IRC_006-1966

IRC

6-1966

STANDARD SPECIFICATIONS AND AN D

CODE OF PRACTICE FOR

ROAD BRIDGES

IRC 6-1966

STANDAR STA NDARD D SPE SPECIF CIFICA ICATI TIONS ONS AND AN D

CODE OF PRACTICE FOR

ROAD BRIDGES

c

1X .~~tk1

IRC 6-1966

STANDAR STA NDARD D SPE SPECIF CIFICA ICATI TIONS ONS AND AN D

CODE OF PRACTICE FOR

ROAD BRIDGES

c

1X .~~tk1

IRC 6-1966

published in December, 1958 Reprinte Repr inted: d: May, 1962 Reprinted: September~1963 2nd Edition: October, 1964 3rd Edition in Metric Units: October, 1966 First

Rcpri~t~ 1—Nov.1971) 1971) Reprinted: March, 19t2 (incorporates Amendment No. 1—Nov. Reprinted:: February 1974 (Incorporates Amendment No. 2—Nov. Reprinted 1972) Reprinted: August 1974 (Incorporates Amendment No. 3—April 1974)

61966

ER(

CONTENTS ~ection II LOADS AND STRESSES

Clause Cl ause No, 201 2022 20 2033 20

Classification Loads, Forces and Stresses Pcrmissihk Increase in the Workmg Stresses ui any Structural Member under Variqus Combiin

Page No. ..

.,

4

5

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 discussed 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 Cornmittee constituded as follows Shri S.L. Bazaz Shri M,P, Nagarsheth

~.,,

Convenor Member-Secretary

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 These amendments, vide and the publication of  Section lE E . Amendment No. I of  November 1971 ‘(amending clauses 204, 207, 209, 212 and 216) and No. 2 of  November 1972, (regarding subclause 201.1) have been included in this Edition. The present reprint also incorpori~tes Amendment No. 3, April 1974, regarding subclause 211.2 and erratum to sub-clause 209.4 (c).

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 construct ion of’ road bridges require an extensive and thorough knowledge o’f  the science and technique involved and should be entrust ed only to spccially qualified engintirs s~ ith idcquatt. pr ictical cxperi

IR C

:

6-1966

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 withstand. 201,2.

Appendix I gives the essential data regarding the limiting loads in each bridge class, ‘and forms the’ basis for the classification of  bridges.

individual bridges and culverts designed to take electric 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. 201.3.

202.

LOADS, FORCES AND STRESSES

IRC :6-1966 PERMISSIBLE INCREASE IN THE WORKING

*203

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 added, 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

When the effects of  seismic forces are also considered in addition to those from any combination of  the loads and forces 203.4.

.

IRC

6-1966

of  the materials in question, in which case the actual weights as thus determined shall be used Weight per cu. m. in tonnes

Materials

1. 2. 3.

4.

Ash lar (granite)

‘

Ashlar (standstond) Stone setts (a) Granite (h) Basalt Ballast (stone screened, broken, 2.5 cm to 7.5 cm gauge, loose): (a) Granite

... ...

... ...

.,,

2.7 2.4 2.6 2.7

1.4

IRC :6~i966

Weight per cu.m. in ton nes

Materials Stone masonry (lime mortar) 24.. Water 23. 25. 26. 27. 28

Wood Cast iron

Wrought iron Steel (rolled or dast)

2.4 ,,;

1.0

..,

08

...

7.2

,,,

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 s~idthof  tho hi idgt slId h thc vU ides ti a~ethng

l:g 1

1 ’ (‘ontd,)

l—~——COUIACS WAY WIDTH

‘IRC : 61 966

 Notv ‘~ ~ S ’~ S

I to “ 1 ’ he s i n y e 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

1

TONNES ii~I5it~~p “~ ‘ii’L I

~h~yll(dl L’.lr1~nLlereLl l~sCl 

TRAdED ~—

VEHICLE

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

m

Hits

— — ~“*4

i.’

ei~’i.nico

whiv,,ticner

3Si’ONNES

I,

1 L i iitt S L

No

flhiyr

lis C 

n h v il l be c m ion

vIe red 0 0 iiII

Ii

II’iii

5,5

9 liv

ole carriagewaY of  the bridge why merit oii cit above train or ychiclys III

ac:..

6~t9Yi

I

fl

I...

lIhdflI~J~I’I

-‘i”——’

ifiC H ii’

S i’

A

class A train of  vehicles

W

UI

h ’W

~

“

7 U

‘Ii it

 No t~t’,s the T’iOtitl to tiiit dustance hilti%iIle’ri si,i.cgesiiise trains shall irot he less shari

i,,~i 1ni, ‘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

‘Ii iiiiI O ” I L III

a

iJ

~

H1IiI~1IIE,

a

NIiIIli’aiiI~~II

,,

‘“

$

1 :1

,,

or 3’IIIui’ r

11J

1

(‘las’s’ Ft tririni

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.

w fl

I’l’in,:i’’:

I

2

8.4 as

‘Ni

o tiu l,”n ’ H,,: Ii”: ii

In In of  r i: : ’ I i iud,’s (In r ira i u iii iii in-Ian .: ‘ I c ’ ]iIIL~di 1 .1

I..’ ~

ii:,

II II

I

~

(“  + (.~+ ~

lcngll’h of  the bridge, and to occul~any posit~onwhich 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 tUt 5 S t or c:rossing vehicles, shown in Figs. I to 3, are not encroached U polL

For each sta ndard vehicle or train, all the axles of a unit of vehicles shall he considered as acting simultaneously in a 2(17, 1.3.

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 standard train of vehicles shall not be assumed as subject to any

MII4iMUM fl,’,

i,

I

~iau5I,tqIaIu~II M~ti~ i ~ ~ a

~

a’iua iii’5 tIa~

II’,

‘‘

---—‘-ar

~

..~‘k

am

~na~9~ ‘t’—r

~ ii  

-II,

au

i,,’ifl’--”-? 1

~  /ii

1u 1 -‘——-—‘u---—~

1I~’,

ft

liii a,

a ,i

m aiM

Class B train cif  sehucles

‘

Nones

I,

w

W

The nose t_u nail du’il,sntc,: wren successive tiniirua r,hall iu ,:’i tin :’ tl’ u an u 18.4 in.

2~

No other

live

Inun ui:I

‘-hal1

y:iii yr

an çuaui of  the eninniaeesu,as ‘. s I’ ’ ,:u u trains of s’c—hiclcus (i a n ’ tnaiius iii’ si_I’ t: ’ ia — in n’ui,,ilti—lntruy: buidgnu~ is , ini’nnssiuu,y d s,u br ids~e, 3 ‘rIce’ i;niuanuil c :o n ln :,n y ’I tiTian ii’

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 pedestrians and anin~als~’and for all footways the loading shall he 400 kg 2. Where crowd loads are likely to occur, such as on bridges per m near towns, located which are either centres of pilgrimage or where large congregational fairs are held seasonally, the intensity of footway 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. Note

Th e h orizontal

force need not t~e cons idet’ed in

the design of  the main

~i.~ fnl,tH th ~~~____ hq— 

—

~

4.6

~_—~

iC ~ CSfl’JGIE DECK~ S~NGLt ‘~

tROLLEr Wa~r

I

I 1

(III

I

[~

1RC

 P r,: the live load in kg per ni

:

6-1966

2,

 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.’ Note 

A footway kerb shall b e considered mountable by vehicles.

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 A or 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

concrete bridges

~‘~‘~L

I    I   

~

 c  ) 

 j   j  ~

“    1 

  Q

I    M P  A   C  T  P  E  R   C  E   N  T  A   G — E 

~

 0

 0  0  

 V ’  ~

  ,I    

—  0

I    R  C

:   

‘       5     ,’     

E       

 0   .

I      .

.~ —

I   - 

 C                S               

 C      ;     

 6  ~ l   

   9   -   1    6    9    9

   a    q   r   p    a    s    ~    4   r   a    o   [   a    p   s

 :

   o  j   a  i   c i   o   Z    Z    £ l   e    d    n    u    s   n    £ I   U    o    u  i   ;   o  i   s    a    a    o   t .   p    n   t   c     D    o   S   t  t   u    p   r  t i    n   S  i !  1   4   1   4    0     L    b   t  ‘    f   J    O     0     ~     J       A     0  i   u    p      m    n    3     a    p   !  t i    ~    J    £   u   1   ~   J    Z     X    0    0    5    5    O    s    d    n    u    s  t  t i    0

    ° !  1  0  1 t  1  1  0  1    n   1    P  ) I   O    P  1   0    1   4   0    J  )  .  I   o  i      M   t  i  (  /   i  l   o   t  s   h     T    u     O     O   (  0   1     Z  i l     V     N    ~    4    ~    3  1 I   1   r   u    b   t    s     Z    0    6    ~    d    o    o   r   p    o    p  r   u   )  [   B    n    s     O    o    u    s    u    p    a  i   a    p  J .     p  ’   c      q      0   s    n    u    b   t i   q   2   (   0   a    0   1     o   t    o  i     w  i    u   r    u     b  l   1    4    0  i  t   o   r  t   1     Z   I  l    ~     ~    o  i   o    o   t i .   n    5    o  5  1  1  1  1  1  1   1  (   0    T  i   S   3   0   1   1   0   5   5   5    n d   o  i    d   )  r  (  j  .    o    d    n    u    s  s  u  u  i  d  1  i    s   c    s    n  i   c    d    o  l  )   a    p   0   1    a    o    u    p    u    n    o    n    s    o   J  j     O    I    u    n    p    e    o    s    u     ¼    5  1  1  1    0    4   1  1   1  1  0     O    J l i .  ) .   J    J     A     O   s   (  0  i   n    u   t    o  j   o   r   p i   s    d    ~    u    s    s    a    p     R  ’  J l l  f  J     O     A     O   J  l l    u    s .   v j  t   o    n  i   s    n    s    d    a    u    p    a    p  )  1 ( (     4    0   1   q i  r   p   b  t   o   s j    n i   s    u i    b  t     D    c    s    s    4    0     a     5     d   ’  t  l     C     5   ‘   “    ~   ‘  ‘  ‘  ‘  ‘  ‘  ‘  ‘      ~   i     0    a    o   i    q   l    f   r   t     b   t     O    J   1   t  t    U  i   u  l   0     A    0   I    J l     O  l  f l  t    A     a    o    A   u  u .  u t  s  i    o    p    4    0   a   1  1    P    S   0   0   1   c i    ~    n    u    p  j   o    a    a  i     ç  1 (  0  1 .   a    o    u    ~     n l   O     n     a     a     p  q

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 of members subject, among other stresses, In direct lensiun, such as hangers in a hos¼string. girder bridge, and the design of members subject to ditect cL’mprrs sion. such as in 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 5¼ hich 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.

IRC: 6-1966

INTENSITY OF WIND PRESSURE

IRC: 6-1966

TABLE OF WIND PRESSURES AND WIND VELOCITIES

 H.

)“.

P.

H.

0

80

30

147

1 41

2

91

40

155

1 5 7 

4

100

40 52 63

50

16 2

1 71

6

107

73

16 8

183

8

113

82

60 70

17 3

193

10

118

91

80

177

2 02

15

128

1 07

90

180

210

20

136

119

100

183

2 17

‘

V.

P.

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, stresses shall also be investigated tbr the condition of decking, being loaded on a traffic lane or lanes on the leeward side only.

IRC: 6.1966

Piers with square ends

(C

piers or semi-circular ends

Circular

piers

with

Piers with triangular cut and ease waters, the angle included between

the

degrees or loss

faces 

being

30

1I4C

6-1966

(vi) Piers with cut an d e a s e waters of equilateral arcs of circles : (vii) !iers with arcs of the cut and ease waters intersecting at 90 degrees :

0.45 0.50

213 1 The value of P in th e 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 th e maximum mean velocity of the current. ~ Square of max. ~

r

~

~ L— u’.-~./ ve1ocity~2c~

Square of velocityi at a height

x  from the. point of deepest scour”.- U2=2

72X  1

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, th e 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 of water currents shall be duly considered upto the level indicated in Clause 2 P 4.7. 214.

214.1.

LONGITUDINAL FORCES

In all road bridges, provision shall be made for longi-

IRC

6-1966

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. 214.3,

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. For rofler bearings

...

0,03

Fbr sliding bearings of  hard copper alloy

...

0.15

.,.

0.25

For sliding bearings of  steel on cast irorror steel on steel

,

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 sublected. 215.2. The centrifugal force shall be determined from the following equation 8 WV 

127R where Cr  centrifugal force acting normally to the traffic (I) at the point of action of th e wheel loads or (2) unifbrmly distributed over every metre length on which a uniformly distributed load act~,in tonnes,

:6-1966

uming th at the till behind th e 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 th e 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 th e 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 (i) Full hydrostatic pressure due to a depth of water equal

IRC 6 - 1 9 ~ l 6

of th e ‘vail above the base instead of 0.33 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 of design, 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 point, in kg per sq. m., Pr.rzr

applied wheel load in k g .,.

on

the

wall

at

any

 :    9   -  1    6    9    9

  I  t   ~  i .   ~     U     Z  l   L  ’    E    ~     M   )  t    U       P       ~       ~       ~     ’       ~       P    p    ~    b  l  f    U    3   )    ~  j   ~ I     !     ~     Z      O      U      D  i  .    ~   .    J  )    ~    i    U    J    o    J  )    z    ~    p    d  i   o    n    p   t    s      N     P   j   1    O     U    1    ~     ~  i   u    o      A q    ~    J   ,    ~   t    L    2    ~    ~    u   i  i  ‘   ~    ~   !     P     P    ~   ’   ~    J   .    ~   i  .   o    u    p    ~    ~    u    c   ~    ~

  i   z   ~     q   u   i    n     ~     n   i    ~   ‘    u    p   o    ~  j    ~   t   ~     p     ~     s     ~   .    ~     u     o     p i   o    u    s  i   ~    s  1     w    ~   o    u    ~    n    n u  i  i   ~    x   )   ~     U    p   i   u    ~  .     U     1    d    d    x ,   o    u    p  i  i   s    d    J    o     A   r   p    ~    p  ‘   t  t     O     O    ~     ~  t  j    L     ~       U     ~     1      q    O     U     U  f   J    U   .   ç     W     ~      U     ~      O    ~   n     ~   J ,     P      ~      p    q     p     s   i    ~     u    O    1     °     ~      P    ~    ~    ~    ~  i    U  i   q   t    U   t    ~     u

    D   t l  f   J l   ~   ,   I    E   I     O     H   i    S    O      V     9    1     3     O     d    d     9      O   l  f  l     A     Y    1     ~     N   i    H      H    ‘

 i    q    o   j      w     ~     u   i    ~    ~   i   o   t  i    p

    3     Y     H     ±     H     S   l  f    H     Q     H     V     U    ~     O    J    ~

 j   o  i .   p   n   ~   )      O    J   t   3    ~     U    8    J     E    p     S    n    ~  t    o i   q    ~    ~  l  f   J    J   t i  )    3 I   O  t  L    P    S   p     O    J    0   t i   P    5   o  J     n     p   i    u     2    s   t   q  ‘   ~ j   o  l i   o     M   !   u    ~  l      W     ~      D  ‘    s    n   r   u    p    a  i   p  l    o   )   J     P     D    ~   )   1

    ~        U     t      ~      J    i     ~    ‘

   1    J     ~   )   3   )   1      V     S     S      V    f  \       V     ~       U     D   I  ’    V    S    S ,  1  0    J   ~   I     T     O     V     G   I  I .  ’  t    D    S

 I   i   l    f  ‘  )     ~    1      V     S     S      V

   1     O     V    J    c   l    Z    ~    f    O

    J    I      ~    )    D    1     V    S    S    1    ~   I   ”     O     V     U   I    N     D

  l   I    U   i    ~     S

  .   .   .

   ~

    S   !    U    ~   I   ~    ~      %   i  l    f  l   1    ~   -  !  r    U    ~

   ~

   .    .

  -

    —

    ~   l   f  i    0    -  I   t  i     U     ~   i    ~   l  f    ~   l  f  -    U      Q     S   I    L    ~   l   ~     4    p

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, th e 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.

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~çed concrete 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 defleclion 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 liv e load s t r e s s e s .

1RC :6-1966 222.

SEISMIC FORCE

222.1. If a bridge is situated in a region subject to earth’quakes, allowance shall be 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 FigS and the seismic forces in the regions shall he taken as nil,

IRC

6-1966

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 earthquakes 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.

o

222.4. These horizontal forces due to the seismic effect shall he taken to act through the centre of gravity of all the loads under consideration. The direction of these forces should be such that the resultant stresses in the member under consideration are tli.e in a xiin um.

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

EQUiVALENT HEIGHTS (Metres)

IEC

OF

PLATE

SI.JRCHARGE O F EARTH WHICH WOULD GIVEOVERTURNING MOMENT AT THE BASE

OF

BRIDGE ABUTMENTS EQUAL TO THE MAXIMUM MOMENT CALCUL ATED BY SPANGLERS EQUATION UNDER CONCENTRATED SURFACE LOADS DUE TO THE WHEEL OR TRACK LOADS OF

I,R.C. STANDARD VEHICLES OR TRAiNS

5.1-n

Vole —The ‘~ai ue\ of  heights of  ‘ui charge given in this Plate are based on the foHo~vingsaIue~for the eon’,tanis for the abutniunts ...A aijcj

~L-. LIIC

Li

4~t1

t;acK lIll

Lengh of abutment (LI  4.5 m for ~ingic lane bridges and 7.6 m für multilane bridges. (2) Angie of iniernal friction of  the backfill (4) 3(3 (3) Weight 0f  backfill ( IV)—1600 kg per cu. m. (4) The resultant earth pressure acts in a horizontal il)

direction. 4i and W  For different values, say. L1. 1 for the constants. the values obtained from their curves should be multiplied by the fo1low~ ing factors

 L (4,5 or 7.6 as the ease maybej  L1

1500

( ~5i ~ ~) 3 (I—sin ~i)

respectively

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

DEPTH OF ABUTMENT IN METRES (b)