IRC_006-1966

(1)

IRC

IRC 6-19666-1966

STANDARD

SPECIFICATIONS

AN

D

CODE OF PRACTICE

FOR

ROAD

(2)

IRC IRC 6-19666-1966 c c 1X 1X .~~tk1.~~tk1

STA

NDAR

D

SPE

CIF

ICA

TI

ONS

AN

D

CODE

OF

PRACTICE

FOR

ROAD

(3)

IRC IRC 6-19666-1966 c c 1X 1X .~~tk1.~~tk1

STA

NDAR

D

SPE

CIF

ICA

TI

ONS

AN

D

CODE

OF

PRACTICE

FOR

ROAD

(4)

IRC

IRC 6-19666-1966

First

published

in December,

1958

Repr

inte

d:

May,

1962

Reprinted:

September~

September~1963

1963

2nd

Edition: October,

1964

3rd

Edition

in

Metric Units: October,

1966

Rcpri~t~

Reprinted: March, 19t2 (incorporates

Amendment

No. No. 1—Nov.1—Nov.1971)1971)

Reprinted

:

February

1974

(Incorporates Amendment

No.No. 2—Nov.2—Nov.

1972)

Reprinted:

August

19741974 (Incorporates(Incorporates AmendmentAmendment No.No. 3—April3—April

1974)

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ER( ER( 6196661966

~

ection

II

LOADS

LOADS ANDAND STRESSESSTRESSES

Cl

ause

No,

Page

No.No.

201

201 Classification

Classification

.... 44

20

2

2 Loads,

Loads,

Forces

and

Stresses

.,.,

5

20

3

3 Pcrmissihk

Pcrmissihk

Increase

in

the

Workmg

Stresses

ui

any

Structural

MemberMember

under

VariqusVariqus

Combi-

Combi-in

(6)

IRC :6-1966

INTRODUCTION

The brief history of the Bridge Code given in the in.._troduction

to Section 1 _‘General Features of _Design’ _applies _to _{Section H} _also.

generally. The draft of Section Ii for “Loads and Stresses” as dis

-cussed at the Jaipur Session of the Indian Roads Congress in 1946

was considered further at a number of meetings of the Bridges Com —

mittee for linalisation, in the years 1957 and 1958, the work of

hnahsing the draft was pushed on vigorously by the Bridges Corn

-mittee constituded as follows

Shri S.L. Bazaz ~.,, Convenor

(7)

IRC : 6~1966

The Executive Committee of the indian Roads Congress

approved the publication of the third edition in metric units, in 1966.

The Bridges. Committee at its meeting held in 1971 approved

certain amendments ip . the light of the Fourth Revision of Section 1

and the publication of Section lE E . These amendments, vide

Amendment No. I of November 1971 ‘(amending clauses 204, 207,

209, 212 and 216) and No. 2 of November 1972, (regarding

sub-clause 201.1) have been included in this Edition. The present reprint

also incorpori~tesAmendment No. 3, April 1974, regarding sub

(8)

i

sc

: 6 — 1 9 6 6

LOADS AND STRESSES

SCOPE

T h e.

object of the Standard Specifications and Code

of Practice is to establish a cpmm.on procedure for the design and

construction of road’ bridges in India. This publication is meant

to serve as a . guide to ‘both the design engineer and the construction

engineer but compliance with the rules therein does not relieve them

in any way of their responsibility fO r the stability and soundness of

the structure designed~’anderected by them. The design an’d

con-struction of’ road bridges require an extensive and thorough

know-ledge o’f the science and technique involved and should be entrust ed

(9)

IR C : 6-1966

201,2. Existing bridges which were not originally constructed

or later” strengthened to take one of the above specified l.R.CT+

Loadings will he classified by giving each a number equal to that

of the highest slandard load class whose effecti it can safely

with-stand.

Appendix I gives the essential data regarding the limiting loads

in each bridge class, ‘and forms the’ basis for the classification of

bridges.

201.3. individual bridges and culverts designed to take

elec-tric tramways or other special loadings and not constructed to take any of the loadings described in Clause 201.1 shall be classified in

the appropriate load class indicated in Clause 201.2.

(10)

IRC :6-1966

*203 PERMISSIBLE INCREASE IN THE WORKING

STRESSES IN ANY STRUCTURE MEMBER UNDER

VARIOUS COMBINATiONS OF LOADS, FORCES AND STRESSES GIVEN IN CLAUSE 202

203.1. The permise.ihle working stresses shalt not be exceedel

fur any combination of the loads and forces,’ specified in items I to 9

of Clause 202.1, that van co-exist.

203.2. When the effects of temperature stresses are also add

-ed, the permissible working stresses may be increased by 15 per cent.

203.3. When the combined effects of any combinations of any

of the forces specified in items 10 to 13 are added, the permissible

working stresses may be exceeded by 25 per cent, and

203.4. . When the effects of seismic forces are also considered

(11)

IRC 6-1966

of the materials in question, in which case the actual weights as thus

determined shall be used

Weight per

Materials cu. m. in tonnes

1 . Ash lar (granite) ‘ ... 2.7

2. Ashlar (standstond) ... 2.4

3. Stone setts

(a) Granite ... 2.6

(h) Basalt ... 2.7

4. Ballast (stone screened, broken, 2.5 cm

to 7.5 cm gauge, loose):

(12)

IRC :6~i966

Weight per

Materials cu.m. in

tonnes 23. Stone masonry (lime mortar) 2.4

24.. Water ,,; 1.0

25. Wood .., 08

26. Cast iron ... 7.2

27. Wrought iron

28 Steel (rolled or dast) ,,, 7.8

206. TRAFFIC LANES

The number of traffic lanes on a bridge shall be determined by

the maximum intqgral number of trains of standard Class A vehicles

described in Clause 207, which can be accommodated on the clear

(13)

l:g 1 _{1 ’}_(‘ontd,) _{‘IRC : 61 966}

l—~——COUIACSWAY WIDTH ‘~~S’~S

3Si’ONNES _ii~I5it~~pTONNES“~ ‘ii’L 1I

TRAdED VEHICLE

~— C A R R I A G E W A Y WIDTH ———*‘-—s~’

m Hits

— — ~ “ * 4

Notv

I “ 1 ’ he s i n _{y e} _to

tail cpa~ing bet

% s ’ i e n iwo r,iIcein’r,i;n’,’v i’chiele,,i y h ;:il l not

lii;r linri Iv i t I , ,i.’ whiv,,ticner ei~’i.nico ~h~yll(dl L’.lr1~nLlereLl l~sCl Ii 1 _{L i}_iitt S L No flhiyr lisC n h v il l be c mion

vIe red 00 9 liv

iiII II’iii 5,5

ole carriagewaY of

the bridge why above merit oiicit

(14)

ac:..

6~t9Yi

I... lIhdflI~J~I’I

-‘i”——’ “

I

fl

ifiC

H

7

ii’ S i’ A UI h ’W ~ U ‘Ii it

Not~t’,s

the T’iOtitl to tiiit dustance hilti%iIle’ri

si,i.cgesiiise trains shall irot he less shari

i,,~i 1ni,

W ‘2 ( No cithei’ liae boast shunt! crlver any part cif the crirria~ewr’iy when a train ci vehicles br trains i:ik ’ vehicles’ multi—lane hridge)I is crossing the

bridge,

3. The irroaisd cnrit:ict area cit tine class A train of vehicles

(15)

‘Ii IIII

iiiiI O ” IL III ‘“ ,, NIiIIli’aiiI~~II

a

i J

~ H1IiI~1IIE, a 1 : 1 $ , ,

1 1 J 1

(‘las’s’ Ft tririni or

3’IIIui’ r

I. I’l’in,:i’’: rI’s,:’ Ii rail .H’~:’ri’:’,,

ii’c:ril s’n:L::L:u:s’,ii y : ii’~iim u ’, ::Iu,iII ii ‘u ii,’

I 8.4 as

2 ‘Ni o tiu l,”n ’ H,,: Ii”: ii

I..’

In In of r i: : ’ I i iud,’s (In r ira i u

iii iii in-Ian .: ‘ I c ’ ]iIIL~di 1 .1 ~ ii:,

(16)

I ~ (“ + (.~+~

lcngll’h of the

bridge, and

to occul~any posit~on

which

WdI

produce

ma simu’rn sti’esses’provided

that

the ‘minirn’un. clearances

between

a . vehicle and tIi e road way face of k.erb

and

between two tUt5 _{S t}

or c:rossing vehicles, shown in

Figs.

I to 3, are not encroached

U polL

2(17, 1.3.

For

each sta

ndard

vehicle or train, all the axles of a

unit of vehicles

shall

he considered as acting simultaneously in a

position causing maximum stresses.

207.1.4.

Vehicles

in adjacent lanes

shall

be

taken

as headed in

the direction producing

maximum

stresses.

207.1.5.

The

spaces on the

carriageway

left

uncovered

by the

(17)

MII4iMUM ‘‘ II’, a’iua iii’5 tIa~

fl,’, ---—‘-ar ~ am

i,

~

..~‘k

i,,’ifl’--”-?

~iau5I,tqIaIu~IIM~ti~

I

~

~na~9~

1I~’, ~ /ii

1u 1 1

i~ _~

‘t’—r

-‘——-—‘u---—~-a ii f t _liii

-II, au maiM a ,i a, Class B train cif sehucles ‘

N o n e s

I, The nose t_u nail du’il,sntc,:

wren successive tiniirua r,hall iu ,:’i tin :’

w

W tl’u an u 18.4 in.

2~ No other live I n u n u i : I ‘-hal1 y:iii yr an çuaui of the eninniaeesu,as ‘. s I’ ’ ,:u u

trains of s’c—hiclcus (ia n ’ tnaiius iii’ si_I’ t: ’ ia —

in n’ui,,ilti—lntruy: buidgnu~ is , ini’nnssiuu,y d s,u

brids~e,

(18)

1RC 6.1966

209. FOOTWAY, KERR, RAILINGS AND PARAPET LOADING

(the provisions under this Clause do not apply to Foot-Bridges)

209,1, For all parts

of

bridge

floors

accessible only to

pedes-trians

and

anin~als~’andfor all

footways

the

loading shall

he

400

kg

per m2. Where

crowd

loads are

likely

to occur, such as on

bridges

located

near

towns,

which are either

centres of

pilgrimage or

where

large congregational fairs

are

held

seasonally, the intensity

of

foot-way

loading shall

be increased

from 400

kg per m~to 500 kg per m2.

209.2. K.erbs, 0.6 m or more in width, shall be designed

for

the above

loads

and

for

a local lateral

force of

750 kg per

metre,

applied

horizontally at the top

of

the

kerb.

if

the

kerb width

is less

than 0.6 m, no live load

shall

he.

applied

in addition to the lateral

load specified above.

(19)

~i.

fnl,tH

th~~~~____

hq— ~ — 4.6

~_—~

S~NGLt‘~iC~CSfl’JGIE DECK~ tROLLEr Wa~r I

I

₁

_(III

I

[~

(20)

1RC : 6-1966

P r,: the live load in kg

per

ni2,

L . t=the

effective

span of the

main girder, truss

or

arch

in m,

and

Wzzr:width

of

the footway in m.

209.5. Each part of the

footway

shall be capable

of

carrying a

wheel load of 4

tonnes,

which shall

be deemed to include impact,

distributed

over

a

contact

area 300 mm in dcameter; the

permissible

working strcsses shall

b .c increased

by 25

per

cent to meet

this

provision.

This

provision

need

not

be made

where vehicles cannot

mount the

footway

as

in

the case

of

a .

_.ioot~~ay

_separated

_from

_the

roadway by means of an insurmountable

obstacle,

such as

truss

or a

main

girder.’

(21)

IRC :6-1966

211~IMPACT

211.1 .

Provision

br

impact

or

dynamic

action

shall

be made

by an increment of the live load by aii impact alIo~anceexpressed

as a fraction or a percentage of the

applied

live

load.

211.2. For Class Aor Class B

Loading:—ln

the

members

of

any bridge designed either

for

Class A or Class B loading

(side

Clause 207.1), this impact percentage

shall

be

determined from

the

curvas

indicated

in Fig.

5 .

The

impact

fraction

shall

be

determined

Irom the lollowing

equations

which

are

applicable for

s p a as het~seen

3 in and 45 in.

(i) Imçaet factor fraction fo r reintht’eed

(22)

I R C : 6 ~ l C ; C S I - .~ — I . 0 . E ‘ 5 ’ , I , 0

j

j ~

~

I

c ) “ 1 Q ~ 0 0 V’ ~ 0 — — I M P A C T P E R C E N T A G E

(23)

i a a o j p u n a 0 4 1 0 0 S P 1 1 O l n ~ u o a . 1 0 ( 1

ç

~

i c q p a a n p o i s t u . u u I 0 A 0 l u i U t t a 0 4 1 J O t b t r f l q i o A o a A t l f l O l J a 0 i ~ ‘ ‘ ‘ ‘ ‘ ‘ ‘ ‘ ~ “ ‘ 5 C l t ’ d 5 p a p u a d s n s i n o t j v . s s s c u l l J O A O J f l l J ’ R D t b i u s i n j s o t b p r i q 1 0 4

(

1 )

p a s s u ~ d s i p r o j 0 ( 1 1 4 0 1 1 1 5 ¼ u o t u n i s O A J J . ) . i l J O 0 1 1 s o e p n u I O j J o s n o n u p u o a 1 0 p a ) l o d c i n s c 1 d i u u s s u n d s i o . j ( r ) 5 5 5 0 1 1 0 3 S i T 0 ( 1 1 1 1 1 1 1 5 o 5 n . i t o o i o d i o nd 0 4 1 l b u r u i w i o t o p . J p a i a p u s u o a 0 ( 1 0 2 q i t b u n 1 t r o t i s 0 q ~

~

c

’

l I Z ~ 6 0 Z O s n B [ ) u r p o p r o o d s t b u r / ( i t M i o I . ) J 0 4 1 0 1 P O I ) P 1 1 0 ( 1 I 1 3 ~ 4 ~ O O u T h s t o l i n 1 0 1 1 t 1 0 1 ! ° N V l i Z ~ 1 u £ Z J O 5 5 0 0 X 0 i t t s u n d s J O J f ‘ t b L ~ i t ! p a 3 n m p u i 0 A J ~ 0 0 4 1 4 1 ! i S S o D c t n p . t o a a n i t r p u t t U I £ Z o i c i n s u n d s i o ; i u o a j o e l £ Z : s a p r q a s p a [ o a r 4 ~ 9 9 6 1 - 9

(24)

IRC: 6.1966.

(c) Ft:r calculating the pressure on the portion ‘f the structure. mote tha ii

3 in heloss die bedblI,ick zero

2.11.8. In lie design ofmembers subject, among other stresses,

In direct lensiun, such as hangers in a hos¼string.girder bridge, and

in the design of members subject to ditect cL’mprrs sion. such as

si~andreIcol ~tmns or s s _{ails in} _an _{open spand}_rd _arch, _the _impact

pore c _nUme _shall _he _taken _the _{same as} _that _{applicable to the} _{c i} _esign

of the correspond np member or ru e mhcrs of the floor sy stem

5¼hich te a nsfer. loads to the tensile or cosnpressis e inembers in

(Ittestion.

211,9. These CIa u s e s on Impact do not appI~to the design of suspension bridges.

(25)

IRC: 6-1966

(26)

IRC: 6-1966

TABLE OF WIND PRESSURES AND WIND VELOCITIES

H. )“. P. H. V. _P. 0 8 0 4 0 3 0 1 4 7 1 4 1 2 9 1 52 4 0 1 5 5 1 5 7 4 1 0 0 6 3 ‘ 5 0 1 6 2 1 7 1 6 1 0 7 7 3 6 0 1 6 8 1 8 3 8 1 1 3 8 2 7 0 1 7 3 1 9 3 1 0 1 1 8 9 1 8 0 1 7 7 2 0 2 1 5 1 2 8

1 0 7

9 0

1 8 0 2 1 0 20 136 119 100 1 8 3 2 1 7

(27)

LR C 6~1’tt~6

than 450 kg per linear metre in the i4ane of the burled chord and

225 kg per linear rtietre in I lte plane of umtloaded chord on through or

half— through truss, l:.itticed or other similar spans, a m id not less than

4 50

kg per linear metre on deck spans.

21 2,7. A wind ~ressure ot 240 kg per m~on the unloaded

structure, applied as specified in Clauses 212.?, and 212,3 shall h e used if it produces greater stresses than those prod need by the coin—

bined winrl fbrces as per (Tlau~es212,2, 212.3, 212.4 and 212.5 or b~

tim e wind force as per Clause 21 2.6.

212.8. in calculating the uplift in the posts and rtnchorages of high latticed towers due to the above ni entionecl lateral forces, stress

-es shall also be investigated tbr the condition of decking, being

(28)

IRC: 6.1966

Piers with square ends

( C

semi-circularCircular piersendsor piers with

Piers with triangular cut and

ease waters, the angle included between the faces being 30

(29)

1I4C 6-1966

(vi) Piers with cut an d e a s e waters of

equilate-ral arcs of circles : _0.45

(vii) !iers with arcs of the cut and ease waters

intersecting at 90 degrees : _0.50

213 1 The value of P in the equation given in Clause 213 2

shall be assumed to vary linearly from zero at the point of deepest scour to the s qu ire ol the maximum s elocity at the free suilace of

water. The maximun i velocity fo r the purpose of this sub-clause shall be assumed to he ~/ 2 times the maximum mean velocity of the current.

~ Square of max. Square of velocityi at a height

~

r

~

x

from the. point of deepest

~

L— u’.-~./

ve1ocity~2c~ 172X

(30)

tRC: 6 -196 6 213.6. in case of a bridge having a pueca floor or having an

inerodible bed, the effect of cross~currentsshall in no ca s e he taken

as less thea that of a s ta tic fo rc e due, to a difference of head of 250

mm between the opposite faces of a pier,

213.7. When supports are made with two or more piles or

trestle columns, the group shall he treated a s a solid rectangular pier of the same overall length an d width and the value of K taken a s

1.25 for calculating pressures-due to water currents both parallel and

normal to the pier.

213.8. The effects of the lbrce ofwater currents shall be duly

considered upto the level indicated in Clause 2P 4.7.

214. LONGITUDINAL FORCES

(31)

-IRC 6-1966

214.3, The force due to braking effect shall be assumed to act along a line parallel to tht roadway and 1.2 m above it, While

transferring the force to the hearings, the change in the vertical

reaction at the bearings should he taken into account.

214.4. The longitudinal force at any free bearing shall be

limited to the sum of dead and live load reactions at the bearing

multiplied by the appropriate co-efficient of friction. The co-efficient

of friction at the beating shall be assumed to have the following

values.

Forrofler bearings ... 0,03

Fbr sliding bearings of hard

copper alloy ... 0.15

For sliding bearings of steel on

(32)

IRC :6-1966 215. CENTRIFUGAL FORCES

215.1. Where a road bridge is situated on a curve, all portions

of the structure affected by the centrifugal action of moving vehicles

are to be proportioned to carry safely the stress induced by this

action in addition to all other stress to which they may be

sublect-ed.

215.2. The centrifugal force shall be determined from the following equation

WV 8

127R

where Cr centrifugal force acting normally to the traffic

(I) at the point of action of the wheel loads or

(2) unifbrmly distributed over every metre

length on which a uniformly distributed load

(33)

:6-1966

uming th at the till behind the abutments has been removed by

ur,

.**216.3, Deleted

216.4. To allow for full buoyancy a reduction is made in the s weight of th,e member affected, in the fOllowing manner

(a) When the member under consideration displaces water

only, e.g., a shallow pier or abutment pier founded at or

near the bed level, thc reduction in weight shall be equal

to that of the volume of the displaced water,

(b) When the member under consideration displaces water and

also silt or sand, e.g., a deep pier or abutment pier passing

through strata of sand and silt a n d fo un d ed o n similar

material, the upward pressure causing the reduction in

weight shall be considered a s made up of two factors

(34)

IRC 6 - 1 9 ~ l 6

ofthe ‘vail above the base instead of0.33 of that height. No structure

shall, however, be designed to withstand a horizontal pressure le s s

than that exerted by a fluid weighing 480 kg per cu. m.

217.2. (a) The distribution of normal pressure on a retaining

wall due to a concentrated surface load on the

backfill shall he obtained by any rational method

ofdesign, the one using Spangler’s equation, which

is giVen below, being acceptable

KP X _~

x

~

r

in which Ii =.r.normal unit pre ss ure o n the wall a t any

point, in kg per sq. m.,

(35)

Q U - f l ~ f l p 4 ~ l ~ L I ~ S

—

- . . . . . D N I U V O ” I ~ 1 S S V 1 D ) ~ I J i ~ U i t I - 0 i f l ~ ~ ~ U r ! - ~ 1 l f l i % ~ ~ I ~ U ! S ~ S ~ i U I l p i t o i ~ ~ i u ~ w j o q i O f ~ Z l c J V O 1 V S S V 1 ~ ) ‘ f l i I S D t ’ . I I G V O T I ~ J 0 1 , S S V ’ I D U ~ V \ f V S S V 1 ) 3 ) ~ J 1 s 2 u i p n o l p i a p u r n s ‘ D ~ W l ~ u ! M o i l o j ~ ‘ q t J o 5 P i t 0 1 ) ~ D P J ) J O ~ ~ q i o t ~ n p S P L t O I 3 ) i t J J f l S p E J 8 U ~ 3 t J O ) ~ n p . i o j ‘ ~ i J ~ t U ~ ‘ H H ± H Y 3 ~ J O ~ U V H Q H f l S d O S i H O I E I H i N ~ 1 Y A l f l O 9 d O 3 1 9 V , ~ l J f l t D t U t P , J O u ~ i s ~ p ~ q i U i ~ ~ q p ~ u ~ P ~ ° 1 ~ O t t ‘ p ~ p r A o J d s i i p u o , x d d n ~ O ~ U ~ W ç . f U U L j t ~ ~ O U J O q 1 ~ U ~ 1 U . ~ u i p U ~ ) x o p u u q ~ i i ~ z i u n n ~ u o i p o u ~ . ~ s ~ p ‘ i ~ n ~ n i ~ s ~ j t ~ u o ~ w 1 s ~ i ~ 1 U O 1 j P N ~ ~ c u ~ ~ p u o . i ~ . J ~ ’ ~ P P ! ~ ~ ‘ i i u ~ ~ 2 L t ~ , J ~ A o ~ i uq s t p n o i d . ~ . i D U O Z ~ p ~ z ) J o J U i ~ ) J P ~ ’ ~ ! ~ ~ P ~ j ~I ) 3 U f l b ~ p U ) t U ~ . i ~ t I M ~ E ’ L l Z 9 9 6 1 - 9 :

(36)

IRC: 6 - 1 9 6 6

21 7,4. All designs shall provide for’the thorough drainage of

back-filling material by means of weep holes and crushed rock or

gravel drains, or pipe drShs, or perforated drains.

217.5, l’he pressure of submerged soils (not provided with

drainage ifrrangements) shall he considered as made up of two

components

( a ) p r e ssu r e du e t o th e e ar th cal cu l ate d in accordance

w ith th e method la id down in Clause 217.1, the unit

weight o f e ar th be i n g reduced for buoyancy, and

(b) full hydrostatic pressure of water.

217.6. in the design of return walls, live load surcharge shall be taken for loads placed beyond the length of the approach slab.

(37)

I1 k C : 6 -1 9 6 6

218.5. The co-efficient o F expansion per degree centigrade shall

h e tak e n a s 0 . 0 0 0 0 1 1 7 for steel and reinfoj~çedconcrete structures and 0.00(0108 f o r p l a i n con cr e te str u ctu r e s

S

219. DEFOF3MATION STRESSES (‘for ste e l bridges on l y )

219.1. A . deformation stress is d e fin e d a s th e bending s t r e s s

i n a n y memher of an open web-girder caused by the vertical deflec

-lion of the girder combined with the rigidity of the joints. No other

stresses are included in this definition,

219.2. A l l s t e e l br i d g e s s h a l l he d e sig ne d, manu factured and

erected in a manner such that the deformation stresses are reduced

to a minimum. In the absence of calculations, deformation stresses

shall he assumed to be n ot le s s Ihan 16 per cent of the dead and

(38)

1RC :6-1966

222. SEISMIC FORCE

222.1. If a bridge _is situated in a region subject to

earth’-quakes, allowance shallbe made in the design for seismic force and

earthquake resistant features shall be embodied in the structural

details of design.

222.2.

The seismic force shall he taken as a horizontal force

equal to the appropriate fraction specified in Clause 222.3 of the

weigh.t of the dead and the live loads acting above the section under

consideration. (Parts of the structure embedded in soil shall not be

considered to produce any seismic forces).

2223 The country is divided into three regions as shown in

(39)

IRC 6-1966

o 20 and C/IC) for the regions shown therein as “Liable to minor

damage or nil”, “Liable to moderate damage”, and “Liable to severe

damage” respectively. For bridges situated in epicentral Iracts

where large devastations have occurred in the past, clue to earth -quakes the percentage shall be fixed by the engineer responsible for

the design, ssith due regard to the local conditions regarding the intensity of earthquakes generally experienced in these regions.

222.4. These horizontal forces due to the seismic effect shall

he taken to act through the centre ofgravity of all the loads under

consideration. The direction ofthese forces should be such that

the resultant stresses in the member under consideration are tli.e

in a xiinum.

222.5. Seismic and wind lhrces shall not be considered to act siniultaneou si y.

(40)

EQUiVALENT HEIGHTS (Metres)

OF

SI.JRCHARGE O FEARTH

WHICH WOULD GIVEOVERTURNING MOMENTATTHEBASE OF

BRIDGE ABUTMENTS

EQUALTOTHE MAXIMUMMOMENT CALCUL ATED BYSPANGLERS EQUATION UNDER CONCENTRATED SURFACE LOADS DUE TO

THE WHEEL OR TRACK LOADS OF

I,R.C.STANDARD VEHICLES ORTRAiNS

IEC 5.1-n

PLATE

Vole —The‘~aiue\ of heightsof ‘uicharge given in this Plate

are basedonthefoHo~vingsaIue~for theeon’,tanis forthe abutniunts

...A ~L-. Li 4~t1

aijcj LIIC t;acK lIll

il) Lengh of abutment (LI 4.5m for ~ingic lane

bridgesand 7.6 mfürmultilane bridges. (2) Angie of iniernalfrictionof thebackfill (4) 3(3

(3) Weight

0f backfill(IV)—1600kg percu. m. (4) The resultantearth pressure acts in a horizontal

direction. For differentvalues,say.L1.

4iandW

1for the constants. the valuesobtained from their curvesshould bemultipliedbythe fo1low~ ing factors

L(4,5 or 7.6 astheeasemaybej (~5i~~)

L1 _{3 (I—sin}~i)

1500

respectively

I.R.C. CLASS ‘A’ LOADiNG MULTI-LANE BRIDGES

DEPTH OF ABUTMENT IN METRES (b)