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ltOL 37 No. 6 JUNE 2009

frlå qr,Î,Tr_sø Ðiùwùet o, ûqr Ew[ g{q,

r{ Rõú * 110 ozz 1ffi¡

INDIAN ROADS CONGRESSKama.Kotil4a¡g, Sector 6, R.K. puram,

Ncw Dclhi - I t0 022 (tndia)

ewvSpTrit (Tele);qËf$f{S (Sccrctary Ccnerat): +9t (il) 26tB 5303yJ|m (secu.):26t8 53t5,26t8 5319, 2617 t548,26t8 5273,2671 6778ù+q (nax): +9t (il) 26lB 3669

Subject:

Encl:As above

IRC:22-1986 "standard specifications and code of Practice fbr Road Bridges,, section vl compositcconstruction was published in oôtober 1986 and reprinted in october 2005 incorporating uptodate amendmentstill that time.

The Indian Roads congress has further decided to bring out an Erra,tum No. 2 to the above document,Accordingly, the Erratum No.2 is notified herewith.

.This Erratum No. 2 shalr be effective from the l June 2009.

NOTIFICATION NO. 52 dared rhe 28 May 2009

Erratum No'Z to IRC:22'1986 ístandard specifications and code of practice for RoadBridges" section vl composite construction( First Revision) (Reprinted in october 2005)

R-!-uø¡uu -(R.P.lndoria)

Secretary General

ERRATUM NO.2 TO IRC:22-ISS6"STANDARD SPECIFICATIONAND CODE OF'PRACTICE FORROAD BRIDGES" sEcrIoN vI coMPosITE coNsrRUcTIoN fri.sì nenision ¡(Reprinted in October, 2005)

Page 28 Add the foilowing matter berow the 7th line and abr¡vc gúh rine

Ilthe number of shear conndctors given by above equation cxceeds the number provided by the spacing from the

::,ilT| iïiiliijîÍ,l,l,J;l ' l'2'' adclitional connectors should be addect ro ensure rhat the urrimate strength ortho

6l 1.4.1.2.3. Mild steet shear conncctor

6ll'4'l'2'3 l'lorrnilcl steel shear connectors, the saf'c shear fbr each shear connector shall be calculated

(a) For welded stud connector of steel with minimurn ultimate strength of 4ó0 Mpa and yield point of 350 Mand elongation of20 per cent -

8llINDIAN HIGHWAYS, JTINE

(i)

( ii)

where

ah:d-

For a ratio of l/d less than 4,2

Q : 1.49 h.d. lm

For a ratio of h/d equal to or greater than 4.2

Q:6.08 d2 {fck

(b)

F,.diÊÉì',qÌi:r'

,rjirì'

,rii:,þ-ìiì-

#r,

*$t'

iîiiir,,iitl:: '

iIn

'.Ti

The safe shear resistant in Newtsn of one shear connectorHeight of stud in mmDiameter of stud in mm

For channel/Angle/Tee connector made of mild steel with minimum ultimate strength of 420 to 500 Mpayield point of 230 MPa and elongation 2l per cent

Q = 3.32 (h + 0.5Ð L.Æ[

The safe shear resistance in Newton of one shear connectorThe maximum thickness of flange measured at the face of the web in mmThickness of the web of shear connector in mmLength of the shear connector in mm

where

a=h:t:L

where

VL

a

VlAe

YM

611.4.1.2.3.2. The spacing of shear connectors shall be determined from the formula

P: IQ_Vr-

The longitudinal shear per unit length as stated in Clause 611.4.1.2.3.3

Safe shear resistance of each Shear Connected as stated in Clause 611.4.1.2.3.1above (Ðe is the totalshear resistance ofall connectors at one transverse cross-section ofthe girder)

611.4.L2.3.3. The longitudinal shear per unit length at the interface of the prefabricated unit and in-situ unit shallbe evaluated from the expression given below:

VL = V.Ae.YI

where

V Vertical shear due to dead load placed after oomposite section is effective and working live load withimpact

Longitudinalshear per unit length

Area of transformed section on one side of intsrface

Distance of the ccntroid of the area uncler consideration from the neutralaxis of the composite seotioR

Moment of inertia of the composite section

INDIAN HIGHWAYS, JLINE 2OO9 89

Ii

611.4.1.2.4. Shear connectors for deck with R.C. or r.s.C. slab and R,C. or P.S.C. prefabrlcated girder

611.4.1.2.4.1. The load factor for design of shear connectors under ultimate load shall be 1.5 fur dead toad ancl2.5 for live load. The dead load to be taken for calculating the ultimate horieontal shear shall bethe dead load operating after composite action is effective.

6ll'4.1-2.42. The ultimate longitudinal shear V, per unit length at the interface shall be evaluated from thexpression as given in Clause 611.4.1.2.3.3 by calculating ultimate verticalshear with thà above

mentioned load factors,

t,

Read

6n.4,t.2.4.3 1

6I.L.4.t.2.4.4 |6n.4.t.2.4.5 l

Page

28

28

29

For

6n.4i,.2.3.

6n.4.2.4.61t.4.2.5

In partialmodificationto Notification No.20dated29.6.2006printed in Indian HighwaysJuly,2006 issue

90 TNDIAN HIGHWAYS. JI.INE

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qrrfiq v-sfi õiùsõrlr õìCl qr{, ù€"t o, qrtl qun Srq,

q{ Êñft - 110 oa2 (ff{'ff)

INDIAN ROADS CONGRESSKama Koti Marg, Scctor 6, R.K. Puram,

Ncw Dclhi - I l0 022 (lndia)

(ttTrV (Tole);q6rqfrS (Secretary Cancral): +91 (l l) 2618 5303qRKmq (secu,):2618 53t5,2618 5319, 2617 1548,26t8 5273,26"t1 6778

ùEW (¡'ax): +91 (ll) 2618 3669

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NOTIFICATION NO.53 dated the 28 Mav 2009

fiubject: Amendments to Clause No. 202.3, Z0g,Z¿0g.1,218.5 and 222 of IRC:6-2000 "standard Specificationsand Code of Practice for Road Bridges" Section : II Loads and Stresses (Fourth Revision)

Fourth Revision of IRC:6-2000 "Standard Specifications and Code of Piactice for Road Bridges" Section :

ll Loads and Stresses was published in December, 2000 and reprinted in April 2006 incorporating uptodate amend-nrents till that time.

The Indian Roads Congress has decided to further amend the above document. Accordingly, the

Amendment No.8 is herebv notified.

These amendments shallbe effective from the I June 2009.

R'!'Y'*u -

(R.P.Indoria)Secretary General

I'incl: As above

Clause No. For Read

202.3 The load combination shown in Table Ishall be adopted for working out the skess-es in members. The permissible increases ofstresses in various members due to these com-binations are also indicated therein. These

co¡nbinations of forces are not applicable forworking out base pressur€ on foundations forwhich provisions made in relevant IRC BridgeCode shall be adopted.

The load combination qhown in Table I shall be

adopûed for working out the shesses in the mem-bers. The permissible increase of stresses in mem-bers. The permissible increase of stresses in vari-ous members due to these combinations are alsoindicated therein. These combinations of forcesare not applicable for working out base pressure

on foundations for which provisions made in rel-evant IRC Bridge Code shall be adopted. For cal-culating stresses in members using working stressmethod of design the load combination as shownin Table I shall be adopted.

The load combination as shown in Appendix 3shall be adopted for working out the stresses inmsmbers using limit state design approach.

INDIAN HIGHWAYS, JUNE 2OO9 9l

:í .i

.l :

:,I

I.

208 Note: However, it should be ensured that the

rçduced longitudinal effecß are not less sever

than the longitudinal ofl'ect, resulting fromsimultaneous load on two adjacent lanes.

Note: Howcver, it should be ensured that the re-

duced longitudinal effccts are not less severe than

tho longitudinal effect, resulting from simulta-neous load on two adjacent lanes. L,onÊitudinal

effccts mentioned above are bendine momen!,

shcar forcc and torsion.

209,7 P-l NormalContainment

Bridges carryingExpressway, orequivalent

l5kN vehicleat ll0 km/hand 200

angle ofimpact

P-lNormalContainment

Bridges carryingExpressway, orequivalent

I 50 kN vehicle

at ll0 km/lrand 20uangle ofimpact

P-2 Low Con-tainment

All other bridges

cxcept bridgeover railways

l5kN vehicleat 80 km/hand 20n

angle ofimpact

P-2 Low Con-tainrncnt

All other bridgesexcept bridgeover railways

150 kN vehicleat 80 km/h and

20" angle ofimpact

P-3 High Con-tainment

At hazardous

and high risklocations, overbusy railwaylines, complexinterchanges, etc.

3OkN vehicleat 60 km/hand 200

angle ofimpact angleof impact

P-3 HighContainment

At hazardous and

high risk loca-tions, over busyrailway lines,complex inter-changes, etc.

300kN vehicleat 60 km/h and

200 angle ofimpact

2l 8.5 Permissible Increase in Stresses and LoadCombination

Tensile stresses resulting from temperature ef-fects not exceeding in the value of two thirdof the mõdulus of rupture may be permitted

in prestressed concrete bridges. Sufficientamount of non-tensioned steel, shall, howev-er, be provide to control the thermal cracking.

lncrease in stresses shall be allowed for calcu-lating load effects due to temperature restraintunder load combinations.

Pcrmissible Increase in Stresses and LoadCombinations

Tensile stresses resulting from temperature

effects not exceeding in the value of two thirdof the modulus of rupture may be permitted inprestressed concrete bridges. Sufficient amount ofnon-tensioned steel, shall, however, be provide tocontrol the thermal cracking. Increase in stresses

shall be allowed for calculating load effects due totemperature restraint under load combinations.Note:Permissible increase i¡ st¡esses and loadcombinations as stated under Clause 218.5 is notapplicable for limit state design of bridges.

INDIAN HIGHWAYS. JUNE 2OO9

Appendix 3

COMBINATION OF IOADS FOR LTMIT STATA DISICN

Loads to be considered while aniving at the appropriate combination for carrying out the necessary checks

for the design of road bridges and culverts are as follows:

Dead Load

Snow load (See note i)

Superimposed dead load such as hand rail, crash banier, footpath and service loads.

Surfacing or wearing coat

Back FillWeight

Earth Pressure

Primary and Secondary effect of prestress

Secondary effécts such as creep, shrinkage and settlement.

Temperature including restraint and bearing forces.

Carriageway live load, footpath live load, construction live loads.

Associated carriageway live load such as braking, tractive and centrifugal forces.

Accidental effects such as vehicle collision load, barge impact and impact due to floating bodies.

Wind

Seisrnic EfÏect

Erection effects

Water Current Forces

Wave Pressure

Buoyancy

Notes:

i) The snow loads may be based on actual observation or past records in the particular area or localpractices, if existing.

ii) 'l'he wave forces shall be determined by suitable analysis c<lnsidering drawing and inertia forcesetc. on single structural melnbers based on rational methods or model studies. [n case of group ofpiles, picrs etc., proximity eff'ccts shall also be considered.

Combination of loads for the verlfication of equilibrlum and structural strength under ultimate state

Loads are required to be cotnbined to check the equilibrium and the structural strength under ultimate limit state.

The equilibrium of the structure shall be checked against overturning, sliding and uplift. It shall be ensured that thedisturbing loads (ovcrturning, sliding and uplifiing) shall always be less than the stabilizing or restoring actions.The structural strength under ultimate limit state shall be estimated in order to avoid internal failure or excessivedeformation. The equilibrium and the structural strength shall be checked under basic, accidental and seismiccombinatious of loads.

1)

2)

3)

4)

s)

6)

7)

8)

e)

t0)

il)r2)

l3)

l4)

l5)

l6)

t7)

t8)

.

,:

.

.n&1I

rT

{

r

rt

I

{

INDIAN HIGHWAYS. JUNE 2OO9 93

(l

3. Combination Principles

The following principles shall be follclwed wlrile using these tables for arriving at the cornbinations:

i) All loads shown under Column I of Table 3.I or Table 3.2 or Table 3.3 or Table 3.4 shall be oombined to carrvout the relevant verification,

ii) While working out the combinations, only one vqriable load shatl be considered as the leading loads at â rime.All other variable loads shall be considered as accompanying loads. In case if the variablJloads producesfavorable effect (relieving effect) the same shall be ignored.

iii) For accidental combination, the traffic load on the upper deck of a bridge (when collision with the pier due rotraffic under the bridge occurs) shall be treated as the leading load. In all other accidental situations rhe trafficload shall be treated as the accompanying load.

iv) During construction the relevant design situation shall be taken into account.

v) These combinations are not valid for verifying the fatigue lirnit state.

4. Basic Combination

4.1. For checking the equilibrium

For checking the equilibrium of the structure, the partial safety factor for loads shown in column no. 2 or 3underTable 3.1 shall be adopted.

4.2. For checking the structural strength

For checking the structural strength, the partial safety factor for loads shown in column no. 2 under Table 3.2shall be adopted.

5. Accidental Combination

For checking the equilibrium of the structure, the partial safety factor for loads shown in column no. 4 or 5under Table 3. I and for checking the structural strength, the partial safety factor for loads shown in column no. 3under Table 3.2 shall be adopted.

6. Seismic Combination

For checking the equilibrium of the structure, the partial safety factor for loads shown in coiumn no. 6 or 7underTable 3.1 and forchecking the structural streng,th, the partial safety factor for loads,shown in column no.4under Table 3.2 shall be adopted.

7. Combination of Loads for the Verification of Serviceability Limit State

Loads are required to be combined to satisfy the serviceability requirements. The serviceability limit statqcheck shall be carried out in order to have control on stress, deflection, vibration, crack width, settlement and toestimate shrinkage and creep effects. It shall be ensured that the design value obtained by using the appropricombination shall be less than the limiting value of serviceability criterion as per the relevanicode. Thè rcombination of loads shall be used for checking the stress limit. The frequent combination of loads shall befor checking the deflection, vibration and crack width. The quasi-permanent combination of loads shall be usedchecking the settlelnent, shrinkage creep effbcts and the pennanent stress in concrete.

7.1. Rare Combination

For checking the stress limits, the partial safety factor for loads shown in column no. 2 under Table 3.3be adopted.

94 INDTAN HIGHWAYS. JTINE

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,,

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.)

7,2. Frequent CombinatÍon

l'or loads shown in column no, 3 under Table 3.3 shall be adopted.

7,3. Quasi-permanent Combinations

in the structure, partial safety factor for loads shown in column no. 4 under Table 3.3 shall be adopted.

tl. Combination for Design of ['oundations

For checking the base pressure under foundation and to estimate the structuräl strength which includes thegcotechnical loads, the partial safety factor for loads for 3 combinations shown in Table 3. 4 shall be used.

The material safety factor for the soil parameters, resistance factor and the allowable bearing pressure forthese combinations shall be as per relevant code.

Note: An Explanatory note will be included in a Special Publication on Limit State Design of Bridges as and whenthe Concrete Bridge Code is flnalized.

Table 3. IFactor for Verification of

Overturningor Sliding orUplift Effect

Overturningor Sliding orUplift Effect

Overturningor Sliding orUplift Effect

Permanenl Loads:Dead Load, Snow loadif present, SIDL ex-cept surfacing, Backfi llweight, settlement, creepand shrinkage effect

Surfacing

Prestress and Secondarycf}èct of prestress

(refer note 5)

Earth pressure due toBack Fill

Variable Loøds :Carriageway LiveLoad, associated loads(braking, tractive andccntrifugal forces) andPcdestrian Live Load

INDIAN HICHWAYS, JUNE 2OO995

lo^g

ll(a) As Leading Load(b) As accompanying Load

(c) Construction Live Load

Therrnal Loads(a) As Leading Load(b) As accompanying Load

Wind(a) As Leading Load(b) As accompanying Load

Live Load Surcharge

effects (as accompanying

load)

Accidental eÍfects:i) Vehicle collision (oÐ Iii) Barge Impact (or) t

iii) Impact due to floatinglbodies J

Seismic EÍfect(a) During Service(b) During Construction

Constr uction Co ndition:C-'ounter Weights:

a) When density or selfweight is welldefinedb) When density or

self weight'is not welldefìned

c) Erection efT'ects

Wincl

(a) Leading Load(b) Accompanying Loacl

Ilvdrøulíc Loads:(Accompanying Loødt:Water cunent forces

Wave Pressurc

Hydro dynanric cffectBuoyancy

1.5

l.l51.35

1.50

0.9

r.500.9

t.20

1.05

1.50

1.20

1.0

t.0

1.0

0

0

0

0

0

0

0

0

0.9

0.8

0.95

0

0

0

:

0,750.2

1.0

0:

1.0

1.0

t.0

1.0

0

0

0

;

1.0

t.0

0.2

1.0

0:

1.0

0.5

1.0

1.0

t.01.0

;0

;

1.0

1.0

INDIAN HIGHWAYS. JUNE 2OO9

{i¡;

Notes:

I ) During launching the counterweight position shall bc allowed a variation of * lm I'crr steel briclges.

2) For Cornbination principles refer Para 2

l) Thermal load includes restraints associated with cxpansion/contraction due to type of construction (Poftal

frame, arch and elastomeric bearings), fiictional restraint in metallic bearings and thennal gradients. This

cornbination, however, is not valid for the design of bearing and expansion joint.

4) Wind load and thermal load need not be taken simultaneously.

5) Partial safety factor for prestress and secondary effect of prestress shall be as recommended in the relevant

codes.

6) Wherever Snow Load is applicable, Clause 224 shall be refened for combination of snow load and live load'

7) Seismic effect during erection stage is reduced to half when construction phase does not exceed 5

years.

H) For repair, rehabilitation and retrofitting the load combination shall be project specific.

Table 3.2

Partial Safety Iractor for Verification of Structural Strength

Ultimate Limit State

Loads Basic Combination Accidental Combination Seismic Combination

(l) (2) (3) (4)

Permanenl Loads:Dead Load, Snow load

if present, SIDL exccpt

surfacing(a) Adding to the effect ofvariable action(b) Opposing the etïect ofvariable action

Surfacing:EfTects adding to thc

effect of variable action

llfl'ects opposing thc effect

of variable action

l)rcstrcss and Sccontlarv

cfïect of'prestrcss(refer note no. 2)

tJack lìll Weight

l:iarth prcssure clue to

Ilack Þ-ill

(a) [.,eading [-oad(b) Accour¡ranying L,oad

r.35 .

1.0

t.75

1.0

1.50

r.s0

r.0

1.0

t.0

t.0

t.0

t.0

1.0

1.0

1.0

1.0

1.0

1.0

t.0t.0

INDIAN I"IICIIWAYS. JUNI] 2OO9

',1',ì

Vøríøble Loøds:Caniageway Live Lqadand associated actions(braking, tractive and

centrifugal forces) and

Pedestrian Live Load:(a) Leading Load(b) Accompanying Load(c) Construction Live Load

Wind during service and

construction(a) Leading Load(b) Accompanying Load

Live Load Surcharge (as

accompanying load)

Erection effects

Accidental Effects:i) Vehicle Collision (or)ii) Barge Impact (or)iii) Impact due to floatingbodies

Seismic Eûfect(a) During Service(b) During Construction

Hydraulic Loøds (Accom-

panlting Loadl:Water Current Forces

Wave Pressure

Hydro dynarnic effcctBuo

98 INDIAN HIGHWAYS. JUNE 2OO9

Notes:

l) For Combination principles, refer Para 2.

2) Partial sal'ety factor lorprestress and secondary effect of prestress shall be as recommended in the relevantcodes.

3) Wherever Snow Load is applicable, Clause 224 shall be referred for combination of snow load and liveload.

tl,:

),

l¡.

;'.

i

fü

:d

ff

f

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l,

I

I

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lt

I

i

I

)

n

t

I

I

É

-f't-

r

t

ïhble No" 3.3Partial safety Facior for Vr{ification of serviceability Limit stntc

Loads RareComblnation

Frequent,Conrbination

Qunsi-permanentCombination

(1) (2) (3) (4)

Itcrmønent Loads:,Þead Load, Snow load if present, SIDL includingsurfacing

llnck fill Weight

Itrestress and Secondary effect ofprestress(l{efer note no.4)Shrinkage and Creep Effects

li¿rrth Pressure due to Back Fill i

Scttlement Effects(a) Adding to the permanent effect(b) Opposing the permanent effect

Variable Loads:(ìarriageway Live Load and associated loads(braking,tractive and centrifugal forces) and pedestrian Live Load

l(a) Leading Load(b) Accompanying Load

'fhennal Loads(a) Leading Load(b) Accompanying Load

Wind(a) Leading Load(b) Accompanying Load

l.ive Load Surcharge (Acc<lmpanying Load)

I'l!¡lraulic Loadss (Acconpanling Load) :

Wa ter C'un'ellt lilrccs

Wavc Pressure

lìuoyancy

1.0

0.7s

t.00.6

1.0

t.0

0. r5

t.0

t.0

1.0

1.0

t.00

0.75

0.2

0.6

0.5

0.60

0.50

0

t.0

1.0

0.15

1.0

1.0

1.0

t.0

1.0

1.0

t.00

1.0

t.0

t.0U

0.5

0'

0

t.00.60

0.80

0.15

I N t)IAN.T{IGT{WAYS, JUNE 2OO9 99

(

(r('r

'{

ì

Notes:

I ) For Combination principles, refer Para 2.

2) Thermal load includes restraints associated with expansion/contraction due to type of construction (Portsl

frame, arch and elastomeric bearings), frictional restraint in metallic bearings and thermal gradients. This

combination, however, is not valid for the design of bearing and expansion joint.

Wind and thermal loads need not be taken simultaneously'

Partial safety factor for prestress and secondary effect of prestress shall be as recommended in the relevant

codes.

Where Snow Load is applicable, Clausg 224 shall be refoned for combination of snow load and live load.

tl

ìl

t]

t

3)

4)

5)

):..ì!i

iti:ji

Table 3.4Combination for Base Pressure and

(0.75 if applicable) or 0

0.2

0.5

Permanent Loads:Dead Load, Snow load if present, SIDL except

surfacing, Back Fill earth filling

SIDL Surfacing

Prestress Effect(Refer note 4)

Settlement Effect

Earth Pressure due to back fill(a) Leading Load

(b) Accompanying Load

Variable Loøds:All carriageway loads and associated loads

(braking. tractive and centrifugal) and pedestrian

load(a) Leading l..oacl

(b) Accorn¡ranying Load

'Ihermal l,oads as accornpanying load

Wind(a) Lcading Load

(b) Accompanying [.oad

Live Load Slrrchargc as Accompanying Loacl (if

t00 INDIAN HIGHWAYS, ruNE

.,M.

{. r

i f;alrhis

tl

):'nl

Notes:

I ) For combination principles, refer para,2.

2) Where two partial factors are indicated for loads, both these factors shall be considered for aniving at the

severe effect.

3) Wind and Thermal effects need not be taken simultaneously.

4) Partial safety factor for prestress and secondary effect of prestress shall be as recommended in the relevant

codes.

5) Wherever Snow Load is applicable, Clause 224 shall be referred for combination of snow load and liveload.

(t) Seismic effect during ereetion stage is reduced to half when construction phase does not exceed 5 years.

7) For repair, rehabilitation and retrofitting the load combination shall be project specific.

222. Seismic Force

222.1 Applicability:

222.t.1

All bridges supported on piers, pier bents, and arches, directly or through bearings, and not exempted below in the

category (a) and (b), are to be designed for horizontal and vertical forces as given in the following clauses.

The following types of bridges need not be checked for seismic eff'ects:

(a) C-ulverts and minor bridges up to l0 m span in all seismic zones

(b) Bridges in seisrnic Zones II and III satisfying both limits of total length not exceeding 60 m and spans not

cxceeding l5 m

222.1.2

Special invcstigations should be carried out fbr the bridges of following description:

( I ) tlridges more than 150 m span

(2) Bridges with piers taller than 30 m in Zones [V and V

(3) Cable supportecl bridges, such as extradosed, cable staycd, antl. suspension bridges

Accidental Effect or Seismic Effect

Seismic effect during construction

llrection effects

Hldrøulic Loads:Water CunentWave Pressure

Hydro dynamic effectBuoyancy:

For Base Pressure

For Structural Design

1,0

1.0 or 0

1.0 or 0

1.0

0.15

t.0

l.0 or 0

1.0 or 0

1.0

0.15

1.0

0.5

t.0

1.0 or 01.0 or 01.0 or 0

1.0

0it 5

101I ?A0e INDIAN TIIGHWAYS, JI.INE 2OO9

:rry : Ìjji:n: tn; ti-:\if:.¡dt¡È,ãÊ*ÌÐtr,affii-e¡nl$ffffif:_ ¡qr.ilflF

(4) Arch bridges having more than 50 rn span

(5) Bridges having any of the special seismic resistant fe atures such as seismic isolatols, clampe rs etc.

(6) Bridges using innovative structuralarrangements and materials.

Notes for sþecial investigations:

l. In all seismic zones, areas covered within l0 km fiom the known active hults are classified as'Near FieldRegions'. For all bridges located within Near Field Regions, except those exempted in clause 222.1.1, specialinvestigations should be canied out, The information about the active faults should be sought by bridgcauthorities for projects situated within 100 km of known epicenters as a part of preliminary investigations at

the project preparation stage.

2. Special investigations should include aspects such as need for site specific spectra, independency ofcomponent motions, spatial variation of excitation, need to include soil-structure interaction, suitable methodsof structural analysis in view of geometrical and structural non-linear effects, characteristics and reliabilityof seismic isolation and other special seismic resistant devices, etc.

3. Site specific spectrum, wherever its need is cstablished in the special investigatiop, shall be used, subject tothe minimum values specified for relevant seismic Zones, given in Fig. 13.

222.1.3

Masonry and plain concrete arch bridges with span more than lOm shall be avoided in Zones IV and V and in near

field region.

222.2 Seismic Zones

For the purpose of determining the seismic forces, thc Country is classified into four zones as shown in Fig. I l. Forcach Zone a factor 'Z' is associated, the value of which is given in Table 5.

tÉff

Fig. I I Seismic Zones of lndi¡¡ ( lS: 1893 (Part I):2002)

INDIAN IIIGHWAYS, JUNE

Note: Bridge locations and towns falling at the boundary line dernarcating two zgnes shall be considered in thehigher zone.

Zone No, Zone Factor (Z)

VruIIil

0.360.24

0. l60. t0

222.3 Components of Seismic Motion

'lhe characteristics of seismic ground motion expected at any location depend upon the magnitude of earthquake,depth of focus, distance of epicenter and characteristics of the path through whioh the seismic wave travels. Therandom ground motion can be resolved in three mutually perpendicular directions. The components are consid-cred to act simultaneously, but independently and their method of combination is described in section 222.4. Twohorizontal components are taken as of equal magnitude, and vertical component is taken as two third of horizontalcomponent.

ln zones IV and V the effects of vertical components shall be considered for all elements of the bridge.The effect of vertical component may be omitted for all elements in zone II and III, excqpt for the following cases:

(a) prestressed concrete decks(b) bearings and linkages(c) horizontal cantilever structural elements(d) for stability checks and

(e) bridges located in the near field regions

222.4 Combrnation of Component Motions

l.The seismic forces shall be assumed to come from any horizontaldirection. For this purpose two separate analysesshall be performed for design seismic forces acting atong two orthogonal horizontal åirections. The design seismiclbrce resultants (i'e. axial force, bending moments, shear forces, and torsion) at any cross-section of a bridge compo-nent resulting from the analyses in the two orthogonal horizontal directions shall be combined as below (f ig. f Z)a) Ir,t0.3r,

h) L0.3r ,+r ,Where

t';= l"'orce resultant due to full design seismic force along x direction.

r,'= Forcc resultant ilue to full design seismic force arong z direction.

2' When vertical seismic forccs are also considered, the design seismic force resultants at any cross section of abridge component shall be cornbinecl as below:

Lr ,*0.3r ,LQ. J¡' ,

*.0.3r ,*r ,*0.3 r ,I0.3r,x 0.3r,*r,

a)

lr)

t')

.i'd

f

.i1Ì

TABLA s ZOND FÄCTOR (Z)

INDIAN HIGHWAYS. JUNE 2OO9103

v/here r t and r 2

are as defined above and r, is the fcrrce resultant due to full design seismic forcc along the verticaldirection.

Z

wflrårüÞ

Bridse Plan Clobal XZ axes

Mx

7,

(Localx-xand z-zaxes)

Fig. 12: Combination of Orthogonal Seismic Forces

Moments for groundmotion

along X -axis

Moments for groundmotion

along Z -axis

DesignMoments

Mx :M{ + osMl Mz :M: +ßM:M*:ßM{ +M| M, :ßM{ +M?

Where, M,and M,are absolute moments about local axes.

Note: Analysis of bridgc as a wholc is carried out for global axes X ancl Z ancl effects obtained are combined fordesign about local axes as shown.

222.5 Conrputation of Seisrnic llesponse

Following rnethods are uscd fbr conrputation of seismic rcsportsc depending u¡ron the complexity of the structureand the input ground motion.

( l) For most of the briclgcs, clastic seisnric acccleration method is adequatc. In this method, the first fundamentalrnode of vibration is calculated and thc correspondirtg accelcration is rcad lrorn Fig. 13. This acceleration is

applicd to all parts of thc bridgc for calculation ol forces as pcr clausc 222.5.1.

t04 INDIAN HIGHWAYS, ruNE 2OO9

li =0q

where,

(2) Elastic Response Spectrunr Methocl: This is 0 geReral method, surtaþie for more eomplex structural systems

(e. g. continuous bridges, bridges with large differencc in pier heights, bridges which are curved in plan,

etc), in which dynamic analysis of the structurc is porformed to obtain the first as well as higher rnodes ofvibration and the forces obtained flor each rnode by use of response spectrum l'rom Fig, I 3 and olause 222.5 .l .

These modal forces arc combined by following appropriate combinationâl rules to anive at the design forces.

Reference is made to specialist literature for the same.

222.5.1 Horizontal Seismic Force

'l'he horizontal seismic forces acting at the oenters of mass, which are to be resisted by the structure as a whole, shall

bc computed as follows:

4,, (Dead Load + Appropriate Live Load)

lì.q = seismic force to be resisted

Ah = horizontal scismic coefficient = (Zl2)*(l)*(S./g)).Appropriate live load shall be taken as per Clause 222.5.2

7. - Zo ne factor as given in Table 5

I = Importance Factor (see Clause 222.5.1.1)

1' = Fundamental period of the bridge (in sec.) for horizontal vibrations.

lìundamental time period of the bridge member is to be calculated by any rationalmethod of analysis adopting the

Modulus of Elasticity of Concrete as per IRC: 2l-2000, and taking gross uncracked section for moment of inertia.

The fundamental period of vibration can also be calculated by the method given in Appendix-2.

S"/g : Average rcsponse acceleration coeflìcient fbr 5 perccnt damping of load resisting elements depending upon

the fundamental period of'vibration T as givcn in Fig. l3 which is based on the following equations.

fior rocky, or hard soil sites, Type I soil with N >30

s"_(tÒ

f 2.50 It r.00/7',

s, I 2.50 ì

c lt.3617'J

s, f 2.50 ìs - I t.67trl

0.0 < r< 0.40

0.40s T<4.00

0.0 < 7'< 0.55

0.40 < 7's 4.00

0.0 s r< 0.67

0.67 <T54.00

ii

t,;.;í

I*T

s

¡J*r

, .c.T.È

\¡,t¡1

\ .!i

ì

lìor mecliurn soilsites, Type II soilwith, l0<N 530

For soli soil sitcs,'Iypc lll soil with N <10

Notc: In the abserrce ol'calculations of tundamcntal pcriod I'or srnall bridgcs, the value of S"/g may be taken as

2.-s.

INDIAN }IICJHWAYS, JUNE 2OO9 105

;

' t4ti1i:r+;jl#j¡sátlåu¡+"1H'iqlF4rcF ñliEs

ì

¡,'f..

$ìr

r

i,-ili:I

lì'.;it.tr,iil' ^'

'l+r':' ) i{

!, ,i

t,:

\ rrËl firr frorl SOtt¡ N <10

\\ I f*nrrn(rúßÞrülu¡orrlta t** I I f "yr.3 I (tîoËrc ort ù.rAÊo ro¡r)

\*+-J__ *'!'

For damping other than 5% offeredused.

r.o I

PGIIOD I ftrcr)

Fig. 13 Response Spectra

by load resisting elcmcnts, the multiplying factors as given below shall be

222.5.1.1 Seismic Importancc Factor-I

Bridges are designed to resist design basis earthquake (DBE) level, or other higher or lower magnitude of forces,depending on the consequences of their partial or complete non-availability, due to damage or failure from seismicevents. The level of design forcc is obtained by multiplyin g(Zl2) by factor 'l', which represents seismic importanoeof the stnrcture. Combination of f'actors considered in assessing the consequences of failure,- and hence choice offàctor'l',- include inter alia,

(a) Extent of disturbance to traflìc anclpossibility of provitling temporary diversion,

(b) Availability of altemative routes,

(c) Cost of repairs and time involved, which depend on the extent of damages, - minor or major,

(d) Cost of replacement, and time involved in reconstruction in case of failure,

(e) lndirect economic loss dt¡e to its partial or full non-availability,

Importance factors are given in Table 6 for different typcs of bridges.

t06

Damping % 2 5 t0Factor t.4 1.0 0.8

Application Prestressed concrete, Steeland composite steel

elements

Reinforced Concreteelements

Retrofitting of old bridgeswith RC piers

TNDIAN HIGHWAYS, JUNE

ffi$tgúutrmporta neo ['actor

Seismic Class lllustrativc Examples Importancc Factor 'l'Normalbridges All bridges except those mentioned in other

classesI

Important bridges a) River bridges ancl flyovers inside citiesb) Bridges on National and State Highwaysc) Bridgos serving traffic near ports and othercenters of economic activitiesd) Bridges crossing railway lines

t,2

Large critical bridges in all SeismicZones

a) Long bridges more than lkm length acrossperennial rivers and creeksb) Bridges for which alternative routes are notavailable

L5

Note: While checking for seismic effects during construction, the importance factor of I should considered for allbridges in all zones.

222.5.2 Live Load components

(i) The seismic force due to livç load shall not be considered when acting in the direction of traffic, but shallbeconsidered in the direction perpendicular to the traffic.

(ii) The horizontal seismic force in the direction perpendicular to the traffic shall be calculated using 20% of liveload (excluding impact factor).

(iii) 'The vertical seismic force shall be calculated using 20% of live load (excluding impact factor).Note: The reduced percentages of live loads are applicabte only for calculating the magnitude of seismic design

force and are based on the assumption that only 20o/o of the live load is prãsent ovei the bridge at the timeãfearthquake.

222.5.3 Water Current, and Depth of Scour

The depth of scour under seismic condition to be considered for design shall be 0.9 times the maximum scourdepth. The flood level for calculating hydrodynamic force and water current force is to be taken as average of yearlymaximum design floods. For river bridges, average may preferably based on consecutive 7 years'data, ãr Uased onlocal enquiry in the absence ofsuch data.

222.5.4 Hydrodynamic and Earth pressure Forces under seismic condition

ln addition to incrtial forccs arising fionr the deacl loa<J anrJ live load, hydroclynamic f'orces act on the submergedpart of thc structurc and are transmitted to the fbundations. Also, additionalearth pressures due to earthqúake acionthe rctaining portions of abutmcnts. For values ol'thcse loacls reference is madc to IS: 1893-2002. These forces shallbc considercd in thc design of bridges in zones IV and V.

Additional earth prcssurc forces dcscribed abovc need not be considerecl on other components such as wing wallsand retum walls since these elements are easily repairable at low cost.

222.5.5 Design Forces for Elcments of Structurcs and Use of Response Reduction Factor'l'he forces on various nrembcrs obtained fi'om thc elastic analysis of bridge structure are to be divided by ResponseRcduction I'-actor given in TableT before cotnbining with othcr forccs ai per load combinations given in tabte t.J'he allowablc increase in permissiblc strcsscs shourd be as per Table l.

INI)IAN IIIGI.IWAYS, JUNE 2OO9

l,,

.¡,

\i;i

1.,

Iti

t:

lhble 7 Response Reduction Factors

Bridge Component R wtth ductiledetailing

R without ductiledetailins

Superstructure N.A 2.0Substructure(i) Masonry /PCC piers, abutments

(ii) RCC short plate piers where plastic hinge cannot develop indirection of length, and RCC abutments

(iii) RCC long piers where hinges can develop

(iv) Column

(v) Beams of RCC portal frames supporting bearings

3.0

4.0

4.0

1.0

1.0

2.5

3.3

3.3

1.0

Bearings 2.0 2.0

Connectors and Stoppers (Reaction blocks)

Those restraining dislodgement or drifting away of bridge elements.These are additionalsafety measures in the event of failure ofbearinss.

1.0 1.0

Notes:(i) Those parts of the structuralelements of foundations which are not in contact with soil and transferring load

to it, are heated as part of sub-structure element.

(ii) Response reduction factor is not to be applied for calculation of displacements of elements of bridge and forbridge as a whole.

222.6 Fully Embedded Portions

Parts of structure embedded in soil below scour level need not be considered to produce any seismic forces.

222.7 Liquefaction

ln loosc sands and poorly graded sands with little or no fines, the vibrations due to earthquake may cause lique-firction, or excessive total and difl'erential settlements. Founding bridges on such sands should be avoided unlessappropriate methods of contpaction tlr stabil sation are a<lopteã. Altãrnatively the foundations should be takenclccpcr; below liquefiablc layers, to firm strata. Ileference should be made to the specialist literature for analysis ofI iq uefaction potential.

222.8 Foundation Dcsign

I;'trundations subjected to scislttic load from all sources $ef.222.5.3 and 222.5.4), and taking combinations andallowable stresses as given in tlìC:78 should be designed as per IRC: 78 to limit the bearing stresses within allow-ablc limits and, avoiding overtunting, sliding, and deep seated failure with safety factor of 1.5,1.25 and l.l5 respeo-tively. For this verification, the seismic loads on foundations should be taken as 1.25 times the forces transmítted toit by substructure, so as ttl provicle suflìcient margin to cover the possible higher forces transmitted by substructurearising out of its over strcngth.

t08 INDIAN HIGHWAYS. JI-INE 2OO9

222.9 Ductile Detailing

Mandatory Provisions

(i) In Zones IV and V, to prevent dislodgernent of superstructure, "reaction blocks" (artditìonal safety measures

in the event of failure of bearings) or other types of seismic anesters shall be provided and designed for the

seismic force (F""/R). Pier and abutment caps shall be generously climensioned, to prcvent dislodgement ofsevere ground-shaking. The examples of seismic features shown in Fig, 14 to l6 are only indicative and

suitable anangements will have to be worked out in specific cases.

(ii) To improve the performance of bridges during earthquakes, the bridges in seismic zones IV and V may be

specifically detailed for ductility for which IS: 13920 or any other specialist literature may be referred to.

Recommended Provisions

(i) In order to mitigate the effects of earthquake forces described above, special seismic devices such as Shock

Transmission Units, Base Isolation, Seismic Fuse, Lead Plug, etc, may be provided based on specializedliterature, international practices, satisfactory testing etc.

(ii) Continuous superstructure (with fewer number of bearings and expansion joints) or integral bridges (in whichthe substructure or superstructure are made joint less, i.e. monolithic), if not unsuitable otherwise, can possibly

provide high ductility leading to better behavior dúring earthquake.

(iii) Elastomeric bearings with arrester control in both directions may also be considered.

Note: A Background Note for 'seismic Force'Clause is given in Appendix-4

F4rårptÛ

1

i

4

Iai

{

i

'i,

I

Eã

gEË

EÉ

HH

Hrry n4¡il qFPmn çAP Er

H4ll PJ,[N.pr.

PtF C^P.P3. ^r.

l?

Fig. l4 Exarnple of Seismic reaction blocks for continuous superstructure

t$tnr¡ilt0

fl#r

109INDIAN I{IGÍIWAYS. .IUNE 2OO9

Ì=

\i

Fig. 15 Examplc of seismic reaction blocks for simply supported bridges

ATARTICULATIONSAT PtÈtsS

WHERE:

N =N1 = NZ "305+2.51 + l0HmmL = SFAN tN METERSH - AVERAGE COLUMN HEíGHT IN METERS

l'lg. ló Mlnlmum dimcnsion for support

f-Ft_t

AT ABITMENTS

il0 INDIAN HIGHWAYS, JUNE 2OO9

ffi

CLAUSE: 222 SEISMIC ttORCE(Background Note)

,Appendíx 4

,,

',.. I INTRODUCTION:.

" A Sub-Committee comprising Late Dr, T.N. Subba Rao, S/Shri S,G, Joglekar and D.K. Kanherê was formed by B-2

:,1 Committee to carry out a detailed review of the interim provision in Clause No .222 relatingto Seismic Forces in the

existing IRC: 6 (post January, 2003 revision of the code) and compare the same with the provision in the pre-January

' version of the code and submit its findings and views to the B-2 Committee for deliberation. The first interim reportof the Sub-Committee was discussed in B-2 Committee meeting on 8th & 9th December 2006. After a series ofdetailed discussions and deliberations in B-2 comnittee, the draft Document titled 'PROPOSED REVISION OF

CLAUSE 222: SEISMIC FORCE in IRC: 6 * 2000'was approved by the B-2 committee in its 9rh Meeting held on

3'd November, 2008 for submission to the BSS committee. It was felt that a background note explaining the rationaleand approach behind theproposed revision of clauses willbe useful forappreciating the various provisions in the

Clause. This report is accordingly prepared to provide an informative background to the proposed revision.

The following documents have been refened to in preparation of this Background Note:-

. IS: 1893 (Part-l) -2002- Generalprovisions and buildings.

. Draft of IS: 1893 (Part 3) -2005 'Bridges and Retaining Walls'(under consideration of BIS Committee).

. The draft of long version of 'Seismic Design Guidelines'under finalization by B 2 Committee.

. Eurocode: 8 - Design provisions for earthquake resistance of structures.

Part-l: General rules, - Part-2: Bridges

. Fundamentals of Seismic Protection for Bridges: by Yashinsky and Karshenas.i

2 BASISOFRECOMENDATIONS

2.1 Force Based and Performance Based AppÉoaches

Approach of the present IRC co<le (post January,2003 revision), like BIS standard IS: 1893 is based on force

based approach, for achieving safety of bridges in seismic event. In this approach, the effect of earthquake is

represented by a set of forces, which should be considered in the design. Internationally, as well as in India, the

force based approach has worked well in regions of low seismicity. However, it is found [o be woefully inadequate

in high seismicity zones (refer Fig l). Most of the intemational codes dealing with regions of high seismicity have

now adopted a new approach known as 'Performance Based Philosophy', which basically attempts to specifo

the response viz. the desired performance of the bridge during and after the earthquake and achieve the same byformulating suitable design rules. A detailed description of this approach and the performance criteria adopted inthis method is outside the scope of'this note. It is realized that at this stage, it is not possible to fully adopt this

approach, till the Indian National Standards i.e tslS also change over to this approach, when Limit State Codes are

introduced by IRC and Long Version of IS 1893 (Part 3) is fìnalized.

Howeve r, it is possible to adopt the underlying concepts, and sonte of the methods, while continuing with the force

based approach, in order to târgct at the desired seismic behavior of bridges during and after the Design tsasis

Earthquake. The targeted behavior shall be stated in ter¡ns of aims to be archived. The use of force based methods

will have to be supplemented by prescriptive recommcndations so that the performance targets (aims) of the design

are at least qualitatively taken into account, if not prcciscly calculated. This has to be done, using engineeringjudgment, on thc basis of thc obscrvations of damages sufi'crecl by bridges in seismic events.

)9 f NDIAN I]IGIIWAYS. JUNE 2OO9 lil

,...

i

From the above point of view the following mixed approach is suggested:-

.:' Desirable funcuonal and structural behaviors of bridges during ancl after earthquake are stated as aims to be

achieved. These are:

The expected levels of service in tenns of ths full or partial availability of bridge for use after the

Design Basis Earthquake (DBE).

. No signifìcant structuraldamage and may be some non-structuraldamagc in the event of chosen level

ol'earthquake f-or design. This level is dcscribed in terms of Design Basis Earthquake (DBE), as defined

by IS: I 893-2002 (Part l). This DBE level is chosen as 50% of the Maximum Considered Earthquake

(MCE), which is considercd as the maximum potential seisnlic event in the zone.

' Targetetl structural response is described in terms of permissible strcsses, permissible overloading

in plastic rcgion of nlatcrial strains, residual deforrnations after the event, types of acceptable but

rcpairable damages of various componcnts and extcnt of tltc salne, when combined with other loads in

cornbinations as per IllC: 6-2000.

I Sincc it is not cconomical to design bridges to remain fully functional in the event of MCE, an overall

þalance is sought bctwcen thc safety in DBE event, limiting risk of damage to the bridge due to

carthquakc antl conscquential indirect economic loss, on one hand; and thc cost of repair, temporary

divcrsion, çr corn¡rlctc rcconstruction alld timc involvetl in partial ol firll closure of the bridge at higher

lcvel of'carthquakc, rtn thc other hand. F-or the ¡rrescnt, tltis b¿rlance is neccssarily based on the overall

cnginecring j uclgtttcn t.

In ap¡rlicarion of'thcsc concc¡tts (irr ordcr to kcep thc cost and titnc ol'dcsign cflìtrt within practical lirrtits),

simplifìctl prcscriptivc rulcs alc to llc given by thc Clodcs clf' Practicc, covclittg nortnal types of structures.

This is achicvcd by :-

. Kccping the analytical antl dcsign cflìlrts within thc ca¡rabililies of Itortually available design tools,

and

. (iivi¡lg prcscriptivc tlctailing rccornrnenclations to achicvc cnhancccl bcltavit'¡r of the bridge, bascd on

thc naliclnal and intcrnatittnal cxpericttcc of nla.ior scisnlic cvents.

Thesc sirnplc rulcs shoulcl bc rcvicwctl fiom tinre lo lilnc to kccp pace with thc cxperience of using thc rt¡les

and thc rtcwly dcvcloping knowlcdgc and nlcthotls.

i;,::

Fig. I : Total collapse of llyover during the Kobe etrthqueke of I 995

2.2 Combination of Force Bascd Approach and Targets of Performance

t.

n2 INDIAN ÍIIGHWAYS, JUNE 2OO9

t.j

fl

1

fç

..4

Iti

;

{,

:

2.3 ldentification of Scismic Haznrds

Although acceleration of variou$ parts of the structurc and resulting inertial forces is the main concern of forcebased seismic design, other hazarclòus situations associated with seismic events do also urirr. rfrri*-J¿.ï;te ;î;;into account' The code dealing with seismic clesign-inan overall way has to cover these aspects. IRC: 6 deals withLoads and Stresses alone and has limited coverage. It should, howevðr, include near field effects also. other hazardsmentioned bellow will have to be covered elsewhere :

Liquefaction.

Landslide

Tsunami

structures which unavoiclably cross a seismically active fault zone and those cxposed to danger of relativepennanent ground movernent.5. Flooding due to dam failure in upstream of the bridge

3 CTIOICE OF DESIGN }'ORCES

3.1 Methorls and Some Observations

Design Earthquake.

l:'":.J:iT,'x1':"'l:::1":y'n,'or zones. rhe basic philosophv and approach ror zoning is best describedj::."Y::r^:lJs-:]l?l lPart.l) 1o re.ferlce is màde to ir'.*ni..'B;t;i;:ï;ffi;ö;iilä;¡ä;i

ofstructure in relation to the rocations of seismicaily active faurts.

r)

IS:in

In any seismic zone, except in the near field regions, the maximum seismic hazardof ground acceleration is definedin terms of Maximum -considered

Earthquake (MCE) in each zone (described by the zone factor). Designingbridges for this level of hazard and keeping them within elastic range is expensive. It is international practice toallow formation of plastic deformationt ¡nìn. structure without r.uùing fallure limit, and to repair the damageJportions in case of MCE event. In many countries, more than one level of earthquake are used to achieve ¿irrerenllcvels olperformances at the specified levels of earthquakes. The performance ievels are usually defined to avoidcomplete collapse, to limit damage to specific repairabll parts, or to have higher capacity for dead load and live loadcombination, but accept damage for dead road condition onry and so on.

hr IS: ltl93, this is achieved by choosing a lower level of'hazard for the design, termêd as Design Basis Earthqu¡k.e(DBE)' which the ls: 1893 has recommended as 50% of MCE. IRC: 6 follow the same method. To account for the¡vut I v @vvuutll tut ¿Il€

;::lï: i::::::-::L::l:""*: "r non availabiliry/railurc or the srrucrure, a ractor termed as seismic rmportance4ù ùçtùltuu uuPuflance

I;':ii::::.:ï:'illï1;:1,:::.-:lyf1¡]¡ "rii",i"crv changes rhc reverorseisn,ic design rorces (increases, irr >r), or

chccks.

c desrgn torThe MCE i

r \rrrulç4ùçù, tL I 2.1 )) Q\

:]il:i:t worcls, thc risk of'clarnageifitilurc in actual scis¡nic cvent is recluced. The MCE is nor used for any design

lnternationally, Maxinrum considcred Earthquakc (MCE) an<l operating Basis Earthquake are based on thestatistical probability' As cxplaincd in Foreworcl of' IS:1893, due to tact of adequate statistical data, this kind ofrationalization anclachicving evcn a semblance of uniformity of risk levcls for different structures in different zonesis not yct possible, ancl a sinrple rcduction factor of Z is uscd.

2) Maxirnunr considcrctr llarthquakc (MCE) and Dcsign Basis Earthquake (DBE)Although thc scismic ¡rotenlials of'thc zoncs as describcd by maximum consiclered earthquake (MCE) are large,

INDIAN HICìHWAYS, JUNIì 2OO'lt,t

{r

rì

only 50% of MCE acceleration has becn rccommended by IS: 1893 as design basis earthquake (DBE). This has

been chosen, as stated in IS: I 893, on the basis of accepting certain level of damage in the event of DBE, based on

the past experience of building damages (described by MSK-64 scale) ând in view of achieving economy in designFor events larger than Zl2, certain risk of significant damage exists and is accepted. This apparently over simplifieduniform treatment for all structures across the zone (by use of common value of Zl2) is corrocted by means of a

multiplying factor 'l'which modilìes the design level of acceleration (and forces) for different types of structures as

explained above. Part l, and other published parts of IS: 1893, recommend the values of '['factors varying from I kr

2 for structures being used for different purposes. The choice seems to depend partly on the need of immediate post

earthquake availability and partly upon the consequential economic implications due to loss of service. Apparently,although not stated explicitly, it seems to have been assumed that the loss of life will be avoided (or minimised) by

engineering design of the structures, as per the codal recommendations.

3) Acceptable Risks as per IRC: 6

The performance targets, or aims, of the seismic provisions of this code are :-

(a) to ensure that the bridge does not collapse under the action ofdesign level ofearthquake,

(b) its components may suffer minor or major damages depending upon the extent to which it enters in a plastic

deformation stage,

(c) damages to minor and replaceable elements like expansion joints, hand rails etc., are permitted.

(d) Serviceability ofbridge can be restored after repairs,

(e) the increased cost to meet the above targeted performance is reasonable.

For some critical bridges, consequences of structure entering in plastic regions, such as residual deformations, or

damage extending to many members, or to inaccessible foundation elements, etc. will lead to long period of closurc,and vary high cost and time of repair. In such cases, the likely damages may be directly verified by special analyses,

Iffound unacceptable, the design forces can be upgraded (by using higher I factor) to control the damage.

4) Estimation of Design Forces Acting on Structure

When subjected to ground motion described by ZlL,the accelerations and the inertial forces experienced by variousparts of the structure depend on their overall dynamic characteristics, which in tum depend on the distribution ol

mass and stiffness of various components. Two methods of calculating the response are permitted by the code:

ln the analysis, two rnethods are permitted depending on the complexity of the structure, as described bellow:

(") The lilaslic Seismic Acceleration Method is more comnonly usedJitr bridge structures which are on straighlalignmcnt und which have regular slructural arrangement in each direction. The natural period of vibration fitreuc:h ofthe two (or three) directions is calculatedþr theJirst fundamenlal) mode of vibration. These periods urçt

used to calc:ulule lhe acceleralion 'A'seen by the bridga as u whole, with help of the response spectra. The re.sponsg :,

specfro cxpresses ucceleralion respon!ìes oJ'single degree ol'.fieedom osc:illators having different time periods <tj:nutural vibrctlion as a Jìtncliott ot'time perktd. The accelerations are expre:ìsed in non dimensional form (S/g) antl

are nt¡rmulizetl to the zero pcriod ground ucceleration, taken as t. In lhis method the maximum acceleralion (AJ,

seen by thc mass ofoscillator is given by [Z* /2] * [5,/g,J , which is further modified by multiplying by the importanaal;

.fut:tor'l'.

(h) The Elastic Rasponsc Spectrum Melhod which is a general methr¡d suitabte þr more complexr;.):.ttcrn,\: such us conlinueus hridges, bridge with large diflërence in pier heights, and bridges which are curved lfi¡tlun.

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IN DI AN Í{IGHWAYS, JLINE

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(a)

In the rigorous method, the bridge structure is modeled as a rnultiple degree of freedom system consisting oflumped masses connected by mass-less members characterized by their elastic stif.fress for bending, shearand axial forces. The structure is analysed f<lr obtaining its response in dilTcrent modes of vibration, *hi.l, ur.combined giving appropriate woights to participating modes. This is repeated for other directions of morionand suitable combinational rules are used to obtain thc integrated response for design verifications.

response obtained is in elastic domain and is used dircctly in the design if the structure is designed to remainin elastic limits, (below yield).

A simplified analysis is permitted for regular bridges with simple foundations, more or less uniform piers andbeam type superstructure. This is called "seismic Coefficient Method'in which a single coefficientAn is usedto convert structure's mass into horizontal seismic force. CoefficientA,, is based upon the funclamentaínaturalperiod of the structure as a whole, and the response spectrum, as in case of the more rigorous method.

Response Reduction Factor

Designing bridges to remain elastic at MCE level is not economical. It is expensive even at the DBE level, ascompared to the designs based on methods recommended by IS: 1893- 1984. IS: I 893 - 2002 has consideredit adequate to ensure that at chosen design level Z 12, the structure is subjected to minor damage, but can beallowed to reach yield at load factor of 1.2, yield being defined by the codal methods of assessment (concrete/steel codes), using characteristic strengths of materials and the partial material factors as per the relevantcodes. In the working load/allowable stress method, as followed presently by IRC, the basic aim remainsthe same as that of IS: 1893, but without the load factor of lt}.In order to permit plastic deformation of thestructure, and verifying the same without using non linear analysis, a method of Response reduction factor isused, basis of which is explained below :

(b) Fig. 2 shows actual non linear response of the stucture, itsidealized bi-linear response, and the fully elastic response assumingthat the structure remains elastic till failure. Â,", and A" representthe maxilnum displaccments of inelastic and elastic systems, whichare assumed to be about equal. The research shows this assumptionto be reasonable for moderate to long period sffuctures. The elasticultimate moment M" (forces in general) is obtained by performingelastic analysis and is reduced by dividing by response reductionfactor'R', to obtain Mo. Mo is then used in design of the structureusing linear analysis and combining results with moments (forcesin general) resulting from other loads. In effect, the seismic forceconsidered in the analysis is reduced from[Z.Il2]*[S"/g] arrived in3(a) to a lower value of [Z.l/2R]*[S"/g], which is the familiar codalcxpressiclrr fìrr 4..

Clhoicc of response reduction factors'l'hc choicc ol' R fàctor depends on the performance

objectives o[ thc bridge. If one intends to keep the bridgewithin rnorc or lcss elastic lirnits, a value of I is indicatcd.ll'full plasticity is to be cxploited, large value is chosen. Ifpartial plastic dcvclopment is preferred, leaving margins f'or

unccrtaintics, or fbr a larger seismic event, some intermcdiate

(c)

F'ig. 2. Elastlc rnd lnclastlc forccdcformstionrelatlonships (ATC/MCtlflR 2001 ).

INDIAN I.IICIIWAYS. JIJNIì 2009 il5

(' value of R is chosen. The choice is also influeneed by the extent of built-in indcterminancy, which leads toextra (reserve) capacity of deformation after development of the first plastic hinge before complete collapsetakes place. The overstrength of the member is another margin to be kept in mind while choosing the valueof R factor. Overstrength is the actual extra built-in strength over and above the dcsign strength, arising outof the conservative estimation of material strengths and detailing practices, Correct calculation of R factoris a complex issue. Much research has gone in this and more is needed. While choosing R factors for Indianconditions on the basis of international codes and practices, the fundamental differences between designphilosophies, reliability of data base, and more importantly, the performancc târgets should be carefullyconsidered.

6) Consideration of depth of scour and combination with the average yearly maximum flood.

The present practice ofconsidering 0.9 times maximum scour depth for seismic checks is rational, and is recommendedto be continued. The logic of not rcducing scour depth further is basecl on the f¿ct that the scour holes filled up

during receding floods are filled with the loose deposits and cannot be relied upon to provide lateral support againstlarge earthquake forces.

The recommendation to consider design level of earthquake with maximum average yearly flood is to provide fora rare, but reasonable, combination and avoid combining two extrernely rare events of high flood of 100 or moreyears ofreturn period and earthquake.

7) Recommendations of Draft of IS: 1893(Part 3) 2005 on Bridges

Draft of the above code which was under discussion in BIS committee was made available by Prof.Thakkar. Thiscode generally follows the philosophy of IS:1893 (Part-I) and is similar to the presently proposed IRC:6 clauses,

with deviations in applicability of hydro-dynamic forces and earth pressure forces.. IS recommends the same for allzones, whereas proposed clauses of IRC:6 limit their application in Zones IV and V, and in near field regions. Thisis based on the rr¡ore or less satisfactory performance of bridges in Zones II and III in the past.

4 PAST PERFORMANCE OFBRIDGES

On the basis of past experience of last 50 years or so of earthquakes, which has been well documented, it can be seen

that very few bridges have collapsed under action ofearthquake. ln fact, major damages have been in the region ofbearings, dislodgcment of superstructure, damage to expansion joints, handrails etc. In very few cases, foundationshave been damaged in the regions of severe soildisturbance, such as liquefaction, and displacement of soilmassjust below the f<lundations. By and large, such situations âre exceptional and highly localised. These can be avoidedwith proper identification of seismic hazards. Briefly, it can be stated that, in spite of having been designed forthe lower seisnric fbrces than those presently proposed in IRC: ó, the st¡'uctures have generally perf'ormed wellrequiring attention to mainly bcarings, dislodgement of superstructure etc.

lwo or lhrcc rcasons coulcl bc behind this satisfactory performance. lìirst, rnost of the bridges have been dcsignedusing stltic ccluivitlcrtt f'orccs without consiclcrations of fìcxibility and long period of vibration. This resulted in extra

built-in slrcnglh fbr bridgcs with tall piers and long s¡lans. For rncdium to small span bridges, the seismic design

l'orces had bcen u¡rder:estirnalccl, but they h¿tvc also survivcd. This coulcl bc because of builrin margin obtainecl byconrbining walcr currcnt furccs at high fltxrd lcvcls with cartlrquakc forccs, antl these floods being absent when large

carthquakcs took placc.

Ilowcvcr, in spitc of'tltc abovc considelations, a lntge gap still exists bctwecn the recommended higher forces by the

plesent IS: I 893/IRC: 6 and uncxplained but satisfàctory pcrfonnance of the existing bridges, especially that of the

li¡unclalions. Thcrcfbrc, whilc accepting mtlre up-to-datc knowlcdgc about seismisity of the Indian sub-coutinentand adopting ncw scicntifìc nlcthods. it is ncccssary to givc due crcdónce to satisfactory performance of the bridges

dcsignetl carlicr lìrr lowcr lbrccs.

il6 INDIAN FIIGHWAYS. JLINE 2()O9

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INDIAN ROADS CONGRESSKama Koti Marg, Sector 6, R.K. Puram,

New Delhi - I l0 022 (lndia)

ffiFr (Telc):qËfqffS (Secrctary Ocncrat); +91 (ll) 2618 5303qfqqfdq (Sccu.): 261 I 53 I 5, 261 8 53 19, 2(rl7 1548,2(tl8 5273,26'116778Èm (nax): +91 (l l) 26t8 3669

NOTIFICATION NO.54 dated 28 Mav 2009

Amendments to Clause Nos. 708 and 709 of IRC:78-2000 "Standard Specifications and Code ofPractice for Road Bridges" Section :VII Foundations and Substructure (Second Revision)

Second Revision of IRC:78-2000 "Standard Specifications and Code of Practice fbr Road Bridges " Scction :VIIl'oundations and Substructure (Second Revision) was published in Dccember 2000 and reprinted in August 2005incorporating uptodate amendments till that time.

The Indian Roads Congress has decided to further amendNo. 6 is hereby notified..

These amendments shall be effective from the I June 2009.

Encl: As above

the abovc document. Accordingly, the Amendment

Q'!"uø'tuÜ -

(R.P. Indoria )Secretarv General

708. WELL FOUNDATIONS

Cl. No. F'or Read

708. r. r 'While selecting the shape, size and the type ofwells for a bridge, the size of pier to be accom-modated need for cflecting streamline flow,the possibility of the use of pneumatic sinking,the anticipated depth of foundation and the na-ture of strata to be pcnetratcd should be kept inview. Further for the type of well selected, thedredge holc should bc large enough to permiteasy dredging, thc minimum dimension bcingnot less than 2rn. ln casc thcrc is deep stand-ing water, propelly designed floating caissonsmav be uscd as Clause 708.12.

Foundations supporting the superstructure locatedin deep water cannels shall comprise of properly di-mensioned caissons preferably having a single dredgehole. While selecting the shape, size and type of wellthe size of abutment and pier to be accommodatedneed lbr cffecting streamline flow, the possibility ofthe use of pneumatic sinking the anticipated depthof fìlundation and thc nature of data to be penetratedshoukl bc kcpt in view. The minimum dimensions ofdro<lgc shall not bc less than 3 m. In case there is deepstanding water, properly designed floating caissonsrnay bc uscd as Clause 708.12.

llowever, in case of larger bridges across rivers inwitlc flood plains prone to scour, delta/tidal rivers,:channels with inl¿nd waterway traffic and bridges incoastal/lnarine locations, the number of intermediate'f'oundations shall be rcduced as far as practicable.

INDIAN }IIGHWAYS. JUNIi 2OO9 lt7

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709. PILII FOUNDATTON

Clause No. For Read

709.t General

709.t.4 For piles in sheams, rivers, creeks, etc., thcfollowing criteria may be followed :

(i) Scour conditions are properly established.(ii) Permanent steel liner should be providedat least upto maximum scour level. In case ofmarine clay or soft soil or soil having aggressivematerial, permanent steel liner of sufficientstrength shall be used for the full depth of such

strata. The minimum thickness of liner shouldbe 5 mm.

In last line under (ii) change 5 mm to 6 mm.

709.1.s

709.1.5.1

Spacing of piles and tolerances

Spacing of piles : The spacing of piles should be

considered in relation to the nature of the ground,their behaviour in groups and the overall cost ofthe foundation. The spacing should be chosen

with regard to the resulting heave or compactionand should be wide enough to enable the desirednumber of piles to be installed to the correct pen-etration without damage to any adjacent construc-tion or to the piles themselves.

Spacing of piles and tolerances

709.1.5.1 Spacing of pilesa) Where pier is supported on multiple piles,

connected by frame structure or by solid pilecap, the spacing ofpiles should be consideredin relation to the nature of the ground, their

Q$fitrviour in groups and the execution conve-niente. The spacing should be chosen with re-gard to the resulting heave or compaction andshould be wide enough to enable the desirednumber of piles to be installed to the correctpenetration without damage to any adjacentconstruction or to the piles themselves.

b) For land bridges pier may be supported onsingle pile having diameter sufficiently large

to accommodate construction tolerances ofpile installation with reference to location ofpiers as well as having shength as requiredby the design. The pile should be designed tocater for the maximum eccentricity of verticalload in such case. Alternatively, pile shaft can

be continued to act as a pier and get connectedto pier cap which is designed to accommodatethc ccccntricities due to construction toler-ancos.

'l'hc cost of a cap carrying thc load from the struc-ture to the pilc heads, or the sizc and cffectivelcngth of a ground beam, may influencc the spac-

ing type and size of piles.

The size of a cap carrying the load from the

structure to the pile heads, or the size and ef-fcctive length of a ground beam, may influ-cncc type, size and spacing ofpiles.

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il8 INDIAN HIGHWAYS. JUNE 2OO9

The spacing of piles will be determined by :

(a) the method of installatioR, e.9., driven or

bored;(b) the bearing capacity of tho group,

Working rules which are generally, though not al-

ways, suitable, are as follows :

For friction piles, the spacing centre should be

not less than the perimeter of the pile oL fbr cir-cular piles, three times the diameter. The spacing

of piles deriving their resistance mainly from end

bearing may be reduced but the distance between

the surfaces of the shafts of adjacent piles should

be not less than the least width of the piles.

709.1.7 The minimum diameter of piles shall be as fol-lows :

Bridges onLsnd

RlverBridses

Driven cast-in-situpiles

0.5 m 1.2 m

Precast piles 0.35 m l.0m

Bored piles 1.0 m 1.2 m

"The minimum diameter shall be 1.0 m for

river/marine bridges. For bridges beyond the

water zone and for bridges on land the diam-

eter may be reduced upto 750 mm".

709.r.8 The settlement, differential settlement, lateral de-

flection at cap level may be limited for any stuc-ture as per the requirement.

Settlement, Differential Settlement and

Pile CapacityThe differential settlement between two suc-

cessive foundations taken at pile cap level,

may be estimated from the maximum settle-

ment expected at two foundations for the dead

load, superimposed loads, live load and scour

effect. The increase in settlement with time

in clayey soils shall be accounted for. In ab-

sence ofdetailed calculations, for the purpose

of prcliminary design, it can be taken as not

more than the maximum settlement of any ofthe two foundations.

The differential settlement shall'be limiteddepending upon the following functional and

structural considerations:

a) Functionally acceptable differentialsettlement between two neighbouringpiers shall not be greater than I in 400

of the span to ensure riding comfort, as

specified in para 706.3.2.1.

INDIAN HIGHWAYS, JUNE 2OO9 il9

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b) The allowablo settlement of a singlepile considered for estimating the

pile capacity shall be arrived fromcomelation of thc sottlement of pilegroup to that of single pile, as per

clause 709.3.4.

c) It is further provided that the work-ing load capacity of pile basod on

the (b) shall not exceed 40% of the

load conesponding to the settlementof l0% of pile diameter (i.e. safetyfactor of 2.5 on ultimate load capac-

ity is ensured).

709.1.9 For both precast and cast-in-situ piles, thevalues regarding grade of concrete, watercement ratio, slump shall be as follows :

'TremieConcrete

Cast -in-situ

DrivenCast -in-situ

Precast' Concrete

Grade ofconcrete

M35 M35 M35

Min, cementcônten¿c

400 kg/m' 400 kg/m' 400 kg/m'

Max. W.C.ratio

0.4 0.4 0.4

Slump lmm) r50-200 100 -130 50

For both precast and cast-in-situ piles, the

values regarding grade of concrete, watercement ratio, slump shall be as follows:

Concrcte Cast-in-situ byTremie

Precast

Concrete

Grade ofconctete

M35 M35

Min. cementcontents

400 kg/m' 400 kg/m'

Max. W.C.

ratio0.4 0.4

Slump (mm) 150 - 200 50 -75

Note:i) For improving resistance to penetra-

tion of harmful elements from soil use

of mineral admixtures (fly ash, silicafume, GGBS conforming to respectiveBlS/lnternational standards) and as perIRC:21 and IRC: l8 is recommended.

In marine conditions and areas exposedto action of harmful chemicals, pro-tcction of pile caps with suitablc coat-ing such as bituminous based, coal-tarepoxy, epoxy based coating may be

considered. High alumina cements, (i.e.quick setting cement) shall not be usedin marine conditions. Also when bothchlorides and sulphates are present, use

of sulphate resistant Cement is not rec-ommended.

i¡)

120 INDIAN HIGHWAYS. JUNE 2OO9

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709.2

709.2.1

Requirement and Steps for Design andInstallationThe initial design of an individunl pile, group ofpiles and final adoption should pass through twotypes of major investi$ation and tssts as fullows:

(i) Comprehensive and detailed sub-surfnceinvestigation for piles to determine the

design parameter of end bearing capacity,friction capacity and lateral capacity of soilsurrounding the pile.

(iD Initial load test on trial pilos for confirmation/modification of design and layout and

routine load test on working piles foracceptance of the same.

Requirement and Steps for Dcsign andlnstallationThe initial design of an individual pile,confirmation of its capacity by either initialload test or by re-confirmation of actualsoil parameters, modification of design, ifrequired, and final adoption should pass

through following steps of investigations,design and load testing:

i) Comprehensive and detailed sub-surfaceinvestigation for piles to determinethe design parameters of end bearingcapacity, friction capacity and lateralcapacity of soilsunounding the pile.

ii) Design of pile and pile group based on(i) above for specified bearing strata.'

iii) Initial load testing:

Initial load test on pile of same diameteras design pile for direct confirmation ofdesign.

The initial load test is a part of thedesign process confirming the expectedproperties of bearing strata and the pilecapacity.

iv) Steps (ii) & (iii) should be repeated fordifferent types of strata met at site.

709.2.2 The steps for design and confirmation by tests are

given below :

(í) Subsoil exploration to establish design soilparameters.

(ii) Required capacity of pile group based ontentative number and diameter of piles in agroup.

(iii) Capacity of pile based on static formulaconsidering ground characteristics. The al-lowablc total/clifïerential settlement should

be duly considered. 'l'his stop along withstep (ii) may bc iterativc.

(iv) Structural design of piles.

The steps for design and confirmation by testsare given below:

i) Sub-soil exploration to reconfirm soilparameters assumed in the design.

ii) Provide for the required design capacityof pile group based on tentative irumberan<l diameter of piles in a group.

i¡i) 'fhe allowance total/differentialsettlement of single pile should be basedon the considerations as per 709.1.8 and

709.3.4. Capacity of single pile is to bebased on static formula consideringground characteristics. This step alongwith step (ii) may be iterative.

iv) Structural design of piles.

t2tINDIAN I{IGHWAYS, JUNE 2OO9

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(v) Initial load tcst for axial capacity, lateralload capae ity and uplilÌ load capacity on trialpiles to verify/confìrm or modify the designconsideration of piles done by steps (ii), (iii)and (iv). The load test shall be conducted fortwo times design load. Initial load test shallbe cyclic load test.

Ifthe initial load test gives a capacity greaterthan 25 per cent of the capacity calculatedby static formula, and if it is desired to takebenefit of the highest capacity, another twoload tests shall be carried out to confirm the

earlier value and minimum of the three shallbe considered as initial load test value. Thenumber of initial tests shall be determinedby the Engineer-in-charge taking into con-sideration the bore log and soil profile.

For load testing procedure ofpiles, referenceis made to IS:291I (Part - IV).

(vi) Routine load test may be conducted againto reconfirm or modify the allowable load.

Tests should be properly designed to coverparticular group for single pile test and dou-ble pile test. The lateral load test may be

conducted on two adjacent piles.

Initial load test as mcnticlned in709.2.1(ii) (a) is for axial load capacity,including uplift capacity, if required,<ln trial piles of the same diameter as

the design pile. The testing shall be

done as per the procedure laicl down inIS:291l, Part-lV. The load test shall be

conducted for not less than ZYz timesthe design load. The initial load testshall be cyclic load test for piles de-riving strength from end bearing andside friction. The maintained load testcan be performed for end bearing pileswithout relying on friction, and for thesocketed piles in rock.

If the initial load test gives a capacitygreater than 25 per cent of the capac-ity calculated by static formula, and ifit is desired to take benefit of the highercapacity, another two load tests shall be

carried out to confirm the earlier valueand minimum of the three shall be con-sidered as initial load test value. Thenumber of initial tests shall be deìer-ntined by the Engineer-in-charge tak-ing into consideration the bore log andsoil profile.

v)

vi)

709.2.4 Routine Tests :

Routine load tests should be done on one pile foralternate foundation for bridgcs. The number maybe suitably increased/reduced taking into consid-eration thc bore long and soil profile, limited tolo/o of total numbcr of piles or two nos. which-ever is morc.

Routine load test should be done at loca-tions of alternate foundations of bridgesto reconfirm or modiff the allowableloads. Vertical and horizontal load tests

should be properly designed to coverparticular pile group. The lateral loadtest may be conducted on two adjacentpiles. Howeve¡ rcsults of routine loadtests shall not be used for upward revi-.sion ol' dcsign capacity of piles. TheMinimum number of tests to be conduct-ed is as given below for confirming pilecapacity:

t22 INDIAN HIGHWAYS, JTTNE 2OO9

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Total number ofPiles for thc

bridse

Minimum No. ofTcst Pilcs

uÞto 50 2

Unto 150 J

Bcvond 150 2% of totalpiles(fractional

number roundedto next higher

integer number).

Note: The number of tests may bejudiciously increased depending uponthe variability of foundation strata.

2. Pcrmissible Over LoadWhile conducting routine test on one ofthe pile belonging to a pile group, the

pile is found to be deficient (based onthe settlement criteria at 1.5 times the

test load) an overload upto l0% of the

capacity may be allowed.

3. For a quick assessment of pile capaciry,strain dynamic tests may be conductedafter establishing co-relation using the

results of load tests. However, results ofstrain dynamic tests shall not be used forupward revision of design capacity ofpile. Detailed guidelines & references

are at Appendix-7 Part I & 2. These

methods can be followed.

4. To have a fairly good idea about the

quality of concrete and constructiondefects like voids, discontinuities,etc., pile integrity tests are extensivelyconducted. Detailed guidelines and

rcl'crences are at Appendix-7 Part 2.

709.3

709.3.1Capacity of PileFor calculating designed capacity of pile / pilegroup methods / recomrnendation of IS:2911

should be followed.

Appenglix-ï gives formulae for estimatingpile capacity based on soil / rock interactionwith pile.

For calculating designed capacity of pile, rec-

ommcndations given in Appendix-S shouldbe followed. For calculating capacity of pilegroup refbr sections 709.3.3 and 709.3.4 and

the allowable settlement criteria as per Clause

709.1.8. For application of these clauses the

following tlefinitions will apply.

INDIAN HICTIWAYS, JUNE 2OO9 123

Çqhc$ivg-coil (clay or plastic silt withs,, s 0.2_5 MPa;

Çranulal s-oi!(sand, grnvcl or non-plas-

tic silt with N (averagc within layer )<50 blows/0.3 m (50 blows / 30 cms);

Intermediate Geomaterial

Cohesive: e.g, clay shales or mud-stones with 0.25 MPa (2,5 tsf) < S" <

2.5 MPa.

Cohesion less: e.g. granular tills, gran-

ular residual soils N>50 blows/O.3m(50 blows/3O cms.);

Rock [cohesive, cemented geomate-

rial with S, > 2.5 MPa (25 tsf) or q" 25.0 MPa.

a)

b)

c)

d)

709.3.2 Factor of safety : The minimum factor of safetyon ultimate axial capacity computed on the basis

of static formula shall be 2.5 for piles in soil. Forpiles, in rock, factor of safety shall be 5 on the

bearing component and l0 on socket side resis-tance component.

Factor of safety : The minimum factor ofsafety on ultimate axial capacity computedon the basis of static formula shall be 2.5 forpiles in soil. For piles in rock, factor of safety

shall be 5 on the bearing component and l0on socket side resistance component.

709.3.3 Capacity of piles/group action : The axial ca-

pacity of a group of piles should be determined

by a factor to be applied to the capacity of indi-vidual piles multiplied by the number of piles ofthe group.

(i) Factor may be taken as I in case of purelyend bearing piles having minimum spacingof 2.5 times the diameter of pile and forfrictional piles having spacing of minimum3 times diameter of pile.

(ii) For pile groups in clays, the group capacityshall be minimum of the following :

(a) Sum of the capacities of the individu-alpiles in the group.

(b) The capacity of the group based on

block failure concept, where the ul-timate load carrying capacity of the

block enclos.ing the piles is estimated.

Capacity of piles/group action: The axialcapacity of a group of piles should be deter:mined by a factor to be applied to the capacityof individual piles multiplied by the numberof piles of the group.

i) Factor may be taken as I in case ofpurely end bearing piles having mini-mum spacing of 2.0 times the diameter

of pile and for frictional piles havingspacing of minimum 3 times diameterof pile.

ii) For pile groups in clays, the group ca-

pacity shall be lesser of the following :

(a) Sum of the capacities of the individualpiles in the group.

(b) The capacity of the .group based on

block failure concept, where the

ultimate load carrying capacity of the

block enclosing the piles is estimated.

t24 INDIAN HIGHWAYS, JUNE 2OO9

t

i

709.3.4 Settlement of pilc group

709.3.4.2 Settlement of pilc group in sands : The scttle-

ment of a pile group is affected by the shapc and

size of group, longth, spacing and method of in'stallation of pilcs. There is no rational method

available to predict the settlement of group ofpiles in sands. It is recommended to use ernpiri-

cal relationship proposed by Vesic for obtaining

the settlement of pile group. In this methotln the

settlement of the group is predicated based on

settlement of a single pile obtained from load test.

The following Table indicates the relationship :

Scttlcmcnt of pile group in sands : The

settlement of a pile group is affçcted by the

shape and size of group, length, spacing and

method of installation of pilos. Methodsgiven in lS:8009 (Part-ll) or any other

rational rnethod may be used. The seftlement

of group of piles in sands can be calculated

by assuming that the load canied by the pilegroup is transfbrred to the soil through an

equivalent raft located at one third of the pile

length upwards from the pile toe for frictionpiles. For end bearing piles the settlement can

be calculated by assuming the raft placed at

the toe of the pile group.V/idth of Group /Pile diameter

5

25

50

60

Where, ôg = settlement of Pile grouP

d : settlement of single pile

709.3.s Resistance to lateral loads

709.3;.5.2. The safe lateral resistance must not exceed the

sum of lateral resistance of the individual piles.

The safe lateral resistance of individual pile shall

be corresponding to a 5 mm deflection at ground

level in accordance with IS:2911 with full 'E'value and for appropriate pile-head condition in

Load Cornbination, I of Clause 706.1.1. For river

bridges with scourable bed, the 5 mm deflection

mav be taken as the deflection at scour level.

The safe lateral resistance must not exceed the

sum of lateral resistance of individual piles.

The safe lateral load resistance of individualpile depends on the modulus of horizontal

sub-grade reaction of the foundation mate-

rial as well as the structural rigidity of pile.

Appropriate rational method of analysis us-

ing soil modulus as recommended by IS:291I

may be used to calculate the same. The safe

lateral resistance of single pile shall corre-

spond to deflection at scour level not greater

than I .0o/o of pile diameter. For a group ofvertical piles, confirmation by load testing is

not required. For pile acting singly the hori-

zontal load test may be performed In accor-

dance with IS:2911. Testing shall be for free

hcad condition for piles having free standing

shaft above scour level upto the pile cap. For

conducting test at scour level, it will be nec-

essary to drive a larger diameter casing upto

scour level so that the test pile above is free to

deflect. The cleflection at scour level

INDIAN IIIGHWAYS, JIJNE 2OO9 125

mây be measured directly, or may be cal-culatcd from deflection measured at higher(ground) level assuming that the pile acts as

a structural cantilever from the point of fixity.The point of fixity can be taken from the anal-ysis porformed fbr the design or calculated bysimplified method given in IS:291l.

For piles in land zone of river bridges or forbridges on land (refer section 709.1.7), Thelateral load capacity may be based on fixedhead condition in appropriatè direction forrigid pilc cap permitting deflection at pilehead of not more than 1.0% of pile diameter.

709.3.6 Uplift load carrying capacity

709.3.6.2 The ultimate uplift capacity may be calculateclwith the expression of shaft resistance/skin fric-tion only, of the static formulae for compressionloads and applying a reduction factor of 0.50 onthe same. However, in the case of rock, the lengthof socket need not be restricted to 0.5 x diameterofsocket.

The weight of pile shall also act against uplift.Pull out tests may be conducted for verificationof uplift capacity,

The ultimate uplift capacity may be calcu-lated with the expression of shaft resistance/skin friction only, of the static formulae forcompression loads and applying a reductionfactor of 0.70 on the same. In case of rock,the socket length shall be measured from 0.3m depth to actual depth of socket. The weightof the pile shall also be taken as acting againstuplift. Pull out test shall be conducted for ver-ification of uplift capacity factor of (2.5 10.7\ =3.57 on the ultimate strength shall be used.

709.3.7 Piles subjected to downward drag : A pilemay be subjected to additional load on accountof downward drag resulting from consolidationof a soft compressible clay, layer due to its ownweight, remoulding or surfacq load. Such addi-tional load coming on pile may be assessed on thefbllowing basis :

(i) In the case of pile deriving its capacityrrrainly lionr friction, the value of downward dragforcc rnay be taken as 0.2 to 0.3 timcs undrainedshear strcngth rnultiplied by thc surf'ace area of'pilc shafT cnrbcdded in comprcssible soil.(ii) ln case ol'pile deriving is capacity rnainiyI'rom end bcaring, the value of downward clrag

t'orcc rnay be considered as 0.5 timcs undrainedshear strength mulitipliecl by the surfhce area ofpile shalt crnbe<Ided in comprcssible soil.

Piles subjected to downward drag : When a

soil stratum through which pile shaft has pen-ctrated into an underlying hard stratum com-presses due to its own weight, or remoulding,or surface load etc., additional vertical loadis generated along the pile shaft in such stra-tum upto a point where soil does not movedown relative to pile shaft. Such adclitionalload coming on pile may be assessed on thefollowing basis :

(i) to (iii) As it is, except ro replace word"lcss" in the last sentence of (iii) by word"higher",Add: (iv) This reduction in capacity of pile isin the ultirnate capacity.

126 INDIAN HIGHV/AYS. JUNE 2OO9

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(iii) For a group of'piles, the drag ftr¡uos nhuflalso be calculated considering thc surlhcc uroaof the block (i.e., perimeter of the group timosdepth) embedded in compressible soil. ln rhcevent of this value being less than the numbcr ol'pile in the group times the individual downwar<ldrag forces, thc same shall be consiclercd in thedesign.

709.4

709.4.1

Structural Design of Piles

A pile as a structural member shall have sufiìcientstrength to transmit the load from structure tosoil. The pile shall also be designed ro withstandtemporary stresses, if any to which it may be sub-jected to, such as, handling and driving stresses.The permissible stresses should be as per tRC:21

Structural Dcslgn of l¡ilcs

A pile as a structural nrcmbcr shall have suffi-cient strcngth to transmit thc load from struc-ture to soil, The pile shall also be designed towithstand temporary stresses, if'any to whichit may be subjected to, such as, handting anddriving stresses. The permissible stressesshould be as per IRC:21.

The test pile shall be separately designed tocarry test load safely to the foundation.

709.4.3 For the horizontal load at the cap level, the mo-ment in the pile stem can be determined by anyrational theory. In the absence of any rationaltheory the method given in IS:2911 (part I/Sec2) may be adopted. If the pile group is providedwith rigid cap, then the piles should be consideredas having fixed head for this purpose. Horizontalforce may be distributed equally in all piles in agroup with a rigid pile cap.

For the horizontal loads the moments in pileshaft can be calculated as described in clause709.3.5.2. For piles on land, if the pile groupis provided with rigid cap, then the piles maybe considered as having fixed head in appro-priate direction for this purpose. Horizontalforce may be distributed equally in all piles ina group with a rigid pile cap.

709.4.4 Minimum reinforcement : The reinforcementsin pile should be provided for the full length ofpile, as per the design requirements. However,thc minimum area of longitudinal reinforcementshall be 0.4 per cent of the arca of cross-sectionin all in situ concrete pilcs. I-atcral rcinforcemcntshall bc provided in the for.m of links or spiralswith ¡ninimum S rnm dianlctcr stccl, spacing notlcss than 150 rnm. Cover to rnain rcinlirrcementsshall ntlt be less that 75 rnm.

I Rcinforcements for cast-in-situ pltes=

I The reinforcements in pile should be provided

I complying with the requiremenrs of IRC:21, as

I per the design requirements. The area of lon-gitudinal reinforcement shall not be less than0.4 per ccnt nor greater than2.S%o of the actualarca ol'cross-scction in all casçin-situ concretepilcs. 'l'hc clear spacing between vertical barsshall not bc less than 100 mm. Grouping of notnlorc than two bars together can be made for

I

achieving the same. Lateral reinforcement shallbe proviãcd in the form of spirals with mini- |rnum 8 nlm dialneter steel, spacing not more Ithan 150 rnnr. For inner layer ofreinforcement, Iscparalc lirnits tying them to each other and to Iouter laycrs shall be provided.

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709.5.3. In marine conditions or in areas exposed to the ac-tion of harmful chcmicals, etc. use of dense com-pacted concrete shall be made, the pile cap shallbe protected with a suitable anti-comosive paint,High allumina cement, i.e., quick setting cementshall not be used in marine constructions.

Delcte

709.5.4 The minimum thickness of pile cap should beat least 0.6 m or 1.5 times the diameter of pilewhichever is more. Casting of pile cap shouldbe at level higher than water level unless func-tionally it is required to be below water level atwhich time suffrcient precautions should be takento dewater. The forms to allow concreting in drycondition.

709.5.3(i) The minimum thickness of pile capshould be at least 1.5 times the diameter ofpile. Such a pile cap can be considered as rig-id. The pile cap may be designed as thick slab/deep beam or, by using 'strut & tie'method.All reinforuement in pile cap shall have fullanchorage capacity beyond the point at whichit is no longer required. It should be speciallyascertained for pile caps designed by'strut &tie' method. Where large diameter bars areused in pile caps as main reinforcement, thecorners ofpile caps have large local cover dueto large radius of bending of main bars. Suchcomqrs shall be protected by locally placingsmall diameter bars.

(ii) Casting of pile cap should be at levelhigher than water level unless functionally it is

required to be below water level at which timesufficient precautions should be taken to dewater,the forms to allow concreting in dry condition.

In marine conditions or in areas exposed tothe action of harmful chemicals, the pile cap

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shall be protected with a suitable anti-cono- |

sive paint. High alumina cement, i.e., quick I

setting cement shall not be used in marineconstructions.

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709.6.2.3. In case of bored cast-in-situ piles tremies of 200mm diameter shall be used f'or concreting. Thetrenrie should have unifurnl and srnooth cross-section insidc, and shall be withclrawn slowlyensuring atlequate height of concrete outside thetremie pipc at all stages of withdrawal. Other rcc-ommendations for tremie concreting are :

(i) The sides of the borehole havc ro tre stablcthroughout;(ii) The tiemie shall be watertight throughour itslength and have a hopper attached at its head by a

watcrtight connection;

Concreting of PilesConcreting shall be done by tremie method.ln trcrnie rnethod the following requirementsare particu larly applicable.a) When concreting is canied out for a pile

a temporary casing should be installedto suffìcient depth, so that fragments ofground cannot drop from the sides ofthe hole into the concrete as it is placed.Thc tcrnporary casing is not requiredoxccpt near the top when concreting un-der drilling mud.

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r28 INDIAN HIGHWAYS, JLINE 2OO9

(iii) The tremie pipe should be lowered to the

bottom of borehole, allowing ground water or

drilling mud to rise inside it before pouring con'

crete;(iv) The tremie pipe should always be kept fullof concrete and should penetrate well into the

concrete in the borehole with adequate margin ofsafety against accidentalwithdrawal if the pipe is

surged to discharge the concrete.

The hopper and trenrie should be a leak

proof system..

Trcrnic diametcr ol'minilnum 200 rnm

shall bc used with 20 mm diameter down

âggrogate.

The first charge of concrete should be

placed with a sliding plug pushed down

the tube ahead of it or with a steel plate

of adequate charge to prevent mixing ofconcrete and water. However, the plug

should not be left in the concrete as a

lump.

The trernie pipe should always penetrate

well into the concrete with an adequate

margin of safety against accidental with-

drawal of the pipe. The tremie should be

always full of concrete.

The pile should be concreted whollyby tremie and the method of deposition

should not be changed part way up the

pile, to prevent the laitance from being

entrapped within the pile.

All tremie tubes should be scrupulously

cleaned after use.

As tremie method of concreting is not

undcr water concreting, there is no need

to add l0% extra cement.

Normally concreting of the piles should

be unintemrpted. In the exceptional

case of intemrption of concreting; but

which can be resumed within I or 2

hours, thc tremie shall not be taken out

ol'the concrete. Instead it shall be raised

and lowcred slowly, from time to time to

prcvent thc concretc from setting. Con-

crcting should be resumed by introduc-

ing a little richer concrete with a slum¡1

ol about 20mnt for easy displacerncnt ol'

the partly sct concrete.

ll'thc ccxrcreting cannot be resunrcd bc.

lbrc lìual set up concrete already plaocd.

thc pilc so cast may be rejectcd or ltc"

ccptcd with modifications.

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In case of withdrawal ol" tremie out ofthe concrete, either accidentally or to

remove a choke in the trernie, the trem-

ie may be reintroduced in the follow-ing manner to prevent impregnation oflaitance or scum lying on the top of the

cqncrete already deposited in the bore.

The tremie shall be gently lowered on to

the old concrete with very little penetra-

tion initially. A vermiculite plug/surface

retarders should be introduced in the

tremic. Fresh concrete slump between

150 mrn to 175 mm should be fìlled in

the trentie which will push the plug for-ward and will emerge out of the tremiedisplacing the laitance/scum. The trem-

ie will be pushed further in steps mak-

ing fresh concrete sweep away laitance/

scum in its way. When tremie is buriedby about 60 to 100 cm, concreting may

be resumed.

The 'L' bends in the reinforcements at

the bottom of the piles should not be

provided to avoid the formation of softtoe.

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709.6.2.4. While concreting the uncased piles, voids in

concrete may be avoided and sufficient head ofconcrete is to be maintained to prevent inflow ofsoil or water into the concrete. lt is also necessary

to take precaution during concreting to minimizethe sottening of the soil by excess water. Uncased

cast-in-situ piles shall not be allowed where

mudflow conditions exist.

709.6.2.4 Re¡noval of concrete above cut-off levelIt is desirable that the concrete above cut

off level is removed before the concrete isset. The concrete may be removed manuallyor by specially made bailer or other device.

Such removal of concrete helps in preventingthe damages of the good concrete below the

cut off lcvcl which results from chipping by

percussion method.

The rernoval of concrete can be within the

*25 nun fiom the specified cut off level

preferably on the (-) side. On removal ofthe such concrete, the concrete should be

com¡racted with ralnmer with spikes or it shall

bo vibratcd.

In casc the concrete is not removed before

setting, a groovc shall be made on outer

perimcter by rotary equipment before chipping

by percussion method.

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APPÊNDIX.5

Section Ito8

As printed Remain unchanged

Section-9 g.CAPACITY OF PILES IN ROCKA pile socketed into rock derives its capacity

from end bearing and socket side resistance.

The ultimate load carrying capacity may be

calculated from

Q": R" * Ru.: K"o.Q..d,-A., + A"q,

Where,

Q, = Ultimate capacity of pile socketed

into rockR": Ultimate end bearing

R"r:Ultimate side socket shear

K,o:An empirical co-efficient whose value

ranges from 0.3 to 1.2

q" : Average unconfined compressive

strength of rock core.

Ao: Cross-sectional area of base of pile

d, = Depth factor = I + 0.4 x Length of socket

Diameter of socket

Length of socket may be limited to 0.5

x diameter of socket

A.: Surface area ofsocketq. : Ultimate shear along the socket value

of q. may be taken as 50 kg/cm2 for normalrock which may be reduced to 20 kg/cnr2

for weathered rocks.

Note: l. For factors of safety on R" & Ro,

refer Clause 709.3.2.2. The maximum allowable end bearingpressure should be limited to 30 kg/cm? aflter

applying l'actor of safety.

Replace with paras given below:

9. CAPACITY OF PILES IN INTERMEDI.ATE CEO-MATERIAL AND ROCK

9.1 Axial load carrying capacity:Piles in rocks and weathered rocks of varying degree

of weathering derive their capacity by end bearing

and socket sidc resistance. The ultimate load carry-ing capacity may be calculated from one of the twoapproaches given below:

Where cores'of the rock can be taken and uncon-

fined compressive strength directly established using

standard method of testing, the appro4ch described

in method I can be used. In situations where RQDshows highly fragmented strata (which is not clas-

sified as a granqlar or clayey soil), the approach de-

scribed in method 2 (Cole & Shoud approach) can be

used. Also, for weak rock like chalk, mud stone, claystone, shale and other intermediate rocks this method

is preferred.

METHOD I :

Q" = R" * R,,.: \o.g".drAo * A. Cu..

Where,

Q" : Ultimate capacity of pile socketed into rock inNewtons

R" = Ultimate end bearing

R"r: Ultimate side socket shear

K"n : An empirical co-efficient whose value ranges

fiom 0.3 to 1.2 as per the table below for the rocks

where corc recovcry is reported, and cores tested foruniaxial comprcssivc strength.

(cR + RØp)

2

Ksp

30% 0.3

100% 1.2

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tc INDIAN I{IGIIWAYS, JUNE 2OO9 t3l

RQP * Rock Quality Designation in %For Interrncdiate valucs, K*n shall be linearly inter-

polated

q. * Average unconfìned compressive strength ofrock core below base of pile lbr the depth

twice the diameter/least lateral dimension ofpile in MPa

Ao = Cross-sectional area of base of piled, = Depth factor * I + 0.4 x Length of socket

Diameter of socket

However, value of d,, should not be taken more than L2,

A* = Surface area ol'socketCu.= Ultimate shear strength along socket

length=O.225{q. For calculation of socket resistance,

the same should bc restricted to 5 MPa.

METHOD 2:

This ¡ncthod is applicable when cores and/or core test-

ing results are not available, or when geo-material is

highly fragmented .The shear strength of geo-material

is obtained from its conelation with extrapolated SPT

values for 300 mm of penetration as given in table

below:Strengtty'

Consistcncy (q)Strong Moderatell

strongModerately

weakWeak Vcry Weak

Approx.N

Value

Above600

600-400 400-200 200-100 100-60

CompressiveStrength in MPa

80-40 40-t0 I0-4 4-t.4 L4 to 0.8

Qu = R" * Rur: cr.t.N..Au * ar...4,Where,

c,,.0 = Average shear strength below base of pile

for the depth twice the diameter/least lat-

eraldimension of pile.

c.* = Ultimate shear strength along socket

lcngth=0.225 !q". The same should be

rcstrictcd to 5 MPa.

l, = I".cngth of sockct.

N. = t)'

Gcueral rìotcs oomnÌon to Method I and Method 2:

l. Iìor thc hingcd piles resting on rock proper

seating has to be ensured. The minimum socket

lcngth should be 300 mm in hard rock, and

0.5 tirncs thc <Jiameter of the pile in weathered,

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2. Thc allowable end bearing component after di-viding by factor of safety shall be restricted to5 MPa.

3. For calculatir:n of socket friction capacity, thetop rock 300mm shall be neglected, The fric-tion capacity shall be limited to further sixtimes diameter of pile.

4. For the termination of working piles in therocky strata methodology given in sub-clausel0 below can be used as â quality control tool,

9.2 Moment carrying capacity of socketed piles:

For the socketed pile, the socket length in the rockmay be calculated from following equation :

4H2 + 6M

o,'D' Ç rDWhere

L" = Socket length

H = Horizontal force at top of the socketM = Moment at the top of the socketD = Diamcter of the pile.o,= Permissible compressive strength in rock

which is lesser of 3 MPa or 0.33 q.

In case of socketed piles, for the satisfactory perfor-mance of the socket as fixed tip, the rotation at the topof the socket for the fixed condition ( 0. ) should beless than or equal to 5% of the rotation for the pinnedcondition at the top of the socket (0, ).

10. Pile termination criteria as a quality controltool in rocks

For establishing the similarity of soil strata actuallymet while advancing the pile-bore with the strata se-

lected for terminating the pile on the basis of N valuesequivalent energy method can be used.

The concept ol'Pile Penetration Ratio (PPR) is usedin this method.

Thc pilc pcnetration ratio ( PPR) reflects the energy inton-meter requircd to advance the pile bore of one sq.

meter cross sectional area by I cm.

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INDIAN HIGHWAYS, JUNE 2OO9 t33

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ln case of SPT test its I,PR can be worked out âs

follows:

Energy Ë spent for N blows * 63.5 kg x 75 cm x Nblows ( in kg *cm units ) * E x l0'5 ton meter. Areaof sampler is 0,785 x (5,2)2 sq.cm e 21.24 sq,cm, pen-etrating 30 cm.

Hence PPR=63.5 x 75 x N xl0'5/ (21.24x l0a x 30)

| = 0.742 N

PPR for N *50, * 37.35 tm/m2/cm, and for N =200,l49,4tm/mzlcm

Where,

tm = energym2 = area

cm : penetration

Whn2) PPR (P ), ( for percussion piles ) = ------------

APWhere,

W = Weight of chisel in MTh - Fallof chisel in'm'n = Number of blows of hammerA = Area of pile in 'm2'P : Penetration in'cm'

2 nnt3) PPR ( R ), ( for rotary piles ):

AP

Where

n : Revolution per minuteT = Torque in 'tm'for conesponding 'n't: time in minutesA: Area of piles in 'm2'

P = penetration in 'cm'

134 INDIAN T{IGHWAYS, JLTNE 2OO9

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ÁI'PENDIX 7

P/lRT:I

METHOD-I: PILE LOAD CÄPACITY BY DYNAMTC TEST USING WAVA AQUATION

This method is based on solving wave equation by using idcalized model using strâtâ wise soil parameters to arrive

at pile'set'for given pile load. The force ancl velocity response of pile to an impact force appliecl axially by drop

of hammer causing large strain at top of pile (of the orcler of rnagnitude of ultimate capacity of pile) the ultirnate

capacity of pile are measured.

Theoretical background

For piles considering resistance from surrounding soil, the internal force and displacements produced on segment

of prismatic bar subjected to impact at one end the wave equation can be derived as

ð2D l¿l fa'ol, "--;=l-ll: " lrròt' t.p i \dr' J

tWhere

D = longitudinaldisplacement of a point of the bar frorn its originalposition

E = modulus of elasticity of bar 'j

p = density of bar material

t = timex = direction of longitudinal axis

R = soil-resistance term

The above equation rnay be solved for appropriate boundary conditions and the relationship among displacement,

time position in the pile and stress are determined usually by numerical methods. Solution requires idealization of

model considering load deformation diagram for each segment, the 'quake' i.e. maximum deformation that can

occur elastically 'Ru' the ultimate soil resistance and the damping factor. The empirical value of 'quake; Damping

factor and perðent side adhesion as reported by Forehand and Reese are ieproduced for reference

Table : Empirical Values of Q, J, and Percent side Adhesion

Soil a(¡n.)

J (p)(Scc/ft. )

SideAdhesion (% of R")

Coarse sand 0. t0 0. l5 35

Sand qmvel nrixed 0.10 0.15 75- I 00

F'ine Sand'0.l5 0.t5 100

Sand and clay or lo¿rcl, at least 50 % of pile in sand. 0.20 0.20 25

Silt and fìne sand underlain by hard strata. 0.20 0.20 40

Sand antl gravcl underlain by hard strata 0.t5 0.r5 25

PILE AND TESI' PREPARATION

t. The testing should be conducted by fixing instrumentation that shotrld include strain sensors and

to the sicles of the pile at a depth of 0.5 x pile, cliameters from top of pile and then connectin¡i

nrcasuring cquiprncnt.

INDIAN IIIGI{WAYS, JUNE 2OO9

I

il2. For this it is desirable that the pile is ext(3nded to suitable length after chipping top loose concrcte. This can

be done either using fonnwork or pemnänent casing. Alternatively if it is a iinei piÎe, two openings/windowsapproximately 300 mrn x 300 mm and dianretrically opposite to each other shall be rnade into the liner at0.5 x pile diameter from top.

In case pile head is extended, it shall be axial, flat and have same strength as pile concrete. The pile head mayeven be one grade higher so as to attain eorly strength. The rebars and helical reinforcement shall also beextended to avoid cracking of concrete under hammer impact,

Refer to Figure: I for a sketch of reinforcement in the extended pile and the diarneter of bars shall generally be thesame as pile reinforcement. Further, the concrete at the sensor level shall be smooth hard and uniform.

a

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3.

4.

Alldimensions are in mm

Clear cover to mesh reinforcement is20 mm.

Diameter of mesh reinforcement bars is8 nrm.

Spacing of mesh reinforcement bars is100 mm.

4.

5.

6.

Plan of Test Pile Elevation of Test Pile

DETAILS OF REBAR CAGE FOR EXTENDED PORTION OF'PILE F'OR PILE DYNAMIC TEST :

A pile top cushion consisting of sheets of plywood with total thickness between 25mm to l00mm or asdctermined by the Test Engineer shall be placed on the top of the pile before testing.

Steel helmet 25 mm-50 mm thick or as determined by the Test Engineer shall be kept ready at the time oftesting.

A hammer of suitable weight (1-2o/o of test load or 5-7Yo of the dead weight of the pile whichever is higher)shall be used for testing the pile unless specified otherwise by the Test Engineer. ih. fult height generallyvaries from 0.5 m to 3 m.

Whercver essential a suitable guide shall be provided to ensure a concentric fall.A suitable crane or equivalent rnechanism capable of freely falling the required hammer shall be arrangedotl site in consultation with the test cngineer, Refer to F-igure: 2 at the end of the specification for a skeJchshowing the setup arrangements.

 suitablc power source supply shall bc provided for fixing sonsors ancl for the test equipment.

PII,E MONI'I'ORING

I' The fcsting may bc conductcd atlcast 15 days after thc pilc is inst¿rllcd and the concrete pile as well ascxtenclcd portion if any has achieved the required strength.

2' Dynamic pilc testing (basecl on wave cquation) should bc conducted by attaching strain transducers and' accelerometers t<l the sides of the pile approximately 0.5 tirnes pile diarneter below the pile top. A pairof transducers to be fixed onto opposite sides of thc pilc so as to detect bending in the piie if uny auiingtestinr¿.

7.

8.

9.

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These transducers should bc then connoctcd through the cåble to measuring equipment to record strain antl

acceleration measurements and display.thcm on an oscilloscope or sc[een,

The testing should be conclucted by impacting the pilc with blows of the hammer generally starting with a

smaller drop of 0.5 m. For each hammer blow, the strain transdueers shtluld tTleasure strains

For each hammer blorv, tbe test system should displays imnrcdiate lìeld results in the fonn of the mobilized

capacity of the pile, pile top compression, intcgrity, stresses etc, The force and velocity curve shall be generally

as defined in ASTM D4945,

Testing should be continued by increasing height fall of the hammer by approximately 0.5 ln increment tillthe time either the pile set or the pile capacity rcaches the required limiting values, A typical force veloci$resoonse is also described for claritv

TyprcAL FORCE VELOCITYTRACE GENBRATED BY VlinSUnnG EQUIPMENT

7. The pile capacity shall be generally considered to bc fully mobilized if the energy levels due to hammer

impact are sufficient so as to cause a measurable net displacement of atleast 3-4 mm per blow for a minimum

threc successive impacts. If thc pile set is less than 3-4mm per blow and the pile achieves required capacity,

then it implies that not all thc static pile resistancc has been mobilized and that the pile still has some capacity

that could not be measured or was not requircd to be rncasured at the time of testing.

tl. Analysis ancl Interpretation : Using strain and accclcration data in suitable model based on local parameters

of pile and soil strata the equivalent static loacl bcaring capacity shall be calculated. The final report should

specify the parameters of'soil and pile strata consiclcrcd and the safe capacity arrived. A typical blow is then

selected lbr Signal Matching Analysis.

TES'I' I,IMITATIONS

1.0 E,valuation of static soil rcsistallcc ancl its clistribution catt lrc based on a variety of analytical methods and is

thc subjcct ol'individual cngineering judgrncnt. 'l'hc input into thc analytical methods may or may not result

in thc dynamic evaluation nratching static load tcst d¿rta. It is necessøry to cølibrøte the result of the dynamic

analysis wilh those of a slatic pìle batl test carried out accordíng to LS. 2911.

2.0 Based o¡l above, it can bc said that it is clitlcult to preclict rock socket friction and actual end bearing for rock

socketcd piles that do not show substantial net displaccrnent under the impacts.

3.0 Unlike static testing, evaluation of clynanric pile tcst rcsults requires an experienced engineer trained in

interpretatiolls of thc rcsults.

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Sketch showing test setup arrangements

PILE DYNAMIC TEST METHOD BASED ON HILLEY'S FORMULAE(BY LASER /INFRARED OPERATED EQUIPMENT)

INTRODUCTION

Since the early days of driven piles the termination criteria based on "Sets observed", are followed. Various formulas

are available. The I.S. Code 29ll Part- I covering driven piles provide one such flormula. The principle followed

is recording the penetration per blow of the hammer and on that basis having obtained the desired set i.e. average

penetration of standard numbers of blows of hammer the ultimate capacity for the pile is worked out and then with

suitable factor of safety the safe capacity is anived at. The bored cast in situ piles after attaining strength (i.e. after

curing) can be treated as precast pile to be advanced fuither in the founding strata (i.e. strata on which the piles are

terminated) by dynamic impact energy. The load carrying capacity of bored cast in situ pile subjected to impact energJ

can then be estimated on measuring consequent displacement by sophisticated optoelectronic instruments on resorting

to I.S. 29ll procedure. The procedure willhelp in ascertaining thc quality of workmanship on a large numberof piles

without much of time wasting and avoiding clelays in a construction activity with relatively less cost.

METHODOLOGY

The methodology of test is based on a large falling weight giving thc dynarnic impact to the elastic body. It equates

thc energy of hammerblow to work donc in evercoming thc resistance of the founding strata to the,penetration,

of the ordinary cast in situ piles as wellas grouted micro piles. Allowance is made for loses of energy due to thrÐ.

elastic compression of the pile, and subsoil as wcll as losses caused by the irnpact of the pile. The (Modified Hiley,ts

formulae) given in the code I.S. 291I part - l, Section I is uscd in estimating the ultimate driving resistance in tonesi

Applying the factor of safety as outlinecl in the code thc safc load on pile can be worked out.

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The instantaneous displacement$ including rebounels of thc pile are preciscly recorded in aptomatic datá acquisitionsystem. This is done for several cycles and the n using formulae as accepted in I.S. 291 I thc safe loading capacity is

calculated. The opto-electrtronic instrument is used fbr position sensitive meâsurement by non contâct continuousmeasurement using instrument placed away fr<lm the vibrations due to impact load. The system is based on combinedlight emitting diode transmitters and a position sensitive detector. The transmitter and receiver are installed so thâtthe infrared light beam forms a ref'erence line from transmittern receiver to the prism group reflectors. The reflectedlight is received and recorded 100 times per second. Using the energy transmitted to the pile and accounting fortemporary compression of pile, ground and dolly occuning during the impact loading the ultimate driving resistaneeis calculated. Applying the factor of safety the safe load for the pile is calculated.

The modified Hiley formula is :

WhnR: ----------

S+C/2

Where

R = ultimate driving resistance in tones. The safe load shall be worked out by dividing it with a factor ofsafety of 2.5;

W = mass of the ram in tonnes;

h = height of the free fall of the ram or hammer in cm taken at its full value for trigger - operated drophammers, 80 prevent of the fall of normally proportioned winch operated drop hammers, and 90percent of the stroke for single-acting hammers. When using the McKiemanTerry type of double actinghammers, 90 percent of the marker's rated energy in tonne centimeter per blow should be substituted forthe product (Wh) in the formula. The hammer should be operated at its maximum speed while the set isbeing taken;

ry = efficiency of the blow, representing the ratio of energy after impact to the striking energy of ram;

S = final set or penetration per blow in cm; and

C = sum of the temporary elastic compressions in cm of the pile, dolly, packings and ground.

P = mass of pile in tonnes

Where W is greater than P" and the pile is driven into penetrable ground,

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w+P

Whcre l/ is lcss than P,. and thc pilc is driven into penetrable grouncl

14/ + P2,,

W1.P

Thc followi¡rg are the valucs ol'r¡ in relation to e and to the lation of P / W :

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INDIAN I{IGIìWAYS, JTJNE 2OO9 r39

ltatioof P/W e*0.5 e=0.4 c = 0.32 e = 0.25 c=0tl 0.7 5 0.72 0.70 0.69 0,67

0.63 0.58 0.55 0,s3 0.50

I tl 0.5s 0.s0 0.47 0.44 0.40

2 0.50 0.44 0.40 0.37 0.33

2'l^ 0.45 0.40 0.36 0.33 0.28IJ 0.42 0.36 0.33 0.30 0.2s

3'1. 0.39 0.33 0.30 0.27 0.22

4 0.36 0.3 t 0.28 0.25 0.20

5 0.31 0.2'1 0.24 0.2 r 0. t6

6 0.27 0.24 0.21 0.19 0.14

1 0.24 0.21 0. l9 0. t7 0.12

8 0.22 0.20 0. I7 0.15 0.l l

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P is the weight of the pile, anvil, helmet and follower (if any) in tones.

Where thc pile finds refusal in rock, 0.5 P should be substituted for P the above expressions for ry

is the coefficient of restitution of the materials under impact as tabulated below :

For steel ram of doublc-acting hammer striking on steelanvil and driving reinforced pile, e = 0.5

For cast-iron ram of single-acting or drop hammer striking on head of reinforced concrete pile, e = 0.4.

Single-acting or drop hammer striking a well-conditioned driving cap and helmet with hard wood dolly indriving reinforced concrete piles or directly on head of timber pile, e = 0.25.

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Tlpical Displacement Record

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Reading Serial Number.

r40 INDIAN HIGHWAYS. JUNE 2OO9

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Numbers of models of Laser/infrared operated ¡nstrumcnts measuring accurately the defonnation are available these

days. The required sensitivity of the equipment shall be such as to read the angular deformation to the accuracy ofI 0"r radians and the instrument capâble of recording ab<lut I 00 re adings per Seconds, From the angular defonn¿ltion

on knowing the distance of the reflector from the instrurnent vertical movenrent of the shafì under the given impactenergy, (both elastic and pennanent) can be measured acculately.These measurements of the displaccment can then

be substituted in modified Hilley's fonnulae stated in I.S, 291L The ultimate load canying capacity of the pile can

be worked out resorting to the modified l"lilley's formulae outlined in the code and from that the safe load carryingcapaciry of pile can be estimated.

APPENDIX-iPART\z

STANDARD TEST METHOD FOR LOW STRAIN PILE INTEGRITYTESTING

I. SIGNIFICANCE AND USE

Pile tntegrity Testing (PIT) is a Non-Destructive integrity test method for foundation piles. The method evaluates

continuity of the pile shaft and provides information on any potential defects due to honeycombs, necking, cross-

section reduction, potential bulbs, sudden changes in soil stratum, concrete quality in terms of wave speed etc. Itis known as "Low Strain" Method since it requires the irnpact of only a small hand,held hammer and the resultant

strains are of extremely low magnitude. The test procedure is standardized as per ASTM D5882 and also forms part

of various specifications and code provisions worldwide as attached in table- l of the specification. The number oftests shall be decided by the engineer to the project.

2. TYPICAL METHODS

Various rnethocls can be used to evaluate the integrity of the pile are briefly described below. The evaluation of PITrecords can be described as f'ollows.

. Pulse-Echo Method (or Sonic Echo - a timc domain analysis)

. Force Velocity Approach

. Transient Responsc l)roccclurc (Frequency f)ornain Analysis)

. Cross l'lolc Sonic L.ogging

J'he lîorce Vclooity approach is sornctirncs used to evaluatc dclì:cts near the pile top that maybe difficult to evaluate

in l)ulse Ucho Methocl Thc Pulsc l.ìcho is the nrost comnlonly used method and is described below.

3. T'BS1'EQUIPMENT

T'hc tcst should be pcrf.ormed using digital data acquisition equipment like a Pile Integrity Tester or any equivalent

that meets ASTM D5882 requircmcnts. Thc equipment nrust also include a sensitive accelerometeç instrumented

rur non-inslnrnrcnted hanrnrcr ctc.'l'hc data must bc displayed in the lìeld fbr evaluations of preliminary data quality

and intcrprctation and a fickl printout shotrld bc possiblc.

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4, TEST PROCEDURE

The testing shall be conducted atleast 7 days aflcr pilc concreting by an expericnced engineer / technician. Thcconcrete at the pile top surface must be relatively snooth with suflìcient space for attachment of the motion sensing

device and hammer impact area. The tcsting involves attachment of an accelerometer onto the pile top (not near its

edge) with the help of bonding material like candle wax, vaseline etc. After attachment, the pile is impacted.with a

hand held device (a hand held hammer).

The test involves collection of several blows during the stage of testing. All such similar blows are averaged beforc

display. For larger diameter piles of 600 mm and above, testing may be conducted on atleast 3 locations, whereas

minimum one location is enough for smaller diameter piles. The gpicaldata sets for good or damaged shall generallybe as per Figure: I and is also defined in ASTM D5882.

5. REPORT SUBMISSION

The final report shall include the following:

l. Project Identification & Location

2. Test Pile ldentification including Length, Nominal Cross - Sectional area & Concrete Mix as per installationrecord

3. Type of Pile and description of special installation procedures used if any.

4. Description of all the components of the apparatus for obtaining integrity measurements and recording/displaying data.

Graphical representation of Velocity measurements in time domain.

Cornments on the quality of the Pile Concrete.

Comments on any potential defects/damage and its location.

Comments on Integrity of Pile based on above.

LIMITATIONS

Certain limitations are inherent in the low strain test method and hence it should be treated only as an indicator ofquality of work and not as conclusive test. These limitations mentioned below must be understood and taken intoconsideration in making the linal integrity evaluation.

l. Integrity evaluation of a pile section below a crack that crosses the entire pile cross-sectional area or â

manufactured mechanical joint is normally not possible since the impact wave likely will reflect completelyat the discontinuitv.

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Pilcs with highly variablc crc¡ss-sections or multiplc cliscontinuities may be difficult to evaluate.

Thc ¡nethod is intended to detect rnajor anornalies and rninor defects may not be detected by this method.

Thc test is not appliczrblc to jointed pre-cast piles or hollow steel pipes or H-sections.

Thc mcthod cannot be used to derive the pile capacity.

t42 INDIAN HIGHWAYS. JI.]NE 2OO9

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INDIAI{ ROADS CONGRESSKama Koti Marg, Sector 6, R.K. Puram,

New Dclhi - ll0 022 (lndia)

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q6lqÞq (Sccretary tenoral)r +91 (l l) 2618 5303

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2618 5273,2671 6778SrR 0'ax): +91 (tl) 2618 3669

NOTIFICATION No 55 dated thc 28 Mnv 2009

Subject: Amendment to IRC:SP:80:2008 "Guidelines for Corrosion, Prevention, Monitoring andRemedial Measures for Concrete Bridge Structures".

In continuation to the Notification No. 47 published in the Indian Highways December 2008 issue, the followingamendment to IRC:SP:80:2008 "Guidelines for Conosion, Prevention, Monitoring and Remedial Measures forConcrete Bridge Structures") is further notified.

Q'!'uøN¡t'' -

(R.P.lndoria)

Secretary Ceneral

Clause No. For Read

6.5.1

Page37The coating protects exposed faces

ofthe superstructure and portions ofthe substructure above water level ofconcrete bridges from the aggressive

action of industrially polluted and

marine/saline environment.

The coating protects exposed

faces of the superstructure and the

substructure of concretê bridges

from the aggressive action ofindustrially polluted and marine/saline environment.

This amendment will be effective from I June 2009

INDIAN I-IIGHWAYS. JUNE 2OO9 t43

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