphurous gases and the sand blast action of
locomotives stopping under it.

A few yards of concrete, used to embed the main and
cross girders and to place a substantial floor, produced
a new bridge, which may last indefinitely.

Trussed bridges can also be reinforced in a similar
way, embedding bottom and top chords, diagonals
and verticals, cross girders and stringers in concrete
and adding new steel rods to increase the strength of
the various members.

Cement is to-day recognized as the best preserver of
iron and steel against rust, and the French railroads
now use, exclusively, cement mortar to paint their

bridges.

205

206 RE-INFORCED CONCRETE CONSTRUCTIONS

o o o o o

WW^7/

>Q<

AVAVA^

Ji'

,. *•

'JX

*J,M,r*/ /ZnatS*

^ \

Figs. 170-172. — Reinforcing an old steel bridge with con-
crete.

REINFORCED CONCRETE CONSTRUCTION 207

The illustrations in these pages were drawn largely
from constructions, executed under French systems
of reinforced concrete construction, both in this coun-
try and abroad.

We are also indebted to the Ferro-Concrete Con-
struction Co., of Cincinnati, for several illustrations.

To-day there are several hundred engineers and con-
tractors engaged in armored concrete construction in
Europe and the United States, whose special sys-
tems differ only slightly from each other, omitting
or inserting more or less 'important details-, from the
principles of construction heretofore described.

During the last few years,certain so-called patent
bars with notches or corrugations, etc., have appeared
on the market, for which extraordinary claims have
been made in respect to the advantages when used as a
reinforcing member. The vendors of these patent
bars claim that the adhesion of the concrete to their
bars is increased 20 to 50 per cent, over round rods,
and, therefore, the strength of a beam or a slab is in-
creased in the same ratio, which is, however, not war-
ranted either in theory or practice. In fact not one
in a thousand of the existing structures are built with
such patent bars. Experiments on reinforced
concrete bridges during the last 10 years prove thac
the adhesion of concrete to plain steel rods increase^
with age, and that there is not the least danger
of rupturing the bond by shocks; and nearly 20,000
structures where plain steel rods were used, prove that
plain steel rods take care of all tjie stresses they are
subjected to. These patent bars are sold at from three
to five cents a pound, while plain steel rods to-day cost
only one and three-tenths cents a pound. The increase

208 RE-INFORCED CONCRETE CONSTRUCTIONS

of adhesion can be secured much easier by simply in
creasing the number of plain bars above that given by
accepted practice, and we will obtain by this expedient
a stronger and less expensive beam, than where the
costly patent bars are used. It is true, that on first
consideration, these patent bars seem to be a good
thing; but the writer is warranted in saying that be
prefers to use three times the amount of plain steel
rods, in a given member, than to pay three times the
price for the patent bars.

GENERAL SPECIFICATIONS. 209

GENERAL SPECIFICATIONS FOR FEINFORCED CONCRETE
CONSTRUCTION.

The work shall be completed in accordance with the
general plans, sections and diagrams submitted by the
concrete contractor to the architect, engineer or owner.
The contractor must prove that the plans are prepared
by competent engineers who have had at least three
(3) years experience in this line of work with a respon-
sible company. No change shall be made in the plans
either in thickness of any member of construction
or in size, or position of steel rods, without written
permit from the engineer in charge of the reinforced
concrete construction.

MATERIALS.

Only first class Portland cement shall be used. Each
car load of cement shall be tested and is to conform to
the standard required by the United States Govern-
ment (see the specifications).

SAND — The sand shall be clean and sharp and free
from loam or other impurities, and, preferably, a mix-
ture of grains of all sizes from 1-4 inch down to the
finest, if such sand can be had at reasonable price.

CRUSHED STONE OR GRAVEL — Shall be free from
loam or other impurities, of hard material and no
single piece be larger than 3-4 inch for floors,
columns, thin walls, or more than I inch in footings.
The material should contain all sizes from the specified
sizes down to and including stone dust ; the percentage
of stone dust shall not exceed 10 per cent of the crusher
run.

CONCRETE — At least one barrel of cement for each
cubic yard of concrete shall be used. The proportion

210 RE-INFORCED CONCRETE CONSTRUCTIONS

of cement sand, and crushed stone or gravel shall not
be less than i \2. 14 for columns or girders,and 1:2 1-2 15
for walls, floors and footings. Whenever the
amount of concrete justifies the use of a concrete mixer,
machine mixed concrete shall be used. Any kind of
batch mixer shall be allowed. The ingredients shall
be placed in the machine in a dry state, and be
thoroughly mixed, after which clean water shall be
added and the mixing continued until a uniform mix-
ture is obtained. Where the mixing is done by hand,
the cement shall be thoroughly mixed dry on a tight
platform of planks or sheet iron, then the previously
wetted stone shall be spread on the mixture of sand
and cement, clean water added, and the whole turned
over two or three times until a perfectly uniform mix-
ture is obtained.

The mixing shall be done as rapidly as possible and
the concrete deposited in the work without delay. The
concrete shall be mixed moderately wet, so that tamp-
ing is required to bring water to the surface. At no
time shall concrete be as wet as to allow the stones to
sink in the wheel barrows, and the cement and sand
and water to rise toi the surface. The concrete may be
fairly wet for walls, which have little to carry, so that
churning of the concrete only is required to get rid of
the air drawn in by pouring.

The materials shall be measured loose, but in a uni-
form manner, so that the proportions can be easily
controlled by workmen and inspectors. The concrete
shall be deposited in a layer of a few inches, never
exceeding six, and rolled or rammed till the water ap-
pears at the surface. Where a complete section of the
work joins a section just being deposited, extra care
shall be taken that the surfaces are well picked out,

GENERAL SPECIFICATIONS.

and washed clean with water, and well grouted, iu
order to make a proper bond between the sections. This
applies especially to the joints of columns with gird-
ers, girders withT floors, floors with walls, etc.

FORMS — The forms shall consist of i to2 inch boards
of uniform thickness joined carefully together, straight
and true to line, so that the irregularities in the ex-
posed concrete surfaces shall not be greater than 1-4
inch. The forms have to be well braced and supported,
so that there be no undue deflection, when the concrete
is deposited.

The forms for girders shall not be removed before
three weeks to four weeks, for floors not before one
to two weeks, according to the temperature. The sides
of columns and walls may be removed in one to two
days ; the surface has, however, to be sprinkled to pre-
vent checking on account of too rapid hardening1 of the
layers. This sprinkling has to be done during warm
and dry weather and continued for several days on
all newly built concrete, especially floors.

CONCRETING IN COLD WEATHER — Concreting above
30 degrees Fahrenheit may be carried1 on without heat-
ing the materials. In temperatures above 26 and below
30 degrees F., the cement, sand and water shall be
heated, and the concrete covered immediately by cloth
and a thick layer of sand. No concreting: of important
parts of the work shall be carried on below 26 degrees
F. The weather reports must be consulted daily and
if a cold spell is predicted the next 12 hours, work must
be stopped.

IRON — Shall have an ultimate tensile strength of
not less than 50,000 Ibs. per square inch ; and the elastic
limit shall not be less than 25,000 Ibs. It must bend

212 RE-INFORCED CONCRETE CONSTRUCTIONS

cold 1 80 degrees. around a rod whose diameter is equal
to the thickness of the piece tested, without any sign
of failure.

STEEL — Shall have an ultimate tensile strength of at
least 60,000 Ibs. per square inch, and an elastic limit of
not less than half the ultimate tensile strength. It must
bend cold 180 degrees around a curve, whose diameter
is equal to the thickness of the piece tested, without
crack or flaw on outside of bend. All iron or steel used
must be free from dirt or other impurities, but may
have a slight coat of rust, which coat facilitates the
forming of a hard coat of ferro calcite, and increases
the adhesion to the concrete.

TESTS — Five per cent, of all girders shall be tested
to at least 11-2 times the specified loads and the de-
flection shall not be greater than 1-800 of the span.
No crack or other indication of weakness shall be per-
missible. Any girder not passing these tests shall be
rebuilt in armored concrete or replaced by steel con-
struction at the discretion of the architect.

SPECIFICATIONS FOR PORTLAND CEMENT,
U. S. ARMY CORPS OF ENGINEERS.

The cement shall be an American Portland, dry and
free from lumps. By a Portland cement is meant the
product obtained from the heating or calcining up to
incipient fusion of intimate mixtures, either natural or
artificial, of argillaceous with calcareous substances;
the calcined product should contain at least 1.7 times as
much lime, by weight, as of the materials which give
the lime its hydraulic properties ; it should be finely pul-
verized after said calcination, and thereafter addition
or substitution not to exceed 2 per cent, of the calcined
products should be allowed, and only for the purpose
of regulating certain properties of technical import-
ance.

The cement shall be put up in strong, sound barrels
well lined with paper, so as to be reasonably protected
against moisture, or in stout cloth or canvas sacks.
Each package shall be plainly labeled with the name
of the brand and of the manufacturer. Any package
broken or containing damaged cement may be rejected
or accepted as a fractional package, at the option of
the United States agent in local charge.

No cement shall be used except established brands
of high grade Portland cement which have beeen made
by the same mill and in successful use under climatic
conditions similar to those of the proposed work for at

least three years.

213

214 RE-INFORCED CONCRETE CONSTRUCTIONS

The average weight per barrel shall not be less than
375 pounds net. Four sacks shall contain one barrel
of cement. If the weight, as determined by test weigh
ings, is found to be below 375 pounds per barrel, the
cement may be rejected, or, at the option of the engin-
eer of officer in charge, the contractor may be required
to supply, free of cost to the United States, an addi-
tional amount of cement equal to the shortage.

Tests may be made of the fineness, specific gravity,
soundness, time of setting and tensile strength of the
cement.

FINENESS — Ninety-two per cent, of the cement must
pass through a sieve of No. 40 wire, Stubb's gauge,
having 10,000 openings per square inch.

SPECIFIC GRAVITY — The specific gravity of the ce-
ment, as determined from a sample which has been
carefully dried, shall be between 3.10 and 3.25.

SOUNDNESS — To test the soundness of the cement,
at least two pats of neat cement mixed for five minutes
with 20 per cent, of water by weight shall be made on
glass, each pat about three inches in diameter and one •
half inch thick at the center, tapering thence to a thin
edge. The pats are to be kept under a wet cloth until
finally set, when one is to be placed in fresh water for
twenty-eight days. The second pat will be placed in
water which will be raised to the boiling point for
six hours, then allowed to cool. Neither should show
distortion or cracks. The boiling test may or may not
reject at the option of the engineer or officer in charge.
TIME OF SETTING — The cement shall not acquire its
initial set in less than forty-five minutes' and must have
acquired its final set in ten hours.

CEMENT SPECIFICATIONS 215

(The following paragraph will be substituted for the
above in case a quick-setting cement is desired :

The cement shall not acquire its initial set in less
than twenty nor more than thirty minutes, and must
have acquired its final set in not less than forty-five
minutes, nor in more than two and one-half hours.)

The pats made to test the soundness may be used in
determining the time of setting. The cement is con-
sidered to have acquired its initial set when the pat
will bear, without being appreciably indented, a wire
one-twelfth inch in diameter loaded to weigh one-
fourth pound. The final set has been acquired when
the pat wall bear, without being appreciably indented,
a wire one-twenty-fourth inch in diameter loaded to
weigh one pound

TENSILE STRENGTH — Briquettes made of neat ce-
ment, after being kept in air for twenty-four hours
under a wet cloth, and the balance of the time in water,
shall develop tensile strength per square inch as fol-
lows :

After seven days, 450 pounds; after twenty-eight
days, 540 pounds.

Briquettes made of i part cement and 3 parts stand-
ard sand, by weight, shall develop tensile strength per
square inch as follows :

After seven days, 140 pounds ; after tenty-eight days,
220 pounds.

(In case quick-setting cement is desired, the follow-
ing tensile strength shall be substituted for the above :

Neat briquettes: After seven days, 400 pounds;
after twenty-eight days, 480 pounds.

Briquettes of i part cement to 3 parts standard
sand: After seven days, 120 pounds; after twenty-
eight days, 1 80 pounds.)

216 RE-INFORCED CONCRETE CONSTRUCTIONS

The highest result from each set of briquettes made
at any one time is to be considered the governing test.
Any cement not showing an increase of strength in
the twenty-eight day tests over the seven-day tests,
shall be rejected.

When making briquettes neat cement will be mixed
with 20 per cent, of water by weight, and sand and
cement with 121-2 per cent, of water by weight. After
being thoroughly mixed for five minutes, the cement or
mortar will be placed in the briquette mold in four
equal layers, and each layer rammed and compressed
by thirty blows of a soft brass or copper rammer three-
quarters of an inch in diameter (or seven-tenths of an
inch square, with rounded corners), weighing i pound.
It is to be allowed to drop on the mixture from a
height of about half an inch. When ramming has
been completed, the surplus cement shall be struck off
and the final layer smoothed with a trowel held almost
horizontal and drawn back with sufficient pressure to
make its edge follow the surface of the mold.

The above are to be considered the minimum require-
ments. Unless a cement has been recently used on
work under this office, bidders will deliver a sample
barrel for test before the opening of bids. If this
sample shows higher tests than those given above, the
average of tests made on subsequent shipments must
come up to those found with the sample.

A cement may be rejected in case it fails to meet
any of the above requirements. An agent of the con-
tractor may be present at the making of the tests, or,
in case of the failure of any of them they may be re-
peated in his presence. If the contractor so desires, the
engineer officer in charge may, if he deem it to be to

CEMENT SPECIFICATIONS 217

the interest of the United States, have any or all of the
tests made or repeated at some recognized standard
testing laboratory in the manner herein specified. All
expenses of such tests to be paid by the contractor. All
such tests shall be made on samples furnished by the
engineer officer from cement actually delivered to him.

*Chas. W.Stevens Cast Stone

With our machine, one man can produce seven
standard building blocks in 5 minutes by one opera-
tion, after the Concrete has been mixed, one man then
removes the entire seven blocks, all together in a sin-
gle operation, and sets themaside to harden.

This is repeated continuously, without intermission.
Thereby we obtain the greatest output at the lowest
cost. Our stone is produced without tamping or pres-
sure. Is strong, durable and shows an exceedingly fine
finish. For manufacturing r'ght and descriptive pamph-
lets address

The Stevens Cast Stone Co.

808 Chamber of Commerce,

CHICAGO, ILL. -

THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW

AN INITIAL FINE~OF 25 CENTS

OVERDUE.

SECTOtD NOVB4

VB 1 1 037

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Full text of "Architects' and engineers' hand-book of reinforced concrete constructions .."

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