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IS 2974-1 (1982): Code of practice for design andconstruction of machine foundations, Part 1: Foundation forreciprocating type machines [CED 43: Soil and FoundationEngineering]

Gr 6

IS : 2974 ( Part I ) - 1982(Reaffirmed 2008)

Indian StandardCODE OF PRACTICE FOR

DESIGN AND CONSTRUCTION OFMACHINE FOUNDATIONS

PART 1 FOUNDATION FOR RECIPROCATINGTYPE MACHINES

( Second Revision)Third Reprint NOVEMBER 2007

( Including Amendment No.1)

UDC 624.159.11: 621.9-12

Copyright 1999BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

December1982

IS : 2974 ( Part I ) 1982

Indian StandardCODE OF PRACTICE FOR

DESIGN AND CONSTRUCTION OFMACHINE FOUNDATIONS

PART I FOUNDATION FOR RECIPROCATINGTYPE MACHINES

( Second Revision)Foundation Engineering Sectional Committee, BDC 43

ClaairmanPRO)' DINESH ~{OlIAN

&pr,sl1Ili"lCentral Building Research Institute ( CSIR ),

RoorkeeMmabers

DIl R. K. BHANDARI

SIrBI V. C. D".aJfP.AlIDESPILl A. GJ-,OS.ALDIRECTOR ( CSMRS )

Central Building Research Institute (CSIR),Roorkee

SRRI DJIVENDBA SHARMA ( AII,rnat, )CBUt.. ENOJNFER Calcutta Port Trust, Calcutta

SRal S. GUBA ( Altmud, )SHRl M. G. DANDAVA1'B The Concrete Association of India, Bombay

SHIH N. C. DUGGAL (Alt,r,",t,)SHBI A. G. DA8TIDAR In penonal capacity (5 Hu"gerf.,d Cnrt, 121,

HUftl'rf0rd Str,n. Caleutta )The Pressure Piling Co (I) Pvt Ltd, BombayStup Consultants Limited, Bomba yCentral Soil & Material Research Station,

New Dt'lhin- DIRIDOTOB ( CSMRS ) ( Altmaat, )

SHJU A. H. DIVANJI A.ia Foundationa and Construction Pvt Ltd,Bombay

SRRJ A. N.J ~NOLJC ( Altnut,)SHJll R. K. DAB GtJPTA Simplex Concrete Piles ( India) Private Limited,

CalcuttaSURI H. GUBA BI8WA8 ( AltIf'fUJI,)

DRJAODJ8H NARAllf Indian Geoterbaical Society, New DelhiPROF SWAMI SABAN ( J41tmuIU )

SJ1RJ G. 8. JAIH G. S.Jain &. Associatet, RoorkeeSItRI A8J10K KUMABJADf ( AltmuIU)

81.1\1 N.JAOANNA'rS Steel Authority oClndia, BokaroSI A. K. MITRA (AlwMU)

( OHtti",,1t/ 0 .. P"'t!' 2 ,--~==~---------C>-(-A1P.-."-"-it:-'''-I99-'------=----- I

BUREAU OF INDIAN STANDARDSThis publication is pretected undP.l' th~ 1-. Colrl"ifM A# ( X IV or 19';7) aDdrf1lroduclion ill wboltt or ill part by &IIy rap"" f!xcepr with writtPD "prmiuioD of theDUhlilb.., "~11 ~ dpf-In..d to be aD iDfriniertuant of conyriaht und-r th,. "aid ~Ct.

18 12974 ( Part I ) 1982( CtmtillUld from /J4g' 1 )

BRIG OKBm SINGH

PRO)' GOPAL RANJANDB V. V. S. RAOSURI T. N. SURDA RAO

SHBI S. A. REDDI ( AllmuJU )SaRI ARJUN RIJRSINOHANI Cement Corporation of India, New Delhi

SHRt O. S. SRIVA.8TAVA ( AllmuJI,)DBA. SABOUNAJf. College or Engin~ringt Guindy

SHRI S. BOKMINATBAN ( AllmuJl, )Saar K. R. SAXENA Engineering Research Laboratories, Government or

Andhra Pradesh, HyderabadEngineer-in-Chief'. Branch, Army Headquanen,

New DelhiLT-CoL K. P. ANAND ( Allmult,)

SHRI N. SIVAGUBU Ministry of Shipping and Transport, New DelhiSHBI K. P. SARKAR (Allmult,)

SUPBRINTBNDIlfG ENGINUa Central Public Works Department, New Delhi( DF.81GN8 )

ExEOUT~ ENQ~( DmS10N8 ) V ( Altmaat, )

SRRI M. D. T A.BEXAR Bombay Port Trust, BombayDR A. V ARADARAJAN Indian Institute of Technology, New Delhi

n. R. KANIRAJ ( Alt,mal, )SBRJ G. RAM.AN, Director General lSI (&-.jJiM M""kr )

Director ( Civ En" )

Public Works Department, Chandiprb Administ-ration

SHRt A. P. MATHUB Central Warehousing Corporation, New DelhiSHRI V. B. M'THUB MachenziPi Limited, BombayS.HRI T. K. D. MUNSI Engineen India Limited, New Delhi

SHRJ M. IYENGAR ( Allmaal, )SDRI B. K. P'NTHAXY The HindUltan Construction Co Ltd, Bombay

SRRI V. M. MADGE (Alumal,)SHRI M. R. PUNJA Cemindia Co Ltd, Bombay

SHRI S. MUKHBRJDI ( AIImuJl4 )SHRI N. E. V. RAGDVAN The Braithwaite Burn &. Jessop Conatruction

Company Limited, CalcuttaUnivenity of Roorkee, RoorkeeNaladi Consultants Private Ltd. New DelhiGammon India Limited, Bombay

M,mlHrs R,prlsmtill,JOINT DIRECTOR ( DElIIGNS ) National Buildings Organisation, New Delhi

SHRI SUNIL Boy ( Alt"nal, )JOI:Kr D['~BOTOR RBSB.&.BOH Ministry of Railways

( GE )-1, ROSaJ,HltT DIRBCTOR RBSBAROH

( B & S ), ROSO (AllmuJII )DR R. K. KATTI Indian Institute of Technology, BombaySHRI S. R. KULKARNI M. N. Dastur & Co Pvt Ltd, Calcutta

S RRI S. RoY ( AltmuJl, )SBRI O. P. MALHOTRA

Sm~SHRI K. M. MATBUB

D('puty Director ( Civ Eng ) lSI,

2

IS : 2974 ( Part I ) 1982

Indian StandardCODE OF PRACTICE FOR

DESIGN AND CONSTRUCTION OFMACHINE FOUNDATIONS

PART I FOUNDATION FOR RECIPROCATINGTYPE MACHINES

( Second Revision)e, ~'O R E W 0 R D

0.1 This Indian Standard ( Part I ) ( Second Revision) was adopted bythe Indian Standards Institution on 26 July 1982, after the draft finalizedby the Foundation Engineering Sectional Committee had been approvedby the Civil Engineering Division Council.0.2 Installation of heavy machinery has assumed increased importancein the wake of the vast programme of industrial development in thecountry. Foundations for these machines have to be specially designedtaking into consideration the impact and vibration characteristics of theload and the properties of soil under dynamic conditions. While manyof the special features relating to the design and construction of suchmachines foundations will have to be as advised by the manufacturersof these machines, still a large part of the .details will have to be accord-ing to certain general principles of design covering machine foundations.This standard is intended to lay down these general principles.This part, which is the first of a series of standards relating tomachine foundations, deals with machines of the reciprocating type forwhich rigid-block type foundations arc generally used. This standard wasfirst published in 1964 and revised in 1969. In this revision, the principalmodifications made are in respect to providing additional information ofpile foundation, grouting and inclusion of guidelines for installation ofanti-vibration mountings and testing and measurement of vibration.0.3 For the purpose of deciding whether a particular requirement of thisstandard is complied with, the final value, observed or calculated, ex-pressing the result of a test or analysis, shall be rounded off in accordancewith IS : 21~60. The Dumber of significant places retained in therounded off value should be the lame as that of the specified value in thisstandard.

-Rules for rounding off numerical values ( "'!1sld).a

IS I 2974 ( Part I ) 19821. SCOPE1.1 This standard covers the design and construction of foundations formachines of the reciprocating type which normally generate steady statevibration and is of a size for which a rigid block type foundation isnormally used.

2. TERMINOLOGY2.0 For the purpose of this standard, the definitions of the following termshall apply ( see Fig. 1 ). .

LateralLODlitudinalVertical

PitchingRockingYawing

o - Combined Centroid of Foundationand Machinery Sy.teal

C == Centroid or Bearm, SurCace

Flo. 1 AxEs AND CO-ORDINATES

IS I 2974 ( Part I ) 19822.1 SapportlDl GrouDd - That part of the ground carrying loadarising from the machine and foundation.2.2 F01lDdatioll - The part of the structure in direct contact with,and transmitting loads to the supporting ground.2.3 Force. aDd Couple.

2.3.1 External Forces.....;. The unbalanced part of the periodic inertiaforces caused by the acceleration and deceleration of reciprocating parts.The primary inertia force has one complete cycle and the secondaryinertia force two cycles per revolution of the crank shaft.

2.3.2 Vertical Force - An unbalanced force at machine operationfrequency or twice the operation frequency, or both, acting in thedirections of axis Z.

2.3.3 Horizontal Force - An unbalanced force at machine operationfrequency or twice machine operation frequency, or both acting in thedirections of axis x.

2.3.4 External Couple ~ A moment which occurs when one inertia forceis balanc ed by another but in a separate line of action. For foundationdesign it is usually necessary to consider only the primary and secondaryvertical and horizontal couples.

2.3.5 Vertical Couple - An unbalanced couple at machine operationfrequency or twice the machine operation frequency, or both acting inthe planes of axes rz.

2.3.6 Horizontal Coupl, _. An unbalanced couple at machine operationfrequency or twice the machine operation frequency, or both, acting inthe planes of axes XT.2.4 Torque

2.4.1 Harmonic Torque Reaction - Turning moment in plane of axelXZ, the frequencies of which depend on number of cylinders andconfiguration of the machine.2.5 Periodic MotloD - The motion which repeats itself in all itlparticulars at regular intervals of time is called the periodic motion.

2.5.1 Apniotlu Motion - The motion which does not repeat itself atregular intervals of time is called aperiodic motion.2.6 Damplal - Damping is associated with energy dissipation and isthe internal resistance offered by a foundation system to the vibration ofmachine. It is termed viscous damping when the force of dam)?ing iadirectly proportional to the lnstantaneous velocity of the oscillatingsystem.

5

IS : 2974 ( Part I ) 19822.6.1 Damping Constant ( C ) - Constant of proportionality relating

force of damping with instantaneous velocity of motion.

2.6.2 Critical Damping ( C, ) - The magnitude of damping at which themotion of the system changes from periodic to aperiodic.

where Co ::: "vmk for single degree of freedom system2.6.3 Damping Factor - The ratio of the damping constant ( C ) to the

critical damping ( Co ) of the system.2.7 Amplitude orMotion - The distance that a body moves from itsposition of rest when subjected to vibration.2.8 Frequency - The number of times a periodic motion repeats itselfexpressed in revolutions or cycles per minute (j).

2.8.1 Operation Frequency - The rotating speed of the main drive incycles per second or the frequency of the periodic force acting on thesystem.

NOTE - System mean, the machine, the foundation block and soil.

2.8.2 Angular Frequency ( w ) - The frequency expressed in radians persecond.

2.8.3 Natural Frequency (jn ) - The frequency of free vibration of abody.

2.8.4 Disturbing Frequency - The frequency of a periodic force.

2.8.5 Limiting F eqnencies - If a system possesses en' degrees of freedomhaving en' natural frequencies~,f~hja, i4' jn, the minimumand maximum of such frequencies,j min and! m(Jz are known as limitingfrequencies of the system.

2.8.6 Frequency Ratio (fifo) - The ratio of the operating frequency tothe natural frequency.

2.9 Degrees or Freedom or a System - The degree of freedom of asystem is defined as the number of coordinates required to describe thedisplaced position of the system ( see Fig. 2 ).2.10 Rea.onaDce - When the frequency of the forced vibration( operating frequency of the machine) equals the natural frequency ofthe foundation soil system the condition of resonance is reached.

2.11 MaS8 Moments orInertl. - The resistance of a mass to rotationand equal to its mass times the radius of gyration squared.

6

IS I 2974 ( Part I ) 1982

ROCKING

LateralLongitudinalVertical

fVERtiC ALZ

YAWING

v

P~ PitchingP, Rockingp. Yawing

The axis rr is parelJel to the crank shaft.

Flo. 2 SYSTEM OF AXES AND THE SIX DEGRERS or FREEDOM

2.12 MaSpriDI.Sy.tem2.12.1 Singl, Mass SpringSystem - A rigid body supported by a number

of springs, such a system has six natural frequencies, three of them beingtranslational or three cartesian, co-ordinate axes and the other three beingrotational on three planes in a cartesian co-ordinate system.

2.12.2 'Multiple Mass-Spring System - A number of rigid bodies connect-ed by a series ofrelatively flexible springs. The natural freqencies dependon the number of degrees of freedom being defined as the number ofco-ordinates required to identify a point on the rigid body.2.13 Fatigue Factor or FatJpe Coeftleieat - The factor of safetyutilized to obtain equivalent static force for a dynamic force so as to takecare of reduction in the strength of the concrete and steel due to repeatedloading. The factor should be assumed as 3 unleu otherwise specified.

7

IS I 2974 ( Part I ) 19823. NOTATIONS3.1 The notations given in Appendix A shall.apply.

4. NECESSARY DATA4.1 Data to be Provided by Machine Manufacturer - The manu-facturer should provide information as outlined in 4.1.1 to 4.1.3.

4.1.1 Generala) Description of driving and driven machinery,b) Operating speed or speed ranges,c) Number and arrangement of cylinders,d) Distance between axis of main shaft of the machine and the top

face of foundation,e) Maximum rated output,f) Gear box ratio where applicable, andg) Maximum operating temperature in the bases of the machine.

4.1.2 For Static Design4.1.2.1 A detailed loading diagram comprising plan, elevation and

section showing details of communication and point of all loads onfoundation.

4.1.2.2 A detailed drawing showing the position and size of mount-ing feet and details of holding down bolts.

4.1.3 For Dynamic Design4.1.3.1 Details of out of balance forces and couples shall be given,

together with associated frequencies for all possible moles of vibrationfor driving and driven machinery. These include the following:

a) External forces,b) External primary couples,c) External secondary couples, andd) Harmonic torques.4.1.3.2 Mass moments of inertia of driving and driven machine

about three principal axes shall be indicated.4.1.13 Additional information relating to specific machines, as given

below, shall be provided where necessary:a) Loads due to dynamic short circuit conditions, andb) Loads due to an abnormal sudden stoppage.

8

IS : 2974 ( Pa.-t I ) 19824.1.3.4 Where it is foun-l necessary to usc anti-vibration mountings,

the type and positions be indicated.

4.2 Data OD Ground and Site Condition. - The following soil datashall be known:

a) Soil profile and soil ch aracteri-t ics up to a c'epth at least threetimes the expected mean plan rliuenaion of the founc ation whichcan be taken as the square root of the expected area, or hardstrata.

b) Soil invostization to the extent necessary in accordance withIS : 1892-1979* and for the determination of dynamic p: opel tiesof soil in accordance with IS : 5249-1977t.

c) The relative position of the water table below ground at differenttimes of the year.

5. DESIGN CRITERIA

5.1 Geaeral5.1.1 The foundation structure of machine shall be isolated at all

levels from the main building and frorn other foundations as far aspossible.

5.1.2 Overhanging cantilevers where unavoidable shall be designed toensure rigidity against vibration.

5.1.3 All machine foundations shall sari- fy two fundamental criteria;that resonance does not occur between the frequcncie- of the pulsatingloads and natural frequency of foundation/soil system and also theamplitude of vibration does not exceed safe limits. Design criteria basedon frequency and amplitude limits can be classed as follows:

a) Limits set by the possibility of c1amagc or uneconomic wear tomachinery or associated equipment or both,

b) Limits set by the possibility of damage to building structures,c) Limits of structural borne vibrations to ensure confort of person,

andd) Limits set by possibility of disturbance of ground resulting in

unacceptable settlement of foundation .

Code of practice for subsurface invesrigation for r('undatjon~ (fir,~t rerision ).tMethod of test for dvn rminarion of d) nam.c prOpt r ues of soil l fir:,/ rtlJiJlOn ).

9

IS s 2974 ( Part I ) 19825.2 Frequency Ratio - Wherever possible the natural frequency ofthe foundation soil-system shall be higher than the highest disturbingfrequency and the frequency ratios shall not be r-orrnally less than 04.Wilere this is not possible, the natural frequency of the foundation-soilsystem shall be kept lower than the lowest disturbing f cquency. The fre-quency ratios in such cases shall not be lower than 150. While the abovecriteria shall be appliei to all possible modes of vibration, it may be per-rntted to operate machines closer to the resonance in certain modes ofvibration provided the resulting amplitudes do not exceed the permissiblelimit.

NO'rlC - Even though machine may be balanced, minor disturbing forces canoccur due to manufacturing tolerances and other causes, for sensitive installation"the frequencies arising from these may have to be considered.

5.3 Permis.ible Amplitude.

5.3.1 Limitations ofVibration Amplitude to Avoid Damag to Machin,ry - Thisshall be specified by the manufacturer and shall in no cases be exceeded.Where no specific limit has been stated by the manufacturer, it may betaken that foundation satisfying the following amplitude criteria shallprovide a satisfactory base for machinery.

5.3.2 Limitations of Vibration Amplitude to AvoidDamage to Machinery -The damage in neighbouring buildings due to resonance will be negligi-ble if the amplitude vibration of the foundation is less than 200 micronsat frequencies below 20 Hz, where the disturbing frequency exceed 20 Hz,a lower amplitude may be necessary for certain instal'ations, when avalue corresponding to the frequency may be read off line ADD' ofFig. 3.

5.3.3 Limitation of Vibration Amplitude to Acoid Discomfort of Persons -For low speed machines, it is unlikely that founlations which satisfy5.3.2 will produce vibrations of sufficient amplitude to be disturbing topersons. In special cases where there are particular reasons to avoiddiscomfort to personnel, a low permissible amplitude corresponding tooperating frequency of machine can be read off from Fi~~. 1.

5.3.4 Limitations of Amplitude to Avoid Settlement - For most soil types,foundations for low speed machines designed to Iirniring' arnnlitudeof 200 microns will not suffer unlue settlement due to dynamic loads.In case of some soils like loose san i4J an i silts in conjunction with highwater table, there is a possibility of significant settlement to occur. Inall such cases, it shall be preferable to consolidate the soil underneaththe foundation.

10

IS : 2974 ( Part I ) 1982

A-e -'I: U" I' !\.

"- ~ ,I\.

"

,~ 1\ \

~r\. ~ i\,~

""\.~~ 1\ "r\ \r\~ '\

'""

,

'"~~ '\.. ,'-.

"~

"~ \

r\. \. ~r\. ~

,1\

r\~ \,

~ ~ 0'r"I~ ,r\

1\ ~ C,

" A'

250200150

100

75

50

..

-en 2SwQ: 20...w

15Zi

~ 10S 75f/)z 500;::Ca:Gl> 250IL 2'000

150ll~0~

'00~-JQ.24(

050

Q255 10 20 30 so tOO 110 ( HZ ,

DISTURB'NO FREQUENCYLine ADD' Limit to Avoid Damage to Buildings

Line ACe' Limit to Avoid Serious Discomfort to PersonsLine ABO' Limit to Ensure Reasonable Comfort to Persons

NOTIl - These Limits do not include any factor of safety.

FIG. 3 AMPl.ITUDE LIMITS OF FOUNDATION l~LOCK11

IS I 2974 ( Part I') 19825.4 Concrete Foundation Desjgn

5.4.1 General Cotzditions - Normally concrete block foundations aredesigned for reciprocating machines. Both the foundations and machinesare usually taken as a single body resting on an elastic bedding. (Sub-soil or resilient mounting). The foundation is subject to oscillations atdeterminable frequencies in six degrees of freedom ( Fig. 2 ).

Pile foundations may be used in cases where the soil con-Iitions areunsuitable to support block foundation or when natural frequency of theblock foundations needs to be raised in cases where it is impossible toalter dimensions or when amplitudes or settlement or both need to bereduced.

Cellular foundations may be used in special cases where it isnecessary to maintain the rigidity of a block foundation but with masssaving of concrete. Wherever possible provision shall be made incelJular foundations to add mass by filling the voids to adjust the naturalfrequency of foundation block provided this does not result in additionalsettlement.

5.4.2 Dimensions of Concrete Foundation Blocks - For initial dimensioningof the concrete foundation blocks, the following empirical rules may beallowed.

5.4.2.1 Mass of the foundation shall be greater than that of themachine.

5.4.2.2 The eccentricity of foundation system along axis xx/rrshall not exceed 5 percent of the length of the corresponding side of thecontact area. In addition, centre of gravity of machine and foundationshall be if possible below the (OP of foun.lation block.

5.4.2.3 To ensure reasonable stability in the case of verticalmachines, the total width of the foundation ( measured to right anglesto shaft) shall be at least equal to the distance from the centre of theshaft to the bottom of the foundation. In case of horizontal machines,where cylinders are arranged laterally the width shall be greater.

5.4.2.4 The proportion of foundation block shall be such to ensurestability.

5.4.3 Final Design of Foundation Blocks - The final dimensions of aconcrete foundation shall be derived from vibration calculations andshall consider:

a) The dimensions of foundations by empirical rules,b) The bearing pressure due to c'ead and imposed load,c) The natural frequencies of the system for six modes of vibrations,

12

IS : 2974 ( Part I ) 1982d) The relationship between the exciting frequency and natural

frequency of the foundation-soil system,e) Calculated amplitudes in the various modes of vibration, andf) Influence of water table specially when at a high level.Appen lix B ~ives the design procedure for an undamped system.

However, damping can also be considered in certain cases.5.4.3.1 Full value of permissible stresses for steel and concrete as

specified in IS: 456-1978- shall be allowed if dynamic loads areconsidered in detailed design by applying suitable dynamic and fatiguefactors.

Dynamic Elastic Moduluskgf/cm2

250 000300 000

340 000370 000

M 15M 20M25M 30

5.4.3.2 The following dynamic elastic modulus of concrete may beused in design:

Grades of Concrete

5.4.3.3 The soil stress below the foundations shall not exceed80 percent of the allowable stress under static loading determined inaccordance with IS: 64031981,. When seismic forces are consideredalJowable stress in the soil shall be increased as specified in IS : 18-)3-1975t

5.4.4 Supporting foundation blocks on end-bearing or friction pile!shall be considered in cases where there is need to make a significantchange in frequency in one or more modes of vibration or dead loads.

Pile caps where used as a founiation block shall be of such a size asto meet all design criteria, and be not IE'sS than 60 em thick.

5.4.4:.1 Rrquiremen: of piledfoundations - The most usual reasons foradoption of pi1e~ foundation are as follows:

a) When pressure on the soil under the block exceeds the permissiblebearing pressure;

.Code of practice for plain and reinforced concrete ( ,1I;,4,ttiriotl ).If"Code of practice for determin rtion of bearing capacity of shallow foundations

( first revision ).*Criteria for earthquake resistant design of structures ( tlaird ,lVisUHt ).

13

18 I 2974 ( Part I ) 1912

b) When a foundation is found to be subject to resonance, or whenan increase in the mass of the block is either unduly wasteful inmaterial or ineffective due to the danger of resonance in othermodel;

c) When a block foundation is low tuned by one mode and hightuned by other and desirable or specified frequency ratioscannot be maintained simultaneously;

d) When the amplitudes of movement of a block foundation are inexcess of their permissible values;

e) Piled foundation shall be used when a raft foundation is liable tosuffer a differential settlement exceeding the permissible limit; and

f) Piles may be used to minimize the effect of ground bornevibration on surrounding foundations and equipment.

5.4.4.2 Evaluation of pile soil stiffness - Pile soil stiffness factors bothin vertical and horizontal ( see IS : 9716-1!181* ) modes of vibration shallpreferably be determined by conducting in situ test on piles. I n cases,where it becomes difficult to conduct this test, the values can be takenfrom some standard publications. The centre of gravity of the system,that is, foundation and machine shall be located within 5 percent of thelength of foundation to concerned axis with respect to the centre ofgravity of the pile group.

5.4.4.3 DeJign considerations

a) Pile-soil stiffness factors both in vertical and horizontal modesof vibration shall be determined by conducting in situ dynamictests on piles. For preliminary design however the computativemethod of estimation of pile-soil stiffness can be adopted.

b) Usually in situ dynamic tests are conducted on single pile withfree head condition. In actual practice the pile shall be used ina group with pile heads largely restrained by the pile cap.Allowance shall be made for these factors in evaluation of pile-soil stiffness to be adopted for design. Failure to take account ofthese factors will lead to error in estimating stiffness of the system.

c) After evaluating the pile-soil stiffness, the design aha]I becarried out in the same way as for the block foundation restingdirectly on soil.

-Guidelines for lateral dynamic load teat OD pilei.

14

IS : 2974 ( Part I ) 19825.4.5 Minimum Reinforcement in Block Foundations

5.4.5.1 Minimum reinforcement in the concerete block shall be notless than 25 kg/m3. For machine, requiring special design considerationsof foundations, like machines pumping explosive gase~ the reinforcementshall be not less than 40 kg/ln3.

5.4.5.2 The minimum reinforcement in the block shall usuallyconsist of 12 111m bars spaced at 200/2jO m m centre to centre extendingboth vartically and horizontally near all the faces of the foundationblock.

5.4.5.3 The following points shall be considered while arranging thereinforcements:

a) The en-Is of mild steel (if used) shall always be hookedirrespective of whether they are designed for tension or com-pression,

b) Reinforcement shall be used at all faces,c) If the height of foundation block exceeds one metre, shrinkage

reinforcement shall be placed at suitable spacing in all threedirections, and

d) Reinforcement shall be provided around all pits and openingsand shall be equivalent to 0-50 to 075 percent of the cross-sectional area of the opening.

5.4.6 ATlti- Vibration Mountings5.4.6.1 Where it is found to be impracticable to design a foundation

consisting of a simple concrete block resting on the natural soils to givesatisfactory dynamic characteristics, it may be possible to reduce thetransmuted vibrat ions to acceptable levels by means of anti-vibrationmounting.

5.4.6.2 Depending upon the nature of the machinery and theinstallation, the anti-vibration mounting may be used:

a) Between machinery and foundation, andb) Between a foundation block and a supporting system.

6. CONSTRUCTION6.1 Concrete - Concrete strength shall be specified on the basic; of28-day cube strengt h. The concrete grade shall be at least M-lS( according to IS : 456-1978 ).

*Code of practice f,)r plain and reinforced concrete ( third revision ).

15

IS I 2974 ( Part I ) ~ 11826.2 CODtiDaity or Work - Foundation block shall preferably be castin single continuous operation. In case of very thick blocks ( exceedingabout 5 m ) if needed, construction joints can be provided. In such aevent construction joint shall be suitably designed by the designengineer and shown in working drawing. In the event of an unforseeninterruption in concrete, the resulting unavoidable joint shall beconsidered as a construction joint and treated in the same way as cons-truction joints.6.3 Cemeat Groat

6.3.1 Cement grout used for fitting or embedding shall consist of onepart of Portland cement and two parts of clean sharp sand mixed to amoist consistency sufficient to facilitate the grout being fully workedunder all seatings. Quick setting cement shall not be used.

6.3.2 Additives may be employed to give non-shrink properties tocement grout. In this case the ratio of cement and sand may be variedaccording to the instruction of manufacturer.

1.3.3 Cement grout shall be placed within a period commensuratewith cement type but not later than one hour from the time of mixing.6.4 GroutiDl

6.4.1 All metallic and concrete surfaces shall be thoroughly cleanedand washed to clean all dirt, oil, grease, loose particles and cementlaitance, The concrete surfaces shall be roughened and saturated withclean water and kept wet for at least 24 hours and all surplus waterremoved and surfaces cleaned, oil free with compressed air if requiredbefore commencement of grouting. .

6.4.2 Provision shall be made if required to avoid trapping air. Airrelief holes shall be provided, if necessary.

6.4.3 Forma shall be high enough to provide a head of the grout onaU sides which shall be about 150 mm high on side from which cementgrout is to be poured. Forms shall be placed with sufficient clearance-to the edges of the bases to enable the grout to be properly worked intoposition.

6.4.4 Forms shall be strong and secure and well covered to preventleakage. The cement grout shall be poured from one side to avoidforming air pockets and be carried out continuously without interruption10 that filJing is continuous and dense,

'.4.5 On completion of the curing of the grout underfill the machine-than be finally checked to ensure that itl alignment is acceptable.

6.4.6 Exposed surfaces of grout and concrete shall be prepared andliven two coau of an oil and alkali resistant coating.

16

IS : 2974 ( Part I ) 19827. TESTING AND MEASUREMENT OF VIBRATION7.1 General - Testing of a foundation block prior to the initialrunning of the machinery may, where warranted be carried out todetermine the natural frequencies in various modes of vibration and theamplitudes due to dynamic forces likely to occur either during normalrunning or during emergency or adverse running conditions of themachine. The observation can also be made durin.'{ the operation ofmachines.7.2 Excitation - In case where blocks are to be tested prior to therunning of machines, foun dation blocks may be excited either by anelectromagnetic or hydraulic vibrator. The block shall be excited insame modes of vibration as is expected from the operating machinery.The amplitudes of motion which can be induced with a scale downdisturbing force may be significantly smaller than those expected in theoperation of machine. Allowance may have to be made for the non-linearity of soil response.7.3 Mea8aremeDt.

7.3.1 The vibrations shall be measured by transducers having a linearresponse over the range 2 to 200 Hz. The accuracy of transducers shallbe better than 10 percent and they shall respond to a uniaxial motionwith more than 10 percent cross sensitivity.

'7.3.2 The transducers shall be preferably piezo electric type or geo-phones meeting the requirements as in 7.3.1.

7.3.3 The transducers shall be mounted firmly to the foundation. Thetransducers shall not be merely rested on the foundation or held withhand.

7.3.4 Transducers shall preferably be placed on extremities of theupper-most surface of the block and as near as possible to the axis of Xand r ( see Fig. 1 ).

7.3.5 In order to gain full picture of the behaviour of a block, it shallbe desirable to use a multiple channel recorder with Cfilter', singlechannel recorder can also be used in small installations.

7.3.6 It sh4,11 be preferable to use Vibration Analyser which canmeasure frequency and amplitude of vibration-simultaneously.

17

IS I 2974 ( Part I ) 1982

APPENDIX A( Claus 3.1 )NOTATIONS

cm

em

UNIT

em!

radian

dimension-leis

kg-s/emkg/cm3

kg/em3

kg/em3

DESCRIPTION

Area of foundation in contact with soilHorizontal amplitude of foundation subjected to

horizontal force P. and moment M tVertical amplitude of foundation subjected to

vertical force P,Rotational amplitude of. foundation subjected to

horizontal force Ps and moment M,Damping constantc

SYMBOL

.If

Critical dampingCoefficient of elastic uniform compression of soilCoefficient of elastic uniform shear of soilCoefficient of elastic non-uniform compression

of soile Eccentricity of eccentric weight of rotating parts ernf Frequency cls1ft Natural frequency cIsf"I,!'" First and second natural frequencies of founda- cIs

tion subjected to horizontal vibrationJ,.l,j"l,j"a First, second and third natural frequencies of cIs

foundation when centre of gravity of mass ofmachine and foundation and the centroid ofthe founration contact area with soil lies onvertical plane bu t not on the same verticalline

fft.

'...

Horizontal resonance frequency of foundationand soil system

Vel tical resonance frequency of foundationand soil system

cIs

cIs

18

SYMBOL

I,,;

h

I

k

L

M".

m

w

w

IS I 2974 ( Part I ) 1982DESCRIPTION UNIT

Rotational resonance frequency of foundation cIsand soil system

Height of the top surface of the foundation emabove the centre of gravity of the found-ation and machine

Moment of inertia of contact area with res- cm'peet to the axis of rotation passing throughthe centroid of the area

Stiffness of spring kg/cm

Distance from mass centre of gravity of the emvibrating system with respect to the axis ofrotation

Dynamic moment kg/em

Mass moment of inertia of the vibrating system kg-em-slwith respect to the axis of rotation passingthrough C G of the system .

Mass moment of inertia of the vibrating system kg-cm-slwith respect to the axis of rotation passingthrough centroid of contact area of founda-tion with soil

Mass of vibrating system kg-s2/cm

Mass of eccentric weight of rotating parts kg-s2/em

Oscillating force applied at the centre of kggravity of vibrating mass

Weight of foundation and machine kg

Eccentric distance from centroid of contact cmarea of foundation with soil to the C G ofmass of machine and foundation

Circular frequency radian/s

Circular natural frequency radian/s

19

18 : 2974 ( Part I ) 1982APPENDIX B

( Clause 5.4.~3 )ANALYSIS FOR THE DETERMJNATIO}\-! OF NATURALFREQ,UENCIES AND AMPLITUDES OF FOUNDATIONS

ACCOMPANIED BY SIMULTANEOUS ROTATION,SLIDING AND VERTICAL DISPLACEMENT ( MASS

SPRING ANOLOGY )B-1. LJmitiDB Natural Frequeucies - The limiting naturalfrequencies.shall be calculated as fo110\\'5:

/2 C,I -- WL",p == 4'1t'M~--

fl eTAand z:: - _.

fie 41t1 m

B-2. Check 08 De.ilB

B-2.1 When the centre of gravity of mass of machine and founr'ationand centroid of contact area of foundation lie 00 the same vertical line,the vertical vibration of foundation is independent of vibrations inhorizontal direction and rotation about the horizontal axis. The naturalfrequencies should be calculated as follows:

1 ~C--In.-=:- ~21t m/1 == _1 [J2 + /2 __ r(fi-~ /2)2 _ 4:,/i72Jia1 2y ft, U I\J -,p' ... '-; ,,~fl _1[fl /2 r(12 /1 )1 - 4y /2 fS J"i - 2y "; + + I\J "; + WI: "; ... _

where Y &:: M ../M.oe

Amplitudes are calculated al follows:

",.. cuIA,----------V ( k - III ce,1)2 + CI wi20

IS I 2974 ( Part I ) 1982

( C tP I - WL + C-rAL2 - M m(u2 ) P.c C",ALMiA;,- "

16 1t4m u; (f2 .- f2 ) (/2 - /2 ),.1 n;!

A __C-r1LPJ: ( C-r.1 - m w2 ) Mi~ 161t4m M m ( f 2 - f 2, ( f 2 - f 2 )

n1 "2

B-2.2 The maximum displacement of the top edge of the foundationis equal to A~ + h AeP where h is the height of the top surface of thefoundation above the centre of gravity of the foundation and machine.8-02.3 When centre of gravity of mass of machine and foundation, andthe centroid of the foundation contact area with soil do not lie on thesame vertical line, the vertical vibration is not independent of horizontalvibration ond rocking. The equation governing the natural frequenciesis

f2 Ei') =" ...

where E

i (f2 - f) (f2 _/2) (/2 -12 ),.z n " 1 n ,,2 n

u -12 )f2n% n nz

Eccentric distance from centroid of contact area offoundation with soil to the centre of gravity of mass ofmachine and foundation

. AIm1 = - ---

TIl

B-2.4 Plot the expression on the right hand side versus 1,.2 assumingarbitrary values of /r. Draw a straight line corresponding to the left handside of the above equation. The abscissas of points of intersectionof the t \\"0 plots give the unknown roots ]2 j~2 and j2 which are the

,,1 n2 ,,3,three natural frequencies of the foundation.

:l'\O'fE ~ For foundations having a relatively sma ll ('(Tt 'nt l'ic ity, srty 5 percent of t hr-l{,1Jg~ h of a side of the' foundation contact art-a its ef1('ft Ina)" L

IS : 2974 ( Part I ) 1982( CiJlllilllll'.l from page 2 )

Foundat ions Subject to Dynamic Loads Subcommittee, BDe 43Represtntiflg

Engineers Tndia Limited, New Dr-lhi

(:: miud ia Cornpany Lim itcd, BombayCentra] Building Research Institute (CSIR).

Roorkr-(~pnlral Elt'ctricity Aut hor it v , New Dp]hi

( Alternate , .Univcrsit y orRo(,rkec, RoorkceMr-ml lurg icn l & Engin('('ring Consultants ( Indi~t )

Limited, Ranchi

Convener

DII: r~;\'Clll ( Tel) )n- nll~,j':C;1'OH ( TCf> )

nit ~'l. K. C;tJP'1 :\SHIt( .\. jl. "Nlu:, In~Il.JFg

SJlltl T. K. I). ~1('N'~iHMembers

S It H , J. K. B\ fl C If r ( .1ftanate t ()Shri 'r. K. D. Munvi \

SHH J :':. K. B \~,: /SHin CII.\~L)lt'\ PH\K.\SH

Snru A. R,"t.\ RAO ( Allernr.fr)SHUT A. K. !\{l'}{}-lF:IClJ':I'; Developrnr-nt Consu lt ants Lirn itcd , Calcutta

SHit IS. K. :\ I \~ }) vr. ( .ttl" na! r ')SHIH P. C. N\(; National 'Fhr-r ma l Power Ctlrpuratiufl Li m itc-d,

Nc\" I)flhiSIIHT ;\SIlOK TI~EII \N ( Altcmate )

SIIIlI \1. V. P.\:"llllT Bharat Heavy lIer n ica ls Lim iu d , BJII)palSflltI E. C. II. r; RF.r)/) ( Altcr.iatr )

SlIHI D. H. P '.'1'1"[. Th Fr-r t il iz r (Planning S: De\/II)pn1t nt) l n.l i..Li m iu-d , Dh.i nba.!

SnItl S. P. r: \ltU ( Alternate )I)ll P. SI~tNtV \~'I.fT Structural rn~~inr(,1 ing- Re

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