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SUPPLEMENTARY
MATERIAL ‘

IN BACK OF BOOK

A Thesis Submitted to

The Faculty of

Michigan State College

of

Agriculture and Applied Science

by

Ernest F. Cross

Candidate for the Degree of

Bachelor of Science

December 19M2

IHES‘Q

A Check Design
of a
Deck Type

Highway Bridge

1&11831

Acknowledgement

 

The author wishes to take this opportunity of thanking those who,
by the generous donations of time and knowledge, have made possible,
the preparation of this fliesis.

The author extends grateful acknowledgement to Mr. G. M. Foster,
Registered Consulting Engineer, Mr. Ralph Timmick, designer, Mr.
Thomas Foster of the Michigan State Hig way Department, and Mr. K.

W. Cosens of the Civil Engineering Department, Michigan State College.

_ 1 -
Bridges are numbered among the most ancient and honored evidences of the
progress of civilization. Their background and tradition extend into the
past almost as far as man's history. Structures built by man reflect his
increased knowledge and progress; each era or age showing a definite style
of design.

Bridges reflect this tendency more than any other type of structure and more
than any other typify progress and have given man.the Opportunity to create
with his hands an almost living monument of himself, his visions, and his
imagination. A study of the history of bridges shows the gradual change in
style throughout the ages, each reflecting the predominating ideas of the
era. Bridges of the early 20th. century show decided efficiency but tend to
be plain and inartistic, comparable to a machine performing its task in the
most efficient manner. It should not be inferred that a bridge should not
be efficient but the esthetic factor must also be taken into account. The
more recent conception of bridge design involves economical and efficient
design combined.with more graceful and artistic lines, harmonizing with the
immediate landscape and other location characteristics.

aile bridges differ in style and design every structure follows and performs
the duties and requisites as stated by Palladio in the 16th. century: "The
convenience of bridges was first thought upon because many rivers are not
fordable, upon which account it may be said that bridges are a principal
part of the way and are nothing else but a street or way continued over
water. Bridges therefore ought to have the self same qualifications that
are judged requisite in all other fabriks, which are; they shall be con-
venient, beautiful, and durable." These are the cardinal principles of
good bridge design and are followed to the letter in the design of the
most modern structures.

It is not the purpose of this paper to develop the history of bridges

I
TO
I

or of bridge design but rather to develop the procedure followed in the
design of a bridge and the variety of problems encountered; using an actual
example as a graphic illustration. The bridge to be specifically used is
a concrete slab, rolled beam, deck girder highway bridge. This type of
structure is somewhat more involved than a railroad bridge due to the
extreme freedom of the load placement.

In this and followirs pages, the terms, good practice, good design, and
stan ard design will be encountered many times. The first two are terms
applied to problems solved on the basis of experience. With years of
experience and increasing familiarity with structures, valuable information
is gradually acquired; sometimes by the tragic results of faulty design,

he bridge engineer and designer acquires a mass of invaluable data for
future reference. .

Standard design is a term applied to design features computed from in-
formation and data compiled over a period of time. This type of design is
constantly changing as the theories involved can be followed further with
additional data. The State Highway Departments and the Federal_Bureau of
Roads are the agencies most directly concerned with this type of design.
These organizations design the standard sections from the formula develOped
from the results of their construction and is intended to create a certain
amount of uniformity of design in all structures under their supervision
and authority. The economic factor also enters into standard design. The
design features which the Department considers to be the best are gathered,
compiled, and put into the form of Standard Specifications. These specifi-
cations are usually taken as the basis of design for all structures on state
highways, and are corrected, che ged, and added to as additional knowledge

from their experience and that of others becomes available.

In the design and construction of a highway bridge, there is a definite
procedure to be followed. First a petition to replace the existing struc-
ture: This requires action by the County Road Commission, the State High-
way Department, and the Federal Bureau of Roads, if Federal Aid is expected.
Second a complete survey is made of the site. This survey includes traffic
surveys, boring legs, cross-sections, complete stream data, and a report of
the type and condition of the existing structure. If the petition is ap-
proved, preliminary plans of the structure are drawn up and sent to the
State Highway Department and the Federal Bureau of Roads for approval. The
necessary changes and corrections are made on the preliminary plans and
after final approval, the plans are detailed and completed along with the
engineer's estimate of cost. The job is then bid on and contracted for
construction. This is a brief resume of what actually takes place.

To illustrate the actual procedure, a definite example has been selected.
The design of this bridge will be followed.through to give a more graphic
picture of the actual proceedings. In a sense this paper will also cone
stitute a check design of the main features, proving the efficiency and worth
of the bridge.

The bridge in question is located in Kalamazoo County, crossing the Kalamazoo
River at Comstock, Michigan. The previous structure consisted of a through
steel Pratt truss of six spans with the following dimensions: clear roadway
17'-6", center to center of pine 150.12', floor of planks covered.with
bituminous material. The structure was erected in 190h. A great deal of
commercial traffic was carried over the truss and it was felt that the
bridge was entirely inadequate under the increasing flow of traffic.

As this paper will be chiefly concerned with the design features of the

bridge, it will suffice to say that it was decided to replace the existing

-u-

bridge under a Secondary Federal Aid Allocation. The first step was the
plotting and thorough study of the survey of the site. Reference to The
General Plan of Site will show the problems to be considered and the in-
formation required of such a survey. The boring logs and contours are shown
as is the proposed re-alignment designed to eliminate a skew crossing. Note
should also be taken of the extent of the stream data required. The next
step is the selection of the type of bridge to be used. It is at this point
that experience play an important role. A great many factors enter into
this choice, many of which are covered in Sections A, B, and C of the Stand-
ard Specifications. Some of the principal points are: a minimum vertical
clearance of one foot shall be provided between maximum high water and the
superstructure, the channel opening shall not be impaired, and the footings
for piers and abutments shall be so placed that there shall be no danger of
failure by erosion. Other considerations are the factor of economy, good
practice, allowances for expected future increases in traffic flow, and the
esthetic factor.

The first step was to specify a MM' clear roadway -ith one 5'-O" and one
2'-6" walk due to the close proximity of the Village of Comstock. The type
of structure was then debated. With the proposed width of roadway a through
truss or girder was out of the question due to economy. It has been found
that such structures are uneconomical for widths greater than 30', except
under special conditions. A deck truss or girder would also be a futile
consideration due to the lack of headroom. The next consideration was that
of multiple spans structures. It was finally decided that a three span,
reinforced concrete slab, deck girder bridge would be the most economical
and intelligent choice for the existing conditions. This type of bridge

can be economically designed in the width desired, the necessary vertical

_ 5 _

clearance could be obtained, and the channel openings would be adequate.
Accordingly this choice was adopted.

The next problem was the choice of piers and abutments. The boring logs
indicate that the soil was of such composition as to have a bearing power

of between 3 and 5 tons per square foot. The control factors were that the
top be of sn‘ficient width to care for the bearing plates and there b pro-
tection against erosion. In the final analysis it was decided to use 18'
cantilever type abutments of reinforced concrete; the footi 2 elevation
being set at 756.0'. Two piers of standard section were used and of the
gravity type were selected; the footing elevations being set at 750.0'.
These tentative selections fulfilled all of the necessary conditions and
requirements and was the most economical choice for the conditions pecul-
iar to this project.

The deck and floor slab are the first problem. Articles 17, 18, 19, 20, 21,
22, 2‘4, 25, and 26 of The Standard Specifications of The Michigan State High-
way Department, as of 1936, cover the requirements of this portion of the
structure. Pavement slabs are usually of a specified standard cross—section.
There are so many varied theories and disagreements on pavement slabs, that
The Federal Bureau of Roads specifies a standard section based on the latest
available knowledge. The strength of such a slab is more than adequate
beyond any doubt. The steel reinforcement is also prescribed for the same
reasons. The rules listed in The Standard Specifications are for use in
detailing the sections. A pavement slab 7.5 inches thick was used witl
standard steel placement. An additional 13/16" was added to the thickness
of the slab to allow it to fit over the flanges of the girder. In com-
puting the dead loads, a 1/2" allowance was made for future wearing surface.
A parabolic crown providing roadway drainage was computed in the following

manner:

C . .0018? R2 Where 0 - crown in inches
R.- width of roadway in feet

0 . (00187) (ru)2

0 n 3 S/S inches
The curb and sidewalk with their steel are also a matter of standard section,
being between 8 and 10 indhes in height. In.this case a height of 10 inches
was used at the curb and 10 1/2 inches at the outside edge, the 1/2 inch pro-
viding for drainage.
The railings and requirements are covered in articles 25 and 35 of The
Standard Specifications. Like the majority of the deck, the railings are
standard, consisting of reinforced concrete posts with steel grillwork
between. The spacing of the posts is usually between 8' and 10', he latter
figure being the maximum. The spacing is proportioned so as to preserve
symmetry, the grill being designed to fit the s.acing. On bridges having no
curb, these railings are designed to withstand the shock of a colliding
vehicle.
The last step in the design of the deck is camber. Camber has absolutely
no structural value but is purely a psychological factor. Under the action
of the dead loads, the beams will deflect a certain amount causing the fascia
and shadow lines to show a decided sag. This action causes some anxiety in
the mind of the average motorist wh does not understand that it is a nat-
ural reaction. To overcome this appearance of failure, concrete is added
to the top of the slab along the urve of a parabola parallel to the gird-
ers. Thus, under dead load deflection, fiie shadow lines and the fascia

appear as straight lines. It amounts to filling

, in the dead load sag with
concrete. Camber concrete is placed along a true parabolic section, the

offset at the center being computed as follows:

-7...

7
Defl. (flax.) : “W13 W': Total Dead Leaos
:1h7‘“
go’s-BI
The offsets for various other points are then.found by use of the parabolic
formula YB': ex. The camber diagram for his structure is shown below and

allowance must be made for this when placing the slab forms.

fauna ‘A’orla’ @KZ/ée /or3zfi Lee/1,4,2;

.
9/6”
////6 :1
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CAMflfB D/A GPA/W
This completes the deck of the bridge and the next portion of 'he bri‘ge
to be considered are the girders.
According to the specifications (77) the girders for the bridge are to be

h.F. rolled sections. The first step in the design of the beams is to
determine the spacing to be used. Good practice dictates that the spacing
used with concrete floor slabs shall be between M'-6" and 5'-€" and the
outside of the f ange of the outer beam must be at least h" from hie fascia.
The problem is to deternine the most economical spacing of the beans, i.e.,
whether it is cheaper to use a small spacing with a small section or to use
a larger section and a greater spacing. Two control factors affecting the
sis particular case are that raffic must be allowed over one

half of the bridge while the other is being constructed, and constructi n

0

joints must lie over a girder. With these facts i. mind the spacing was
set at 12 spaces at M'-3 3/4". The spacing having been determined, the

beans may now be designed and a section selected. (See Articles 77 and

_ g _

79 of The Standard Specifications.)

Using a depth ratio of 1/20, the tentative depth of the beam was set at 30".
Referring to a table of standard sections a 30 x 10 1/2, 116 lb. W.F. beam
is assumed. The beam is now checked for dead and live loading plus impact.
The dead load is made up of the weight of the deck and the weight of the
beam. The live load is the standard H—2O loading plus impact.

Dead Load Moment: (See Article 30)

The weight of deck supported y one bean is equal to 1/2 of the

span on either side of the beam in question.

 

 

 

 

 

 

 

 

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" e éyscf'a fie/w; 36/, 2 $7672 ,
.e ’-/76’ L 2 fi/Va'
Ave/I 453%
__J_. __L_ ;Zl_.
Slab : (11 7/5 4 3 5/8 4 3/b) (ht-3 3/h) (150) — 639 lbs./ft.
Future wearing surface - 2O lbs./sq.ft. - So
Beams - 120
Diaphragms (Est. 5 lbs./ft.) -

 

a
ll

5,
sue lbs./ft.

D- L. hon. = w12

 

It should be noted that the span was not taken as 50' but some 13" less.
This is due to the fact that the beams are designed from the center to
center of bearing. r"he center of bearing being considered at the point
where the beans fit over the anchor bolts.

Live Load Moment: (See Articles 31, 32 and M3.)

The live load moment assumes the loadin_ to be so placed as to obtain the

maximum possible moment. This may be accomplished by so placing the loads

l
\O
I

that the equivalent of one complete axle load comes upon the beam.

 

 

 

 

 

 

 

 

 

 

 

2‘:
32A. /¢.0' 81:
33/ _ /.¢’ _ 42.6 ’ //. 9'
l 46.92’ 8
EM =0
8: 32" é’ggf‘rfl” = are by: z = fine/.2 =/za.é¢e

O
The distribution factor is found by application of Article #3, and in this
case is found to be .Mjl, assuming a traffic lane of 10' in width. The

total live load moment is then found to be
4.1. M u/7. 8x ash/1.4a”
=VCCZ¥rlédb {44

The impact allowance of the live load is found by application of the

formula given in Article 37:
.Z a 4+20 = M
611‘20 (6)670) “130)
=.29G?

Afi“~$bao"fagyn44

Impact Moment:

1.4/11. x1 = /7ZJ.r..8/.9
“38144) 64

Total moment:
75‘A/ 460.4% =33”me 25¢

The section modulus, Z, is equal to the total moment divided by the allow-

able stress in the steel. (Section F of Standard Specifications.)

Section Modulus:

1Q906ND
“HJ34¢922JL Agégpéi’

- 10 -

Referring again to the table of standard sections it is found that the beam
assumed provides a section modulus of 327.9 in.3 The next smaller size has
a modulus of onl' 299 in.3 so that the assumed beam is the necessary size
for the bendir? requirements.

In beams of this length bending moment rafizer than shear is the controlling
factor. The shear, however, is checked as a precautionary measure. The

maximum shear is found to occur at an infinitesimal distance from the

support.

The dead loads are the same as for the bending moment.

4 . w! _ 3426.43.93
2 ' .e

= 20. My»;

Live Load Shear:

For live shear, the loads are placed on fize beam in the position

 

 

 

 

 

 

 

shown below. léé #40,. 4A
xbéu: '
.SXear
4&393’
" ' ,e . /. l4é. e
.£.=:/Ei£iélé.
Impact:

The same impact allowance is made for shear as for bending.

I= .2/9: /8.86 =¢</.aé.

The maximum shear occurs at the section indicated above and is equal

numerically to the reacticn.

V ”.20. 7*/43.86+‘¢. A?
=‘fiE2171945mr

The area required for shear is:
_ V __ 43. 7x/doa
.4 5 A2000

2 efilfizAflz

The girder in question gives a cross—sectional area 3u.13 sq.in., which

is more than adequate for the shearing demands.

It will be noted that this choice of beam and spacing is somewhat lec-
onomical. As mentioned before, however, the requirements of the deck exert
a controlling influence on the beam selection. These ideas are now con-
sidered obsolete, construction joints having no control of the beam spacing.
Under the existing conditions the assumed beam will be accepted.

To provide against lateral buckling and bending, diaphragms are specified

at the third points of the girders (Article lab). The diaphragms are con—
nected to the beams by the use of hitch angles, E/M in. rivets being used
throughout. The intermediate diaphragms consist of the largest size plate
which can be fitted between the flanges of the girders. The sections at the
ends of the beams consist of fairly small channels, connected to the girders
in the same manner as the intermediate type. These latter members serve a
slightly different purpose than the intermediate sections. The expansion
distance between the girders plus the necessary steel coverage in the con:
crete deck slab leaves some little distance of the slab without any rein-
forcement. To avoid the danger of failure at these points, the slab is

cast to the top flange of these diaphragms, thereby giving a supporting
effect to the slab.

The bearing plates in this case are specified by The Federal Bureau of Roads
and consist of structural plates 10" x 3 l/2" x l'-O" continuously welded to
he lower flange of the beams. There are two reasons for specifying a plate
of these dimensions. In the first case it tends to raise the girder off of
the abutment bridge seat and gives free access to all parts of the beams

for the purpose of protective painting. The second reason is that a plate

of this size insures the prOper distribution of the load over the piers

f‘
— C -

and abutments and avoids the introduction of a large concentrated loadin5
with the deformation of the beari.e plate. In ordinary desi5n the bearing
plate would be desitned for the actual loads and would not be of this size.
The next point to be considered is that of expansion. Articles 110 and 111
of The Standard Specifications state that provision shall be made for ex-

pansion and contraction to the extent of 1/8" per 10' of span. For s ans 70'

*G

or less, the erpansion may be cared.for by metal plates sliding upon one
another. In this case 1/2" steel sole plates were used; the bearing plate
ridin n5 upon them and forming: an expansion bear Nng. The sole plates have no
movement, being firmly anchored to the abutment and piers. The movement of
the beams is taken up by means of slotted holes in the expansion ends of the
beans flanges and bearing plates.
The last point in the design of the superstructure are the anchor bolts as
specified in Article 117. The bolts used were 1" in diameter, l'-6" in
length,.and provided.with hex heads. The pier ancl ors were threaded for a
lcn5th of 3 1/2" and provided with nuts and washers for securely fastening
the beam to the substructure. The abutment anchors are left unthreaded and
the flanges of the beam are not dr 'lled at this point due to the possibility
of becomin5 fouled with concrete when the b ackwall is cast. To insure firm
anchorage the bolts are so desi5ned that at least 10" of the bolt may be im—
bedded in the concrete.

The superstructure havin5 been designed, attention is no: focused on the sub-
structure. The Standard Specifications 5 +ate that such strictures, to resist
file pressure e: certed by fill material, shall be designed in accordance with
Ranlcine' 5 Theory of pressure distribution and that there shall be no structur

designed for an equivalent pressure of less than 30 lb./sq.ft. To provide
for live load, an equiv: lent surcharge of four feet shall be applied over all

surfaces subject to highway loadin5.

The practical design in this case utilized the equivalent pressure of 30
lb./so.ft. and assumed as a starting point, dimensions similar to other

A.

structures having like characteristics. The assumed cross—sections are then

checked to ob ain the most efficient size. Care must be taken, however, to
insure stability of the structure and to keep the pressure within the bear-
in5 power of the soil.
Plate I shows the size and shape of the section selected and the pressure
distribution trian5le. Abutments are usually checked for three cases. First,
backfill only; second, superstructure loads and live load surcharge; and
third, superstructure live and dead loads with no live load surcharge. All
cases are checked but the third case is usually taken as the criteria ”us to
the fact that there must be no failure of the wall under backfill and truck
pressure before the deck is placed.
Case I - Backfill only.

Moments are considered about the toe of the footing.

OVefvé/r/I/léf Mm eo/

 

{gr/4.25 Vé/ox z 42 e //, 460
#43,: @25an 75 *, #14620
36870 4/5.

Res/:54”? M”? e’”! ‘ /,36.96/A " 65750 #/A
Beau/710% Momen/

.79, 3/0/3/ /A
_. .293 ..
AEP";EEZEEfi%2-JZI(/5{
M'a’J/e TAJ— .gé’ = 233/?!

/, 3.93/0 __
25170 ‘K ~53?

fl

Under these conditions the wall is safe against overturning and the resultant
pressure falls within the middle third. The wall also has a safety factor

of 1.53 against sliding.

_ 1h _

08 58 II - Siners‘"*ct eL. L. and D. L plus L. L. Surcharge

0 vet/0,7”? Mame/7%! - 35 M0#//.
E 95/374177 Momen/ ' / 7306/5 -' 83 930' 44/1.

3: %——9=2. 66;!

3 33980
‘5 / 332327 =2.2/

M/b/J/e flx'ra/' ¥= 2.835.!

The structure is also safe under the conditions of the second case loading.

Case II - Superstructure L.L. and D-L. No L-L. Surcharge.

0 var #4077 ”ff Mom ew/ " 258 70 M/A
£3313 11/? Mame/7%- /68é6/J. ’ 903% ’44 fl
.6354/449/7/ fl/amezr/ " 6 W 7 0 ’44 [1.

_, egg
,8- 7’3370 3,412.44

Ala/0% 723'n/v 3.834

/_, 903¢0
' ' 25874

‘36"

The abutment is also safe under the third condition of loading. The resist-
ing moment is sufficient aggainst overturnir", the result: nt falls within
the middle thir , and the wall is safe against sliding.

The results of the last computation indicate that to some extent the wall
might be more economically designed by the use of a more exact application
of Rankine's Theory using a pressure coefficient for the type of soil in-
volved. The saving in all probability would be of less value than the time
i i

consumed in rechechin? tim design. The abutmm t as it stands is adequate

for the loadings.

q ..

fire streng th of the wall must now be de velOped by the introduction of re—
inforcing steel. The stem steel will be computed first.

Stem Steel:

 

Overturning Mom. at top of Footing
V3 4805 -— M= ZWéO/K/A

/ AZ. 2¢/6 01/
sz'o/ mace 1.825'7/75' /. 053/”. 6

/'¢@ 7" /-&¢"/'/7.‘a
.2 _. 4306' _. .
2:024]! " /JDr-8‘76‘x/Z~5" " 2.09/4.

./‘VF£469,9W” " 4114a?/}7.

Overturning Mom. 3' above top of footing

M - 2270 ’4! M.

__ Al 3 /22 7&1/2
i ‘41.! /£doox.87.s'x/7.5-

-05‘36’/l.7.z

are /'¢@ /6"’

As the height above the top of footing increases, the moment decreases
rapidly. Therefore, the wall steel is spaced at 9" and every other ar is
cut off M'-O" above the tOp of the footing.

The steel necessary in the footing is the next step. The footing nressure

at heel and toe are found as follows: The weights used are the same as

_ 15 -

used in checking the waliwdimensions.
.. £9;
P-‘g—[fl‘ b]
= $514M + «4.25.3, 4e)
5 [7" 5.5

=3520 /é.//9€z 0/ 7403
9.80 /6./#& 0/ Aee/

 

 

3.5.1750 =32;

 

 

 

 

 

 

 

 

e ¢’-3" #9” zté’
‘Q a
est g Q
i» °° t t
\ '5
§ 5:: a 5.;
73¢:

These values are well within the bearing power of the soil, which, as stated
before, runs between 3 and 5 tons per square foot.

Toe Steel:

24/5 =v0

.2350 12.5 = 5.950 x /5"’ =- 8.9250

7‘57. 3-5.: 957120 .-..- / 9/30
V: é 90 7 /06’380 ”'7. /A.

 

 

’45 :6 JO’
3 /08380 ._
/aooox. 8767.37
='.22<527)258'
i§¥4¢flé942P‘-:.JZ/zéi‘5

‘

5-0 7‘5?“

6 90 7'
Asvx. 8757.8 7

= /. 771/7.
5% I/¢@/z”= /. 94”}.

 

V= was” M= /06’c5'oo ”'7. /z

A 3. = /06’6'00
.5 " {,J'a’ /6’000x. 875x27

=.Z¢5/}713 .
igz'fljéibé?wéuwj?97753

" _.__..._—-—-—--—— =
50 2'7?“ Army. 87.57.87 . 908/27.
” O
eg'era/z a/ 24,”.
This constitutes the is in steel but in addition reinforcing must be pro-
vided for shrirkage, tenpera.ure, and beam eXpansion stresses. Article So

of The Stan ard Specifications states that such steel shall be placed normal
to the main reiniorcing and shall provide not less than 1/8 sq.in. of re-

c. . J-

inforcement per foot of width of surface, an: shall be placed at all exposed

Two way steel was placed in the top and bottom of ti e footin.;3 and in both
faces of the wall in accordance with this speciIication. Ref rence to steel
tables indicated that 5/8" ¢ and 1/2” ¢ steel suitably placed gave the best
results.

The selection of the elevation of the abutment footings are of special in-
terest in this on se. Reference to the genere.l plan of structure will s?ow
that this po oint is some 7' above the bed of stream. The usual practice is
to place the footi 3 at least two feet below this point, preventing under~
mining of the footing and possibility of failure, and as a protection against
heaving resulting from frost.

To follow that practice in this case would involve a much larger wall section
and greatly increase the cost. Again re: rri 3 to the plans, it will be seen

that interlocking steel sheet pilin? was driven to the waters edge in front

3.)

of the abutmen and left in place. in this manner the cost was substantially

reduced and a safe abutuent 'iirovide d..

_ 13 _

The gravity type piers of reinforced concrete measured 2M'-O" from crown of
roadway to bottom of footing. A.standard pier section was utilized, dimen-
sions being selected to fit the individual conditions. he plan and eleva-
tion of the section are shown on Plate II. A section is also shown on the
General Plans of Structure. It will be noted that the rounded noses of the
piers offer a minimum amount of water resistance, thereby reducing erosion,
and at the same time offer a pleasing appearance. The control factors in

the design of such a pier are that the top of the wall be of sufficient

width to hold the beari-3 plates and that the stability of the wall is
maintained.

The results of previous designs are often utilized as a starting point for
new designs. The superstructure loads and the weight of the pier are computed
and divided by the area of the base giving the unit bearing at the base. The-
oretically the design is charred until the most economical dimensions within
the bear'ng power of the soil is obtained. Care is exercised to see that the
will is kept within stable limits.

Bearing of Pier:

 

 

feight of Footing - 153,156.25
Weight of Wall - 5Mo,u87.50
Superstructure — _370,200

L.L. & D.L. 1,098,842} lbs.

fx 1 ‘ ‘ r‘», 7'
1,0;8,844 / use . 2910 lb./ft.
The bearing of the pier is 2510 lb./sq.ft. which is well within the bearing
5.“ 1 ‘
power 01 as 5011.
This is the theoretical procedure in the design of the pier and is followed
as closely as conditions will permit. In this case the pier is of more
massive construction than is absolutely necessary. One reason for this is
that the necessary width for the bearing plates must be provided along with

the necessary area for bearing. The other reason is that it looks safe and

is more pleasing to the eye.

_ 19 -

At times it becomes necessary to sacrifice economy for psychological and
esthetic factors.

The reinforcing steel in the pier section is mostly for shrinkage, tempera-
ture, and the stresses set up by the expansion of the beams. There is also
assumed to be a slight bending introduced at the top of the pavement slab
by the traction of the moving loads. These stresses are cared for by the
use of slightly heavier steel than would be used ordinarily. Dowels of

B/M" ¢ steel were used to bind the wall to the footing. These extended up
from the bottom of the footing into the wall a distance of 2'-6". To take
any bending introduced in the wall B/M" ¢ bars were placed vertically up
both faces of the wall. The remainder of the wall steel was placed in a
horizontal position along the face of the wall, B/M“ ¢ bars being used in
the center section and 1/2" ¢ bars in the rounded noses.

The actual design of the structure is com lete at thi point. The wing walls
are merely continuations of the abutment sections and the back wall is cast
monolithically with floor slab to the bridge seat, and is intended to keep
the backfill from spilling out from between the girders.

The de ailed drawings are not taken into consideration in this paper, as they
have no bearing on the design features. The detailed drawings are very come
plete plans of the structure intended for the use of the construction men.
They show the placement of the steel, water stop, extent of pours, and so
forth.

In addition to actually designing the structure, the engineer is als re-

0

quired to calculate the amounts of wet and dry excaration, auantities of

.5

concrete, reinforcing steel, structural steel, railing, field.painting,
and in fact the quantities of all materials entering into the structure.
He is also required to prepare a set of specifications supplemental to

the Staniard Specifications, specially applying to the bridge in question.

The engineer sust also in Mliie w'th the plans an engineer's estimate of cost.
A set of the Supplemental Specifications, quantities, and the engineer's
stimate of cost actually used in the bidding and construction of this bridge
is included in this paper. It should be noted at this point that the
authority for all desi 3n features is "Specii'ications for the Des'gn of High-
way Bridgges as adopted by the him igan State Hi3heay Department January 1935".

_C‘)

This structure was placed under construction and completed during the latter

portion of 1330. Below are sW1o.n several View of the oridg e as seen July

u.

19h2. Ther adway views show the roadway looking in each direction. Note

.

the expansiveness of the deck and the manner in.v1ri en the roadway continuity

has been preserveda rose the structure. The traffic csa pacity of this
structure is apparer nt. The elevation of the bridge is shown from the upstream
side. The structure preser .ts a pleasin“ amap m1ce and this particular pic—

ture gives a fine indication of the individual features of the structure.

It a so indicates the importance of the car aber as seen by the horizontal

}._J

I 1 o
‘

hadow lines at the fascia. T31e next two pi ct 11“ es how the railings and the

TD

beans and diaphragms. In the background of die latter may be seen.the large
aring slabs elevat1in3 the beams from the piers. The last picture shows one

of the bridge plates required on all Federal Aid Projects. Similar alates are

usually placed on all State projects.

The structure has given satisfactory service since its construction and it is

felt that the cost of replacing tb 1e old or dge has been more than justified by

the inc: ea 1sed cap acity and improved apps rance of the new structure.

A resume of the material presented in this paper will show that the responsi—

bility of the bridge engineer and designer is no sma ll matter. As has been

rejeatedly pointed out throughout this paper the problem of the bridge en-

gineer is that of providi13 a safe structure that is the most economical under

iar to a particular structure. The engineer must be

a

the conditions pec1
able to exercise his ingenuity, keep the cost to a minimum, and at the same
time remain on the safe side. A.good illustration of this is shown in the
placing of the abutment footings at a high level and protecting them by he
use of steel sheet piling. The ancient bridge builders did not have this
problem to contend.with. Cost was of no importance to them and they built
the structure as they pleased. If it failed, they merely rebuilt it on a
larger, stronger scale. The modern economic structure would not permit this
type of construction. Any individual of normal intelligence could construct
a safe bridge by using enough material to insure the strength; he duty of
the bridge engineer is to scientifically design the same structure on an

economic basis.

LOC2 ion: 0n Count; Road in the village of Constock between stations 5
plus 92.5 and lo plus M7.0, in Section 1;, Town 2 North, Ran e 10 ?est,
Constock Township, Kalamazoo County, crossing Kalamazoo River.

Descrrgtion: The proposed work consists of the construction of a bridge
structure and *

 

the grading 2nd surfacing of the apnroaches together with
incidental work and the removal of the existing stricture.

The new ‘ridge substructure consists of two reinforced concrete canti-
lever ty oe atutnents 18 '-0" high, measured from crown of roadway to bottom
of footings and 2 reiniorced concrete piers 2H'-0" in height, nea sure from
crown of roadway to bottom of footing.

The new bridge superstructure consists of three 50'-0" rolled bean
spans or th deck gird tgrpe, W1th 4M'- 0" clear ro nvay with two s1deW2lLs,
one 5'-0" in width and9 the other 2'-o" in width. Tie structure is on a 90
degree aisle of crossing and 0.00% grade.

(I!

ITEMIZED BID

 

 

UNIT

T333 05 WCRK QUANTITY UEIT P1.I 33 TO AL

STLWCT‘
Lump

Re.'ioval of Existi n6 Structure Sum
Dry Excavation 415 Cu.Yds.
Wet Excavation 780 Cu.Yds.
Steel Sheet Piling Left in Place 1771.5 Sq.~
Concrete Grade A Suostructure 732.6 tu.Yds.
Concrete Grade A Su perstructure 337.6 01.1ds.
Cement 1516.3 Bbls.

teel R; in fiorcement 702MO LbS.
St: Mic;ur Steel Fabrication and

Erection 256032 Lbs-
Railing 332.3 Lin.Ft.
Field ainting tructural Steel Lump

1nd Railing Sum

Riiooed Sir1ace Fini§1 MM52 Sq.Ft.

- 23 -

 

 

ITEM OF WORK QQAHTITY UNIT T0
STRUCTUPE - (Cont'd)

Copper Water Stop h¥6 Lbs.

1/2" Joint Filler, Soft

Asphaltic Felt 36 So.Ft.
1" Joint Filler, Soft

Asphaltic Felt 61+ Sq.Ft.
Porous Backfill 9M Cu.Yds.
Sodding Slopes 325 Sq.Yds.
AEPRQACH GRADING
Earth Excavation 3000 Cu-Yds.
Gravel Base Course - 5" Com— ,

pacted 2000 Sq.Yds.
Gravel Surface Course - 3" ,

Compacted 2000 Sq.Yds.
1+" Concrete Sidewalk 377 Sq.Ft.
7" Concrete Sidewalk 55 Sq.Ft.
Concrete Curb 80 Lin.Ft.
10" Vitrified Tile in Place 106 Lin.Ft.
Grade .3: Concrete 0.]. Cu.Yds.
Inlet 2-Cover D 2 Each
Removal of Existing C.M.P. and Lump

Head walls Sum
Driveway Gravel 10 Cu.Yds.
Removal of Old Walks Ills Squt.
Class A Seeding 0.20 lines
Maintaining Traffic Lump

Sum

TOTAL OF BID

 

 

- 2h -

SUPPmiENTAL: SPEC IFICATI OHS

 

Maintaining_Traffic

Traffic Shall be maintained at all times during construction operations. The
contractor shall maintain traffic over the existing bridge and roadway until
he has completed the west half of the structure and approach grading and
surfacing sufficient to maintain 2-way traffic thereon, after which the old
bridge shall be dismantled and the structure and approaches completed, The
contractor shall then remove the existing bridge and substructure and com—
plete the east half of the structure and approach grading and maintain traf-
fic over the west half of the bridge and roadway. The lump sum item for
maintaining traffic shall include the construction of a temporary guard rail
on the structure and approaches, complying with the requirements of section
5.03.0h in so far as applicable.

Cofferdams

All cofferdams for the structure shall meet the requirements of Section 5.05
of the Standard Specifications except as follows: No payment will be made
to the Contractor for "Cofferdams" as such, but the cost thereof shall be
included in.the prices submitted by him for the various items of work under
this contract.

Removal of Existing Structure

A.lump sum bid for the removal of existing structure shall include removal

of trusses and floor system, and the substructure to 3' below existing ground
line or finished slopes as called for on the plans and any portion thereof
that comes within the limits of the construction of the new substructure.
Broken concrete shall be disposed of as riprap as directed by the Kalamazoo
County Road Commission. The existing trusses and floor system shall become
the property of the Contractor and shall be completely removed from the site
at the completion of the Job.

Forms

In the event that wood liners are used for face forms, backing may be of
lumber not less than B/M" actual thickness, laid without Openings and with
true and uniform surface on the side to which liners are applied. Studs
shall be spaced not more than sixteen times the actual thickness of backing.

Floated Surface Finish

After striking, bridge seats shall be finished with a wooden float to a
smooth even surface without any unevenness of more than 1/8 inch showing
under a ten.foot straight edge or more than 1/16 inch under any bearing
plate.

The surface of the floor slab which will be subject to highway traffic shall
be finished as specified for Surface Courses and Pavement, Article 11.01.03
(p_and g) of the Standard Specifications in so far as applicable. The Con-

_ 25 -

tractor shall furnish a 10 foot straight edge for the purpose of testing
surfaces thus finished. Taps of walks shall be finished as specified.under
Article 7.07.03 (h) of the Standard Specifications in so far as applicable.

Structural Steel

The requirements for Mill inspection is hereby waived. Shop inspection will
be required and will be paid for by the Kalamazoo County Road Commission.
The Contractor will be notified of inspection arrangements immediately upon
receipt of information from.him as to source of materials.

Railing

The superstructure railing will be measured in lineal feet and will be paid
for at the contract unit price per lineal foot, exclusive of cement and steel
reinforcement, but inclusive of structural steel, concrete and surface
finish.

Rubbed Surface Finish

Rubbed Surface Finish shall be in accordance with Article 5.10.03 (h) of
the Standard Specifications except as follows: In lines 12 and in of the
first paragraph, change 1 foot to 2 feet.

Shop Painting of Structural Steel

The first and second paragraphs of Article 5.13.03 (g) 5 of the Standard
Specifications shall be superseded by the following: All paint for shOp
coat shall be Michigan State Highway Department Painting Mixture No. 1.

When fabrication is complete and.the work has been accepted, all steel shall
be given one complete coat of paint.

Field Painting of Structural Steel and Railipg

The fourth.paragraph of Article 5.13.03 (g) 6 of the Standard Specifications
shall read as follows: Surfaces to be riveted in contact shall not be paint-
ed. Surfaces which will be inaccessible after erection, except surfaces to
he in contact with concrete, shall be painted with such field coats as are
called for on the plans or authorized.

After the completion of all concrete work which is supported by steel work,
all exposed surfaces shall be thoroughly cleaned and.the Contractor shall
apply one complete coat of Painting Mixtures No. 2 and 5A to the steel of
the new structure, including the railing. All paint is to be furnished.by
the Contractor.

The lump sum bid for "Field.Painting-Structural Steel" shall be payment in
full for all items of cost necessary to complete the work as specified.

- 26 -

Handpicking of Coarse gggregates

Coarse Aggregates for railing posts shall be handpicked of objectionable
particles to the satisfaction of the Engineer. No additional payment
will be made for this work and cost of same shall be included in contract
unit price bid for Railing.

Earth Excavation

This work consists of all excavation, other than foundation excavation
necessary to complete the approaches as called for on the plans, or as
otherwise directed by the Engineer. .All work shall be done in accordance
with the provisions of the Division 2 of the Standard Specifications except
as follows: The Contractor shall secure his own borrow pit, or borrow pits
and right of way for obtaining same, and no allowance will be made for
overhaul in connection with this classification of work. Borrow pits can
be secured approximately one-half mile from the Job site.

Rounding_Slopes

Where trees or other restrictions do not interfere, the top of backslapes
and the bottom of fill slopes shall be rounded on a vertical curve varying
from four foot in length in case of cuts or fills less than.four foot to
an approximate maximum of ten.feet in length in case of cuts or fills
greater than sixteen feet. All transitions in length of vertical curves
shall be gradual and so executed as to present a uniform and attractive
appearanc 8 o

Guard Bail

The placing and furnishing of cable guard rail is not a.part of this con-
tract. All cable guard rail as called for on the plans will be furnished
and placed by the Kalamazoo County Road Commission on the completion of
this contract.

Public Utilities
All public utilities interfering with the work will be moved by others.
Removal of Existing Guard Bail

The cable guard rail at the ends of existing bridge shall be removed by the
Contractor and stored at the job site for salvage by the Kalamazoo County
Road Commission, and the costs thereof shall be included in.the lump sum
bid for removal of existing structure.

Removal of Rubbish
The Contractor shall remove all rubbish at the south end of the proposed

structure prior to making the approach grade and shall be Considered as
incidental to the items of work as specified in the itemized bid.

- 27 -

RLght of Way

The right of way required for this project has been secured as shown on
the plans.

Steg; Sheeting Left in Place

Sheet piling left in place as specified on the plans may be used sheeting
in good condition. It shall be of the interlocking type and of a section
weighing not less than 22.0 lbs. per square foot. It shall be driven to
the depths below bottom of footing as shown on the plans and.with tops
driven to or cut off at the elevation specified.

Removal of weed Piling in River

The Contractor shall cut off at bed of stream and pull all old.wood.piling
under existing bridge and in abandoned railroad trestle immediately west
of the existing structure, and the cost of cutting off or removing the
piling shall be considered as incidental to the items of "Removal of
Existing Structure" as specified in the "Itemized Bid".

Progress Schedule

The progress schedule shall provide for the completion of the following
units:

Substructure, West half, July 15, 1939.
Superstructure, West half, August 1, 1939, including traffic provision.
Substructure complete, September 15, 1939.

Job complete including approach grading and surfacing, November 1, 1939.

Shrubbegz

Shrubbery interfering with or in the way of approach fill slopes at the
Nertheast quadrant shall be removed and reset in a satisfactory manner and
any losses shall be replaced.with good live stock of the same variety.
Such work shall be considered as included in the price bid for "Earth
Excavation“.

- as -

ENGINEERS ESTIMATE 0F COST

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bridge File No. Bl of 3915-21 Date February 23, 1939
Location In the Villagggof Comstock Kalamazoo County

Overall Length 150%" Roadvag uni-0" ' Spans 3e 50i-0"
Overall Width 531-11" Walks __1; e 2'!" a. 1 @fl-O"Grade 0.05’

Angle of Crossing 4900 Type of superstructure Steel Girder

Type of Abutments Cantilever Height 18'-O"

Type of Piers Concrete Height 2M'-0"

STRUCTURE

Removal of Existing Structure - Lump Sum $ 1,000.00
Dry Excavation - 1115 Cu.Yds. e .50 207.50
Wet Excavation - 780 Cu.Yds. e 3.00 2,3u0.00
Steel Sheet Piling Left in Place - 1771+.5 Sq.Ft. @ .80 13419.60
Concrete Grade A Substructure«- 732.6 CutYds. @ 16.00

includes cofferdam and pumping 11,721.60
Concrete Grade A Superstructure - 337.6 Cu.Yds. 0112.00 9,051.20
Cement - 1616.3 Bbls. e 2.00 3,232.60
Steel Reinforcement - 70.2% Lbs. e .011 2,809.60

tructurel Steel - Fabrication and Erection -

256,0LL2 Lbs. e .0u5 11,621.89
Railing - 382.3 Lin.Ft. @ 5.00 1,911.50
Field Painting Structural Steel and Railing - Lump Sum 600.00
Rubbed Surface Finish - 11152 Sq.Ft. e .10 #14520
Copper Water Stop - Rho Lbs. @'.NO 178.N0
1/2" Joint Filler - Soft Asphaltic relt -

36 Sq.Ft. @ 050 18.00
1" Joint Filler - Soft Asphaltic Felt - 6h Sq.Ft. @ .70 1411.80
Porous Backfill - 9M Cu.Yds. e 1.00 911.00
Sodding Slopes - 325 Sq.Yds. @».25 81.25

Structure = $Ul,777.1u

(Estimate Continued)

APPROACH GRADING

Earth Excavation.— 3,000 Cu-YdS. @i.40

Gravel Base Course-5" Comp. - 2,600 Sq.Yds. e .50
Gravel Surface Course-3" Comp. - 2,000 Sq.Yds. @,.35
M" Concrete Sidewalk - 377 Sr.Ft. @ .20

7" Concrete Sidewalk — 55 Sq.Ft. €7.30

10" Vitrified Tile in Place - 106 Lin.Ft. e 1.00

Concrete Grade A.- 0.1 Cu.Yds. 0'20.00

Renoval Existing C.M.P. and Headwalls - Lump Sum
Driveway Gravel - 10 Cu.Yds. @12.00

Removal Old Walks'- H18 Sq.Ft. ©i.lO

Class A Seeding — 0.20 Miles @ 100.00
Maintaining Traffic - Lump Sum

Concrete Curb - 80 Lin.Ft. @ .80

Approach Grading

Total Estimated Contract
Engineering and Contingencies 10%

Total Estimated Cost

$ 1,200.00

1,300.00

930.00

75.90

600.00

\

6443;

n.530.70

s M6,307.8u
_E,6”0. 8

_ 30 _

 

 

 

Roadway Looking North Roadway Lo okim South
Toward U. S. 12 To mva- d 00 mstock

 

 

 

Elet ati on Looking Downstream

 

 

 

 

Girders and Piers Showing
Intermediate Diaphragms

 

  
   

 

 

 

Bridge Plate

rm”

PIBLIOGHAPE:

 

Bridge Architecture
Watson, Wilbur J.

Bridges in History and Legend
Watson, Wilbur J.

Bridges
Whitney, Charles Smith

Portland Cement Bulletin

S;ecifications for the Design of Highway Bridges as
Adopted by the Michigan State Highway Department,

’\

’1_f
January 1930

Sets: A great deal of the material used in this thesis has
been obtained from practical experience and personal
interviews with the persons mentioned in the intro-

duction.

.‘1.4w.

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