MES INDIA STD TI 1 of 82

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TECHNICAL INSTRUCTIONS

NEW DWI-130 m18 APRIL 'f981. ,


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(0 Unsupported height and length ofwalls and slenderness ratio(g) Eccentricity in the bading(h) Combination of various loads to which walls are subjected.

.$; -, ,-. 8.1 These are generally of the following types:

INSTRUCTION NO 1 OF 1982CQP~TRUC~IONN LOAD BEARING WALLS

0.1 Load bearing masonry walls/brick work isnot new but suitably designedload bearing walls/br~ckwork s of comparatively recent origin. The first IndianStandard Code was issued in 196 1 and subseq uen tly revised in 1%9 and I 980,:IS1905 of 1980 'Code of Practice for structural safety of buildings Masoniywalls'. Inthe past twenty years there has been emergence of modern structuraI masonry formu1tistoreyed construction in many countries. The development has beenbased on application of structural engineerin principles to design of masonrystructures, thus overcoming the limitations of 'Kule of humby rocedures.0.2 Basic advantage of masonry construction lies in the fact that in loadbearing construction masonry performs a variety of functions viz; sup flingloads, sub-dividing space, providing thermal and accoudic insulation, i%andweather protection etc., which in framed buildings have to be provided forseparately.0.3 I n Western countries 12 to 20 storeyed well designed load bearingmasonry buildin s have been constructed havingonly 20 to, 4Ucm thick walls. Pnfndia quality o bricks manufactured are comparatively poor and maximumcrushing stren th generally is of order of 70 to 150 k cm*. In many Westernf fountries bric s of even medium quality have crus ing strength 400 o 600kg/cm4. A few mechaniseilbrick plants have since been set up at few laces in ourcountry and bricks af 150 to 250 kg/cmY trength are bein manu actured. Itk Pshould now be possible in some parts of India to go in or 5 to 6 storeyedload bearing structures at costs 15 to 20% less than RCC ramed construction.I . Z The structural adequacy of masonry waIls depends upon a number offactors as under:-

(a) Strengthofmasonry unit bricks or bIocks(b) Strength of mortar(c) Workmanship and method of bonding(d) Location of longitudinal and cross walls(e) Position and size of openings in the walls

. - (a) Cornman burni cloy brickSpecif icat ions are laid down n IS 1077of I976 'specifications for common burnt clay building bricks' (third re-


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, 2,..vision), Brkksareclassifiedasclass35,50,75,100,125,150,175,200,250,3O and 350 accordin toaveragecompressivestrength in kg ]cm9, Thesei!re further suklassi ed as of sub-classA or sub-class B. Brick of sub-class A have srhooth rectangular faces with sharp edges and corners anduniformity ofwlour. Bricks of sub-classB have slight distortion.(b) SIones (in reguIar sizes unifs)-- Detailed specifications'are given inIS 1 597 of 1967 Part I & I1 'Code of Practice for construction of stonemasonry*.(c) Sand lime bricks-IS 4139 of 1976 'Specificationsfor sandlimebrick'classified as class 75, 100, 150, and 200 according to their average com-pressive strength as for common burnt clay bricks.d) Concrete Blocks- Minimum average compressive strength speci-ked is 50 kdcmf as per IS 2185 of 1967 'specifications fbr hollow wmentconcrete block'. The IS Code is however, under revision and theblocks are being proposed to be divided into various grades dependingon their compresswe strength varying from 20 to 70 kg/cmS or HollowConcrete Blocks.(e ) Precast slone masonry Block -Sp i fications are laid down in CBRlData Sheet No 8 of building kchnlque series Sep 1977 and CBRI in-formation Note 1 of Sep 1978. Stone masonry blocks of30x20x15cmnominal size using spalls of 12cm size and lean cement concrete ,mixof :5 :8 remade. The block should be compacted during casting byusing piate vibrator. The nominal length and height of the block iskept 30cm and 15 cm respectively but the breadth may be 2 h , t5cmor I0 cm according to thickness of wall. The 28 days compressivestrength of blocks with the above mix is 70 kg/cma. Theconcretemixproportion is to k uitably adjusted with available materialsto meet the required strength. This lock constructioniseconomical in areas where stones are abundance and ateconomical cost. Method of production of blocks and spwial pre-cautions to be taken and details of masonry construction are given inthe aforesaid data sheet No 8 and information note Na 1 issued byCentral Buildi

5. Mortar3.1 Requirements of good mortar for masonry are strength, workability,water retentivity and low drying shrinkage, Mortars wu1d Be broadly dassi-fied as cement mortars, limemortarsand cement-Iime rqortars. Main character-istics are as under:

(a ) Cement Mortars-These consist of cement and sand varying inproportionsfrom 1:6 to 1:3. Mortars leaner than 1:btendto becomeharshandunworkableand areprone to seggregation. Rich mortars thou-ghhaving good strength have high shrinkage and thus liable to cracking.Cb) Lime mortars-These consist of lime, sand and burnt clay/surkhiin the proportion 1 :2 :3. The main advantage of lime miortat lies intheir good workability, low shrinkage and better resistance againstrainpenetration. However strength ismuch less than that of cement mortar.(c ) Cement: Lime mortars-These havegood qualities of both &ment aswe11 as lime mortars i.e. good strength aIongwith good workability,


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retentivity, freed~mrom cracks and g o ~ desistape agahstram penetrqtion. Commonly adopted mixes are' 1 : :6,1:2:9 dd 1 :3 : 12Details of mortars for rnasonr are contained in IS 2250 of 1965 'Code

Bf Practice for preparation and use a masonryMortars' and,*iifd;' .(a) Use of dry b r i c u ~ o t roperly s o w n w a t e JT~ ,Q c , ~ .. . .


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(c) Failure.to bed joints(d) Deviation from verticaI Plane or alignment i.2. out of plumb masonry.(e) Unfavourablecuring conditions.Tolerances permissible in the masonry are given in table 2 below :

TABLE 2 MAXIMUM PERMISSIBLE TOLERANCES IN MASONRYSI No. Item Tolerance(1) Deviation from the position shownonplan of any brickwork more than onestorey in height(2) Deviation from vertical within a storey 6mm per 3m height(3) Deviarion from vertical in the total height of .12.5mmbuilding.(4) Relative dispIacement between load bearing 6mmwalls in adjacent storeys intended to

be in vertical alignm,nt(3 Deviation from line in Plan

6mm12.5.mmtotal

12.5 mm otal


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9fig. r , ma wdl A .has very good mistance a inst a lateral load,B, offem little resistance to Ioad acticg in the p~gitudinai irection. The deformations in the two caseswe shown by dottd lines. Theloads acting on the f a ~ a d eof a building are transmitted through floors

act as horizontal beams) to cross walls, which act as shear walls. Fromwalls, loads are transmitted to the foundation. This act ion is illustratedn Fig. 2 & 3.A s a r e s u l t o f l a t e r d l o a d , t h e r e w i l l ~ a n i n c r e a s e o f c o m p r e s s i v eon the leeward side, and decrease of compressive stress on he wind-wardThe cross wall is designed f ~ rero tension, and permissible compressiveIt will be of interest to note that a wall which is carrying greater verti-load,will be,in a better position to resist lateral load than one which is lightlyin the vertical direction. This feature should be kept in view while plan-the structure so as to obtain an economical design.A structure should have adequate stability along both the principal

The so called 'cross wall' construction would not have much lateral re-in the longitudinal direction. In case of high-rise buildings, it is de-to adopt 'cellular or 'box type' construction as illustrated in Fig. 4.,

Size,shapeand1~tionofopningsintheexternalwaIbhaveconsi-influence on stability and magnitude of stresses dcz to lateral loads.has been illustrated in Fig. 5.If the opening in longitudinal walIs are so 1-ted and portionsof theseact as flanges to cross walls, the strength of the cross walls get consider-

increased and structure becomes much mare stable, as will be. seen from6. +.3 In a load bearing wall the length of openings should be minimum possibleaIIow more wall Iength to carry the loads. The more the openings, the lessbe the effective wall area and the more will be the induced st-. As arule the length of openings in a Ioad bearing wall should not exceed 50O/,he total Iength of wall. %

(a) Walls--Slenderness ratio for a wall shall be the effective hei ttive thickness, whichever is less. w"ivided by the effective thickness or effective length divided by the e ec-(b) Column-Slenderness ratio for a column shall be the effective heightdivided by the corresponding laterd dimension (thickness or width),Forthepur seofdesign, higherofthe twovaluesis taken intoaccountsince the wP"mn can buckle in any direction.(c) Maximum slenderness ratio-For walls built in cement mortar& ame#41ime mortar, it shall not,ad7. When lime m Q m r isused limits bf slenderness ratio shall be 13 and 20 for dewellingsa c e d i n two storeysand not ex&h two storeys. respeetivdy* Fqrd fon-loa bearing walls like and wa Is, c b W d s nd.p p e twalk, slendernessmtio shd not ex@ 30. Parapet nd shallhowevbr be designed to be strong enough ta withstand' j a w 1 forcesand other loads. For columns sIenderness ratio shall not exceed 12.

IC Y \1;1- >.-. ..,.!- ,,,a i~. . . ' . L o -- r -'. - ,L . ..d?;~).:: .-

-- --z L- -- 1 - - .-


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. .- - , . . - 6b , , - si ' 7 -. J ', . - , I , - . -- A%td:-@&&t#W-vekei#t&a watl ar cpoiumn &dl ba,thaschal height multi;pNed'byiddop rophate factop de ridiag n eud wndijtiom as given in tableP(Fig7); S M y EeaEive I&OL s-w x h d l be aotullllengthmdwd byappropiate factor as per fable4. Bht&w W r @ 7& 8.. I . . I . Table 3

EPF'ECTJiVE HElBWW Fig 7. 'Condition of support . I Wall

I effective .o .,. . height

I - " I , . .1 , Adequate lateral support and partial rotaional mt- 0.75 Hraint at top and bottom-where the floor (or roof')has

a direction of span at right angles to the wdJ, srr&atthe reaction to the load of the floor or roof is rwihRed by the walls or whtre the concrete floors aye w I4 bearing onwalls, irrespectiveof the dimtion of s@n.

2. Adequate lateral support and partial rotational rest- 0.85 Hraint at either top or bottom, and lateral restraint at . I #other end. Fully braced construction which is itselfadequately supported and incorporates (a) timberfioors immediately below or above a reinforced con-crete floor, (b) roof trusses above @I reinforced con-crete floor or the like.3. Ade uerta lateral support at top and bottom-whereS 1.00 Hthe oors (or roofs) have a direction of pan parallelwith the wall, topand bottom, and do not bear on it: Ior fully braced constructionwhich i s itself adequatelysup orted and which incorporates roof trusses and&im r upper storey floors.4. Adequate lateral support and partial rotational rest- I . 1.59 Hrainl at bottom and no ateral sup r~ OP rotationalrestraintatthetopwherethewdlg no la t e ra l sup . .Fort at top construction not fully anchored or not, ully bracedI I5 . Free standing non-load bearingmembers. ' i & ~

Table 4EFFECTIVE LENGTH OF THE~h

SL@. CONDITIONS OF SUPPORT + I&&lpe ks@h 1


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a butt- or crass wa6.n)1 & L= he :length s,swalls,. , +, piers*or buttress . d m ? ) ; , . ,;. :

%1. Eccentric loading affects theufifoihd'stress on' ne' side becomes more thanricity ratio reaches I/6 (for a 1.ecmngularzero and on the otherside compressive stress becomes twice the average valuei.e, the stress distribution block is a trlan@e. V ecantricity ratio exceeds 116,tension is .developed in one side. Since masonry is not expected !o take anytension a part of hickness ofmasonry member becomes ineffective. For eco-nomical designs, therefore, eccentricity of l oad i~ghould he he leastmb&not completely avoided., -- h L . :. I ;.I (1 !Allowable compressive stress in the masoary gets reduced withm n t r i c loads, . . .. .' D* consideratiom

( 4 ' 8 :9.1 General-Load b r i n gwalls are structurallymore efficientwhen the loadis uniformlydistributed andwhen the eccentricity of oading on the wallis as small as possible. For ensuring uniformity of loading, openin@in walls should notb oo large, bearings for lintels and bed b h k s under' i d - ! :5-beamsshould be liberal in size, heavy concentratim of loads should, be

avoided. One of the commonly occuring causes of cracks in masonryis wide variation in stress in masonry in adjoiningcity 'of loading on walls s vi~ a * ~ng 'fullEcccntri-earing-of floors/rootonthe wal&- *&&< > - ( : d . '1proc.&m. ;r, ,.:: t.: , I

I 'A f ; 2 . , J #iibuilding as a whole shall be a n a l y d by accepted principles ofmechanics. All component parts of the structure shall be capable of~ u s b i n h ghe most adverse combination o f l o d s whbh ftbC blrildiogmay be reasonably expected to be subjected to during or a ter erection.3wing constmotion the effects of wind, back fillins behind walls, or

4th~rection conditions shdl be so controlled that no adverse or un-conditions occur in the masonry.


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9.3 h&mYl la l l . . I. r.9.3.1 The thickness of a load bearing d 1 hall be sufficient at all points toensure that the stresses due ts worst conditions of loadin are withinthe limits prescribed for that rticular type of wali. e thicknksP" dused for design calculations sha 1 be the actual thickness of the masonry,not the nominal thickness. See Fig. 9. In masonry with raked joints,the thickness shall be reduced by the depth of the raking out. See Fig 10.9J.2 However, if joints are raked to provide key for subsequent plaraking could be ignored. tf any face of a wd l is to be pointedesirable to do rnkin and pointing while the mortar is green toany loss of strength 'f e to raking. For solid walls adequately binto piers or buttresses at intervals, the effective thickness shallactual thickness of solid wall multiplied by the appropriate stiffenincoeffici~nt iven in table 5 given below. For cavity walls, the c!rectiv

thickness s I I be two-thirds of the sum of the actual thickness of thtwo leaves8,El4 "

STWFENNG C O E F F I C m FOR WALLS -'BY d UT-TMBSES/QR INTERSECTING WALLS I' ! , - .Ratio, sp- IFFENING CQEFFIGIENT

WP . -p 'R 3 pr morec w ,wmwm&rfs6 1 .O 1.4 .-8 1 .O 1.3 - 1.7*I0 1.o 1.2 s.! 4 1.415 1O 1.1 1.220 or more 1 .O 1O 1O

Wheresp - centre to centre spacing of the pier or intersectingwalltp = the thickness of piertw = e u a l thickness ofwall oper;and

rp = wldth of the pier in the i~ction f the wall or tk'e actuaI thicknessoftheintersectrng wall., Note:--' Linear interpolation between the values given In M a abk i spermis-sible but nat extrapolation outside rhe limit givec.

In case of veneered walls, veneer shall not bems;dered to be part ofthe wall when computing the strength or required thickness of thewall. -r b i


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5 A

-' . ,, ~ B ~ E . = @ F ~ ,::!;..i: < - :. - :I c. , ' - - , -&&icmb';atia \ . ~ kasonry&meat , l. , , ' - 7 / ; ' 1 1 ( . ! ; ,$&ntrhity of loading I , I . ,,! . .. .'I . , . ' .. , . ' .., . . . , . ' - 1 . ICross-section aria bf masonry

r ' , , ' .' I .*- : : ,:, r m ( .,, " t ; IShape and size of the masonry unitEflect of these factors is explained in sub-pqrqs, l m 0 3nd JQ.4 .blow.

W. Permigsibla st* ess.shaI1e rehtpd.to bask stress. as. :vyq B !q 6 a: Page 1 5 d q m d i ~upon the, myskiogstnasfhof m ~ r y u n ~ tnnix of m0~ttL.rUse . . ,, . 4- dI10.3 For slenderness rati0.a rqductiq? af actor given in table 7 b l o w is to. . , be appl id. W l q I y , for $afls or c ~ l u ~ nhjktkd td &ehtkic loadsar v d r t i d lciads plus lateral 108ds; a ieductioii factbf is to treappliedgiven in the Table 7 below. Fot e c ~ n t i ~; loads plea s r@r fig 12. .!0.4 W b p ~ 'fie [email protected]$@&& @ . e ~ n ~ ~ ~ c i t y , ~ ~ l q ~ ~ p n dp~dprci$s, e max~muhgesultant stres$ may e x w d the allowatjb kfr&by n ~ f @r4ifaq35%,.vpro~jwa that Such ~ m s ss &o)et] g-Jd . ~ e.' lp -nLtricity of* oading ! 1 ' , , I .Case I - xial load onlyPermjssibIe stress = ,apptoprigte basiq gtress from table 4 mtdtipued by appro-(PxWfl pri& stredd factor:hs 1 ~ h d e r n ~ s ' ~ ~& zierd mfi-tricitv from table 7." , i7ase 11'- ccentric load , 'Permissible compressive stress (Axial = appropriate b sic stress multiplied byand bending compression) stress factor r%r slenderness rato andeccentricity multiplied by 1.25.Note;- In ilo case shall the stress due to axial toad alone exceed the values aiven

REE3UCTICTN FACTORS FOR S L E N D E R N ~ ATIO AND ECCENT-Ba;CPI"Y OF LOADINGREDUCTION FACTOR

Si f ;&m~ Equivalent eccentricity of loading dividd by the thickness ofRatio the member0 0.04 0.1 0.2 0,33 0.55(1) : (2) (3) (41 (8


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Note-1 wnear interpolation betwcen valuesfg he stressfactors is pormissibb.d * * i l : p , \ a i < . " ; . J ~ ; - L I : I t h i ; * . J:S ', : -1 1No t c 2 For u n r e i n f o d masonry, the valuw , in wl8 are for,p u r ; p m ofinterpdation on1y. , .. , , , . . ,*;I !Im, , I . ! > , , I

1 - q ,.,

4,:,-. . '$64 ,, 1 &"&s: Gate&:it &w:;; *Ff&. ",, v B r , p ~ i ;ikc1 !(o' , ,.. I -'i&~?,&,ib'15WQc~;'kere'pthg8i, . I .:_ . 'dewfhdsI I I , + , ~$qs.#'t$$~~rhiah. . ' . I Code.8 .10,'6.1. I E ~ r n i i s d n ~ u a i w o f ~ ~ ~ b h i ntrCq h 4 * b t l r V ' t j 5 3 k ' c m 3 i i d

'W ~ H. ratio.Mhei A I b thip,i'n* as .laid)4.& O.#but not" * ' " ~ & f e r i b ~ h 3 , ~ t b & b i c s t t s s s ~ modlA#dr, , I yi~e'~&~of+pccifiedas under in table 8.. .,?il,-, , , , ! , , J . - : .- ,Table 8

. . l i d f i + : 4 i - I - , ..., L ;&;miEwTvNfiYm,- .; - I 1r '9 -.- * : t i . 3 . ;:-'Ratio ofht to Q.75 1.0 2.0 o 3 . ~thickness of brick . .. .,.> ... ,I I . ,

or block1- .'. ~ ' ~ .. ' .' I '~, , t , . !;: , , , 8 . . b + , , .F W r t t ; . . . .. 9 .. , . ' .;.'L2. 1.6 .. : ., . -.. -; 2.0, -. . 8 + " !;: .:.;. -

. C . ' . i ' i l ; . i~ l ' ! i t !,'::',: I >


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. - - ortar not weaker than?1:l :6 wmcnt: lime: sand, he pmjssible tensile stress irt bending shouidI n~ i , y $ c q du @ ~ o t I P.. 2' k . , - - - - .,'. I . . . - r r ' k i l . , : t . 4L.6,3ml; )I ! ' -

' I . ... . I12. Pqm&dli iI t+&~'"


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Note92Pot uunaidod mawpry, the .lafl in lPd are-foynipyses finterpolation ody. , "....,. , : ' I i*i:rn 2 $ ~ , : b t * i!!rlr; X L : . .

10.7.1 Addition s t r ew 8 d a d y ocal naturc as at gi~W&h~11;.wiurnntbases9 lint& or other c m n t r p d loads shalt be cal.cuhtd a d hemaximum ~ & m s l t i n g f i d $ 7 m m b i n g h of stms&sw'th @her s shsll no# cad tb pmiss iMe s -re thaniit , I $ r i a w ! r t . m d b . qdv ,a %bf &sp&n d e lading s s ~ lt takes uair*rsb W 4 3 !R: ..*thed i r dmof raeh opding.

a I 4fhb', , , !

: j ' - ' q v j 4 1 . ~ ~ . f l ~ k ' l I rdQiJ.(j ih ' j } , 1 ;;i3Uk3.a In P~dibe Gtile, strew of bricg -11 :-.(jwo fM&atim,:T h ~ g mthe. sectiw in knslons will bpt+hr.tlas$- to b&mctiwf@ them~ain&-willw,oompres s i ve strev.)8& I oa41clab SW@ typto6.WlMwib s tm ep is & ~ d b gmay be takgp


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MES INDIA STD TI 1 of 82

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