Indian Standard

GUIDELINES FOR IMPROVING THE CYCLONICRESISTANCE OF LOW RISE HOUSES AND

OTHER BUILDINGS/STRUCTURES

ICS 91.120.99

0 BIS 2004

BUREAU OF IN DIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

October 2004 Price Group 7

-.

1Cyclone Resistant Structures Sectional Committee, CED 57

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the CycloneResistant Structures Sectional Committee had been approved by the Civil Engineering Division Council.

Cyclonic storms form faraway from the sea coast and gradually reduce in speed as they approach the seacoast.Cyclonic storms generally extend up to about 60 km after striking the coast. Cyclones associated with highspeed winds followed by heavy rains and accompanied by surge have been causing untold misery to the populaceand wide spread devastation of properties in the coastal belts of India. The frequency of cyclonic storms ismore along the east coast as compared to the west coast of India. The coastal regions of Tamil Nadu, AndhraPradesh, Orissa and West Bengal on the east coast and Gujarat on the west coast are cyclone prone. Damageto houses is most responsible for loss of life and thus the need to have greater emphasis on the safety of houses.Due to this, need has been felt to evolve national standard for design and construction of cyclone resistantstructures so as to ensure desirable level of safety. The provisions given in this standard are intended to reducethe damage to buildings and structures in the event of a cyclone.

This standard covers the guidelines regarding planning, design and construction aspects for improving thecyclonic resistance of low rise houses and other buildlngs/structures.

The composition of the Committee responsible for formulation of this standard is given in Annex B.

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For the purpose of deciding whether a particular requirement of this standard is complied with, the final value,observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance withIS 2:1960 Rules for rounding off numerical values (revised). The number of significant places retained inthe rounded off value should be the same as that of the specified value in this standard.

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IS 15498:2004

Indian Standard

GUIDELINES FOR IMPROVING THE CYCLONICRESISTANCE OF LOW RISE HOUSES AND

OTHER BUILDINGS/STRUCTURES1 SCOPE

This standard covers the guidelines regardingplanning, design and construction aspects forimproving the cyclonic resistance of low rise housesand other buildings/structures.

2 REFERENCES

The standards listed in Annex A contain provisions,which through reference in this text, constituteprovisions of this standard. At the time of publication,the editions indicated were valid. All standards aresubject to revision, and parties to agreements based onthis standard are encouraged to investigate thepossibility of applying the most recent editions of thestandards as given in Annex A.

3 CYCLONIC WIND FIELD

3.1 Cyclones are vortices in the atmosphere having acore called the eye of extreme low pressure and lightwinds, surrounded by strong winds having nearlycircular contours of equal pressure called isobars. Thecirculatory system is in the anti-clockwise direction inthe northern hemisphere. The radial distance from thecentre of the eye to the region where the maximumtangential wind velocity occurs is called the radius ofmaximum winds (RMW). The wind speed falls offgradually beyond this region and the approximatewind velocity distribution is given by:

whereV(r) =r. =

v. =

cr. =

a()V(r)=VO ~velocity of wind at a radial distance, r;radius of maximum wind (RMW);velocity of maximum wind; anda power law exponent varying between 0.4to 0.6.

NOTE r and ro are to be measured from the centre of the eyeof the storm.

3.2 In the interior region to the radius of maximumwind the velocity distribution may be assumed aslinear varying from zero at centre of eye.

4 CYCLONIC WIND SPEED FOR DESIGN OFBUILDINGS AND STRUCTURES

It is known that higher wind sped occurs duringcyclones compared to non-cyclonic storms. Further,there is a greater degree of turbulence in such stormsand the probability of occurrence during the life timeof a structure is also large. Therefore, structures aresubjected to greater risk under cyclonic storms. Toaccount for the enhanced risk, an enhancement factorf, whose value is equal to unity for dwellings, 1.15for industrial buildings, and 1.30 for structures ofpost-cyclone importance shall be considered whiledetermining the design wind speed. The design windspeed vd

where

f=

kl =

kz =

ks =

vb =

z =

at any height z in mh shall be taken as:

vd =fkl kz k3 vb

enhancement factor for cyclonic risk;

probability factor (risk coefficient);terrain, height and structure size factory

topography factoq

basic wind speed; and

a height or distance above the ground.

The values of kl, h, kq, and Vb shall be as specified inIS 875 (Part 3).

NOTE In the design of special srnrctures, such as, chimneys,overhead transmission line towers, etc, specific requirements asspecified in the respective Cbdes may be followed.

5 PRESSURES AND FORCES

5.1 The ptwstues and forces, both global and local,shall be computed using the coefficients given inIS 875 (Part 3) for various types of buildings andstructures.

5.2 Unless measures have been taken to ensure thatdoors and windows would stay in position during astorm, failure of the closing element over the largestopening shall be considered for computing thepercentage opening (permeability) in addition to anyfully vented openings.

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IS 15498:2004

6 GUIDELINES FOR PLANNING

Though the cyclonic storms always approach from thedirection of the sea towards the coast, the windvelocity and direction relative to a building remainrandom. Hence, reduction coefficients fordirectionality and orientation of buildings in apreferential direction are not feasible. The generalguidelines on planning include:

a)

b)

c)

d)

e)

0

g)

h)

As far as possible, the building shall befounded on good ground. Part of the buildingon good ground and partly on made upground shall be avoided [see Fig. 1 (a)].

Regular plan shapes are preferred. Re-entrant corners are to be avoided [see Fig. 1(b)].

For individual buildings, a circular orpolygonal plan is preferred over rectangularor square plans but from the view point offunctional efficiency, often a rectangularplan is commonly used. Where mostprevalent wind direction is known, a buildingshould be so oriented, where feasible, that itssmallest facade faces the wind.

A symmetrical building with a compact plan-form is more stable than an asymmetricalbuilding with a zig-zag plan, having emptypockets as the latter is more prone towind/cyclone related damage [see Fig. 1(c)].

In case of construction of group of buildingswith a row type or cluster arrangement,cluster arrangement can be followed inpreference to row type. However, in certaincases, both may give rise to adverse windpressure due to tunnel action and studies needto be conducted to look into this aspect [seeFig. 1 (d)].

Long walls having length in excess of 3.5 mshall be provided with cross walls or in-tegrated pilasters [see Fig. 1 (e)].

Buildings are not to be located in low-lyingareas as cyclones are invariably associatedwith floods.

In hilly regions, construction along ridgesshould be avoided since they experience anaccentuation of wind velocity whereas

j)

k)

m)

n)

P)

Except in case of buildings with large spanwith sloped roofs, roof pitches having a slopeless than 1 in 3 shall be avoided [see Fig. 2(a)].

Hipped roofs are preferred to gabled roofs fornon-engineered and semi-engineered build-ings as the peak suction pressures for allangles of attack are lower in the former case,and may be taken as 80 percent of those onpitched gabled roof in the absence of moredetailed information [see Fig. 2 (b)].

The percent of the total opening in the cross-section of the frontal wall shall be less than50 percent of the width of the wall, Openingin load bearing walls should not be withh adistance of h/6 from the inner comer for thepurpose of providing lateral support to crosswalls, where his the storey height up to cavelevel [see Fig. 2 (c)].

While planning a lay-out for group housing,if the inter-building spacing is less than twicethe width of the building considerable shield-ing is available for the interior buildingsthough the first two columnshows attractlarger forces compared to a stand alone build-ing.

In regions where storm surges lead to coastalinundation, buildings should be located athigher ground levels. If high ground is notavailable buildings may be constructed atraised earthen mounds suitably surroundedby retaining walls. Alternatively, buildingsmay be constructed with stilts with nomasonry up to maximum surge level.Suitable bracings may, however, be providedin case of multiple hazard zones, particularlydue to earthquake, to avoid failures arisingout of large variations in stiffness betweenstilt and higher floor levels.

7 GUIDELINES FOR NON-ENGINEEREDCONSTRUCTION

All construction though using the conventionalbuilding materials but made intuitively withoutcarrying out a proper structural design and orconstructed without adequate control at site, withrespect to both materials used and constructionpractices employed, may generally be termed asnon-engineered construction. All construction in lowstrength masonry or clay mud and similar other forms

valleys experience lower speeds- in general[see Fig. 1 (f)].

of biomass with fall under the category ofnon-engineered construction. The measures suggested

2

H

-.,, -

LESS PREFERRED ORUNDESIRABLE IMPROVED / PREFERRED

MADE - UPa GROUND MADE - UP GROUND

AYAYAY A\ A\A\A ------ ------ .

GOOD GROUND

b

PLAN OF THE BUILDING PLAN OF THE BUILDING

c 1

FIG. 1 IMPROVEMENTSFORBUILDING LAYOUTS TO REDUCEDAMAGES DUETO CYCLONES (Confinued)

3

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LESS PREFERRED ORUNDESIRABLE IMPROVED / PREFERRED

d BBR 0095

~35m) -u

[II

e n

INTEGRALPIIASTER

m

ROSSWALL

ONG WALL WITHOUTINTERMEDIATE PIIASTERS

C35m

f

FIG. 1 IMPROVEMENTSFORBUILDING LAYOUTS TO REDUCEDAMAGESDUE TO CYCLONES

-. .,,

IS 15498:2004

LESS PREFERRED ORUNDESIRABLE

PITCH < y6SPAN

I

t----

----

*$ I/@\\

GABLE ROOF SHOULD BE AVOIDED

y l

~t+&l T

a-

0 _-

a h

//A\\ ?//A-(A+B+c)>D12

a < h/6

lMPROVED/ PREFERRED

EplTCH>f/SPAI

--------

. .

HIPPED ROOF SERVES BETTER

r?

{A +B)< D/~a > h/6

t

-{

FIG. 2 IMPROVEMENTSFORROOFSAND WALLS OFBUILDINGSTO REDUCEDAMAGES DUE TO CYCLONES

5

- . . ......

IS 15498:2004

LESS PREFERREDOR UNDESIRABLE

-+

a

Max. FLOODLEVEL . . .... -== ----

L

MUD WALL

lMPROVED/ PREFERRED

THATCH ROOF

PLASTERINGWITH WATER -MUD WALLpROOF MORTAR-

Max FLOOD LEVEL----

. ---

PROTECTIVE _iiARRIEROR REVETMENT BUILTWITH STONE OR BRICI$

FIG. 3 IMPROVEMENTSFORTHATCHED ROOFSAND MUD WALLS TO REDUCEDAMAGES DUE TO CYCLONES

here-in enhance the cyclonic wind resistance tosignificantly higher levels, but still lower thansemi-engineered and engineered buildings covered in8 and 9.

a)

b)

c)

d)

e)

f)

g)

h)

The aerodynamics of flow around buildings,leads to large suction pressures on the roof.To reduce problems due to flying-off ofthatched rix)f, it may be held down to theframe work of the roof or the building en-velope using organic ropes. As organic ropeshave short life, the holding down ropes alonemay be changed every year prior to the mostprobable month of occurrence of cyclones.Diagonal pattern of rope is preferred [see Fig.3 (a)].The overhang of the roof beyond the wallshall be limited to 450 mm. In case it exceedsthis value, the projected portion of the roofmay be properly tied back to the wallframework.All the posts buried below ground level shallbe painted with a coat of coal tar up to thelevel of maximum flood dk+charge.The main posts shall be firmly anchored tothe ground using suitable anchor poles. Theminimum depth of anchorage for the mainposts shall be 900 mm and the minimumlength of anchorage bars shall be 450 mmwith a minimum bearing areaof22500 mm2.Each post shall have four anchor poles, asshown in Fig. 3 (b) at two levels at least at500 mm interval in different directions.As mud wall is erodable, protection barrier orrevetment built with stone or brick shall bebuilt up to the maximum flood level, andplastering with special water proof clay orcement/lime mortar on outer surface isessential [see Fig. 3 (c)].In case of sloped roof, triangular frames asshown in Fig. 4 may be located with a maxi-mum spacing of 2.0 m. The members of thistriangular frame shall be sufficiently strongto hold back the cross runners. Suitable con-nections shall be ensured between variouselements of this frame using metal straps,bolt and nuts, and steel flats to enable betterintegrity for the structure as a whole (seeFig. 5 and Fig. 6).The main triangular frames are to be firmlyconnected to anchorage elements/bondbeams at the level of the eaves. Theanchorage elements in turn are to be con-nected to the main posts of the wall using Ubolts.Brick work in weak mortars and randomrubble masonry can be used for the walls. Inthese cases, the bond beam/anchorage beam

j)

1S 15498:2004

provided on top shall be anchored to thefoundation using mild steel rod properly en-cased in cement mortar. Alternatively if con-tinuous lintel is provided with reinforcedconcrete or wood with sufficient height ofbrickworldrubble masonry, the roof can beanchored to the continuous lintel. The totaldownward load due to weight of masonry androof shall have a factor of 1.50 over the totaluplift force on roof. The total area ofanchorage reinforcement provided shall betwice that required for transmitting the upliftforce.Discrete anchorage of roof into bricldrubblemasonry can be accomplished throughanchorage reinforcement. An angle of dis-prsion of two verticals to one horizontalmay be assumed. The shear strength ofmasonry shall be neglected in any computa-tion, and the effective weight of masonryabove shall be 1.5 times the uplift force atthe given anchorage based on simplifiedload-flow pattern.

~-v,fmw

I!iii!E+6mm GI BOLTaxzsmm MS PLATEHoRIZONTALJOINT A

6 LONGITUDINALAT CROWN3X Zsmm MS PLATE BJOINT B

_&le3x25mmMs~ LONGITUDINAL

AT EAVES HEIGHT

JOINTC

FIG.4 TYPICAL JOINT DETAILS

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IS 15498:2004

LONGITUDINAL

F

POLEGI/MS

STRAP 30 mm X26 GAUGE

r g4/ WIRE90 .mm CROSS PIECE.

I_

4S0 LONG

FIG. 5 ANCHORAGETO FOUNDATIONSIN THATCHED BUILDINGS

rlf 2 TURNS HEAVY~ NAILS WIRE 16 GAUGE

/MS STRAPmm x 26 GAUGE 4 TURNS

HEAVY WIRE

CORNER OF HIP ROOF RAFIERBRACE AND POST OETNM

FIG. 6 CONNECITONSUSING WIRES AND STRAPSIN THATCHED BUILDINGS

8 GUIDELINES FOR SEMI-ENGINEERED a)CONSTRUCTION

Semi-engineered buildings are buildings which havecertain elements structurally designed, such as, roofslabs and foundations but certain elements notproperly designed such as walls of masonry buildingsand in which the supervision may be throughEngineering staff or otherwise. The followingguidelines are useful in detailing semi-engineeredbuildings:

To achieve a certain measure of restraint fortiled roofs provide concrete or masonryrestraining bands at a spacing of ap-proximately 1.2 m to 1.5 m, These bands maypreferably be located over wooden raftersforming integral part of the truss system. Incase the bands are connected to the purlins Ubolts may be used and suitably anchored overthe reinforcing rod. The dimension of theband may be about 100 mm x 50 mm. Therestraining bands shall have at least one

.....

i)

c)

d)

e)

10 mm diameter bar placed inside the band.Typical details of improvements to tiledroof are given in Fig. 7. Hip, valley and ridgetiles shall be firmly embedded in continuousband of cement mortar. If nailing holesare available in these tiles, nails can beinserted through these into the mortar bedand these can effectively serve as shear con-nectors.The tiled roof system shall be securely fixedto a bond beam. The bond beam in turn is tobe connected to the foundation by holdingdown bolts. The holding down bolt shallbe designed with a factor of safety of2.0.Wherever asbestos sheets are used for roofcladding, U bolts are preferred when com-pared to J bolts. The numbers of U bolts atvarious locations are indicated in Fig. 8.In case hollow concrete block masonry isused for walls the designed reinforcementscan be taken through the hollow concreteblock forming a pilaster with reinforcementas shown in Fig. 9. The spacing of suchpilasters shall not be greater than 3.0 m. Thereinforcements are to be anchored well intothe foundation and integrated with lintel bandand bond beam (see Fig. 10).Good connections are required among thevarious wooden elements- in the roo~ andwall. Typical details shown in Fig. 11 andFig. 12 maybe adopted with modifications to

GABLED ROOF

f)

IS 15498:2004

suit the structural scheme. The important re-,quirement is that the uplift force on the roofis to be safely transmitted to the foundation.The connections must have adequate strengthto transfer the uplift force.If strong wall made of good quality brickwork is provided, the roof can be anchored tothe continuous lintel band through cyclonebolts.

9 GUIDELINES FOR ENGINEEREDCONSTRUCTION

Engineered buildings are buildings designed byArchitects and/or Engineers and properly supervisedby Engineering staff during construction, such as,reinforced concrete and steel framed buildings.Public buildings, such as, schools and hospitals,cyclone shelters, etc, have to be carefullyengineered.

In a cluster of buildings having similar heights andwhere the inter building spacing is less than 2 timesthe width of an individual building the followingenhancement/shielding factors are to be considered:

a)

b)

c)

For comer buildings located on the peripheryof the building clusters, the pressure loadingsshall be enhanced by a factor of 1.50.For all interior buildings a shielding factor of0.80 can be considered.The roof pressures on comer buildings of theouter rows shall be enhanced by a factor of1.50 in industrial sheds.

.. --

HIPPED ROOF

-q 100 pCONCRETE STRIPS

TILE MANGL

RAFTER _ *~30mm x 24 GALJGE

ORE

CONNECTION OF CONCRETE STRIPTO RAFTER

FIG. 7 IMPROVEMENTSTO TILED/AC SHEETSROOFTO REDUCEDAMAGES DUE TO CYCLONES

9

#

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IS 15498:2004

+

+----2nd Lth 5th 7th

#?

+@

SEALING WASHERFOUR FIXING PER SHEET ICORNERS)

k

2nd k th 6th

GI U HOOK BOLT THREE FIXING PER SHE E1(RIOGES)8 mm OIA

2nd 6th

J-HOOK BOLTS ARE NOT EFFECTIVETWO FIXING PER SHEET ( INTERIOR]

U-HOOK BOLTS AND WASHER ASSEMBLY ARERECOMMENDED LOCATION OF HOOK BOLTS

FIG. 8 DETAILS OFBOLTS

,ASTER

REINFORCED CONCRETE MASONRY PJLASTER WITH CONTINUOUS BOND BEAM

ODD COURSE 000 COURSEpa

EVEN COURSE EVEN COURSE

FIG.9 CONSTRUCITONOFCONC~E BLOCK MASONRY

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IS 15498:2004

RAFTER

d)

e)

f)

g)

RB

FIG. 10 FIX~G OF WALLS TO THEFOUNDATION USING TIE-DOWN BOLT

For evaluating the roof pressures on interiorbuildings, a shielding factor of 0.80 can beconsidered for gabled roofs.In all buildings where wind loading is thedominant loading no increase in allowablestresses in steel over and above that specifiedin IS 800 is permitted.In all buildings where load bearing masonryis used a parapet of minimum height 600 mmmay be provided. Also the roof slab may beanchored to the continuous lintel throughadequate ties.In multi-hazard prone areas with earthquakezones III and above, even if the design forcesare governed by wind loading, ductile detail-ing provisions as given in IS 13920 shall befollowed. The design forces would however

h)

j)

k)

be computed based on wind loading in suchcases.

In flood prone areas all public buildings in-cluding cyclone shelters shall be constructedon raised ground with appropriate peripheralretaining walls.If buildings are constructed with openingsat the ground levelhtilted buildings, ade-quate symmetric shear walls shall beprovided in both the principal directions ofbuildings. This is absolutely essential inmulti-hazard prone areas for earthquakeregions with zone-III and above.Wherever feasible, without compromisingfunctionrdity, the comers of the buildingsshall be rounded off with suitable radius ofcurvature so as to reduce the drag forces.

k.. ,..

IS 15498:2004

RAFTER

CONNECTING ROOFFRAMING TO WALL FRAMING

tER

FIG. 11 CONNECHON OFROOF FRAMETO WALL FRAME

~RAFTER

*

1

METAL(#!2

P RLINBRACKET

a) (X&E.CET;ON BY SHEET METAL

PURLIN7~RAFTER

b) CONNECTION BY WOOD CLEATS

FIG. 12 CONNECTIONDETAILS BETWEENPURLIN AND RAITER

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IS 15498:2004

m) In industrial buildings with gable roof plan to distribute the horizontal loading frombracing shall invariably be provided at the gable ends (see Fig. 13). Upper chord bracingbottom chord level of trusses to avoid bottom is also desirable at least near gable end walls.chord buckling due to uplift force as well as

,MS

NOTE:PURLINSNOTSHOWN

FIG. 13 WIND BRACING FORROOF TRUSSES

ANNEX A

(Clause 2)LIST OF REFERRED INDIAN STANDARDS

[S No. Title 1S No. Title

800:1984 Code of practice for general con- and structures: Part 3 Wind loadsstruction in steel (second revision) (second revision)

875 (Part 3): Code of practice for design loads 13920:1993 Ductile detailing of reinforced con-1987 (other than earthquake) for buildings crete structures subjected to seismic

forces - Code of practice

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IS 15498:2004

ANNEX B

( Foreword)COMMITTEE COMPOSITION

Cyclone Resistant Structures Sectional Committee, CED 57

OrganizationIn personal capacity (61, Civil Lines, Roorkee - 247667)Adlakha & Associates, New Delhi

Andaman Public Works Department, Port Blair

Building Materials & Technology Promotion Council, New Delhi

Central Buildhg Research Institute, Roorkee

Central Public Works Department, New Delhi

College of Engineering, GITAM, Visakhapatnam

Director of Town& Country Planning, Chennai

Engineer-in-Chiefs Branch, New Delhi

Housing & Urban Development Corporation Ltd, New Delhi

Indian Institute of Science, BattgaloreIndian Institute of Technology, Roorkee

Indian Institute of Technology, New Delhi

Indian Institute of Technology, Chennai

Indian Meteorology Department, New Delhi

Irrigation & CAD Department, Hyderabad-

Jadavpur University, Kolkata

Larsen & Toubro Limited, Chennai

Ministry of Agriculture, New Delhi

Public Works Department, BhubaneswarStructural Engineering Research Centre, Chennai

Structwell Designers & Consultants Pvt Ltd, MumbaiIn personal capacity (B XI18091 Vasanr Kunj. New Delhi-ll~7@BIS Directorate General

Representative(s)DR PREMKRISHNA(Chairman)SHRIPtWMODADLAKHA

SHRSNARSNDERKAPUR(Allemate)SHRIS. P. LALLA

SHRtB. N. NAGARAJA(Alfernate)SHRIT. N. GUPTA

SHRSJ. K. PRASAD(Alternate)SHRSB. S. GUiTA

SHruAJAYCHAURASIA(Alternate)CHtEFENGtNEER(D)

SUPEIWWENDINGENGINEER(D)(Affernae)DR S. SURYARAO

DRK. V. G.D.BALAJI(Alternate)SHRSR. ANBHAZAJAN

SHRtS. VENKATACHALAM(Alternate)LT-COLS. K. SHARMA

SHRIR. DAMODARAN(Alternde)CHAIRMAN-CUM-MANAGINGDtRFCTOR

SHRSMALAYCHATTERtEE(Alternate)PROF S. P.GOvtNDAMmDRS. K. KAUSHIK

DR N, M. BHANDARS(Alternate)PROF T. K. DAITA

DR A. K. JAtN (A1/ernate)PROF M. f?. PRANFSH

PROF C. P.VENDHAN(Alternate)SHSU A. V. R. K. RAO

SHRtS. C. GOYAL(Alternate)CHrEFENGINSER(CDG)

CHtSFENGtNEER(MAIlRRIOATION)(Alternate)DRBRATISHSENGUFTA

DRSOMNATHGHOSH(Alternate)SHRIP. R. VARADAR.WLU

StrrttT. V. B. S. SATYANARAYANAMURIWY(Alternate)SHRIBABUJACOB

Ms JANAKJUNEJA(Alternate)ENGtNEER-IN-CHt5F

DRN. LAKSHMANANSHRtS. GOMATHtNAYAOAM(Alternate)

SHRIR. N. RAttwrSHRtO. P. GGELSHruS. K. JAtN, Director and Head, CED

[Representing Director Generat (fix-~cio)]

Member SecretarySHSUALOKKESAIU

Deputy Duector (CED), BIS

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Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promote harmoniousdevelopment of the activities of standardization, marking and quality certification of goods and attending toconnected matters in the country.

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Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewedperiodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian StandardsSI1OUId ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of