1.
NO· 141
GOVERNMENT OF WEST PAKISTAN
HIGHA!AY
DEPARTMENT
/
LAHORE
CODE OF PRACTICE
HIGHWAY BRIDGES
1967
SAEED AHMAD, T.Pk., P.S.E.1
DIRECTOR GENERALHIGHWAYS
HOWARD, NEEDLES, TAMMEN & BERGENDOFF, INT. INC.
GENERAL HIGHWAY CONSULTANTS
2.
Tl1e purpose or tlLtn <,;Jd~.l ot ?ra.c~:ic,L "1.:; to e.stabl:.sh
tnini1nun1 standards and 'l'DLic:i r: p.:cc::;d,Jres End p~e.cti<:efl
for
the
des:Lgr:
ot' us!.1al
~ c.f 1tigtr~va:.r
struct:.:.:...~~s :_n
th.e
Province of West Pak1stan.
T~·~au~h
s~ch
st~sdarJization
of
methods, a Tnuch greater
be realized in design
With this in mind
this first ~ditlon of th2 r~de hs~ b~en written co cover
pr i.mc;.r t
reinforced and ~r~strsssed conc=~te design Referenc.e has. be.er1 tnade to th"E.~ :s·l_it·!.sh l;t~::..r:.dard Spec.ific;:rtions
for those special cases vit1~:re ~:t2;:::1 desLgn ~~~ill be required.
ex pet iei:JCe and the iutu_rs
c_~.;s.i.l~.:;~)
Ll.i ty of more econou1ical and
different structural mate~ials wiLl dictate the necessity that
this Cod2 be revised pericdtcally. It is expected that all
those respo.nsibl0 fer ::otructm:e designs 1<vi1l be alert to the
need for such revisions. Suggestions for updating the Code
along these lim':s are encouraged.
3.
CONTENTS
Article
SECTION 1  GENERAl, FEATURES OF DESIGN
1.1
L2
L3
1.4
1.5
1.6
1.7
L8
L9
l, 10
1.11
1.12
1.13
1.14
1.15
1.16
1.17
1.18
1.19
1,20
L21
Preliminary Data
Determination of Waterway Area
Spacing and Location of Piers and Abutments
Vertical Clearances
Restricted Waterways
Obstruction and River Training
Determination of the Haximum Depth of Scour
Depth of Foundations
Size of Culverts Openings
Length of Culverts
Width of Roadway and SidewalL
Clearances
Curbs & Safety Curbs.
Railings
Roadway Drainage
Supereleva.tion
Floor Surfaces
Utilities
Roadway Width, Curbs and Clearance for Tunnels.
Roadway Width, Curbs and Clearance for Underpasses
(undivided Highways)
Roadway Width, Curbs and Clearances for depressed
Roadway
1l
15
18
18
19
19
19
111
113
113
113
113
114
114
l15
115
l15
115
116
117
118
SECTION 2  LOADS
2.1.
2,2
2,3
2.4
2.5
2.6
2.7
2.8
2 ,.9
2.10
2 011
2.12
2.13
2.14
2.15
2,16
2.,17
2.18
T oads
...
Dead Load
Live Load
Highway Loadings
Standard TruckTrain Loading
Application of Loadings
Reduction in Load Intensity
Sidewalk, Curb, Safety Curb and Railing Loading
Impact
Longitudinal Forces
Wind Loads
Thermal Forces
Uplift
Force of Stream Current
Buoyancy
Earth Pressure
Earthquake Stresses
Centrifugal Forces
i
21
21
23
23
23
25
25
26
27
28
29
211
212
212
213
213
214
214
4.
Article
SEC'!'ION 3 3o 1,
DISTRIBU'I'IO:~
U? LOAI;S
Distribution of Wheel Loads to Stringers,
Lcr:git:.~dL1ai
Beams and Floor Beams
Distribatic.n of Loads and Design ot Cor:crete Slabs
Distribution of Wheel Loads through Earth Fills
31
32
36
SECTION 4  HILITARY l.0ADING
4.1
Loading
4.2
Horizontal Clearance
Distribr;tion of Load to 1.o::gitudinal Stringsrs
Impact
Distribat io:.~ cf Loads and Dt:'.s ig;:1 of Concret<.:>. Slabs
4.3
4.4
4,,5
!.;
1
42
42
SECTIO"N 5  illiiT STRESSES
5.1
5.2
General
Concrete Stresses
5 .. 3
ReinforcP.ment
5.4
Steel Stressr.:s
5l
52
53
53
SECTION 6  CONCRETE DESIGN
61
62
6. 3
Ge;:1eral Assumptions
Span Lengths
Expansion
6.4
TBea.ms
63
6.5
6.6
6.7
Reinforcement
Compression Reinforcement
Web Reinforcement
Columns
Concrete Arches
Viaduct Bents and Towers
Box Girders
6.8
6.9
6.10
6.11
c. "
uL
6··4
L:'t
B<::ams
66
66
69
616
617
618
SECTION 7  PRESTRESSED CONCRETE
7.1
7.2
7.3
7 o4
7oS
7.6
7.7
7 .. 8
7.9
71
71
73
73
73
General
Notation
Design Theory
Basic Assumptions
Loading Stages
Load Factors
Allowable Stresses
Loss of Prestress
Flexure
74
74
75
77
ii
5.
Article
7.10
7.11
7.12
7.13
7.14
7.15
7.16
7.17
7.18
7.19
Ultimate Flexural Strength
Maximum and Minimum Steel Percentage
· Nonprestressed Reinforcement
Shear
Composite Structures
End Zone of Concrete IBeams
Cover and Spacing of Prestressing Steel
Embedment of Prestressing Strand
Concrete Strength at Stress Transfer
Reinforcement in Beams
77
79
79
710
711
712
712
713
713
713
SECTION 8  PILE LOADS AND BEARING
POWER OF SOILS
8.1
8.2
8.3
Bearing Power of Foundation Soils
Angles of Repose
Bearing Value of Piling
SECTION 9 
9.1
9.2
9.3
9.4
9.5
SUBSTRUCTL~ES
81
81
82
& RETAINING WALLS
Piles
Footings
Abutments
Retaining Walls
Piers
91
94
97
98
99
SECTION 10  STEEL DESIGN
10.1
Design and Construction
101
iii
6.
SECTION l  GENERAL
l l
<
FEA1~RES
OF DESIGN
PRELl NI ;lARY DATA
The following information <,.;ill normallJ' be required for the proper
design of structur2s.
A.
STREAM
(])
CROSStNG~
An 1ndex map to a suitable smdll scale ltopo
she~ts
scale one
i Pch to one mile would do ir. most cases) showing the proposed locat ton
of the bridge, the alternative :.;i.tes investigated and rejected, the
ex·i_st ing comm•1nicat ions, the general topography of the country, and
the important towns, etc., in the 'Jicinity.
[ contour survey plan of the stream showing all topographical
fentures extending to the distance shown below(or such other greater
distances as the engineer restonsible for the design may direct)
upstream and dmvnstream of any of the preposed sites ar,d to a
sufficient distance on either side to give a clear indication of topographical or OT:her features that might influence the location and
design of the bridge and its a~proaches. All sites for crossings worth
consideration shall be shown on the plan.
{2)
(a)
300 feet for catchment area less than one square mile
(scale not less than one inch to 100 feet).
(b)
1000 feet for catchment areas of 5 square miles
(scale not less than one inch to 100 feet).
(c)
One mile for catchment areas of more than 5 square miles
(Scale not less than one inch to 330 feet).
Note: In djfficult country and for crossings over artificial
channels the engineer responsible for the design may permit discretion
to be used regarding the3e limits of distance,provided that the plans
give sufficient information on the course of the stream and the topographical features near the bridge site.
(3) A site plan to a suitable scale showing details of the site
selected and extending not les(:> than 300 feet upstream and downstream
from the centre line of the crossing and covering the approaches to
a sufficient distance which in the case of a large bridge shall be not
less than a quarter of a mile on either side of the stream. The plan
shall include all information that is essential for complete and proper
appreciation of the project. The normal requirements are given below;
(a)
The name of the stream or bridge and of the road and
the identification number allotted to the crossing;
11
7.
(b)
The approximate outlines of the banks, the high water
channel(if different from the banks), and the lmv water
channels with contours at suitable level intervals in
the bed anJ beyond the banks and the line of the deepest
points along the dry weather channel;
(c)
The direction of flow of 1vater at maximum discharge end
if possible, the extent of deviation at lc~er discharge;
(d)
The alignment of existing approaches and of the proposed
crossing and its approache,s;
(e)
The angle and direction of sk2w if the crossing is aligned
on a skew;
(f)
The name of the nearest inha:).Lu"d identifiable locality
at either end of the crossing on the roads leading to the
site;
(g)
References to the position(vir:h description ar.d reduced
level) of the bench mark used as datum;
(h)
The lines and identificatiou numbers of the crosssec::ions
and logitudinal section taken Hith!_n the scope of the site
plan, and the exact location of their extreme points,
(i)
The locations of trial pits or borings each being gh'en
an identification number;
(j)
The location of all nullahs, buildings, wells, outcrops
of rocks, and other possible obstructions to a road
alignment.
(4) A crosssection of the stream at the site of the proposed crossing
( Scale not less than one inch to 100 feet horizontally , exaggerated
vertically to a scale of not less than one inch to 10 feet) and indicating the following information:
(a)
The name of the stream and the serial number allotted
to the crossing;
(b)
The name of the road with mileage and chainage of the
centre of the crossing;
(c)
The bed line up to the top of the banks and the ground line
to a sufficient distance beyond the edges of the stream, with
levels at intervals sufficiently close to give a clear
outline of markedly uneven features of the bed or ground
showing right and left bank and names of villages on
each side;
12
8.
(d)
(e)
The low water level;
(f)
The ordinary Flood level;
(g)
The highest flood h:vel and the yo::,ars in which it occur,
red. State iE the flood level is affected by backwater
and if so, give details;
(h)
The catchment area, maximum discharge specified in
Article 1.:2(A.) arvl correspo~1ding average velocitiJ a:: tbe
site of the crossi~g;
(i.)
(5)
The nature of the surface soil in bed, banks and approa,
ches, with trial pit or bore hole sect ion.s showing the
levels and nature of the various strata down to hard
strata suitable for foundation and the safe intensity
ot pressure on the foundation soil; (as far as practicable,
the spacing of trial pits or bore holes should be such
as to provide a full description of all substrata layers
along the vl:ole lengt.b and >,vidth of the crossing);
The estimated depth of sco:.;r oc, if the scour depth has
been observed, the depth of scour, with details of
obstructions or of any other special causes responsible
for the scour.
 lo·;·J_gitudinal ~:;ection of the strecr~n snov11Eg tbt .site oj
the
bridge with the highest flood lev2l, the ordiGary flood level, the
low water level, and the bed levels at suitably spaced intervals
along the approximate centre line of the deep water cha~nel between the
extreme p~.dnts ~:; vhich the survey map required in Article 1.1A(2)
e:ztends, The horizontal scah' not let=:s than one inch to 100 f.efi!t.
{6)
A note givi:~.g as iar as possible ti;e following particulars
relating to the catchment area;
(a)
Jbe size of the catchment;
(:;)
The shape
(c)
The intensity and frequency of rai.nfall in the
catchment;
(d}
The slope of the catchment, both longitudinal and
transverse;
(e)
The nature of the catchment, whether under forests,
under cultivation, urban etc;
(f)
The nature of the soil crust, porous or rocky, etc;
or
the catchment;
9.
(g)
The possibility of subsequent changes in the catchment
like afforestation, deforestation, urban development,
extent of reduction in cultivated area, etc;
(h)
Storage in the catchment artificial or natural.
(7)
A chart of the periods of high flood levels for as many years as
the relevant data are recorded.
(8)
A note giving important details of the bridges, i f any, crossing
the same river within a reasonable dist:auce oE the proposed bridge.
(9)
The minimum permissible vertical ch~Hl!le:l clearar:ce and the b<1sis
on which it has been determined mentioning any special requireme<lts for
navigation.
(10)
Liability of the site of earthquake disturbances.
(11)
A brief description of the reasons for selection of the particular
site for the crossing accompanied, if necessary , '"ith typical crosf"=
section of the stream at suitable alternative crossing places both
upstream and downstream of the selected site.
(12)
Subsoil data of the stream at the site of the bridge should
obtained at four or more points in the cross section.
(13)
te
All other pertinent information affecting the design such as:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
Width of roadway curb to curb
Vertical and horizontal a~ignment
Cross Slopes
Live Load to be applied
Safety Curb, footpatb and/or animal path
Utilities to be carried by the superstructure
Location and type of piers and foundations
Freeboard Clearance
(14)
In case of streams having discharge over 50,000 cusecs, the
hydraulic design should be checked by model studies.
The following
data shall be required.
(a)
A site plan showing the location of the bridge with
respect to the stream. A stretch at least 5 miles up stream
and 3 miles down stream or two 'S' curves up stream and one
'S' curve down stream of bridge, whichever is longer, should
be given on the plan.
In order to indicate its dominent course,
the course"·Of the river or stream over a five (5) years
period should be shown.
(b)
The cross sections of the stream should be observed
14
10.
at intervals 1000 ft. apart in straight reaches and 500 ft.
apart along curves for proper representation on the model.
The location of all cross sections should be marked on the
site plan.
(c)
Gauge discharge curves and hydrograph of the stream
at the bridge site should be collected for the last 5 to 10
years. If such data is not ave.ilable, data pertaining to the
hydrographs and guage discharge of the rr;_ain stream, up stream
and down stream of the site may be used.
B.
H1GHIIA'f AND RAILROAD CROSSINGS
(1)
An index map to a suitable small scale (topo sheets scale one
iw_h to one mile wou.ld do in most cases) shmving the proposed location of
tht.: bridge, t:he exist5_ng communications, the important towns etc., in the
vicinity.
(2)
A plan and elevation of the proposed bridge showing span lengths;
critical vertical clearance of superstructure required above roadway or railroad; critical horizontal clearance to piers and abutments; depth of structure
hom profile grade to bottom of grider; location and number of bore holeL;;;
and the profile of the bridge and its approaches.
(3)
A cross section of the proposed bridge showing the number,
£ype and spacing of girders; the thickness of slab; the cross slope; width
,,f roadway curb to curb; the width of <>afety walk, footpath and/or animal
path, and the utilities to be carried by the superstructure.
(4)
A profile of the highway or railroad.
(5)
A cross section of the highway or railroad.
(6)
Type of pier to be used.
(7)
Type of footing to be used, whether rock bearing, soil bearing
or pile bearing and the allowable capacities of each.
(8)
1. 2
Live load to be applied.
DETERMINATION OF WATERWAY AREA
For the determination of the vaten1ay area UJ. be provided for a
stream crossing or culvert, a careful study shall be made of local
conditions, including flood height, flov;r and frequency, size and performance
of other openings in the vicinitY
carrying the same stream, characteristics
of the channel and of the watershed area, available rainfall records and any
other information pertinent to the problem and likely to affect the safety
'or economy of the structure.
l5
11.
'(A)
The maximum discharge >Ihich the stream crossing or culvert shall be
designed to pass shall be determined by a consideration of the following
methods:
(1)
From the rainfall and other characteristics of the catchment
which together from the general formula;
Q =
c
n
X
A
Where Q is the maximum flood discharge in cubic feet per second
(cusecs), A is the area of catchment of the stream in square miles, 11 n 11
an exponent varying from 0.5 to 1.0, and C a varying coefficient
depending upon the characteristics of the terrain. Some typical
formulas are:
(a)
Dicken's formula
Q =
c
3/4
X
A
Where C is equal to 750 for mountainous areas and 500 for
planes
(b)
Ryves formula
Q =
c
X
A213
Where C is equal to 500 for mountainous area and 350 for
planes.
(C)
Inglis formula
7000 A
Q
(d)
VA+
4
M.E.S. formula
Q = 2100
X
1/2
A
(2)
From the hydraulic characteristics of the stream such as the
crosssectional area, and slope of the stream allowing for velocity
of flm.;r. In this method the velocity is obtained from the formula
1.486
2/3
1/2
V
=
X r
X
S
n
Where
r = hydraulic mean depth in feet
S
Slope
V
mean velocity in feet per second
n
coefficient of rugosity of stream bed
16
12.
0.020 for ea.rth in good order and regimen~ free
from stones and weeds
0.025 for· earth in fair order and regimen, free
n
from stones and weeds
0.030 for earth in bad order, with occasional
stones and weeds
0.035 for streams in bad order and. regimen with
stones and weeds
0.050 for torrential rivers in beds covered with
detritus and boulders.
The velocity thus obtained is then multiplied by the crosssectional area to give the required discharge Q.
(3)
From the Unit Hydrograph method
The results from the above methods should then be compared and
with proper judgement, arrive .. at the design discharge to be used.
(B)
Having arrived at an estimate of required discharge either by the
calculations from the preceding sections or by flood data secured fro1n
~vailable reports of gauging stations or local high water marks, the next
step is to design an opening that ·will pass this amount of water without
damage to the Btructure or to adjacent work or properties.
(1)
For artificial irrigation, navigation, and drainage channels,
the effect~ve width of waterway shall generally be equal to the width
of channel at mid~depth, but concurrence shall be obtained invariably
from the authority controlling the channel.
If it is proposed to flume the channel at the site of the
bridge, the flurning shall be subject to the consent of the same
authority and in accordance with its essential requirements.
(2.)
For nonmeandering natural streams not widE. than 100 feet in
alluvial beds but with welldefined banks and for all natural channels
in beds with rigid inerodible boundries, the width of waten1ay shall be
the distance between banks at that water ;.;ul·face elevation at which the
designed discharg~ was determined.
(3)
For large natural streams in alluvial beds and having undefined
banks, the width of waterway shall be determined from the design
discharge, using some accepted rational formula such as Lacey's formula
for a regime flow condition where
p
= 2.67 Q
1/2
P being the wetted perimeter in feet,
and Q the discharge in cusecs of a stream consisting of alluvial
beds like sand, or clay, transported and deposited by flowing water.
17
13.
The vetted perimeter thus obtained for a straight reach of the stream
is very nearly the effective width of waterway in such cases.
SPACING AND LOCATION OF PIERS AND ABUTMENTS
The following consideration shall govern the spacing and location of
.nd abutments:
(a)
Piers and abutments shall be so located as to make the best
use of the foundation conditions available.
(b)
Subject to (a) above, the suitable economical span shall be
adopted, modified, if necessary, to suit navigational and
aesthetic requirements.
The number of piers should be
limited as much as is practicable, they catch debris and thus
the effective waterway could be reduced substantially.
(c)
The alignment of piers and abutments shall, as far as possible,
be parallel to the mean direction of flmv in the stream but
provision shall be made against harmful effects on the stability
of the bridge structure and on the maintenance of adjacent
stream banks caused by any temporary variations in the direction
and velocity of the stream current.
VERTICAL CLEARANCES
Clearance shall be allowed according to navigational or anti:tion requirements or, where these condition do not arise, ordinarily
.OWS:
(a)
For o1~enings of high level bridges, which are approximately
rectangular, or with a very flat curve of the soffit of
superstructure, as for instance in the case of beam, frame,
or bowstring superstructures, continuous girders or open
spandral arches •vith suspended decking, the minimum clearance
shall be in accordance with the following table:
DISCHARGE
MINIMUM VERTICAL
CLEARANCE
Below 10 cusecs
10100 cusecs
1011000 cusecs
100110,000 cusecs
10,001100,000 cusecs
Over 100,000 cusecs
Ft.
0
1
2
In.
6
6
0
3
4
0
5
0
0
The minimum clearance shall be measured from the lowest point
18
14.
of the deck structure inclusive of main girders in the central
half of the clear opening.
(b)
(c)
,.
1
"1_,..
~.
J
In structures provided '>vith metallic bearings such vertical
clearance shall be allowed as will ~revent the submergence
of those bearings.
In the case of artificial channels, e.g., irrigation canals
having controlled flov1 and carrying no floating debris, the
Engineer~in·Charge may at his discretion provide less vertical
clearance than that specified in subclauses (a) and (b) above.
RESTRICTED WATERWAYS
When it is necessary to restrict the waterway to such an extent that
the resultant afflux will cause the stream to discharge at erosive velocities,
protection agains~ damage by scour shall be afforded by deep foundations,
C'J.rtain or cut·"off walls~ riprap, bearing piles, or other euitable means"
Likewise embankment slopes adjacent to a 11 structures subject to erosion
nhall be adequately protected by pitching, revetment walls or other suitable
construction.
1. 6
OBSTRUCTION AND RIVER TRAINING
Obstructions in the river bed likely to divert the current or c3use
undue disturbed flow or scour and thereby endanger the safety of the bridge
shall be r:::mov('.'d as far as practicable for some distance upstream and down~
stream of the bridge depending on the river characteristics. Attention shall
be given to river training and pro tee tion of banks over such lengths of the
river as require it.
L /c
DETERMINATION OF THE MAXIMUM DEPTH OF SCOUR
(A)
The maximum depth of scour in a stream shall be ascertained
whenever possible, by actual soundings at or near the site proposed for
Lhe bridge, during a flood before the. scour holes have had time to silt
up appreciably. Due allowance shall be made in the observed depth for
increase in scour resulting from
(1)
The design discharge being greater than the flood discharge
during which the scour was observed;
(2)
The increase in velocity due to the obstruction in flow
caused by construction of the bridge.
(B)
Where the practical method of determining scour described at(A)
above is not possible, the following emperical approach may be used as guide
15.
when dealing with natural streams in alluvial beds:
For regime conditions in a stable channel
1/3
d = 0.473(+)
For restricted flow
d
= k 0.9 ( q2
)1/3
f
d
Normal depth of scour below H.F.L.(high flood level)
Q
Total design discharge in cusecs
q
Design discharge per foot of width in cusecs
k
A factor varying
conditions. For
to be used shall
Directors of the
f
Lacy's silt factor for a representative sample of the
bed material. The silt factor is' approximately equal
to 1. 76 m% where m is the wetted mean diameter in
milimeters (rnm) of the bed material. See table for
value of f given by Lacy for various grades of bed
material
from 1 to 3 derending on local
a major stream crossing the factor
be decided on consultation with the
Bridge and Research Directorates.
LACY'S SILT FACTOR
l1aterial
f
Medium silt, canges canal distributary
Standard silt, Punjab data
Medium sand
Coarse sand
Fine Bajri and sand
Heavy sand
Coarse Bajri and sand
Coarse gravel
Gravel and bajri
Boulders and Gravel
00.233
00.323
00.505
00.725
00.988
01.290
02.420
07.280
26.100
50.100
00.850
01. 000
01.250
01.500
01. 7 50
02.000
02.750
04.750
09.000
12.000
The maximum depth of scour shall be taken as follows:
(1)
In a straight reach
1. 5 d
(2)
at a right angle bend
2. 0 d
110
16.
(3)
at noses of piers
2.0 d
(4)
at upstream noses of guide
banks
2.5 d
Due allowance shall be made for a::.1 increase in concentration
through a portion of the waterway.
of flovJ
There the computed depth of scour ceachss 'AI'"ll into layers, as
iadicated by boring informatior;, oi: relatively scour free material (i, e, gravel
and boulders) the computed depth of scour may be red1.<ced.
1.
of
8~
~he
DEPTH Of FOUNDll'IONS
(A)
The depth of foundations shall be d~termi:J.ed by consideration
safe hearing capacity of th~ soil after taking into account the effect
of scour.,
(B)
In all doubtful cases, the bearing capacity of the foundation
shall be determined by actual loading tests. The adequate th.ickne133
cf the foundation bearing layer of the soil shall be ascertained by borings
o:r trial pits .
,oni}
l'he maxirnum toe pressure o:n the foundatir:;r. bearing l"l.y~r
~vorst: cornb:l~~1ati.on. of dir£,_ct forc2s a::td ov·ert:jrilirtg mo1nex.1~.s
:~hn11 h<.; cB.lcuJat!"d f:or each individt:al fouadaticn.
In calcul'l'::ing this
prcssure 1 the. (~ffect of passi,/e. rr.::~i.stance of the earth of t.~he. sides of th~)
foundation structure. ,nay be taken h:to Hcco:.mt be low the ma;...:1mum depth of
the scour only
The effect of skin friction on the sides of the foundation
:;tructure may be ignored normally except in the ca~;e of well and pile.
ntructures where skin friction may be allowed on the pcrtion below the
maxi:mum d~'pth of scour.
)
t"e.sulting fro!n t1:te
(D)
lllhere a substantial stratum of solid rock, or other material
inerodible at the anticipated maximum velocity and of adequate safe bearing
capacity, is encoJntered at a shallow depth below the surface, the
foundatic•n shall be taken into that stratum and securely bonded or if
necessary anchored to it.
(E)
Where only erodible strata are available, the fo:.mdations may be
designed either as "Deep" or as ~:Shallow" but in such a manner that ii:l
either case the safe bearing capacity of the sub~soil is not exceededo
(1)
DEEP FOUNDATIONS (in erodible strata) If 'd' is the anticipated
maximum depth of scour below the designed highest flood level includ"
ing that on account of possible concentration of flow, the minimum
depth of foundation below H.F.L, shall be 1.33 d.
The Depth below the
scour line shall in no case be less than six feet for piers and
111
17.
r · 1
HORIZONT.D..L CLElf.<ANCE
~·~,~~=1
'
MINIMUM ROADWAY WIDTH
:T LEAST 4FT. GREATER THAN
APPROACH PAVEMENT WIDTH
..,1
BUT NOT LESS THAN 24 FT.
CLEARANCE DIAGRAM
TWO LANE HIGHWAY TRAFFIC
FIGURE
I
Note:
For heavy traffic roads, roadway widths greater than the above
minima are recommended.
For all bridges under 50 feet in length, the overall width should
conform as nearly as practicable to the full shouldertoshoulder width
of the highway.
For recommendations as to roadway widths for the various volumes of
traffic see the Highway Design Manualo
112
18.
abutments supporting other types of superstructure. The foundations
shall in all cases be taken down to a depth vhich will provide proper
grip according to some rational method.
(2)
SHALLmv FOUNDATIONS (in erodible strata). Foundations may be
taken dmm to a comparatively shallow depth belov the bed surface
provided the foundation bearing stratum is practically incompressible
(e.g.sand), is prevented from lateral movement, and is also protected
against scour.
1.9
SIZE OF CULVERT OPENINGS
In general, culverts shall be proportioned to carry the maximum flood
discharge without head. If the maximum flood discharge occurs only at rare
intervals,culverts may be designed to carry i t under slight head, provided
they are protected against undermining by means of adequate pavement and
apron or cutoff walls and that adjacent embankments are protected from
erosion by riprap or other suitable means.
1.10
LENGTH OF CULVERTS
The length of culverts shall be sufficient to provide the required
1ATi.dth of roadway embankment. 111e assumed slope of the embankment shall be
suitable for the particular filling material and shall be such as to eliminate
any tendency for the embankment slopes to slip or slide.
1.11~
WIDTH OF ROAmvAY AND SIDEWALK
The vidth of roadway shall be the clear width measured at right angles
to the longitudinal centre line of the bridge between the bottoms of curbs or
guard timbers, or, in the case of multiple height curbs, between the bottoms
of the lower risers. The width of the sidewalk shall be the clear width,
measured at right angles to the longitudinal centre line of the bridge, from
the extreme inside portion of the handrail to top of the face of the curb or
guard timber, except that if there is a truss, girder, or parapet wall adjacent
to the roadway curb, the width shall be measured to its extreme walk side
portion.
1.12·
CLEARANCES
The horizontal clearance shall be the clear width, and the vertical
clearance the clear height, available for the passage of vehicular traffic
as shown on the clearance diagrams.
Unless otherwise provided, the several parts of the structure shall be
constructed to secure the following limiting dimensions or clearances for
traffic.
The clearances and width of roadway for 2lane traffic shall be not
less than those shown in Figure 1. The roadway width shall be increased at
least 10 feet and preferably 12 feet for each additional lane of traffic.
113
19.
1.13~
CURBS AND SAFETY CURBS
The face of the roadway curb is defined as the battered or sloping
surface on the roadway side of the curb.
Preferably vertical c•.abs shall not:
be used, Horizontal measurements of roadvn'l and curb >•Jidth q;::c_. given fTom cl:ce
bottom of the face, or, in the case of stPp8ei back curb, fro~ the ~ottom of
the lmver face for roadway width,
The fuce of Lhe roadway curh pre fccaLl;· sha 11 he not 1e::: s t!.:n1 12
inche::; and in no instance less than 9 i.~•r:i,".:·· !rc.m ::ha: p,wt :c:''' ,,f •:h·=: structu;,'
above the elevation of the top of the CL.lTb awl n2are.st the road',vay.
1.r1 ca.;:;es
of bridges in which the clear roadvJay widtr1 :i:; eqt:al !.o or great,,,, ,_:,,~;:, th~;
sho,~lder width but: not less than the approa~·rt pavenl9Et width plu:c; 12 fe.;>::,
curbs may be omitted.
In urban areas~ the cur~1 ht•igl1t shall no:. b"! less ~1:;;..:::
7 inches above the adjacent finished surfac(' of the :roadway, anr:l L1 c;ra.l areas
not less than 9 inches above the adjacent f ird. ''h,:·.d "Jurfac2 of ttH~ rva(hvay.
That portion of a curb more than 10 inches above the roadwa·y sur:a.c~o: sba.ll b2
stepped back or sloped back so that no part of the vehicle except the tires
may come in contact with it. Curbs widened to provide for occasional
pedestrian traffic shall be designated "Saiety cnr::,3n.
Safety curbs shall
be not less than l 1 6" wide.
RAILINGS
Railing shall be
of traffic, or for the
footpaths are provided
between the two with a
pedestrian railing may
provided at the edge of scntctures for the prouci.:Lon
protection of pedestria::,s, or both. W11ere pe.d'::stri_':l!1
adjacent the roadways, n :r3.ffic railing ma.y he provided
~edestrian railing outsid2, or a combination trafficbe provided outside.
Curbs shall be provided between roadways and
a traffic barrier separates the two.
A,
pedP~trian
footpaths unlesa
TRAFFIC RAILING
While the primary purpose of traffic railing i;> to contain the average
vehicle using the structure, consideration should al2o be given to protection
of the occupants of a vehicle in collision with the railing, to protecl:ioo of
other vehicles near the collision, and to appearance a~d freedom of view of
passing VBhicles.
Material for traffic railing shall i::e concre t.e, clletB.l, 1.mber c1· rt
combination. Metal materials with less than 10 per cent tested elongat:icn•
shall not be used.
Preference should be given to pro'Jiding a smootb,
continuous face of rail on the traffic side with che posts set back £rom the
face of the rail. Structural continuity in the rail members, including
anchorage of free ends is essential. Where joints are required in the lengths
of railings, the construction shall be reinforced by reduced post spacing,
by splice material in the rails, by bolting or welding.
114
20.
The height of traffic railing shall be not less than 2'3" measured
from the top of the roadway, or curb, to the top of the upper rail member.
Careful attention should be given to the treatment of railing at the
bridge ends. Exposed rail ends and sharp changes in the geometry of the
roadway shall be avoided.
B.
PEDESTRIAN RAILING
Railing components shall be proportioned commensurate with the type
and volume of anticipated pedestrians, takir.g account of appearance, safety
and freedom of view of passing vehicles.
Materials for pedestrian railing may be concrete, metal, timber,
or a combination" 1be minimum height of pedestrian railing shall be 3'0"
(a preferred height is 3'6") measured from the top of the footpath to the
top of the upper rail member,
J., 15· ROADWAY DRAINAGE
The transverse drainage of road~vays shall be secured by means of a
tmitable crown in the roadway surface and longitudinal drainage by camber
or gradient. If necessary, longitudinal drainage shall be se~ured by means
of scuppers, inlets or other suitable means, which shall be of sufficient
;.;J.ze and numbe:r to drain the gutters adequately.
If drainage fixtures and
downspouts are required, the downspouts shall be of rigid corrosionresistant material not less than 4 inches in least dimension, provided with
suitable clean~ out fixtures. The details of floor drains shall be such as
to prevent the discharge of drainage water against any portior. of the
structure. Overhanging portions of con£rete floors preferably shall be
provided with drip beads,
L 16 SUPERELEVATION
The superelevation of the floor surface of a bridge on a horizontal
curve shall be provided in accordance with the geometric design criteria
for highways, except that the superelevation shall not exceed .08 foot per
foot width of roadway.
L 17 FLOOR SURFACES
All bridge floors shall have skidresistant characteristics.
1. 18 UTILITIES
Where required, provlslon shall be made for electric conduits,
telephone conduits, water pipes and gas pipes.
115
21.
1. 1 :J
ROADWAY WIDTH, CURBS A~1D CLEARANCES FOR TUNNELS
(See Figure 2.)
(A) Roadway Tidth  The clear width bet,Jeen curbs shall be Lot
than that specified for bridges.
(B) Clearance bet'Jeen Halls  The minimum ':vid th bet1een
twolane tunnels shall be 30 feet.
(C) Curbs  The '#idth of curbs shall be not less than
height of curbs shall be as specified for bridges.
.U:J
VJd lls
lc~::o
of
ch.t~s.
The
(D) Vertical Clearanc:e  TI1e vertica1 clearance, betAJeen (::~1rbs sht1L1
be not less than 16'6 11 •
CLEARANCE DIAGRAM FOR TUNNEL
TWO LANE HIGHWAY TRAFFIC
FIGURE 2
116
22.
F()tD!.1.Y
t~)"j"
CLEARANCE
T~NO
LA
v~rlOTH
LESS
YTi'~i~.Pi
.t'U11l FOR UNDER
HIGHW.LW TRAFFiC
FIGURE 3
1. 20
ROAmvAY WIDTH, CURBS AND CLEA.H;.NCES :FOR UNDERPASSES
(UNDIVIDED HIGHfAYS)
(See Figure 3.)
(A) Jidths  The clear lividth betIeen .;valls or columns shall be
not less than 6 feet wider than the approach pavement, but in no
case shall the width be less than 30 feet.
(B) Vertical Clearance  A vertical clearance of not less than
16 '6 11 shall be provided between curbs, or if curbs ar.e not used,
over the entire width that is available for traffic.
(C) Curbs  Curbs shall not be less than 18 inches in width,
The height of curbs shall be as specified for bridges.
117
23.
l.
21~
ROAmJAY
WIDTH~
CURBS AND CLEARANCE FOR DEPRESSED ROADWAYS
(A) Roadway Width~ The clear vidth between curbs shall preferably
be not less than that speciEied for bridges.
(B) Clearance Between Walls  The minimum width between walls for
depressed roadways carrying t>vo lanes of traffic shall be 30 feet.
(C) Curbs= The width of curbs shall be not less than 18 inches.
The height of curbs shall be as specified for bridges.
118
24.
SECTION 2  LOADS
2.1 
LOADS
Structures shall be proportioned for the following loads and forces
when they exist:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Dead load
Live load
Impact or dynamic effect of the live load
Wind loads
Horizontal forces due to water currents
Longitudinal forces caused by the tractive effort of
vehicles or by braking of vehicles and/or those caused
by restraint to movements of free bearings.
Centrifugal forces
Buoyancy
Earth pressure
Thermal forces
Shrinkage stresses
Rib shortening
Secondary stresses
Erection stresses
Earthquake stresses.
Hembers shall be proportioned as specified under stresses, Section 5
and 7.
Upon the stress sheets a diagram or notation of the assumed live loads
shall be shown separately.
tJhere required by design conditions, concrete placing sequence shall
be indicated on the plans.
2.2 
DEAD LOAD
The dead load carried by a member shall consist of the portion of
the weight of superstructure (and the fixed loads carried thereon), which
is supported wholly or in part by the girder or member including its own
weight. The following unit weight of materials shall be used in
determining loads:
Naterial
Lbs./Cu. Ft.
1. Ashlar or Coarse Rubble
Masonry
2. Brickwork
3. Cast Iron
4. Asphalt Concrete
5. Cement Concrete, plain
150
120
450
140
140
21
25.
Materials
Lbs./Cu.Ft.
6. Cement Concrete,reinforced
7. Earth (Compacted)
8. Macadam (binder premix)
9, Rolled Steel
10. Sand (loose)
11. Sand (wet compressed)
12. Stone Metal
13. Hater
14. Wood
15. Wrought iron
A.
150
110
140
490
90
120
100
62.5
so
480
LOAD ON CULVERTS
Earth pressure or load on culverts will be computed as the >veight of
earth directly above the slab.
B.
RIGID CULVERTS
For definite conditions of bedding and backfill, the principles of
soil mechanics rnay be applied. The following are recommended formulas for
these conditions:
(1)
Culvert in trench or unyielding subgrade, or culvert
untrenched on yielding foundation.
P =
WH
(2)
Culvert untrenched on unyielding foundation (such as rock
or piles)
P
W (1.92 H 0.87B) for H
P
k
2, 59 BW ( e  1) for H
Where K
= 0 · 385
>
<:: 1. 7
1.7 B;
B
H
B
Where P
the unit pressure in pounds per square foot due to
earth backfill
E
width in feet of trench, or in case there is no
trench, the over=all width of the culvert
H
depth in feet of fill over culvert
w
effective weight per cubic foot of fill material
E
2.7182818 =base of natural logarithms,abstract
number
2=2
26.
C.
SHEAR IN SLABS
The maximum shear in the top and bottom slabs shall be assumed
to occur at a distance out from the face of the wall or abutment eqL:al to
the thickness of the slab, Hhen haunches are provided at the corners of
the cells, their effect shall be excluded from the design.
D.
NEGATIVE MG1>1ENTS IN SLAB AND t;JALLS
The maximum negative moments shall be taken at the face o£ the
wall for the top and bottom slabs and at the underside of th6 top slab and
top of the bottom slab for the walls or abutment, Bond shall be computed
at the same section as for moments.
2.3
LIVE LOAD
The live load shall consist of the weight of the applied moving
load of vehicles, cars and pedestrians.
2,4
HIGHWAY LOADINGS
General
The highway live loading on the ro2v:hvays of bridges or incidental
structures shall consist of a standa.rd truck ·· train. Two systems of
loading are provided for Class nA" loading artd Class "B" loading,
B.
Class "A" Loading,.
The class "N' loading ts illustrated in figure 4,
a fouraxle truck with two twoaxle trailors ..
C,
It consists of
Class "B 11 Loading
The Class 11 B11 loading shall be identica 1 to Class ''N' loading except.
for the axle loads which shall be 60';~ of Class A Loading.
2.5
STANDARD TRUCK 
TP~IN
LOADING
The wheel spacing, weight distribution, and clearance of the
standard loading shall be as shmv'l1 in Figures 4 with the following conditions;
(1)
Hthin curb to curb width of the roadway, the standard
vehicle or train shall be assumed to travel parallel to the length
of the bridge, and to occupy any position, which will produce maxhnum
stresses, provided that the minimum clearanc:es bstween a. vehicle and
the roadway face of a curb and bet~veen two passing or crossing
vehicles, as shown in figure 4, are not encroached upon,.
(2)
For each standard vehicle or train, all the axles of a unit
23
27.
10'0"
65~~
10'0"
15,000
15,000
Lbs.
__
Lbs.
15POO
Lbs.
6,000 6,000
Lbs.
Lbs.
~~
·N
•
.f"
~]
:;1
l
·:!
s~~ .~ ..
""''"'1,_~.
CLASS OF LOADING
r

s (, '
;:,_
~
i
1~
.
I'"E
........
...J..L.w.,.~~"~~~"···
OF
L!UITJNG POSITION
STANOMD ''fRUCK ~TRAil! LOArHI•§G
WITH REFERENCE TO A TRAFFIC LANE
(For ground con! oct areo and value of ·~ •: se& tobh! i r.m<l 2 )
ll
15,000
_111"''1
108
W
zo
8
.
·~~6,00~ ~
.
~
I
"A''
GRrJl:JND CONTACTi
WAD (L.hs)
r'2:5,ooo
·)";";1
~
I 
I.
"B"
'
';:g~
L ___________ j__3, soo
:
15
8
I
,'i
_s __j______!__
_
TABLE I
'li0TE. Closs "e" loading will hove similar
speGificotions to class "A" loading
with the only differefce !hoi the
oxie loads of class "a" :shall be
oOfo of cia s s ':0.'~
,I'IJfl
CLEAR ROAD WIDTH
16' a" or less
0
16. 8 .. to fa'O"·pm;·.:;.:,eiog uniformly from o to 1':.. 4"
18'0"to~
ditto
1'tJ!'to 4'o''
~4'~__j__ _____ ._ 4' o"
~
~
FIGURE 4
LOADING CLASS '~" FOR
HIGHWAY BRIDGES
TABLE 2
r1
28.
of vehicles shall be considered as acting simultaneously in a
position causing maximum stresses.
(3)
Vehicles in adjacent lanes shall be taken as headed in the
direction producing maximum stresses.
(4)
The spaces on the carriage vJay left uncovered by the standard
train or vehicles shall be assumed as not subject to any additional
live load.
APPLICATION OF LOADINGS
TruckTrain Units
In computing stresses, each single standard trucktrain shall be
considered as a unit, and fractional widths or fractional trucks shall not
be used,
B.
Numoer and Position, TruckTrain Loadings
Th~ number of the truck train loadings and position as specified in
Art. 2.5 shall be such as to produce maximum stress, subject to the reduction specified in Article 2.7.
C.
Continuous Spans
On continuous spans one or both trailers sl,:Jll be removed if vorst
conditions are produced by doing so.
72 .'
REDUCTION IN LOAD INTENSITY
Where maximum stresses are produced in any member by more than one
3imultaneous truck=train load, the following percentages of the result;,;~t
ltve load stresses shall be used in view of improbable coincident maximum
loading:
Per cent
One or two,truck:· _;train ..Loadings
'. : ·: ·" .,
   "l
Three ·nuck train load i_l1~.~~
Four or more
·~~
~
100
90
75
The reduction in intensity of floor beam loads shall be determined
as in the case of main trusses or girders, using the number of truck train
loadings which must be used to produce maximum stresses in the floor beam.
29.
2. 8
SIDEWALK, CURB, SAFETY CURB AND RAILING LOADING
A.
Sidewalk Loading
Sidewalk floors, stringers, and their immediate supports, shall be
designed for a live load of 85 pounds per square foot of sidewalk area.
Girders, trusses, arches and other members shall be designed for the following
sidewalk live loads per square foot of sidewalk area:
Spans 0 to 25 ft. in length
85 lbs.
Spans 26 to 100 ft. in length
60 lbs.
Spans over 100 ft. in length according to the formula
p
P
L
W
(
55~1iJ
l
so !
in >vhich
live load per square foot (maximum, 60 lbs. per sq.ft)
loaded length of a sidewalk in feet
width of sidewalk in feet
In calculating stresses in structures which support cantilevered
sidewalks, the sidewalk shall be considered as fully loaded on only one side
of the structure if this condition produces maximum stress.
B.
Curb Loading
Curbs shall be designed to resist a lateral force of not less than
500 pounds per linear foot of curb, applied at the top of the curb, or at
an elevation 10 inches above the floor if the curb is higher than 10 inches.
Where sidewalk, curb and traffic rail form an integral system, the traffic
railing loading shall apply and stresses in curbs computed accordingly.
C.
Safety Curb Loading
Safety curbs, or wide curbs provided for occasional use of pedestrians, shall be designed for loads specified in paragraph (A) if the curb
is more than 2 feet in width. If 2 feet or less in width, no live load
shall be applied.
D.
Railing Loading
(1)
Roadway Railings
Top members of roadway railings shall be designed to resist
a lateral horizontal force of 150 pounds per linear foot together
with a simultaneous vertical force of 100 pounds per linear foot
applied at the top of the railing. When curbs are not less than 9
inches in height, lower rails shall be designed to resist a lateral
horizontal force of 300 pounds per linear foot. 1iJhen curbs are less
than 9 inches in height, this force shall be increased 40 pounds per
linear foot for each inch the curb is less than 9 inches in height
except that the adJed increment of horizontal force to be applied
26
30.
to the lmver railing shall not exceed 200 pounds. If there is no
lower rail, the web members shall be designed to resist a horizontal
force of 300 pounds per linear foot applied not less than 21 inches
above the roadway. For each inch of height of curb above 10 inches
this lateral horizontal force may be reduced 15 pounds per linear
foot, but this force Ehall not be less than 150 pounds per linear
foot. The horizontal forces shall be applied simultaneously. Railingi:'
without webs and with single rails shall be designed for the forces
specified above for low2r rails.
Sidewalk Railings
(2)
Sidevalk railings shall !:>e designed to resist the same forces
as those specified for roadway railings, subject to the same restrict~
ions concerniHg curb heights. w11ere through trusses, girders, or
arches separate the sidevwlk and road1vay or where sidewalks are
protected by curb railings, the sidewalk railings shall be designed
only for the forces specified for the top rail.
2.9
IMPACT
Live load stresses produced by the standard TruckTrain loading shall
be increased for i terns in Group A by allowance as stated therein, for dyuamic ,,
'Jibratory and impact effects. Impact shall not be applied to items in Group
B.
(A)
Group A
(1)
Superstructure) including steel or concrete supporting
columns, steel towers, legs of rigid frames and generally those
portions of the structure >vhich extend down to the main foundation.
(2)
The portion above the ground line of concrete or steel
piles which are rigidly connected to the superstructure as in
rigid frame or continuous designs.
(B)
Group B
Abutments, retaining walls, piers, piles, except Group A(2)
Foundation pressures and footings
Timber structure
Sidewalk loads
Culverts and structures having cover of 3 feet or more
(1)
(2)
(3)
(4)
(5)
Impact Formula
The amount of this allowance or increment is expressed as a fraction
of live load stress, and shall be determined by the formula:
(C)
I
=
15
L
+ 20
in which
31.
I
1
impact fraction (maximum 30 per cent)
length of span in feet
For uniformity of application the span length "V' shall be especially
considered as follows:
For roadway floors, use the design span length.
For transverse members, such as floor beams, use the span length
of member centre to centre of supports,
For computing truck load moments use the span length, except for
cantilever arms use the length from moment ce.ntre to the farthermost
axleo
For continuous spans use the length of span under consideration for
positive moment, and use the average of tvm adjacent loaded spans for
negative moment.
For bridges having cantilever acms with suspended spans, use the span
of the cantilever arm plus half the length vf the suspended span when
designing the cantilever and tti;:: span length of the suspended span
designing the latter.
For shear due to truck loads use the length of the loaded portion
of span from the point under consideration to the far reaction.
For culverts with cover O'
H
II
i'f
li
1'
II
II
!!
1!
2'
2. 10,··
1''
111
to 1!
to 2 I
to 2'
~·
~
~
O" inc,
!=30~~
inc.
llll inc.
I=20'1o
I=lO%
on
LONGI'I'UDINtL FORCES
Provision shall be made for longitudinal forces arising from any one.
or more of the follmving causes~·
(a)
Tractive effort caused through acceleration of the driving
wheels or brak1ng effort from the application of the brakes to the
braking wheels,
This force shall be equal to ;'30/~ of the >veigt1.t. of the
vehicle or any portion of the vehicle on the loaded span, the truck
loads in one lane only being considered. For military loading this
force shall be equal to ~57;of the weight of the military vehicle,
·The centre of gravity of this longitudinal force shall be assumed to
be located 6 feet above the profile grade of the roadway slab,
, The change in the vertical reaction due to the transfer of the
longitudinal force to the bearings 1 shall be accounted for.
(b)
Frictional resistance offered to the movement of expansion
bearings due to change of temperature or any other cause.
This force shall be equal to the dead load reaction multiplied
by the coefficient of friction as shown below for the various
28
32.
types of bearing:
For roller bearings
0.03
For sliding bearings of hard copper alloy
0.15
For sliding bearings of steel on cast iron or
steel on steel
0.25
For sliding bearingsof steel or ferro asbestos 0.20
For sliding bearings of concrete on elastomeric
bearing pads
0.20
2 . 11
WIND LOAI1S
The follm..ring wind load forces per square fov t of exposed area sh::!ll
hE:, B()plied to all structures (sec Article 5.1 for percentage of basic unit
,sc.re;,;s ~:o he used uuder various combiru1tions of loads and forces).
The
'"xposed Hrl?d considered shall he the sum of the areas of all members, i:lclud:Lng fJ.oox system and railing, as seen in elevation at 90 degrees to the
.Longitudinal axis of the structure. The forces and loads given herein are
for a wind VBlocity of 100 miles per hour. For Group II loading, but not
br Group III loading, they may be reduced or increased in the ratio of the
square 0f the design wind velocity to the square of 100, provided the maximum probable wind velocity can be ascertained with a reasonable accuracy,or
':here .are permanent features of the terrain which make such changes safe and
advisable. If change in the design wind velocity is made, the design
•vtnd velocity shall be shown on the plans.
(A)
Superstructure Design
A moving uniformly distributed wind load of the following intensity
shall be applied horizontally at right angles to thefiongitudinal axis of
the structure :Ln the design of the superstructure:·
For trusses and arches,.c.75 pounds per square foot
For girders and beams
50 pounds per square foot
The total force shall not be less than 300 pounds per linear foot in
the plane of the loaded chord and 150 pounds per linear foot in the plane of
the unloaded chord on truss spans and not less than 300 pounds per linear
foot on girder spans.
The above forces shall be used for Group II loading. For Group III
loading there shall be added thereto a load of 100 pounds per linear foot
at:plied at right angles to the longitudinal axis of the structure and 6 feet
above the deck as a wind load on a moving live load. ~~en a reinforced
concrete floor slab or a steel grid deck is keyed to or attached to its
supporting members, it may be assumed that the deck resists within its
plane, the shear resulting from the wind load on the moving live load.
29
33.
(B)
Substructure Design
Forces transmitted to the substructure by the superstructnr2 and
forces applied directly to the substructure by wind loads shall be assumed to
be as follows:
Forces from Superstructure
(1)
The transverse and longittldinal forces transmitted by the
superstructure to the substructure for varying angles of wind direct
ion shall be as set forth in the following table" The skew angle
is measured from the perpendicular to the longitudinal axis, The
assumed wind direction shall be that which produces the maximum
stress in the substructure being designed, The transverse a:1d
longitudinal forces shall be applied simultaneously at the elevation
of the centre of gravity of the exposed area of the superstructure.
Trusses
Skew Angle
of Wind
(Degrees)
Lateral Load
per Sq, FL
of Area
(Pounds)
Longitudinal
Load per sq.
Fto of Area
(Pounds)
75
70
65
47
25
0
15
30
LJS
60
Girders
0
12
28
41
50
l,at:eral Load
per Sqo Ft.
of Area
(Pounds)
Long it ud ina 1
Load per sqo
Ft. of Area
(Pounds)
50
44
41
33
17
0
6
12
16
19
The loads listed above shall be used. in Group I I loading as given in
Article 5" 1
For Group III loading, these loads may be reduced 70 per cent
and there shall be added thereto, as a wind load on a moving live
load, a load per linear foot as given in the following table:
Skew Angle
of Wind
(Degrees)
Lateral Load
per Lin, Ft.
( Pounds )
Longitudinal
Load per Lin. Ft.
( Pounds )
0
100
0
15
30
45
88
66
12
24
32
60
34
38
82
This load shall be applied at a point 6 feet above the deck,
For the usual gird2r and slab bridges having maximum span
210
"'
"''
34.
lengths of 125 feet, the following wind loading may be used in lieu
of the more precise loading specified above.
W ( wind load on structure)
SO pounds per square foot, transverse;
12 pounds per square foot, longitudinal.
Both forces shall be applied simultaneously.
WL(wind load on live load)
100 pounds per linear foot, transverse;
40 pounds per linear foot, longitudinal.
Both forces shall be applied simultaneously.
2)
Forces applied directly to the substructure
The transverse and longitudinal forces to be applied directly
to the substructure for a 100 mileperhour wind shall be calculated
from an assumed wind force of 40 pounds per square foot. For >vincl
direction assumed skewed to t.he substructure this force shall be
resolved into component[.; perpendicular to the end and front
elevations of the substructure according to the functions cf the skew
angle. The component perpendicular to the end elevation shall act on
the exposed substructure area as seen in end elevation and the
component perpendicular to the front elevation shall act on the
exposed substructure area as seen in front elevation.
These loads
shall be assumed to act on horizontal lines at the centres of gravity
of the exposed areas and shall be applied simultaneously vJith the wind
loads from the superstructure. The above loads are for Group II
~oading and may be reduced 70 per cent for Group III Loading.
(0)
Overturning Forces
The effect of forces tendi>:tg to overturn structures shall be calculated
under Group II and Group III of Article 5.1. An up1vard force shall be applied
at the 1.vind•vard quarter point of the transverse superstructure width. This force
shall be 20 pounds per square foot of deck and sideT.valk plaa area for Group
II combination, and 6 pounds per square foot for Group III combination.
The wind direct ion shall be assumed to be at right angles to the longitudinal
axis of the structure.
2.12
THER~~L
FORCES
Provision shall be made for stresses or movements resulting from
variations in temperature.
The ri.se and fall in temperature shall be
fixed for the locality in whL·h the structure is to be constructed and shall
be figured from an assumed temferature at the time of erection. Due
consideration shall be given to the lag between air temperature and the
interior temperature of massive concrete members or structures.
211
35.
The range of temperature shall generally be as follow
Metal Structures
Moderate climate from.0°to 120°F
Extreme climate from minimum30° F to 120° F
Concrete Structure
Moderate Climate
Extreme climate
2.13
Temperature Rise
30° F
'45°F
Temperature Fall
30°F
·'"""'45'0 F
UPLIFT
Provision shall be made for adequate attachment of the superstructure
to the substructure should any loading or combination of loading, increased
by 100% of the live load plus impact, produce uplift at any support.
2.14
FORCE OF STREAM CURRENT
(A)
All piers and other portions of structures which are subject to the
force of flowing water shall be designed to resist the maximum stress
induced thereby.
The effect of stream flow on piers shall be calculated by the formula:
KV 2
p
p
=
v =
K
=
'
where
Pressure in pounds per square foot
velocity of water in feet per second
a constant having the following values for different shapes
of piers
Square end piers
Circular piers or piers with semicircular ends
Piers with triangular ends where the angle is
30 degrees or less
Piers with triangular ends where the angle is
more than 30 degrees but less than 60 degrees
Piers with triangular ends where the angle is
more than 60 degrees but less than 90 degrees
Piers ends of equilateral arcs of circles
Pier ends of arcs intersecting at 90 degrees
1. 50
0.66
0.50
0.50  0. 70
0. 70  0.90
0 .£~5
0.50
(B)
The value of v2 in the equation P = KV 2 shall be assumed to vary
linearly from zero at the point of deepest scour to the square of the maximum
velocity at H.F.L. The maximum velocity shall be assumed to be equal to 1.4
times the maximum mean velocity of the current.
(C)
The intensity of pressure P, shall be applied to all portions of
212
36.
the pier extending above the point of deepest scour.
piles when a pile foundation is used.
This will include
(D)
When the current strikes the pier at an angle, the velocity of the
current shall be resolved into two components, one parallel, and the other
normal to the pier. The value of the coefficient K to be applied to the
component parallel to the pier shall be as per paragraph A of this article.
The value of K to be applied to the component normal to the pier shall be
1.5 except for circular piers in which case the value will be 0.66.
(E)
When piers are designed parallel to flow an allowance of a 20 degree
oblique flow shall be included in the design.
2.15sub~
BUOYANCY
Huoyancy shall be considered as it effects the design of either the
structure, including piling, or of the superstructure.
'No provision need be made for buoyancy if the bridge is founded on
hcmogeneo'JS, impermeable strata. For bridges founded on coarse sand or
shingle, ful1 buoyancy shall be allowed. For other foundation conditions,
including foundations on rock, the calculated effect o£ buoyancy may be taken
as a fraction of the full buoyancy, at the discretion of the engineer
responsible for the design.
2.16
EARTH PRESSURE
Structures which retain fills shall be proportioned to withstand
pressure as given by Rankin 1 s formula; provided, however, that no structure
shall be designed for less than an equivalent fluid pressure of 30 pounds
per cubic foot.
For rigid frames a maximum of one~half of the moment caused by
earth pressure (lateral) may be used to reduce the positive moment in the
beams, in the top slab, or in the top and bottom slab, as the case may be.
"''hen highway traffic can come within a horizontal distance from the
top of the structure equal to one half its height, the pressure shall have
added to it a live load surcharge pressure equal to not less than 2 feet of
earth.
Where an adequately designed reinforced concrete approach slab supported at one end by the bridge is provided, no live load surcharge need be
considered.
All designs shall provide for the thorough drainage of the backfilling material by means of weep holes and crushed rock, pipe drains,
gravel drains, or perforated drains.
213
37.
2.17
EARTHQUAKE STRESSES
In regions where earthquakes may be anticipated, provlslon shall be
made to accommodate lateral forces from earthquakes as follow:
EQ
=
CD
where
EQ
Lateral force applied horizontally in any direction at centre
of gravity of the weight of the structure.
D
Dead load of structure
C
0.02 for structures founded on spread footings on material
rated as 4 tons or more per square foot.
0.04 for structures founded on spread footings on material
rated as less than 4 tons per square foot.
0.06 for structures founded on piles.
Live load may be neglected.
2.18
CENTRIFUGAL FORCES
Structures on curves shall be designed for a horizontal radial force
equal to the following percentage of the live load, without impact, in all
traffic lanes:
6.68 s2
c == o.00117 s 2 D
R
where
c
s
D
R
the
the
the
= the
centrifugal force in percent of the live load, without impact
design speed, in miles per hour
degree of curve
radius of the curve, in feet
The centrifugal force shall be applied 6 feet above the roadway
surface, measured along the centre line of the roadway. The desigil speed
shall be determined with regard to the amount of superelevation provided in
the roadway. The traffic lanes shall be loaded in accordance with the
provision of Article 2.5 and 2.6
When reinforced concrete floor slab or a steel grid deck is keyed
to or attached to its supporting members, it may be assumed that the deck
resists, within its plane, the shear resulting from the centrifugal forces
acting on the live load. The effects of superelevation shall be taken into
account.
38.
Section 3  DISTRIBUTION OF LOADS
3.1
DISTRIBUTION OF HHEEL LOADS TC STRINGERS, I.DNGITUDINAL BEAHS
AND FLCC'"R 3EAHS
(A)
Position of Loads for Shea1
In calculating end shears a~d end reactions in transverse floor beams
and longitudinal beams and str:i_ngers, no lateral or longitudinal distrihutioa
of the ;,Jheel load shall be assumed for the whee~ oc axle load adjacent. to the
end at which the stress is being determ~died. For lo.:ods in other positions on
the span, the distribution for shear shall be determined by the method
prescribed for moment.
(B)
Bending Noment in Stringers and Longitudinal Beams
In calculating bending moments in longitudinal beams or stringers no
longitudinal distribution of !:he wheel load shall be assumed. The lateral
distribution shall be determined as follows:
(1)
Stringers and Beams
The live load bending moment for each stringer shall be
determined by applying to the stringer the fraction of a wheel load
(both front and rear) determined by the following table:
Kind of
Floor
Bridge Designed for
one traffic lane
Bridge designed for two
or more traffic lanes
Concrete:
On steel Ibeam
Stringers (a)
S/7.0
If
s exceeds
1 ,, 1
v
see note (b)
On concrete
Stringers (c)
S/5.5
s
exceeds 6'
see note (b)
If
Concrete box
girder (d)
S/8.0
If s exceeds 12'
see note (b)
S/5.5.
s exceeds 14'
see note (b)
If
S/5.5
If s exceeds 14'
see note (b)
''
/:;
S/7.0
s exceeds 16'
see note (b)
If
The dead load considered as supported by the outside roadway
stringer or beam shall be that portion of the floor slab carried
by the stringer or beam. Curbs, railing and wearing surface, if
placed after the slab has cured, may be considered equally distributed
to all roadway stringers or beams.
31
39.
Notes:
S
(a)
Design of I=Beam Eridge by N.M. NewmarkProceedings,
ASCE, March 1948.
(b)
In this case the load on each stringer shall be the
reaction of the wheel loads, assuming the flooring
between the stringers to act as a simple beam .
(c)
Design of Slab an~ Stringer Highway Bridges by N.M.
Newmark and C. 2. C~ie:::;s~ Public Roads, January:FebruaryMarch 1953.
(d)
(2)
average stringer spacing in feet
The sidewalk 1 iVt' load (see 2. 11) shall b2 omitted for
interior and exterior box girders designed in accordance
with the wheel load distribution indicated herein.
.
Total capacity of Stringers
The combin~d design load capacity of all the beamb in a span
shall not be le~:s than required to support the total live a~. d dead
load in the span,
(A)
Span Lengths ( See also Article 6.2 )
for simple spans the span lengU! shEill bP the distar"cce cec,tre c:o cc:ntre
of supports but not to exceed clear span plus thickness of slab.
The following effective span lengths shall be used in calculating
distribution of loads and bending moments for slab continuous O'.'er more th&n
two supports:
Slabs monolithic with beams or walls (without haunches)
S
Clear Span
Slabs supported on steel stringers
S
(B)
distance between edges of flanges plus
stringer flange width
~
of the
Edge Distance of Wheel Load
In designing slabs the centre line of wheel load shall be assumed to be
1 foot from the face of the curb.
32
40.
(C)
Bending Moment
Bending moment per foot ~·7id~h
methods given under Cases A and H.
o[
sJab shall be calculated according to
In cases A and B:
S
Effective span length, in feec, as defined under "Span
Lengths" (Art. 3.2(A) and 6.2)
E
Width of slab in feet over vhich the load is distributd
P
Load on one wheel of truck
12,500 pounds for Class A loading
7,500 pounds for Class B loading
Case  A
Hain Reinforcement perpendicular to traffic
The live load moment per foot width of slab for a simple
span shall be determined by the following formula
(Impact not included)
M
(S+2) P/25
In slabs continuous over three or more supports a
continuity factor of 0.8 shall be applied to the above formulas
for both positive and negative moment.
Case  B
Main Reinforcement Parallel to traffic
For distribution of wheel loads
E
2+0.68
For roadway widths
K =
7.0 1
X
K
> 28'
:;;;
1
For roadway widths
~
28'
Roadway width
K
14 x Number of Truck Train Load
ings
Truck train moments for continuous spans and simple spans, except as
noted, shall be determined by suitable analysis and distributed over a
width of 2E. The lateral distribution of wheel loads for multibeam precast
concrete bridges shall not exceed that specified for slabs.
The live loadmoment per foot width of slab for simple spans shall
be determined by the following formulas.
33
41.
(Impact not included)
For simple spans up to 35'
Use N == 0.9S
K
X
For simple spans 35' to 70'
Use H = (1.35
(D)
c
..:>

16)
X
1Z
(Foot
)~ips)
Edge Beams ( Longitudinal)
Edge beams shall be provided for all slabs having main reinforcement
parallel to traffic. The beam may consist of a slab se.ction adrlitionally
reinforced, a beam integral with and deeper than the slab, or an integral
reinforced section of slab and curb.
It shall be designed to resist a live load moment of
0.5 x simple span truck train Moment
Value for continuous spans may be reduced 20 per cent unless a greater
reduction results from a more exact analysis.
(E)
Distribution Reinforcement
Reinforcement shall be placed in the bottoms of all slabs transverse to
the main steel reinforcement, to provide for the lateral distribution of the
concentrated live loads, except that this specification will not apply on
culverts or bridge slabs when the depth of fill over the slab exceeds two
feeL The amount shall be the percentage ·:;Jf the main reinforcement steel
required for positive moment as given by the follovJing formula:
For rnain rein.forcemer.;_t parallel to ':raffic;
100
.F'or
:nr:~i:1
Where S
~FOr
icular to traffic:
::20
rei·nforce:rnent p
=
the 0ffective
spa~
l~2grh,
Lfi teet
rna. i.n rein for c ent£;·nt per pec1f.i i c u la t· Lo t r s. f f i ~ th ~~ s pee· if Led ctJnou n ~.:: o.t
distribution reinforc.ern,=::nt sl:all bt~ us2d i
the rntddle half of the spc.n but t~Il_i.~
may be reduced by 50% in the end quarLers of the span.
Longitudinal reini:orcement. in tLe top of slab ha,Jing ti:H' main
reinforcement perp,:>nd icu1ar ro traffic shall not be les:~ rhail 0, 20 square
inch per foot of widt:h.
42.
(F)
Shear and Bond stress in Slabs
Slabs desi~ned for benrlin~ moment in accordance with the foregoing
shall be considered satisfactory in bond and shear.
(G)
Unsupported Edges, Transve:·se
The design assumptions of . . his article do e10t pro'Jide for the
effect of load near unsupported ·c::dges. There fore, at the ends of the
bridge and at intermediate points ';~here the continuit.y of the slab is
broken, the edges shall be suprcrted by diaphragms or other suitable means.
The diaphragms shall be designed to r2sist the full moment and shear
produced by the wheel loads which can come on them.
(H)
Cantilever Slabs
Under the following formulas for distribution of loads on cantilever
slabs, the slab is designed to support the load independent of edge support
along the end of the cantilever.
Case A. Reinforcement Perpendicular to Traffic
Each wheel on the element perpendicular to traffic shall be
distributed according to the following formula:
E
o.6x+2.5
PX
Moment per foot of slab =  E
in which X = distance in feet from load to point of
support
Case B. Reinforcement Parallel to Traffic
The distribution for each wheel load on the element parallel to
traffic shall be as follows:
E
1.2X + 1.6
For roadway widths ~ 28'
E
max
7.0
X K
K= 1
For roadway widths <28'
Roadway width
K=
14x Number Truck Train Load in
In calculating the moments one axle load of 36000 lbs. may be
substituted for the two 25000 lbs tandem axles of the standard truck
train if this produces a greater stress.
35
43.
(I)
Slab Supported on Four Sides
In the case of slabs supported alo~:tg four edge;o. and reinforced in both
directions the proportion of the load carried by the short span of the slab
shall be assumed as gi'Jen by the follmving equations:
b4
For load uniformly distributed, p
a4 +
b4
b3
For load concentrated at centre,p
a3 +
b3
ifhere p
proportion of load carried by short span
a = length of short span of slab
b
length of long span of slab
Where the length of the slab exceeds 1~ times its width, the entire
load shall be assumed to be carried by the transverse reinforcement.
The distribution vidth, E, for the load taken hy either span Bhall
be determined as provided for other slabs. Moments obtained shall be used
in designing the centre half of the short and long slabs. The reinforcement
steel in the outer quarter of both short: and long spans may be reduced 50
per cent.
In the design of the supporting beams, cons ideratio•1 shall be
given to the facr that the loads rle}h!ered to thE· supporting beaws are not
uniformly distributed along the beams.
3. 3
DISTRIBUTION 01:
lrT!:lt<:E1~
l.OPI.DS T!:lR01!GFi EAR'f!1 .FILLS
Whe!t the depth of fill is 2 fe;~t or more, conceEtrated loads shal i he
considered as uniformly distributed over a square, the sides of >:vhich an:
equal to 13/4 times the depth of fill.
'i.l!e shear produced by such loads shall be calculated as provided for
dead loads.
When such areaa from several concentrations overlap, the total load shall
be considered as uniformly distributed over the area defined by t:he outside
limits of the individual areas, but J:h.e tota1 vJidth of distrihnion shall nor
exceed the total width of the supporting slab. For single span the effect of
live load may be neglected when the dept.h of fill is more tlH:trl 8 feet and
excec.;ds the span length; for nmltipl2 spans it may be neglected ,,Jhen the depth
of fill exceeds the distance betveen races of enJ supports or abutments. When
the depth of fill is less than 2 feet the 1iheel load shall be distributed as
in slabs with concentrated loads. V.Jhen the calculated live load and impact
moment in co::1crete slabs based on distribution of the wheel load through fills·
as herein outlined exceeds the live load and impact momen! calculated according
to Article 3.2 then the latter moment shall be used.
36
44.
Section 4 l'l.ILITARY LOADING
4.1
LOADING
1':'1e military loading on the roadways of bridges or incidental
structures shall consist of 70 long ton tracked vehicle as shown in Figure
5 subject to the restriction that the nose to tail distance between two
successive vehicles is not less than 300 feet. No other live load shall
cover any part of the roadway of the bridge when this vehicle is crossing
the bridge. Only one such train shall occupy the roadway of the bridge.
.....
"'v
~
"v
co
,.._
00
,.._
(/)
(/)
0
z
z
~
I
C1
0
1
1n
J'()
10
J'()
70 TON MILITARY LOADING
FIGURE 5
41
45.
HORIZONTAL CLEARANCE
The minimum clearance betweec1 th2 rc.advn:;.y i;:;.ce o"" ctcrb and the
outer edge of ch2. track shall be assumf'd aH tollo"'rs ~
..Jid th ot roadway
11 1 6 1; to 13' ~6<1====•c•===== 1'0"
13 '6! 1 to 18 '0''=======~~~ 2'=0 11
4'·~0n
4,3=
Unless a more exact annlysis is made the 70 T
be distributed to the stringers as indicat;;:d ':ielow~
4.4
~1ilitary
L:J&d shall
IMPACT
Live load stresses shall be increased for items in Group AJ n,,ferred
to in Article 2.9 by an allowance as stated herein, for dynamic vibratory
and impact effects.
Impact shall not be applied to items in group B referred to in
article 2.9.
A,
Impact Formul§J:.
1.
Concrete Structures
Spans less than 30 feet
Spans 30150 feet
Spans greater than 150 feet., ,
2.
25%
10/~
8. 8/o
Steel Structures
Spans less than 30 feet
All spans greater than 30 ft ••
4.5
DISTRIBUTION OF LOADS AND DESIGN OF CONCRETE SLABS
(A)
Span lengths
(B)
25%
10/o
Edge distance of track
See Art. 3.2
In designing slabs the center line of track shall be assumed
to be minimum 1'6" from the face of curh,
42
46.
(C)
Bending Moment
B..::r::ding moment per foot of ;,d.d::J·; or s:c;.b sha.lJ. be
according to methods give.n nnder Ca.se':; A and B,
calcDlat2c~
In cases A and B:
s
E~fective
"~)pan
span length ~n feet, as defined under
Length (Article 3,2.)n
E
Width of slab in f6et over which a track is
P
Load on one track
Case A 
=
di~tributed
78.4 Kips (35 Long tons)
Hain Reinforcement Perper1dicular to 'iraffic
Moment for simple spans
L 1 s
For spans continuous ·over three or more supports use 0,.8 x simple
span moment for both positive and negative moment.
Case B :Main Reinforcement Parallel to Traffic
For simple spans greater than 12 feet
M
P(S~6) /I..~E
For simple spans less than 12 feet
For moments in continuous spans a suitable analysis shall be used.
The width of distribution, E, shall be computed as follows:
.458
+ 4.0
43
47.
Section 5 · UNIT STRESSES
5.1
GENERAL
Unless otherwise noted the allowable unit stresses indicated herein
are given in pounds per square inch.
The following groups represent various combinations of loads and forces
to which a structure may be subjected. Each part of such structure or the
foundation on which it rests, shall be proportioned for all combinatio~s of
such of these forces as are applicable to the particular site or type, and
at the percentage of the basic unit stress indicated for the various groups
except that no increase in allowable unit stresses §.lJ..aJLb.e perglitted for
members or conn~~tions carrying wind loads oniy. See article 2.1 to 2.l8
fOr 'Toads. and forces.
The maximum section required shall be used.
Percentage of Unit
Stress
..;,{"''
".
:..~l<"'#8~>1'11~
Group
Group
Group
Group
Group
Group
Group
Group
Group
'.D
IL
l
/I
'E
I
II
III
IV
v
VI
VII
VIII
IX
;B
w
WL
LF
CF
F
R
S
T
EQ
SF
ICE
D+L+I+E+B+SF
D+E+B+SF+W ,...
'
.....~
.·/.
;; "·~ ~··,;· .
Group I+b.~+F1CF+~p% ~;2!!,&i'
== Group I+R+S+T
..  ......·
Group II+R+S+T
= Group III+R+S+T
 D+E+B+SFilEQ}
== Group I+fcE
== Group II+ICE
Dead Load
= Live Load
Live Load Impact
/ (,
= Earth Pressure
Buoyancy
== Wind Load on Structure
Wind Load on Live Load100 pounds
per linear foot
= Longitudinal Force from Live Load
= Centrifugal Force
Longitudinal Force due to friction
Rib Shortening
Shrinkage
== Temperature
Earthquake
Stream Flow Pressure
Ice pressure
.
51
100%
··125%
125%
125%
140%
.140%
133%
140/o
150%
r
I
48.
5.2
CONCRETE STRESSEs(i)
(A)
Standard Notations and Assumptions
fc
=
Permissible Extreme fiber stress in compression
Unit ultimate compressive strength of concrete. as determined
by 6 inch cube tests ar: 28 days,
f 1c
(f'c) ==
n
Unit ultimate compressivE: strength of concrete as determined
by 6" cylinder test at 28 d::tys.
ratio of modulus of elasr.icity of steel to that of concrete.
The 'value of n, as a function of the ultimate strength of
cone:. rete, shall be assumed as follows:
Cube
f 1c
::::
2600
3200
3800
5100
6000
Cylinder
3100
3700
5000
5.'·900
or more
(f'c) = 2000
2500
3000 =
4000 =
5000

2400
2900
3900
4900
or more
n=l5
n=l2
n=lO
n= 8
n= 6
for computations of deflections the value of n=8 shall be used.
Coefficients:
Thermal
Shrinkage.
(B)
.000006
,0002
per
Allowable Stresoes (ii)
(1) :flexurco.
Extreme fiber in compression.
Extreme fiber in tension 0
plain concrete, primarily in
footings=
Extr·.::me fiber in tension,.
reinforced concrete
Cube
Strength
fc= 0.33 f'c
Cylinder
Strength
0.40(f'c)
ft:= 0,025 f'c
O.OJ(:Cc)
None
None
The ratios and :,ralues in thiB SE,ction apply to concrete made with convef1t
ional hard rock aggregate, values applicable to light weight aggregate
concrete should be established by adequate investigation,
(ii) In no case shall the allowable stresse.s be basE:d on an ultimate cube
strength greater than 5800 psi or ultimate cylinder strength greater than
4500 psi except for prestressed concrete.
52
49.
(2)
Shear
Cube
Strength
Beams without web reinforcement
Longitudinal bars not anchored
or plain concrete footings
0.016 f'c
0.02(f'c)
Max 75 psi
Longitudinal bars anchored
0.024 f'c
0.03(f'c)
Max 90 psi
Beams with web reinforcement
V=0.060 f'c bjd
0.075(f'c)bjd
Horizontal shear in shear keys
between slab and stem of T
beams and box girders
(3)
Cylinder
Strength
0.12 f'c
O.lS(f'c)
0.08
0.10(£' c)
BonJ, Deformed bars:
With deformation complying with
specifications ASTM A 305
Straight or hooked er:ds,exclus=
ive of top bars
(a)
In beams, slabs, o~e way
footiu.gs,
(b)
In two w.TJ footingt: B(;'Y,
of mw ;,1ay footi.Tt>U'
Top bars= Hsrs t1F:ar top o~: b?BElS
and gird·:;rs having more thBn 12
inches of concrete under th8 bar2 0.05 f 1 c
For plain bars the
ed by 5W,
5 ' ,,,=
)
VBll1fcS
0.06
list:nd ior defonued bB.rs sh,;ill be d.ecn,as
REINFORCJ<:MFNT
Nild Steel co;:tforming to !LS, 785 or A3'i'H A15
~)peci:ficHtionR
SteP.l P.e:Lnforcement:
Tens ion in flexural nerr!bersc"  ·· 18,000
Te::~s ioD in web men1aers~  · ~ ~·~ 18, 000
Compress ior1 in co lum::::.s~  = 13 ~ 200
Co;!ipression in
5.4=
SIEE~
Steel
Parr: 3 B,
be;;tr:lS
See Article 6. 6
STRESSES
stre~>SEs shall conforn, to the British ;Jesign Sta:1{'iard 153
Stresses, of the British Standard Institution 1958 Edition.
53
50.
SECTION 6  CONCRETE DESIGN
6.1
GENERAL ASSUMPTIONS
The design of reinforced concrete members under these specifications
shall be based on the following assumptions:
(1)
Calculations are made with reference to unit working stresses
and safe loads, as elsewhere specified herein, rather than 1iJith reference to
ultimate strength and ultimate loads.
(2)
A plane section before bending remains plane after bending.
(3)
The modulus of elasticity of concrete in compression is
constant within the limits of working stresses; the distribution of compressive stress in flexure is, therefore, rectilinear.
(4)
The ratio
11
n" shall be assumed as follows:
Value of n
Es
Ec
Ultimate strength
of concrete, Lbs. per sg.in.
6 11 cube
6 11 cylinder
]trength
strength
2600
3200
3800
5100
6000
 3100
3700
 5000
 5900
or more
2000
2500
3000
4000
5000
 2400
2900
 3900
 4900
or more
For computations of
strength
15
12
10
8
6
For computtation of
deflection
8
In computing the ultimate deflection of slabs and beams, the value
of the modulus of elasticity should be assumed as onethirtieth that of steel
in order to allow for the effect of plastic flow and shrinkage.
(5)
Concrete shall be assumed as offering no tensile resist
ance.
(6)
The bond between concrete and metal reinforcement is
a.s;:;umed to remain unbroken throughout the range. of working stresses. Under
compression the two materials are therefore stressed in proporation to
their moduli of elasticity.
(7)
Initial stress in the reinforcement due to contraction
or expansion of the concrete, is neglected, except in the design of
reinforced concrete columns.
61
51.
(8)
For the determination of external reactions, moments, shears,
and deflections, moments of inertia of rigid frame and continuous structures
shall be computed for the gross concrete sections, neglecting the effect of
steel reinforcement, except that the transformed area of the steel 3hall be
included for columns, arches or other compressive members.
1be moment of inertia of the entire superstructure sections,
except railings or any curbs or sidewalks not placed monolithically with the
superstructure before the falsework is released, and the moment of inertia
of the full cross section of the pier or bent shall be used to determine the
elastic properties of the various spansand supports.
(9)
(10) The depth of girder or L~lab to be used in computing momer1t of
inertia at the centerline of the support shall be ohtair1ed by extending the
slope of the intrados of the member to the centerline.
(11) Rigid frames ahall be considered free to sway longitudinally
due to the application of vertical dead loads and vertically applied live
loads except when the structure is restrained from movement by extertEll
forces.
(12) The assumption of no moment restraint at the base of column
shall be m<'3d in the analysis of rigid fra:nes (superstructures) unlsss the
bas~=: is knmvn to be fully fixed.
When a pim!ed end condition is assumed for
the analysis of the superstructure, the base of column, footing and piling
shall be designed to resist the mor.1ent resulting from a!l a2sumed restraint
varying from zero to full
fixity.
The degree of restraint shall he
deterrt1i.ned by the type of footing and the character of the foundation
material.
(13) Piers or bents constructed integrally with footings placed on
a skew exceeding 10° shall be considered fixed at the top of footing.
6.2
SPAN LENGTHS
The effective span lengths of slabs shall be as specified in
Article 3. 2.
The effective span length of freely supported beams shall not exceed
the clear span plus the depth of beam.
For the analysis of all rigid frames, the span lengths shall be taken
as the distance between the centres of bearings at the top of th12 footings.
The span length of continuous or restrained floor slabs and beams
shall be the clear distance between faces of support.
6.3
EXPANSION
In general, prov~s~on for temperature changes shall be made in all
simple spans having a clear length in excess of 40 feet.
62
52.
In continuous bridges, prov~s~ons shall be made in the design to
resist thermal stresses induced or means shall be provided for movement
caused by temperature changes.
Expansion not otherwise provided for shall be provided by means of
hinged columns, rockers, sliding plates or other devices.
6.4
TBEAMS
(A)
Effective Flange Width
In beam and slab construction, effective and adequate bond and
shear resistance shall be provided at the junction of the beam and slab. The
slab may then be considered an integral part of the beam, but its assumed
effective width as a Tbeam flange shall not exceed the following:
(1)
(2)
(:3)
One fourth of the span length of the beam.
1he distance centre to centre of beams
Twelve time the least thickness of the slab plus
the width of the girder stem.
For beams having a flange on one side only, the effective overhanging flange width shall not excet.~d one twelfth of the span length of
the beam, nor six times the thickness of the slab, nor one half the clear
distance to the next beam.
(B)
Shear
The flange shall not be considered as effective in computing the
shear and diagonal tension resistance ofTbeams, except in the determination
of the value of j.
The horizontal shearing unit stress at the juncture of the. flange
and the monolithic fillet joining it to the girder stem shall not exceed
that given in Article 5.2(B)(2), shear of beams with web reinforcement.
(C)
Isolated Beams
Isolated beams, in which the Tform is used only for the purpose of
providing additional compres:::io::1 area, shall have flange thickness of vot
less than onehalf the width of the web, and a total flange width of not
more than 4 times the width of web.
(D)
Diaphragms
For Tbeam spansJdiaphragms or spreaders shall be placed between
the beams at the middle or at the third points.
63
53.
(E)
Construction Joints
When a construction joint is required between the slab and the seem
of the beam, the shearkeys shall be designed in accordance with allowable
stresses given in Article 5.2(B)(2).
6.5
REINFORCEMENT
(A)
Spacing
The minimum spacing centre to centre of parallel bars shall be 2~ times
the diameter of the bar, but in no case shall the clear distance between the
bars be less than 1~ times the maximum size of the coarse aggregate.
(B)
Covering
The minimum covering, measured from the surface of the concrete to the
face of any reinforcement bar, shall not be less than 2 inches except in slabs
where the minimum covering shall be 1 inch at the bottom and P2" at the top.
Where an additional wearing surface is to be used the required clearance at
the top of slab may he reduced to 1". In the footings of abutments and
retaining walls and in piers the minimum covering sh<:tll be 3 inches. In work
exposed to the action of sea water the minirlmm covering shall be 4 inches
except in precast concrete piles 3 where a minimum of 3 inches may be used. For
stirrups in Tbeams, the minimum cover shall be. 1~ inches.
(C)
Splicing
Tensile reinforcement shall not be spliced at points of maximum stress.
When reinforcement is spliced, the spliced bars shall lap sufficiently to
develop the full strength in bond.
(D)
End Anchorages and Hooks
End anchorage may be an extension of the bar, either straight, bent
or hooked. A properly dimensioned hook is: (a) one in wb.ich the bar is bent:
in a complete semicircular turn with a radius of bend on the axis of the bar
of not less than three bar diameters, plus an extension at the free end of
at least four bar diameters?(b) a 90° bend having a radius of not less than
four diameters plus an extension of twelve bar diameters.
Hooks having a radius of bend of more than six bar diameters shall be
considered as extensions to the bars. Hooks shall not be considered effective
in adding to the compressive resistance of bars. Any mechanical device capable
of developing the strength of the bar without damage to the concrete may be
used in lieu of hooks or extensions.
(E)
Extension of Reinforcement
(1)
To provide for contingencies arising from unanticipated
distribution of loads, yielding of supports, shifting of points of
inflection, or other lack of agreement with assumed conditions
governing the design of elastic structure, the reinforcement shall
64
54.
be extended at the supports and at other points between the supports
as indicated in (2) to (5) below. These paragraphs relate to
ordinary anchorage and are the minimum requirements under which
normal working stresses for bond or shear are permitted.
(2)
Negative tensile reinforcement at the supported end of a
restrained or cantilever beam or member of a rigid frame shall be
extended in or through the supporting member in such a manner as to
develop the maximum tension in the bar with a bond stress not
exceeding the normal working stress provided in Article 5.2.
(3)
Between the supports of continuous or simple beams, every
reinforcement bar shall be extended at least 25 diameters but not less
than 1/20 of the span length, beyond the point at which computations
indicate i t is no longer needed to resist stress .A i!typ•:o hcok si:1al1
be: co:.~sidered equal tc' 16~ and an I, type hook equal to
(4)
In simple beams and freely supported ends of continuous
beams, at least 1/3 of the positive reinforcement shall extend beyond
the face of the supports a distance sufficient to develop ~ the
allowable stress in the bars.
s,.
(5)
In restraiued or continuous beams at least i; of the positive
reinforcement shall extend beyond the face of the supports and the
remainder treated as provided in (3).
(6)
Dowels and bars carrying little or no theoretical stress
should be embedded at least ten bar diameters from the construction
joint.
(F)
Maximum Sizes
lbe maximum size of bar reinforcement shall be 1~ inches in
diameter, unless the particular conditions warrant the adoption of special
reinforcement design.
When structural steel shapes are used for reinforcement, mechanical
bond should be provided which will effectively bond the memher to the
surrounding concrete mass.
(G)
Position of Negative Moment Reinforcement in IBeams
Wben the floor slabs or flange of a continuous or cantilevered
Tbeam is placed after the concrete in the stem has taken its set, at
least 10 per cent of the negative moment reinforcing steel shall be
placed in the beam stem in order to prevent cracks from falsework settlemert
or deflection. 'This reinforcing steel shall extend a distance of onefourth
the span length each side of t:he intermediate supports of continuous spans,
onefifth the span length from the restrained ends of continuous spans, and tte
entire length of cantilever spans .In lieu of the above requiremer:.t two number
65
55.
8 bars full length of the girders may be used
( ")
n
Reinforcement of Beam Sides
The depth of the beam between the main reinforcement and the flange
or the top reinforcement shall be reinforced with horizontal bars in both
faces to prevent temperature and shrinkage cracks. The total area of steel
in each face shall not be less than eq. in. per foot of height of the
unreinforced beam side. The spacing of bars shall not exceed 2 feat.
6.6
COMPRESSION REINFORCEMENT
II~
BEAMS
Compression reinforcement in girders and b~ams shall be secured
against buckling by ties or stirrups adequately anchored in the concrete,
and spaced not more than 16 bar diameters aparL Where compression
reinforcem~nt: is used, its effective;:~.ess in resisting bending ma:Y' be tc:~ken
as twice th~ ·.;alue indicated from the calculations as3uming a straigh t1 ine
relation between stress and strain and the modular relatio~ of stress in
steel to stress in concrete given in Article 6.1(4). However, in no case
should a str~ss in compression reinforcement gr2ater than 16,000 pounds per
square inch be allowed.
6.7=
WEB REINFORCEMENT
(A)
Gt:c.neral
When the allowable unit shearing 3tres& for concrete is exceeded,
web reinforcement shall be provided by one of th<::: following methods:
(1)
(2)
(3)
Longitudinal bars bent up in s0ries or in single plane.
Vertical stirrups.
Combination of bentup bars a:<1d vertical stirrups.
Wh.er1 any of the above methods m: reinforcement are used, tb.e concrete
may be assumed to carry external vertical shear not to exceed .024 f'
(cube
strength) or . 03 (f~), (cylinder strength) (Maximum 90 pounds per sq~are inch)
the remainder of shear being carried by the web reinforcement.
The we~s of Tbeams and box girders shall he reinforced with stirrups
in a 11 cases,
(B)
Calculation of Shear and Bond
Diagonal tension, shear, and bond iQ reinforced concrete beams shall
be calculated by the following formulas:
NOTATIONS:
A
v
total area of web reinforcement in tension within a distance
66
11
s 11
56.
(measured in a direction parallel to that of the
main reinforcement), or the total of all bars bent
up in any one plane.
b
width of beam.
d
effective deptl1, or depth from compression surface of
beam to centroid of tension reinforcement.
tensile unit stress in web reinforcement.
j
ratio of lever arm of resisting couple to depth ;;d".
s
spacing of web reinforcement bars, measured at the neutral
axis in a direction parallel to that of the main reinforcement.
u
bonJ stress per unit area of the surface of the bdr.
v
shearing unit stress
V'
external shear on any section after deducting shear carried
by concrete.
sum of perimeters of bars
angle between web bars and axis of beam
FORMULAS:
Shearing unit stress, as a measure of diagonal tension
v
v
bjd
Stress in vertical web reinforcement
f
v
V' s
When a series of web bars of bentup longitudinal bars are used, the
reinforcement shall be designed by the following formula:
V' s
fv jd ( sinO:+ coso()
When the web reinforcement consists of bars bent up in a single
plane so as to reinforce all sections of the beam which require reinforcement, the bentup bars shall be designed by the following formula:
67
57.
V'
A
f
v
sino(
1be bond between concrete and reinforcing bars in beams and slabs
shall be computed by the following formula:
u
v
jd ~0
(For approximate results
11
j
11
in the above formulas may be taken as
7/8)
Bond shall be similarly computed on compressive reinforcement, but
the shear used in computing the bond shall be reduced in the ratio of the
compressive force assumed in the bars to the total compressive force at the
section. Anchorage shall be provided by embedment past the Bection to
develop the assumed compressive force.
(C)
Bentup Bars
Bentup bars used as web reinforcement may be bent at any angle
between 20 and 45 degrees with the longitudinal reinforcement. The radius
of bend shall not be less than 4 diameters of the bar.
The spacing of bentup bars shall be measured at the neutral axis
and in the direction of the longitudinal axis of the beam.
l'his spacing shall
not exceed thre.:~~fourths the effective depth of the beam. The first bar
from the support shall eros~ the middepth of the heam at a distance from thE
face of the support, measured parallel to the longitudinal axis of the beam,
not greater than one=half the effective depth.
(D)
Vertical stirrups
Where stirrups are required to carry shear, the maximum spacing of
vertical stirrups shall be limited to !;z the depth of the beam, and where not
required to carry shear, the maximum spacing shall be limited to 3/4 the depth
of the beam.
The first stirrup shall be placed at the distance from the face
of the support not greater than one fourth of the effective depth of the
beam.
(E)
Anchorage
(1)
The stress in a stirrup or other web reinforcement shall not
exceed the capacity of its anchorage in the upper or lower onehalf of the
effective depth of the beam.
(2)
Web reinforcement which is provided by bending into an
inclined position one or more bars of the main tensile reinforcement where not
required for resistance to positive or negative bending, may be considered
completely anchored by continuity with the main tensile reinforcement, or by
68
58.
embedment of the requisite length in the upper or lower half of the beam
provided at least one half of such embedment is as close to the upper
or lower surface of the beam as the requirements of fire and rust protection
allow. A hook placed close to the upper or lmver surface of the beam may
be substituted for a portion of such embedment.
(3)
Stirrups shall be anchored at both ends by one of the
following methods or by combination thereof:
'
(a)
Rigid attachment, as by welding, to the main longitudinal
reinforcement.
(b)
Bending round and clostly in contact with a bar of the
longitudinal reinforcement, in the form of a Ustirrup
or hook.
(c)
A hook placed as close to the upper or lower surface of the
beam as the requirements of fire and rust protection will
allow. In estimating the capacity of this anchorage the
stress developed by bond between midheight of the beam and
the centre of bending of the hook may be added to the
capacity of the hook.
(d)
An adequate length of embedment in the upper or lower onehalf of the effective depth of the beam, whether straight
or bent. Anchorage of this type alone should not be relied
on for stirrups in cases where the shearing stress in the
web exceeds that recommended for beams without end anchorage
of the reinforcement.
(See Article 5.2)
6.8
COLUMNS
(A)
General
Other provisions of Section 6, Concrete Design, shall apply in the
design of columns unless specially modified by this article.
In the design of columns the unsupported length shall be defined as the
clear distance between struts, cross beams, footings or other types of adequatE
restraint to lateral movement. Where a bracing member has haunches at its
junction to a column, the unsupported column length shall be measured from
the junction of the haunch with the column provided that the face of the
haunch makes an angle with the face of the column of at least 45 degrees.StrutE
or cross beams joining columns at angles greater than 30 degrees from the
plane of symmetry of the column shall not be considered as adequate support.
69
59.
The least lateral dimension of a column shall be taken as: (1) for rectangular
columns, the overall thickness along a principal axis; (2) for spirally
reinforced columns, the overall diameter including the encasement of the
spirals; (3) for HT 11 shaped columns, the width or depth of the T.
In a column which, for archic:ectural or other reasons, has a larger
cross section than required by the load carried, the minimum amount of longitudin::tl steel hereinafter specified may be reduced provided that in no case
shall less 'longitudinal steel be used than that: required by the mir:imum
column designed with one per cent of longitudinal steel.
The notations used in this article are as follows:
over~all
or gross crosssectional area of spirally reinforced
or tied pier, pedestal or column in square inches.
crosssectional area of core of spirally reinforced columns
measured to the outside diameter of the spiral, square inches.
As
=
A
crosssectional area of longitudinal steel
Ag
+ (n1) As , effective area of column
fa
c
fa
or
factor used in the design
of members subject to
combined axial and bending
stresses
least lateral dimension of column, inches
0.30 f'c*
d
e
eccentricity of resultant load on a column, measured from a
gravity axis.
f'c =
crushing strength of 611 cubes at age of 28 days, psi
(f'c)=
crushing strength of 6"xl2" cylinders at age of 28 days, psi .
.J.
0.175 f~" + fs p
for spiral columns and
fa
1
+ (n1)
p
80% of that amount for
0.225(f'c)
+ fs
p
tied columns.
or
1
fe
fs
*
'ld~
+ (n1)
p
maximum allowable compressive stress in members subjected to
combined axial and bending stress, psi.
nominal working stress in longitudinal reinforcing steel (see
Article 5.3)
610
6" cube strength
6 11 cylinder strength
60.
f's
yield stress of spiral reinforcement (for steel grades not
having a definite yield point, the str~ss causing a 0.2 per
cent plastic set), psi
t
2
a factor used in the design of members subjt:cted
K
to combined axial and bending stress.
L
n
Pe
Pp
Ps
Psl
Pt
Ptl
p
pi
r
t
(B)
=
unsupported length of column, inches.
ratio of modulus of elasticity of steel to that of concrete.
a load eccentrically applied.
total load on pier or pedestal, pounds
total load on spirally reinforced column, pounds
total load on spirally reinforced long columns pounds
total load on tied column, pounds
total load
on tied long column, pounds
ratio of longitudinal steel area to gross column area
ratio area of spiral reinforcement to core area
radius of gyratio!l of section (transformed section) in the
direction of eccentricity or bending.
over=all depth of column in the direction of eccentricity
or bending
Piers and Pedestals
The ratio of the unsupported length of unreinforced concrete piers
or pedestals to their least dimension shall not exce~d 3, The total load
on any unreinforced concrete pier or pedestal shall not exceed that give.n
by the following formula:
Pp
0.20 Ag f'c*
(1)
or 0.25 Ag (f'c)**
(C)
Spirally Reinforced Columns
(1)
Longitudinal Reinforcement
Longitudinal reinforcement shall be placed within the area
contained by the spiral reinforcement. The ratio between the area
of longitudinal reinforcement and the gross area of the column,
including the encasement outside: the spiral reinforcement, shall be
not less than 0,01 nor more than 0.08. The:re shall be a minimum
of six longitudinal bars evenly spaced around the periphery of the
column core. The clear spacing between individual bars or pairs
of bars at lapped splices shall be not less than 1~ inches or 1~
times the maximum size of the coarse aggrt>gate used, subject to the
further requirement that the centretocentre spacing shall be not
less than 2~ times the diameter of bars. The diameter of bars
shall be not less than fiveeighths inch. For columns with a
611
~':
**
6" cube strength
6 11 cylinder strength
61.
circular spirally reinforced core having excessive size or other
outside shapes, the gross area to be used in determining percentage
of reinforcement shall be a circle with a diameter equal to the
minimum core required for structural design plus the specified
outside cover.
(2)
Spiral Reinforcement
Spiral reinforcement shall consist of uniform spirals held
firmly in position by attachment to the longitudinal reinforcement.
Spiral reinforcement may be plain ar deformed reinforcing hars or
cold drawn wire. Splices in spiral bars should be avoided if
practical and, if necessary~ shall be made by welding or by lap of
1~ turns.
The pitch of spirals shall not exceed 1/6 of the core
diameter, The clear distance between individual turns of the spiral
shall not exceed 3 inches or be less than 13/8 inches or 1~ times
the maximum size aggregate used. Spiral reinforcement shall exte;:·:d
from the footing or other support to the lEvel of the lowest horizontal
reinforcement of members supported by the column.
The ratio of the volume of spiral reinforcement to the
volume of core of the column, out to out of spirals, shall be not less
than
0. 35
p1
or
0,45
(~
Ac
1)
1)
(~
Ac
f'c
'{(
f's
(2)
.1:,c
(f'c)
f's
The yield strength for design assumption, f's shall not be
taken higher than 60,000 p.s.i.
(3)
Allowable Load ·· Short Columns
The provision of this subarticle shall apply only to columns
having ratios of unsupported height to least lateral dimension of not
more than 10. The total axial load on a column shall not exceed
that given by the following formula.
p
0.175 f'c
s
Ag + As fs
'i.(*
or
(4)
"'k
0.225 (f'c)
(3)
Ag +As fs
Long Columns
The total axial load on a column having a ratio of unsupported
height to least lateral dimension greater than 10, but not greater than
~'(
*i~
6"cube strength
6 11 cylinder strength
62.
20, shall be not greater than given by the following formula:
Psl ~
Ps (1.30.03 L/d)
(4)
If L/d ratio of columns exceeds 20, the column shall be
investigated for elastic stability.
(D)
Tied Columns
(1)
Longitudinal Reinforcement
The longitudinal reinforcement shall consist of at
least four bars, and when only four bars are used • they shall be
placed at the corners of the section. Bars shall be placed at each
intersection of column faces. The bars shall be not less than fiveeighths inch in diameter. The ratio of the total crosssectional
area of the bars to the total crosssectional area of the column
shall be not less than 0.01 nor more than 0.04.
(2)
Hoops and Lateral Ties
Hoops shall surround the longitudinal reinforcement:. The·y
shall be not less than onefourth inch in diameter and shall be
spaced not more than 12 inches apart except that this spacing may be
increased in the case of pier shafts or columns having a larger eros&
section than required by conditions of loading, Adequate auxilLe.ry
ties shall be provided to support intermediate longitudinal bars
whose distance from any tied bar exceeds 2 feet.
(3)
Allowable Load  Short Columns
The provisions of this subarticle shall apply only to columns
having ratios of unsupported height to least lateral dimension of
not more than 10. The total axial load on a column shall be not
greater than 0.8 of that given by equation 3, which results in
p
0.8 (0.175 f' *
· c
~
t
Ag
+ As
or 0.8 (0.225 (f'c)Jd; Ag
(4)
+
fs)
(5)
As
fs)
Long Columns
The total axial load on a column having a ratio of
unsupported height to least lateral dimension greater than 10
but not greater than 20 shall be not greater than given by the
following formula
Ptl
=
Pt (1.30.03 L/d)
613
*
6" cube strength
6" Cylinder strength
(6)
63.
If the L/d ratio exceeds 20, the column shall be investigated
for elastic stability.
(E)
Bending Moments in Columns
When beams or slabs are connected to columns; the moments induced
in the columns by such beams or slabs shall be provided for in the column
design.
(F)
Combined Axial and Bending Stress
A reiaforced concrete column which is syrru.'1letrical about two mutually
pe.rpendicular planes through its axis and wh.ich is subjected to an ax.i.al
load f't>. s combi!ted with bendi:J.g in one or both o:i: the planes of syrn1netry
may he designed on the basis of uncracked sections provided the ratio of
eccentricity to depth e/t, is not greater than 0.5 in either plane, ·:r:he
combined fiber stress in compression is given by the following formula:
K~t:
p
··e
fe
Au
<::>
(
1
1
+

+
t
(nl)p
)
(7)
The column may be designed for an equivalent axial load P 8 or Pt .s.s
given by the following formula:
p
Pe ( 1
+
K•e )
(8)
C t
The maximum allowable compressive stress in the concrete, fe, in
columns subjected to combined axial and bending stre.ss as described above
shall not exceed that given by the following formula:
K· e
fe
(
1
+t K•e
1
)
(9)
+c
t
In the case of square or rectangular columns subjected to bending in
both planes of symmetry the column shall be designed on the basis of uncracked
sections only when the sum of the e/t ratios about both axis does not exceed
0.5. In this case formulas (7), (8) and (9) may be used by substituting for
Ke/t the sum of the Ke/t ratios in both planes of bending.
In formulas (7), (8) and (9) for an approximate or trial design K may
be taken as 8 for a circular spiral column and as 5 for a rectangular, tied
614
64.
or spiral column.
adopted section.
The assumed value of K shall be checked for the
Reinforced concrete columns, in which the e/t ratio is
grea.ter than 0.5 in the case of bending in one plane or in which the sum
of the e/ t ratios is greater than 0. 5 in the. case of bending in both
planes of symmetry, shall be designed on the bas is of the rEcognized
th<::ory for cracked sections, based at: the assumption that no tensim~1
is resi2ted by the concrete.
In such <::.iOlses the modular ratio 0 n, for tr,e compressive
reinforcement may ht:: assnmed !iS twice thG value giv.on in Artie lt; 5. 2 (A);
hmvever, the stress in the compresBi'.'e rei.rt:f.or<::ement wheE caleulated on this
bs.sis, shall not be greater than the allowabl•.:o stress irt te:r:1sion,
rosr.ncr::r
AND fiiRECTION OF
NEUTRA.:L X'CIB
A method of determining the locG.tioc. and din::ctiou of the
neutral axis is as follows:
Wh<?.n the plar:e of bendir:.g cos,:; not lie ort principal axi"' o:f: thf:'
cohm1r1 s;:,ctio<l or whe'.1 the poict: of applic.:ttio:.' of: r.he .resulta:~J.: load
does not lis witl,_in t.l:t2 ken:;. area. o:: tht. gros3 trJ.:bformEod ':'~'ct:i.on~ tJ,<::,
posit ion a:1d direction. of the. nEutral !.ixis r.r.ay b<:: determined by the
followiug formula:
p
+
Mi
H'v
Xo±~
I~
A
=
I'
A
Yo
0
I 'y
load parallel to the axic; oi the columE in pound;:;
transformed area of crae;ke.d section in squa.re inches
.:. :~f:~y.:
M'x
:;
y
Iy
(I
I'
X
=
I
X
M'y =
M
Hx
X
y)
My
Ixy
:0..x
IX
2
(Ixy)2
I'y = IyIy
~
Ix
~
= Moment
of external forces about Y. axis
~
= Moment
of external forces about X axis
X
0
Y = coordinate referred to axes passing through the
0
centroid of the section.
615
65.
Ix
moment of inertia about the y axis
T
moment of inertia about the X axis
T
Product of inertia about axis, X and y
y
.Lxy=
In solving the above formula it is necessary to assume a value
for either X0 or Y0 •
FORMJJLAS FOR STRES3ES
With the position and direction the neutral axis determined, the::
maximum unit stress in the concrete shall be computed with the formula,
M' y
f
M'x
Yn
or
I' y
f
=
I' X
xn
in which
distance from the neutral axis to the extreme fiber
in compression measured parallel to the Y axis,
X
n
distance from the neutral axis to the extreme fiber
in compression measured parallel to the X axi~.
ThE: limiting steel ratio of 0.04 provided in Article 6.8(D) (1)
may be increased to 0.08 for tied columns designed to withstand combint:d
axial a:c.d bending stresses provided that the amount of steel spliced by
lapping in any 3 foot length of colum...11 shall not exceed a steel ratio of
0.04. The size of the column shall be not less than that required by axial
load alone.
6.9~
CONCRETE ARCHES
(A)
Shape of Arch Rings
Arch rings shall be selecte.d. as to shap!? in such manner that the axis
of the ring shall conform, as nearly as practicable, to either the equilibrium
polygon for full dead load or to the equi.librium polygon for full dead plus
one=half live load over the full span 1 whichever produces the smallest
bending stresses under combined loads.
(B)
Spandrel Walls
When the spandrel walls or filled spandrel arches exceed 8 feet in
height above the extrados they shall be designed as vertical slabs supported
by transverse diaphragm walls or deep counterforts. Vertical cantilever
walls over 8 feet in height, or counterforts having a back slope of less
than 45 degrees with the vertical, shall not be used, on account of the
616
66.
excessive and indeterminate stresses set up in the arch ring by
torsion.
(C)
Expansion Joints
Ven:ical expansion joints shall be placed in the spandrel walls
of arches to provide for movement due to temperature change and arch
deflection. These joints shall be placed at the ends of spans and at
intermediate points, generally not more than 50 feet apart.
(D}
Reinforcement
Arch ribs in reinforced concrete construction shall be reinforced
with a complete double line of longitudinal reinforcement consisting of an
intradosal system and an extradosal system connected by a series of &tirrupe
or tie rods.
For barrel arches, a sys t.e.m of transvers£ reinforcement, thoroughly
anchored to tb.e longitudinal reinforcement, shall be used in both intrados
and extrados. 'I'he transverse reinforcement sbdll be proportioned to resist
the bending stress due to any overtuc1.ing action of the spandrel wall.
For rib arches, hoops or tie bars ahall Le used in connection with
the longitudinal rib reinforceme:1c, a;,: in the case of reinforced concrEte
columns.
(E)
Waterproofing
Preferably, the top of the arch ring and the interior faces of the
spandrel walls of all filled spandrel arches shall be waterproofed with a
membrane waterproofing.
(F)
Drainage of Spandrel Fill
Tl:1e fills of filled apa::1.drd arches shall be effectively drained
by a system of th(;' tile drains or Fre.nch drains laid along the intersection
of the spar:drel walls and arch rings s.nd discharging through suitable outlets
in the piers and abutments, The location and det:ail of the drainage outlets
shall be such as to eliminate, as far aq possible. the discoloration by
drainage water of the exposed masonary faces.
6.10=
VIADUCT BENTS AND TOWERS
VJhen concrete columns are used in viaduct construction, bents and
towers shall be effectively braced by means of longitudinal and transverse
struts. For height greater than 40 feet, both longitudinal and transverse
cross or diagonal bracing, preferably, shall be used, and the footings for
the columns, forming a single bent, shall be thoroughly tied together.
617
67.
6.11~
BOX GIRDERS
(A)
Effective Compression Flange Width
In girder and flange construction, consisting of a girder stem with
top and bottom slab, effective and adequate bo:1d and shear resistance shall
be provided at the junction of the girder and slab. The slab may then be
considered an integral part of the girder, but its effective width as a
girder flange shall not exceed the following:
(1)
One fourth of the span length of the girder
(2)
The distance centre to centre of girder
(3)
Twelve times the least thickrLess of the slab plus the
width of the girder stem
For girders having flanges on o:1e side only, the effective overhanging flange width shall not exceed the £allowing:
(1)
(2)
Onehalf the clear dis t.ance to the next girder
(3)
(B)
One. twelfth of the span length of the girder
Six times the least thickness of the slab.
Flange Thickness
(1)
Top Flange
lbe mudmum flange thickness shall be 1/16 the clear distance
between girders, or 6 inches, whichever is greater.
(2)
Bottom Flange
The minimum thickness of the bottom flange shall be determined
by maximum allowable unit stresses as specified in (C) and (D) but in
no case shall be less than 1/16 of the clear span between girders or
5~ inches, whichever is the greater.
Adequate fillets shall be provided
at the intersection of all surfaces within the cell of a box girder.
(C)
Flexure
(1)
Parallel to Girder
The compressive unit stress in extreme fiber of concrete in
both girder stem and flange shall not exceed that given in Article
5.2(B)
68.
(2)
Normal to Girder
The compressive unit stress in extreme fiber of concrete in
the girder flange shall not exceed that given in Article 5.2(B).
(D)
Shear
The flange shall not be considered as effective in computing the
shear and diagonal tension resistance of girder o,tems 0 except in the
determination of the value of j.
TI1e hurizontal shearir1g unit stress at th<? jtmction of the flange
and the monolithic fillet joi:ling it to th~ girder stem shall D.ot excesd
that given in Article 5.2(B), shearbt:ams with web reinforcernenL
Changes in girder stem thickness shall be tapered for a minimum
distance of 12 times the difference in stem thickness.
(E)
Reinforcement
'I11e unit stress in steel for both girder stem and ilange shall ro.ot:
exceed that given iTJ. Article 5.3.
(F)
Flange Reinforcement
(1)
Parallel to Girder
Minimum reinforcement of 0,6 per cent of the flange section,
but in no case lesa than requir~d by Article 3.2(E) shall be placed
in both top and bottom flangeE, distributed over both surfaces.
Where necessa.ry, a single layer of bftrs may be centre.d. in th~;; bottom
slab. Bar spacing shall not exceed 18 incht~S.
(2)
Normal to Girder
Hinimum reinforcement of 0.5 per cent of the flange section
shall be placed in the slab~ di.stri.buted over both f>Urfac.es, Ba:c
bpacing shall not exceed 18 in.eh.e;:.;. These bars shall be bent up
into the e.xterior· gi.n:l.t:r ,;tem. at le:Lst 10 bar diameters.
Reinforcement in the top flange in a direction transverse to
the girders shall extend to the exterior face of all outside girderE',
and a minimum of 1/3 of such reinforcement shall either be anchored
with 90° bends or ext.t:nded beyond the girder face a sufficient
distance to develop the strength of the bar in bond provided the
flange projects beyond the girder face a sufficient distance to
provide this bond length"
(G)
Diaphragms
Diaphragms or spreaders shall be placed between
619
the girders at
69.
intervals not to exceed 40 feet.
(H)
Flanges Supporting Pipes and Conduits
Flanges supporting both vehicle live load and pipes or conduits shall
be designed using unit stresses set forth in Article 5.2 and 5.3.
Flanges supporting only dead load of structure and pipes or conduits
shall be designed in the direction normal to the girder using unit stresses
not exceeding 75 per cent of those set forth in Article 5,2 and 5.3.
(I)
Position of Negative Noment Reinforcement.
I;Jhen the floor slab of a box ginier is placed afcer the web walls
have taken their set, at least 10 per cent of the negative moment reinforcing steel shall be placi:ed in the web walls. The reinforcing steel shall
exten.1. a distance of one fourth the spa:1 length each side of the
intermediatE: supports of continuous spans, one·~fi:Zth the ,:;pan length from
the restrained ends of continuous spans, and the entire length of ca:2ti=
lever spans" Ia lieu of the above requi.rf·.'Jlent tv.Jo number 8 bars full
length of the webs may be used.
(J)
Reinforcement of Web Wall Sides
The web walls between the top and bottom slabs shall have rei~forcing
bars placed horizontally in both faces to preve~t temperature and shrinkage
cracks. The total area of steel shall not be less than 1/8 sq. in. per foot
of height of the unreinforced web walls. The spacing of bars shall not
exceed 2 feet.
620
70.
Section 7 = PRESTRESSED CONCRETE
7,1=
GENERAL
The design of prestressed concrete members of highway bridges shall
conform to the requirements of 3ection 6, Concrete Design, insofar as the
requirements of that section apply and are not .specifically modified by
requirements set forth herein. The specifications of this section are
L~lt,;,nderi f•Jc use '.n the ·~esigr: ot simp lee· span structures of mode:rate length.
:.oic~ r gr: ·.:) l~ ti.:l.t: s ;_cl 1 ::: ~ ~~ ~ ~ ·: =~ ;f; :; ;_· ':~·: ~ i::: _:~ ,~pee i a 1 c~ t lJd:,: :3.r.l.d d.::· t a j_ J. ed ·,.:o c: r:.:.;. i.{1 E'.r.:::: f~· L rJr!
1
1_;
Ab
bearing area of anchor plate of posttensioning steel.
Ac
maximum area of the portion of the anchorage surface that is
geometrically similar to and concentric with the area of the
bearing plate of posttensioning steel.
As =
area of main prestressing tensile steel
A's=
area of conventional steel.
Asr
steel area required to develop the ultimate compressive strength
of the web of a flanged section.
A
v
area of web reinforcement.
b
width of flange of a flanged member or width of a rectangular
member.
b'
width of web of a flanged member.
d
distance from extreme compressive fiber to centroid of the
prestressing force.
I
Moment of inertia about the centroid of the cross section.
I
Impact load
j
ratio of distance between centroid of compression and centroid
of tension to the depth d.
p
As /bd, ratio of prestressing steel.
p'
A's/bd, ratio of conventional reinforcement.
s
longitudinal spacing of web reinforcement.
71
71.
t
average thickness of the flange of a flanged member,
Q
statical moment of cross section area, above or below the level
being investigated for shear, about the centroid.
D
effect of dead load.
L
effect of design live load including impact, where applicable.
Vc
shear carried by concrete
Vu
shear due to ultimate load and effect of prestressing.
Ec
flexural modulus of elasticity of concrete.
Es
modulus of elasticity of prestressing steel.
f 1c
compressive cube strength of concrete at 28 days (6 11 cube)
(f'c)= compressive cylinder strength of concrete at 28 days(6n cylinder)
f'ci
=
(f'ci)=
f' s
compressive cube strength of concrete at time of initial prestress
compressive cylinder strength of concrete at time of initial
prestress.
ultimate strength of prestressing steel.
effective steel prestress after losses
average stress in prestressing steel at ultimate load.
fsu
nominal yield point stress of prestressing steel (at 1.0 per cent
extension)
f' y
yield point stress of conventional reinforcing steel.
n
base of Naperian logarithms.
e
K
T0
=
friction wobble coefficient per foot of prestressing steel.
steel stress at jacking end.
steel stress at any point x, located at a distance x from the
jacking end.
~
~
friction curvature coefficient.
total angular change of prestressing steel profile in radians
from jacking end to point x.
72
72.
length of prestressing steel element from jacking end to point x.
1
7.3~
DESIGN THEORY
The elastic theory shall be used for tht design of prestr~ssed concrere
members unde.r design loads at 1;1orking stresses. Tbc members shall be
checked by ultimate strength theory for compliance with specified load faclur.
7.4
BASIC ASSUT''l.PTIONS
The following assumptions an,, made for design purposes:
(a)
(b)
,,".)
{
7.
5~
Strains vary linearly over the depth of the YUemGer throughout
the entire load range.
Before cracking, stress i& linearly proportional to strain.
After cracking, tension in the cor!.crete is neglected.
LOA~)ING
STAGES
The stat;~ of stress shall be invest:igat:ed under each loading
condition that is anticipated in tht' manLlfacttae, handling and service lift:.
of l.he structure. The following are some o[ the conditions tbctt may exist:
(A)
Initial Prestress
The concrete and steel stresses in the initial stressing of the
rnemher before the dead load from other members is effective and hefore loss.c.s
due to lengt.h change3 of the concrete aad steel b.ecve taken place. The
condition of marJtfacture shall be taken into accoun.t, particularly !'lS to
whether the dead load of the member itself is pffective.
(B)
Transportation and Erection
J?recast members that are to be moved from their place of manufacture
shall be designed so that handling is practicable.
(C)
Design Load
Stresses in effect after losses and under dead load and the assumed
working live load.
(D)
Cracking Load
Complete freedom from cracking may or may rwt be necessary at any
particular loading stage. Type and function of the structure and type,
frequency, and magnitude of live loads should be considered.
(E)
Ultimate Load
The ultimate load that a member can withstand without failure shall
73
73.
be the sum of the multiples of live and dead loads specified in the formulas
given in Article 7.6. The ultimate load capacity shall be that producing
moments equal to the ultimate moment of the concrete or steel as given in
Article 7.10.
7,.6
LOAD FACTORS
Load factors are multiples of the design load applied to the structure
to insure its safety.
The computed ultimate load capacity shall not be less than
1.5 D + 2.5 (L+I)
These load factors are intended for simple spans of moderate length.
For long spans, continuous spans and unusual design, special investigation is
advisable with probable increase in the ultimate load factors.
7.7
ALLOWABLE STRESS
In general the design of prestressed members shall be based on a
maximum concrete cube strength of 6000 psi or a maximum concrete cylinder
strength of 5000 psi
(A)
Prestressing Steel
(1)
(2)
(B)
Tf}mporary stress before losses due to creepand shrinkage ... 0. 70f's
(Overstressing to 0.80 f's for short periods of time may
be permitted provided the stress after seating of the
anchorage, does not exceed 0.70 f 1 s)
Stress at design load(after losses) 0.60 f' or 0.80 f
which
~~
s
sy
ever is smaller, or 0. 70 r s less all computed losses.
Concrete
(1)
Stress at Transfer before losses due to creep and shrinkage:
Cube
strength
Pretensioned members .50 f'ci
Compression
Post.,tensioned members
.45 f'
ci
Cylinder
strength
0.60(f'ci)
0.55(£' .)
Cl.
Tension
Members without nonprestressed reinforcement:
Single element 2. 75 ~
ci
Segmental element Zero
7.4
3
VCf' Cl.
,)
Zero
74.
Cube
Cylinder
Strength
strength
Beams and girders may be
comprised of 'single element',
or a number of precast elements
hereafter referred to as
'segmental elementd.
Hembers with nonprestressed
reinforcement sufficient to
resist tensile force in the
concrete without cracking
vJher, computed on H,e basis
of au uncracked section:
5 ..)'"~
fL C i
Single element ~Jegmental element(·,Jithin the
2.r1 1 r~
1 ' ci
element itself)
(2)
3
vcf·
~)
c~
Stress at design load after losses
ha·~·e occurred:
0.33 f
Compression==
0. 40 { f' c )
.,
1
c
Tensio~(in precompressed tensile zone)
?osttensioned members
Pretensioned Members
,
lbut not to exceej 250
(3)
Z€·ro
2.75
.
3 V(f'
I! 
c~
.
. ,,
c~
Cracking Stress
Anchorage bearing stress
Posttensioned anchorage(_bt!.t not to exceed· '·ci "
"''
··
~
(A)
I 
/f' .
ps~;
1:'lexure tensile strength(Hodulus
of rupture)from tests or if nor
6, 8
8Vailable
(4)
Zero
/f
~~
I
C

3
0. 50 .f' cH{A:
~~
Friction Losses
Friction losset~ in posttensioned members occur :from angle chat,_ge in
draped cables and from wobble of the ducts.
These losses can be estimatei
75
75.
by the following formula:
Tx e
(Kl
+.P""" )
using the follo,;,Jing average values of K and .P
:For small values of K 1
and.,.u~
the following formula can be used.
Type of steel
Type of Duct
Wire cables ... , .. , ,
fright metal sheathingGalvanized metal sheathingGreased or asphaltcoated
and wrappedDirect contact with concreteBright metal sheathingGalvanized metal sheathingDirect contact with concreteBright metal sheathing(~alva:Jized metal sheathingDirect contact witb. concrete
H.ighstrength bars .....
Cal'!anized Strand ..... .
K
0.0020
0.0015
0.30
0.25
0.0020
0.0015
0.0003
0.0002
0.0005
0.0015
0.0010
0.0015
0.30
0.45
0.20
0.15
0.40
0.25
0,20
0.50
Friction losses occur prior to anchoring but ,::;hould be estimated. for
design and checked during stressing operations.
(B)
Prestress Losses
The following sources of loss cf prestress in addition to friction
losses, shall be considered to determine the effective prestress.
1.
Elastic shortening of concrete
This loss is equal to n (!::!. fc). For pret:e;1sioned concrete A fc is
the concrete stress at the centre of gravity of the prestressing steel for
which the lo,:;ses are being computed. For posttensioned concrete where the
steel elements may not be tensioned simultaneously, A fc is the a"verage
coucrete stress along one prestressing element from end to end of the beam
caused by subsequent posttensioning of adjacent elements. Taking one
half the loss of the first element by subsequent application of prestress
from other elements closely approximates the average loss of all elements.
2.
Creep of Concrete
Creep is the timedependent strain of concrete caused by stress.
For pretensioned and posttensioned bonded members, concrete stress is
taken at the centre of gravity of prestressing steel under effect of
prestress and permanent loads ( normal conditions of unloaded
structure).
76
76.
In posttensioned unbonded members, stress is the average
concrete stress along the profile of centre of gravity of prestressing
steel under the effect of prestress and permanent loads. Additional
strain due to creep may be assumed to vary from 100 per cent of elastic
strain for concrete in very humid atmosphere to 300 per cent of elastic
strain in very dry atmosphere.
3.
Shrinkage of concrete
The following value of unit strain for shrinkage shall be used:
For pretensioned members
For posttensioned members
4.
0.00030
0.00025
Relaxation of Steel Stress
Loss of stress due to relaxation of prestressing steel should be
provided for in the design in accordance with test data furnished by the
steel manufacturer. The loss, generally, is in the range of 2 to 8% of
the intial steel stress.
5.
Slip at Anchorage
Where a slip of the tendons is expected to take place in seating
the anchorage device, the resulting loss of prestress shall be allowed
for. An average value of 0.10 inches may be used to compute this loss
at each end.
The total prestress losses(except the friction and slip
be assumed to be
los~may
for pretensioned members
for post=tensioned members
35000 p. s. i.
25000 p. s. i.
when data is not available to calculate losses more exactly.
7.9
FLEXURE
Prestressed concrete members may be assumed to act as uncracked
members subjected to combined axial and bending stresses within specified
design loads. The transformed area of bonded reinforcement may be included
in pretensioned members and in post tensioned members after grouting.
7. 10 ULTHiATE FLEXURAL STRENG'l'H
(A)
Rectangular Sections
For rectangular or flanged sections in vhich the neutral axis lies
within the flange, the ultimate flexural strength shall be assumed as:
77
77.
A
M
u
(B)
fsu
s
d (1 0. 7 0 p
f
I
c
f su )
M
u
~'<
d ( 1
0, 60 p f
su
)
(f I C) 'i~·/(
Flanged Sections
If the neutral axis falls outside the flange, the ultimate flexural
strength shall be assumed as:
0. 70 Asr fsu)
( 1   ·    '"/(
b'd f'c
""k
+ 0, 70 f'c (b~)t(d0.5t)
+0.85(f'c)
(bb')t(d0.5t)
Where
A8 r
=
the steel area required to develop the ultimate compressive
strength of the web of a flanged section
A
Asf
A
(C)
sf
sr
A
s
A
sf
Steel area required to develop the ultimate compressive
strength of the overhanging portions of the flange
=
0. 70 f'
c
(b~)t
/f
su
A
=0.85 (f' ) (bb1)t/f
sf
c
su
Steel stress
Unless the value of fsucan be more accurately known from detailed analysis,
the following value may be used:
Bonded members
Unbounded members
su = f se + 15000
Provided that
f
1)
2)
The effective prestress after losses is not less than 0.5 f's
The stress relieved wire for prestressing should display a high
yield strength and a reasonable elongation before rupture. Minimum
yield strength at 1 per cent elongation under test load should be
'i;
6 11 compressive cube strength
*'~'
6 11 compressive cylinder strength
78.
equal to 80 per cent of specified ultimate strength.
Minimum elongation after rupture should be 4 per cent
in 10 inches.
High strength bars for perstressing should have a m1n1mum yield
strength measured by the 0.7 per cent extension under load method
equal to 90 per cent of the specified ultimate tensile strength.
Hinimum elongation after rupture should be 4 per cent in a
length of 20 diameters.
High tensile strength seven vire strands should conform to the requirements of ASTM designation A416.
7 .11=
MAXIMUM AND :t:·flNUHJM STEEL PERCENTAGE
Prestressed concrete members shall be designed so that failure of the
steel rather than of the concrete will occur at ultimate load. In general
the percentage of steel shall be such that:
For rectangular sections
.s.
" <
fsu I f'c = 0.25
p
~ 0.30
For flanged sections
For steel vith percentage greater than this the ultimate flexural
strength shall not be assumed as greater than
For rectangular sections
"'<
2
= 0 . 20 f' c bd
2
'id:
Mu
= 0.25(f'c)
bd
For flanged sections
M
u
0. 20 b 'd2 f'
+ 0. 70 f'
....
"
c
2
*"k
M =0.25 b'd (f'
)
u
c
c
I
(bb)t(d0.5t)
+0.85(f' )(bb')t(d0.5t)
c
In prestressed concrete members reinforced with tendons of high tensile
strength steel wire or high tensilestrength strand in which t.he anchorage
of the tendons is by bond alone, the cross sec.tio::1al area of the tendons shal
be not less than 0. 3 per cenc of the cross sectional areas of the member at
the time of the transfer of stress from the prestressing bed to the member.
7.12 NONPRESTRESSED REINFORCEMENT
Nonprestressed reinforcement may be considered as contributing to the
7=9
6 cube strength
6 11 cy 1 in d er strength
11
79.
tensile strength of the beam at ultimate strength in an amount equal to its
area times its yield point, provided that
For rectangular sections
p
fsu
f'
+
•k
c
p' f' y
p fsu
~ 0.25
f' c *
(f
1
c
p' f' y
+
(f I )1d;
)1c7'>
<
= 0.30
c
For flanged sections
Asr fsu
b'd f
'~'~
c
+
A' sf' sy
A
~0.25
b'd £'*
c
A'
sr fsu
b'd (f'
+
c
)~~*
s f'
s y ~0.30
...;... ...t ..
b 'd (f'
)
lb1.
c
7.13 SHEAR
A.
The effects of shear may reduce the resistance to cracking ar1d the
ultirr.ate strength of flexural members. for uncracked sections, the
principal tensile stresses should be calculated at points of maximum shear
and at points where there is a significant change of shear or change of
section. Shear reinforcement should be provided where necessary in
accordance with the provisions of this clause.
Where the principal tensile stress d>Je to prestress, bending and
shear at working loads exceeds that given in the table below shear reinforcement should be introduced. The proportion of shear to be resiste::l by this
reinforcement should be assumed to vary linearly with the principal tensile
stress from a value of O,for the stress given in the tableJto 1,0 for a
stress of 1.5 times that given. When the principal tensilE: stress is greater
than 1. 5 times that given in the Table the whole of the shear should be carried
by reinforcement. The area of web reinforcement shall not be less than 0.0025
b's. The spacing of web reinforcement shall not exceed threefourth the depth
of the member or 24 11 , whichever is less, and shall provide transverse
reinforcement across the bottom flanges.
B.
C.
Shear reinforcement is often desirable for major structural mFOmbers eve:J.
when the principal tensile stress is less than the appropriate value in the
Table particularly for beams with thin webs, for which recommendations are
given in Article 7.19
Specified Strength of Concrete
(lbs / sq. in. )
Limiting principal tensile stress
for concrete in uncracked sections
Cube
Strength
Cylinder
Strength
at working loads
(lbs/ sq. in. )
at ultimate load
(lbs/sq. in.
4500
6000
7500
3500
4700
5900
125
150
175
300
350
400
710
~~
**
6" cube strength
6" cylinder strength
80.
D.
Where the principal tensile stress due to shear and effective prestress·
at uncracked sections, under the ultimate load, exceeds that given in the
Table aboveithe whole of the shear in excess of that resisted by tendons
inclined· to the neutral surface should be resisted by shear reinforcement
acting at a stress not exceeding 80 per cent of the yield stress( or 0.2
per cent proof stress, where appropriate).
E.
Special consideration should be given to the shear resistance under
ultimate load conditions where. the section is cracked in bending. The
possibility of developing such resistance by means of truss, arch or similar
actions should be examined and, where reliaace is placed on one of these,
adequate reinforcement, complying with the requirement of the preceding
paragraph of this clause, should be provided.
7.14(A)
COMPOSITE STRUCTURES
General
Composite structures in which the deck is assumed to act integrally
with the beam shall be interconnected to transfer shear along the contact
surfaces and to prevent separation of the elements. Transfer of shear shall
be by bond or by shear keys. Tne elements shall be tied together by
extension of the web reinforcement or by dowels.
(B)
Shear Capacity
The shear connection shall be designed for the ultimate load and
may be computed by the formula v
V Q/I.
u
(C)
Bond Capacity
The following values for ultimate bond resistance at the contact
surfaces shall be used in determining the need for shear keys:
When the m~n~mum steel tie requirements of (D) of this
article are met 75 psi
When the minimum steel tie requirements of (D) of this
article are met and the contact surface of the precast
element is artificially roughened=150 psi
When steel ties in excess of the requirements of (D) of
this article are provided and the contact surface of
the precast element is artificially roughened225
psi
If bond capacity is less than the computed shear, shear keys shall
be provided throughout the length of the member. Keys shall be proportioned
according to the concrete strength of each component of the composite
member.
711
81.
(D)
Vertical ties
All web reinforcement shall extend into castinplace decks. The
spacing of vertical ties shall not be greater than four times the minimum
thickness of either of the composite elements and in any case not greater
than 24 inches. The total area of vertical ties shall not be less than
the area of two No.3 bars spaced at 12 inches.
(E)
Shrinkage stresses
In structures with a castinplace slab on precast beams, the
differential shrinkage tends to cause tensile stresses in the slah and in
the bottom of: the beams, Stresses due to differential shrinkage are
important only insofar as they effect the cracking load. When crackiEg
load is significant such stresses should be added to the effect of loads.
7. 15 END ZONE OF CONCRETE IBEAN[:l
For beams wit:h posttensioning ten.Jons, end blocks sh.all be used to
di.strihute thP coneentratec prestress:Lrrg forces at the anchorage. Where
all tendons are pre tensioned ·wires or 7wirt;, .strand, the use of end bloeks
will not be required.
End blocks shall have sufficieni: area to allow the sps.cing of the
prestressing steel as speci~ied in article 7.16 . Preferably, they shall
be as wide ar: the narrower flange of the beam,
Th,:;y shall have a le:Jgth
at least equal to three fourth of th2 depth of the beam and in any case
24 inches. In post ten,:;ioned members a closely spaced grid of bo•:h
vertical and horizontal bars shall be placed near the face of the end block
to resist bursting and closely spaced rein£orceme.nt shall be placed both
vertically and horizontally throughout the length of the block.
In pretensioned beams, vertical stirrups acting at a unit stress of
18000 p.s.i. to resist at least 4 per cent of the total prestressing force
shall be placed within the distance of d/4 of the end of the beam, the end
stirrup to be as close to the end of the beam as practicable.
7. 16 COVER AND SPACDlG OF PRESTRESSING STEEL
(A)
Minimum Cover
The following m:Lnlmum concrete cover shall be provided for prestressing
and conventional steel:
Prestressing Steel and Main reinforcement
1~
Slab reinforcement: bottom of slab 1 inch, top of slab 1~
Stirrup and ties
1
**May be reduced to one inch where an additional wearing
to be used.
712
inches
inches >'ci:
inch
surface is
82.
In location where members are exposed to salt water, salt spray or
chemical vapor, additional cover should be provided.
(B)
Minimum Spacing
The mlnlmum clear spacing of prestressing steel at the ends of beams
shall be as follows:
Pretensioning Steel: Three times the diameter of the steel or
4/3
the maximum size of the concrete aggregate, whichever is grea':er.
Post tensioning duets: 1Iorizontally = l}z inches or l}z times the
maximum size of the aggrP.gate, whichever is the greater. However,there
should be sufficient gaps between the tendons to allow the largest
size of aggregate used to move, under vibration, to all parts of the
forms. At the ends the spacing will be governed by the end details
of the type of the system used. The inside diameter of post
tensioning ducts shall be at least one fourth inch greater than the
diameter of the prestressing steel.
(C)
Bundling
When prestressing steel is draped or deflected, not to exceed three
ducts may be bundled in the middle third of the beam length provided that the
spacing specified in (B) is maintained in the end three feet of the member.
7.17 EMBEDMENT OF PRESTRESSING STRAND
To insure proper bond in pretensioned members designed to resist
flexure, the following minimum length of embedment of sevenwire strand,
measured from the free end of the strand to the point of maximum steel
stress at ultimate flexural strength, shall be as follows:
1/2 inch strand
7/16 inch strand
3/8 inch strand
1/4 inch strand
135
120
100
65
inches
inches
inches
inches
7.18 CONCRETE STRENGTH AT STRESS TRANSFER
Unless otherwise specified, stress shall not be transferred to
the concrete until the compressive strength of the concrete, as indicated
by test cubes or cylinders cured by methods identical with the curing of
the members, is at least 80% of the 28 day compres~ive strength.
7 . 19 REINFORCEMENT IN BEAMS
Reinforcement may, in cert3in circumstances, be desirable in
prestressed concrete beams.
It should be noted that steel reinforcement lying parallel to the
713
83.
axis of prestress in a prestressed concrete member may at some time act as
longitudinal reinforcement in compression.
Transverse binding may be required
to prevent buckling of this reinforcement particularly if its diameter is
large.
Reinforcement will often be required at the ends of members to take
the tensile stresses that may be induced near the ends by the prestressing
force and particularly stresses caused during transfer.
Reinforcement may be necessary, particularly where post~tensioning
systems are used, to control any cracking resulting from restraint to longitudinal shrinkage of members provided by the formwork during the time before
the prestress is applied.
Web reinforcement is desirable in beams with thin we~s, particularly
whe:1 ducts or tendons are located in the webs.
Generally in beams of depth
exceeding 2 ft. and length exceeding 30 ft. in which the depth of the web is
more than four times the web thickness, vertical reinforcement is desirable
in the form of stirrups. Jhere this reinforcement is provided in the form
of mild steel bars its total croSS"'Sectior• area should be not less than 0.1
per cent of the sectional a.rea in plan of the web. Where high tensile steel
is used, the area of this reinforcement may be reduced with respect to the
area of mild steel otherwise required, ic the inverse ratio of the corresponding permissible stresses. In either case, this reinforcement should
preferably not be spaced further apart than a distance equal to the clear
web depth. The size of such reinforcement should be as small as practicable.
Where prestressed concrete beams may be required to resist shock
loading, the beams should be reinforced with closed stirrups and longitudinal
reinforcement of mild steel.
714
84.
SECTION 8  PILE LOADS AND BEARING POWER OF SOILS
8. 1
BEARING POWER OF FO!JNDATION SOILS
When required by the engineer, the bearing power of the soil in
excavated foundation pits shall be determined by loading tests. The following tabulation of the bearing power of broad basic groups of materials may
be used as an aid to the judgement in the absence of more definite
information:
Safe bearing power
Tons per square foot
Min,
Max.
Material
Alluvial soils Clays
~Sand, confined
Gravel
~=
Cemented sand & gravel Rock

="
!z
1
1
2
5
1
4
4
4
10
5
Loading tests have a limited depth influence and may not disclose
longtime consolidation.
When the consolidation of foundation soils causes the settlement of
the backfill against an abutment or the settlement of the soil under an
ahutment: which is placed on piles dri'l;'en through a fill, the load transmitted
may result in overloading the piles.
When the hydraulic gradient is increased as in excavating material
from below the water table, foundation soils may be loosened by the upward
flow of water. Such a condition should be guarded against.
Intrusion failures should be prevented by requiring a base course
between rip rap and fine soils and by requiring proper gradation of drainage
backfill behind abutments.
8.2~
ANGLES OF REPOSE
Earth, Loam =30°to
Dry Sand
25 to
____ ;,.30 to
Moist Sand
=15 to
Wet Sand
Compact earth 35 to
45°
35
45
30
40
Gravel
Cinders
Coke
Coal
30°
25
30
25
to
to
to
to
4D0
40
45
35
In the absence of exact data which has been determined by field
investigation and soil analysis, the angle of repose of the material shall
be assumed to be the minimum given in the table.
81
85.
8.3
BEARING VALUE OF PILING
(A)
General
The design loads for piles shall not be greater than the minimum
value which shall be determined for Case A, Case B, and Case C; where Case A
is the capacity of the pile as a structural member, Case B is the capacity of
the pile to transfer its load to the ground and Case Cis the capacity of the
ground to support the load delivered to it by the pile or piles. The values
assignable to each of the three cases shall be detErmined by making subsurface investigations or tests of sufficient extent to justify the assumed
design values used for the particular condition of support under consideration.
In determining the bearing value of piles for use in designiag,
consideration shall be given to all information available relative to the
subsurface conditions. Consideration shall also be given to:
(l)
(2)
The capacity of the underlying stra.ts. to support the load
of the pile group.
(3)
The effect of driving ad~ i.tional piles aod the effect or:
their loads on adjacent structureso
(4)
(J3)
The difterence be tween the supporting capacity of: "'· sieic!;le
pile and group.
Possibility of scour and its effect
Cc.se
(1)
.!J,.•
Capacity of Pile as a.
~itructural
Member
Structural Columns:
Piles shall be designed a;;; structural columns
Concret:e
piles shall be designed in accordance with Article 5.2 1 steel pile&
in accordance with Article 504, and cor..cretefilled pipe piles
in accordance with Article 5. 2, except that the allowable unit
stresPes may be increased 20% provided the shell thickness iA not
less tha!t ~ inch. The are&. of the shell shall be included i'1
determining the value p, (percentage of reinforcement), Where
corrosion may be expected l/16 inch shall be deducted from the
shell thickness to allow for reduction in section by corrosion,
The allowable stresses of Article 5.4 and 5.2 may be used in all
cases where all of the stresses to which the piles may be
subjected have been included. These stresse,::; may be increased
in accordance with Article 5 .1. For trestle piles or other
piles without lateral support designed for dead load and live
load only and where temperature, traction, water pressure and
other forces are not considered, the allowable unit stresses
specified in Article 5.2 and 5.4 shall be decreased 20%.
0
82
86.
(C)
Sub~;urL;.ct: invest.igat.ions :,hall bE' 'nade which >vll1 de.t:er>.T•it:<"
the proba.hle depth of H.ou.,r or flotB.tiO'' of mat.:eria.l d'1d tie corcditim;
of lateral ~upport of lhe pile.
Ca;>e :!). Capaciry of Pilt:> 1·o 'Transfer lo;;d to che GroilLd:
(1)
Pointbearing Piles
A pile shall he co01sidered to be a point=be.3.r iug pile whei<
placed or driven on or into a material .fhich is capa!::Jle of developing
the pile load by direct bearing at the point with reasonable factor
of safetyo
The allowable load at t:ip of the pile shall not exceed i.·h.e
following:
(a)
For concrete piles. 0.26 f'c *or 0.33(f'c)**
(b)
:!Tor concrete= filled pipe piles . 32 f; c·k or . 40 (f' c)?e*
in accordance with Article 5.2~ applied to the total
actual area of the concrete and steel.
(c)
For steel piles 9000 pounds per sq. in. over the cross
sectional area of the pile tip.
The limitation in (b) and (c) govern except where the poh1t bearing
capacity of the piles is determined by loading test piles.
(2)
friction Piles:
A pile shall be considered to be a friction pile if its point
does nol re.st on or in a material '1.vhicb is capable of de~7 eloping the
pile load by direct bearing at the point,
The loadcarrying capacity o:f friction piles shall be
determined by one or more of the following methods:
(a);
Driving and loading test piles.
(b)
Pile=driving experie::1ce in the vicinity, When pile.s are
designed on the basis of experience in the ~icinity, du(:'
consideratimt will he given to the variation in pile types
and lengths, and in the variation of the soil strata.
Where possible the complete drtving records of <ill piles
in the vicinity shall be exami:1ed and comparEd to the
driving recordd of the project piles.
(c)
Adequate tests of the soil Btrata t:hrough which the pile
is to be driven. These tests should be projected a:o.d
compared, if posaible, to tests of similar material
through which piles of known capacity have been driven,
83
6 11 compressive cube strength
6 1' compressive cylinder strength
87.
(3)
Required Subsurface Investigations
(a)
Point=bearing piles. Sufficient borings shall be m3de to
determine the presence, position, and thickness of the material
which is capable of developL:g poi:1t=bearing, and the log of
borings shall show the nature of the overlying strata in
order that the extent of lateral support may be determined.
If the point< bearing str3 tum is of doubtful thickness and
quality, the borings shall be made to such sufficient depth
belm,; this stratum tha.t the cBpacity of a friction pile may
be determined.
(b)
Fricticn piles. Borings shall be made to an elevatio~l well
helow the expected elevation of the pile tips ai'.d accu.rate
logs of the::;e borings shall be made. I::;. ttose casE:s where
t1~ piles are to be designed on the basis of soil tests,
undistrubed samples shall be taker.. on all strata which will
have appreciable influer,ce on the capacity of the pile.
(c)
(D)
Combination pointbearing and friction piles. Piles shall
be classified as either (1) point=bearing or (2) friction,
ThosP cases where adequate strength is developed by both
point bearing and friction may be designed under either of
these classifications.
Case C. Capacity of the Ground to Support the Pile L,Jad
Preference shall be given to the determination of. maximum loads on
piles by test loading or by satisfactory subsurface investigation.
The capacity of the ground to support the load delivered by the
pile shall be determined from the results of the applicable subsurface
investigations:
(1)
Pointbearing Piles
Sufficient borings shall be made to determine the thickness and
quality of the stratum {n which the point bearing is developed, If
that stratum is of sufficient thickness and is underlain by a firm
material, no reduction will be made for group action of piles. In
general, piles should not rest on a thin stratum of hard material
which is underlain by a thick stratum of soft or yielding material,
but ivhere this condition cannot be avoided, group action should be
considered and the design loads reduced accordingly.
(2)
Friction Piles
Borings shall be carried well below the tips of the piles in
order to determine the characteristics of the underlying material. In
most cases a study of those borings will suffice to determine whether
or not the underlying soil will support the loads delivered to it, but
84
88.
in doubtful or special cases, especially large foundation areas and
important footings the material should be in,restigsted more thoroughly
by soil mechanics methods.
A single row of piles shall not be considered as group provided
that they are not spaced closer ce::.1tre to centre than 2.~ times the
nominal diametsr or dimEmsiorL 1':": th.o3E: cae<:;s '"'here piles are drive':.
iE group.t; into plastic materi~l the. d0sig::1 load. shall !:le determi~tsd
by th8 loading of a group of piles or definite gllowauce shall be
made for i:he difference het:wee·::. the suppo.rt:ing capacic:;· of &. r:ingle
pile and a group of pile:;. Refer to (G)
(E)
Maximum Design Loads for Piles
In those cases where it i.s not feasihle to make the required sucdnr:Eace iav~Cstig'ltions or test load.s the maximum assumed desigE load for
piles shall be as given in the table b•dow, Tl:ese yalut:i3 may be L:lC:rt:oa<:'ed
f0r certain combinations of loadtl as spPcified i:1 ~".rticle 5, 1,
'l'YPFS
Size or Diameter
in inches
Concrete
Tons
8
10
or
P:I:LI::S
,
Steel
,
(·~
tr~Ctl.OD.
16
12
14
28
9000 pounds per
sq. in, of point
area
32
20
24
Steel
l'oin.t Bearing
28
16
(F)
24
20
24
)T 0:15
·
40
50
20
liplift
Friction piles may be considered to resist aa intermittent but not
suetained uplift equivalent to 40 per cer.t of the above loads pro7iding
proper provision i.::. made for th.e. s:c:;.chor.age at top and sufficie:.lt skin
fr:icti.oD is dev£;loped a!ld in r,.o case Bhall it exceed the weight of mat<.:rial
(buoy&.:ncy considered) surrom1.di':tg ttt embeded portion of the pile,
(G)
G:coup Pils Loading
Where the capacity of a gro:c.p o:f frictio:::J. piles driver: iro.to plastic
material is not determined by test loading, the following Co::lverse~LabEtrre
formula is suggested to determim: the reduc tio·c. oi a singlE, pile load
for a group pile load:
(n = 1) m + ( m  l) n
E = 1  ~
90
1Jl TI
85
89.
Where
E
the efficiency or the decimal fraction of the single
pile value to be used for each pile i~ the group"
=
n
the number of piles in each row
m
the number of rows in each group
d
the average diameter of the pile
s
Tan
=
~
= d/s
~
centre to centre spacing of piles
is numerically equal to the angle expressed in degrees.
86
90.
SECTION 9  SUBSTRUCTURES AND RETAINING ..JALLS
9" 1..
PILES
(A)
General
In general, piling shall be used when footings cannot, at a reasonable
expense, be founded on rock or other s0lid foundation material. At locaticms
where unusual erosion may occur and the soil conditions permit the driving of
piles, they, preferably)shall be used as a protection against scour, even
though the safe bearing resistance of the natural soil is sufficient to support
the structure without piling.
In general, the penetration for any pile shall be not less than 10 feet
in hard material and not less than 1/3 the length of the pile nor l2.ss than 20
feet in soft material ..
For foundation work, no piling shall be used to penetrate a very soft
upper stratum overlying a hard stratum unless the piles penetrate the hard
material a sufficient distance to rigidly fix the ends.
(B)
Design Loads
The design loads for piles shall be according to Article 8,.3,
Piles shall be desLgned to carry the entire superimposed load, no
allowance being made for the supr;orti.ng value of the material between the pile 3,
The supporting power of piles shall be determined by the application
of test loads.
(C)
Spacing, Clearances and Embedment
Footing areas shall be so proportioned that pile spacing shall be not
less than 2 feet 6 inches centre to centre, <Jhen the tops of foundation piles
are incorporated in a concrete footing, the distance from the side of any pile
to the nearest edge of footing 3hall not be less than 9 inches.
The top of steel piles shall project not less than 12 inches into the
concrete after all damaged material has been removed. The penetration of
concrete piles shall be not less than 6 inches.
(D)
Batter Piles
When the lateral resistance to the soil surroundiP.g the piles is
inadequate to counteract the horizontal forces transmitted to the foundation
or t1hen increased rigidity of the entire structure is required, batter piles
shall be used in the foundation.
91
91.
(E)
Buoyancy
The effect of hydrostatic p=essure shall be considered in the design as
provided in Article 2. 15.
(F)
CDncrete Piles (Precast)
Precast concrete piles shall be of approved size and shape. If a
square section is employed, the corners shall be chamfered at least one inch,,
P:Ues, preferably, shall be cast with a driving point and for hard driving,
preferabl:J shall be shod with a metal shoe of approved pattern" Piliug :nay be
either of uniform section or tapered" In ge:::~eral, tapered piling shall not be
used for trestle construction except for that portion of the pile which lies
below the ground line; nor shall tapered piles be used in any location where
the piles are to act as columns
In general, concrete piles shall have a cross
sectional area, measured above the taper, of not less than 140 square inches
and when they are to be used in salt water they shall have a cross sectional
area of not less than 220 square inches .
c.
The diameter of tapered piles measured 2 feet from the point shall be
not less than 8 inches, In all cases the diameter shall be considered as tr:e
least dimension through the centre. The point in all cases, where steel points
are not used, shall be not less than 6 inches in diameter and the pile shall
be beveled, tapered or sloped uniformly from the point to 2 feet from the point.
Vertical reinforcement shall be provided consisting of not less than
four bars spaced uniformly around the perimeter of the pile. It shall be at
least l];z per cent of the total cross scctio!1 measured above the tapper, except
that if more than four bars are used, the number may be reduced to four in the
bottom 4 feet of the pile.
The full length of vertical steel shall be enclosed with spiral reinforcement or equivalent hoops.
The spiral reinforcement at the ends of the pile shall have a pitch of
3 inches, and gauge of not less than NooS(Eirmingham). In addition the top 6
inches of pile shall have five turns of spiral winding at oneinch pitch.
For the re;:nainder of the pile the vertical steel shall be enclosed with
spiral reinforcement No.5 gauge(Birmingham), with not more than 6i.nch pitch,
or with l:Lnch round hoops spaced not more than 6 inches on centres.
4
The reinforcement shall be placed at a clear distance fror.J. the face of
the pile of not less than 2 inches and when the piles ar2 for use in salt water
or alkali soils this clear distance shall be not less than 3 inches.
In computing stresses due to handling, the computed static loads shall
be increased by 50 per cent as an allowance for impact and shock.
92
92.
(G)
Concrete Piles (CastinPlace)
CastinPlace concrete piles shall be , in general, cast in metal
shells which shall remain permanently in place. However, other types of cast·
inplace concrete piles, plain or reinforced, cased or uocased, may be used
if, in the opinion of the engineer, the soil conditions permit their use and
if their design and the method of placing are satisfactory to him.
Castinplace concrete piles may be of either uniform section or tapered or a combination thereof. The minimum size, measured at the butt, or above
the taper, and embedment of reinforcement shall be as specified for precast
piles, except that foundation piles may have a minimum butt crosssection area
of 100 square inches. The minim~~m diameter at tip of pile shall be 8 inches.
Cast in~plae:e piling shall be reinforced when specified or shown on
the plans. Cast~ inplace foundation piling, carrying axial loads only and
where the possibility of lateral forces being applied to the piles is ircsignificant, need not be reinforced ~1en the soil provides adequate lateral
support. Those portions of cast· in·place piling which are not supported
laterally shall be designed as reinforced concrete columns in accordance with
Article 6.8, and the reinforcing steel shall extend ten feet below the plane
~vhere the soil prov~des adequate lateral restraint.
Where the shell is more
than 0.12 inch in thickness, it may be considered as reinforcement.
Sufficient reinforcement shall be provided at the junction of the pile
with the superstructure to make a suitable connection.
The metal shall be of sufficient thickness and strength so that the
shell will hold its original form and show no harmful distortion after it
and adjacent shells have been driven and the driving core, if any, has been
withdrawn. The design of the shell shall be approved by the engineer before
any driving is done.
(H)
Steel Piles
(1)
Thickness of Metal
Steel piles shall have a m~n~mum thickness of web of .400 11
Splice plates shall be not less than 3/8 inch thick.
(2)
Splices
Piles shall be spliced to develop the net section of pile.
The flanges and web shall be either spliced by butt welding or with
plates, welded, riveted or bolted. The bolted splices shall only be
used on projects where a small number of piling are required and
where facilities for riveting or welding are not available.
Splices shall be detailed on the contract plans.
93
93.
(3)
Caps
In general, caps are not required for steel piles embedded in
concrete. Reference is made to Research Report No.1, "Investigation of
the Strength of the Connection between a Concrete Cap and the Embedded
end of the Steel .HPilelf  Department of Highways, State of Ohio, U ,, S ,A,
for a discussion of this subject and for the results of the tests pertinent
to it.
(4)
Scour
If heavy scour is anticipated, consideration shall be given to
design of the portion of the pile which would be exposed, as a column.
(5)
Lugs, Scabs and Corestoppers
These devices may be used to increase the bearing power of the
pile where necessary. They may consist of structural shapes, welded,
riveted or bolted, of plates welded between the flanges, or of concrete
blocks securely fastened.
(I)
Steel Pile and Steel Pile Shell Protection
Where conditions of exposure warrant, concrete encasement shall be used on
steel piles and steel shells or 1/16 inch depth of thickness shall be deducted
from all exposed surfaces in computing the area of steel in the piles or
shells.
9.2
FOOTINGS
(A)
Depth
The depth of footings ahall be determined with respect to the character
of the foundation materials and the possibility of undermining. Except
where solid rock is encountered or in other special cases the footings of all
structures other than culverts, which are exposed to the erosive action of
stream currents, preferably, shall be founded at a depth of not less than 4
feet below the permanent bed of the stream. Stream piers and arch abutments,
preferably, shall be founded at a depth of not less than 6 feet below strean1
bed. Yne above preferred minimum depths shall be increased as conditions may
require.
Footings not exposed to the action of stream currents shall be founded
on a firm foundation and below frost.
Footings for culverts shall be carried to an elevation sufficient to
secure a firm foundation, or a heavy reinforced floor shall be used to distribute the pressure over the entire horizontal area of the structure. In any
location liable to erosion, aprons or cutoff walls shall be used at both ends
94
94.
of the culvert and, where necessary, the entire floor area between the wing
walls shall be paved. Baffle walls or struts across the unpaved bottom of
a culvert barrel shall not be used where the stream bed is subject to erosion.
When conditions require, culvert footings shall be reinforced longitudinally.
(B)
Anchorage
Footing on inclined smooth solid surfaces which are not restrained by
an overburden of resistant material, shall be effectively anchored by means of
anchor bolts, dowels, keys or other suitable means.
(C)
Distribution of Pressure
All footings shall be designed to keep the maximum soil pressures
within safe bearing values. L1. order to prevent unequal settlement, footings
shall be designed to keep the pressure as nearly uniform as practicable. In
footings having unequal pressures and requiring piling, the spacing of the
[Jiles shall be such as to secure as nearly equal loads on each pile as may be
practicable.
(D)
Spread Footings.
Spread footings which act as cantilevers may be decreased in thickness
from the junction of the footing slab with column or wall toward the edge
of the footing, provided sufficient section is maintained at all points to
provide the necessary resistance to diagonal tension and bending stresses.
This decrease in section may be accomplished by sloping the upper surface of
the footing or by means of vertical steps. Stepped footings shall be cast
monolithically.
(E)
Internal Stresses in Spread Footings
Spread footings shall be considered as under the action of downward
forces, due to the superimposed loads, resisted by an upward pressure exerted
by the foundation materials and distributed over the area of the footings as
determined by the eccentricity of the resultant of the downward forces. Where
piles are used under footings, the upward reaction of the foundation shall be
considered as a series of concentrated loads applied at the pile centres, each
pile being assumed to carry its computed proportion of the total footing load.
When a single spread footing supports a column, pier or wall, this
footing shall be assumed to act as a cantilever. When two or more piers or
columns are placed upon a common footing, the footing slab shall be designed
for the actual conditions of continuity and restraint.
Footings shall be designed for the bending stress, diagonal tension
stress and bond at the critical section designated herein.
95
95.
The critical section for bending shall be taken at the face of the
column, pedestal or wall. In the case of columns other than square or rectangular, the critical section shall be taken at the side of the concentric
square of equivalent area. For footings under masonary walls, where bond
between the wall and footing is reduced to friction value, the critical
section shall be taken as midway between the middle and the face of the wall.
For footings under metallic column bases, the critical section shall he taken
as midway between the face of the column and the edge of the metallic base.
The load shall be considered as ueiformly distributed over the column,
pedestal or wall, or metallic column base.
The critical section fer bond shall be taken at the same plar..e as for
bending, and the shear used for computing bond shall be based 0:1 the same
loading and section as for bending. Dor:d should also be im~estigated at
planes where changes of section or of reinforcemen~ occur.
The critical section for diagonal tensio:1. in ::':ootings on soil or rock
shall be considered as a conce:1tric vertical section through the footing at
a dif'tance "d" from each iace of the colurrm, pedestal, or wall; 11 d 11 being
equal to the depth fror,1 the top of the section to the centroid of the
longitudir:.al tensiol! reinforcement.
The critical section for diagonal ter.:sion in footings supported on
piles shall be considered as the concentric vertical section through the
footing at a di:~tance, d/2, from each face of the colur.m, pedestal or wall,
and any piles whose centres are at or outside this sectioD shall be
cotLsidered in computing the diagonal tension.
In sloped or stepped footings, stresses should be investigated at
sections where the depth changes outisde the critical section as defined
at)ove.
Bending need not be considered ualess the projection of the footing is
more than twothird of the depth.
In plain concrete footings, the stresses shall be computed on the
basis of a monolithic section having a depth measured from the top of the
footing to a phme 2 inches above the bottom of the footing. The maximum
fibre stress due to bending shall not exceed that specified in Article 5.2
and the average shearing stress 0!.1 the concentric vertical section through
the footir1g at. a distance (d minua 2 i::1ches) from each face of the colurm:1,
pedeatal or wall, shall not exceed the shearing stress specified in Article
5.2 for beam without web reinforcement and with longitudinal tars not
anchored.
(~)
Reinforcement
Footing slabs shall be reinforced for ber..ding stresses and, where
necessary, for diagonal tension. The computed stress in the bar shall be
developed in bond.
96
96.
The reinforcement for square footings shall consist of two or more bands
of bars. The reinforcement necessary to resist the bending moment in each
direction in the footing shall be determined as for a reinforced concrete
beam; the effective depth of the footing shall be the depth from the top to
the plane of the reinforcement. The required reinforcement shall be spaced
uniformly across the footing, unless the footing width is greater than the
side of the column or pedestal plus twice the effective depth of the footing,
in which case the width over which the reinforcement is spread may equal the
width of the column or pedestal plus twice the effective depth of the footing
plus onehalf the remaining width of the footing. In order that no considerable area of the footing shall remain unreinforced,additional bars shall be
placed outside of the width specified,but such bars shall not be considered a,:
effective in resisting the calculated bending moment. For the extra bars a sp~·
cing double that used for the reinforcement within the effective belt may be
used.
(G)
Transfer of Stress from Vertical Reinforcement
The stresses in the vertical reinforcement of columns or walls shall be
transferred to the footings by extending the reinforcement into them a sufficient distance to develop the strer..gth of the bars in bond,or by means of
dowels anchored in the footings and overlapping or fastened to the vertical
bars in such manner as to develop their strength. If the dimensions of the
footings are not sufficient to permit the use of straight bars, the bars may
be hooked or otherwise mechanically anchored in the footings.
9. 3
ABUTMENTS
(A)
General
Abutments sb.all be designed to withstand earth pressure as specified
l.n Article 2.16, the weight of abutment and superstructure, live load over
any portion of the superstructure or approachj fill, wind forcee,longitudinsl
force when the bearings. are fixed, and longitudinal forces due to frictional
bearings. The design shall be investigated for any combinatio:il of these
forces which may produce the most severe condition of loading.
Abutments shall be designed to be safe agah~st overturning about the
toe of the footing, against sliding or. the footing base and against crushing
of foundation material or overloading of piles at the point of maximum pres
In computing stresses in abutments, the weight of filling material
directly ovc=r an inclined or stepped rear face, or over a reinforced concrete
spread footing extending back from the face wall, may be considered as part of
the effective weight of the abutment. In the case of a spread footing, the
rear projection shall be designed as a cantilever supported at the abutment
stem and loaded with the full weight of the superimposed material,unless a
more exact method is used.
The cross section of stone masonry or plain concrete abutrnents shall
be proportioned to avoid the introduction of tensile stress in the material.
97
97.
(B)
Reinforcement for Temperature
Except in gravity abutments, not less than 1/8 square inch of horizontal reinforcement per foot of height shall be provided near exposed surfaces
not otherwise reinforced, to resist the formation of temperature and shri~kage
cracks.
(C)
Wing Walls
Wing walls shall be of sufficient le:1gth to retain the roadway err,bankment to the required extent and to furcish protection against erosion. For
ordinary materials, in the absence of accurate data, the slope of the fill
shall be assumed as 1~ horizontal to one vertical and wing lengths computed
on this basis.
1Jbere deflec~ion joints are not used reinforcement rods or other suit·~
able rolled sectioEs preferably shall be spaced across the junction betweerl
all wing walls a~d aht1tments to thoroughly tie them together. Such bars shall
extend into the masoary o:1 each side of the joint :far enough to develop the
strength of the bar as Gpecified for bar reinforcement, &:r:d shall vary ir.
le:lgtt, so as to hVoid planes of weakness in the cor,crete at their ends. If
bars are not used, an expansion joint shall be provided at this point in
which the wings shall be mortised into the body of the abutment.
(D)
Drainage
The filling material behind abutment shall be effectively drained by
weep holes witt French drains, placed at suitable intervals.
9. 4~
RETAINING ..JALLS
(A)
General
Retaining v:alls shall be designed to withsta:;d eacth pressure, includ·
ing any live load s·1reharge, and the weight of the wall, in accorda:1ce with
the general principles specified above for abutments.
Stone masonry and plain concrete walls shall be of the gravity type.
Reinforced concrete walls may be of either the cantilever. counterforted,
buttressed, or cellular types.
(E)
Base or Footing Slabs
The rear projection or heel of base slabs shall be designed to sepport
the entire weight of the superimposed materials, unless a more exact method is
used.
The b~se slabs of cantilever walls shall be designed as cantilevers
supported by the walls.
98
98.
The base slabs of counterforted and buttressed walls shall be designed
as fixed or continuous beams of spans equal to the distance between cou~ter=
forts or buttresses.
(C)
Vertical Walls
The vertical stems of cantilever walls shall be designed as cantilever
supported at the base.
The vertical or face walls of counterforted and buttressed walls shall
be designed as fixed or continuous beams. The face walls shall be securely
anchored to the supporting comiter forts or buttressed by means of adequate
reinforcement.
(D)
Counterforts and Buttresses
Counterforts shall be designed as Tbeams. Buttresses shall be desig~
as recta:.1gular beams. In con:r1ection with the mai:l tension reinforcement of
counterforts there shall be a system of horizontal and vertical bars or
stirrups to eff(O,ctL•ely a.:1chor the face valls and base slabs, 'I'hese stirrups
shall he anchored as near the outside faces of the face walls, and as near ~o
the bottom of the base slab as practicable.
~·ed
(E)
Reinforcement for Temperature
r~xcept in gravity walls not less than 1/8 square inch of horizontal
reinforcement per foot of height shall be provided near exposed surfaces not
otherwise reinforced, to resist the formation of temperature and shrinkage
cracks.
(F)
Expansion and
Contractio~
Joints
Contraction joints shall be provided at intervals not exceeding 30
feet and expansion joints at intervals not exceeding 90 feet, for gravity or
reinforced concrete walls.
(G)
Drainage
The filling material behind all retaining walls shall be effectively
drained by weep holes with French drains, placed at suitable intervals. In
counterforted walls there shall be at least one drain for each pocket formed
by the counterforts.
9. 5
PIERS.
Piers shall be designed to withstand dead and live loads superimposed
thereon; .vind pressures acting on the pier and superstructure; the force due
to stream flow, centrifugal force, earthquakes, floating drift; and longitud~
inal forces at the fixed end of spans.
99
99.
SECTION 10  STEEL DESIGN
10.1DESIGN AND CONSTRUCTION
The design of steel bridges shall conform to the British Design Standard
153, Part 4. Design and Construction of the British Standards Institution
1958 Edition.
101
l_}
Views
Actions
Embeds 0
Report content