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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 o~gitudinai direction. The deformations in the two cases we shown by dottd lines. Thelateral loads acting on the fa~ade of a building are transmitted through floors(which act as horizontal beams) to cross walls, which act as shear walls. Fromcross walls, loads are transmitted to the foundation. This act ion is illustratedin Fig. 2 & 3.5.3 Asaresultof laterdload,therewill~anincreaseofcompressivestress on the leeward side, and decrease of compressive stress on the wind-wardside, The cross wall is designed f ~ zero r tension, and permissible compressivestress. It will be of interest to note that a wall which is carrying greater vertioalload, will be,in a better position to resist lateral load than one which is lightlyloaded in the vertical direction. This feature should be kept in view while planningthe structure so as to obtain an economical design.5.4 A structure should have adequate stability along both the principalaxes. The so called 'cross wall' construction would not have much lateral resistancein the longitudinal direction. In case of high-rise buildings, it is desirableto adopt 'cellular or 'box type' construction as illustrated in Fig. 4.,6.1 Size,shapeand1~tionofopningsintheexternalwaIbhaveconsiderableinfluence on stability and magnitude of stresses dcz to lateral loads.This has been illustrated in Fig. 5.6.2 If the opening in longitudinal walIs are so 1-ted and portionsof thesewalls act as flanges to cross walls, the strength of the cross walls get considerablyincreased and structure becomes much mare stable, as will be. seen fromFig. 6. +6.3 In a load bearing wall the length of openings should be minimum possibleto aIIow more wall Iength to carry the loads. The more the openings, the lesswill be the effective wall area and the more will be the induced st-. As ageneral rule the length of openings in a Ioad bearing wall should not exceed 50 O/,of the total Iength of wall.(a) Walls--Slenderness ratio for a wall shall be the effective hei tdivided by the effective thickness or effective length divided by the e ectivethickness, whichever is less.(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 w P" umn can buckle in any direction.(c) Maximum slenderness ratio-For walls built in cement mortar& ame#41ime mortar, it shall not ,ad 27. When lime mQmr isused limits bf slenderness ratio shall be 13 and 20 for dewellingsacedin two storeys and not ex&h two storeys. respeetivdy* Fqrnon-loa d bearing walls like and wa f Is, c b W d s and. ppetwalk, slenderness mtio shd not ex@ 30. Parapet nd shallhowevbr be designed to be strong enough ta withstand' jaw1 forcesand other loads. For columns sIenderness ratio shall not exceed 12.w"%ICY \1;1- >.-. .- r'.,.!- - ,,,a i~ . . - .. '. L o --'.d?;~).:- ,L. .- : .--1-- - --_ --z .- L- -
1".-... .- - , .. -. b, ,6si ' 7 -. J ', . -,I,-. -- A%td:-@&&t#W-vekei#t&a watl ar cpoiumn &dl ba,thaschal height multi;pNed'byidd op rophate factop de ridiag n eud wndijtiom as given in table3 (Fig 7); S M P d y eEeaEive I&OL s- wxhdl be aotulll length mdwd byappropiate factor as per fable 4. Bht&w Wr @ 7 & 8.. I. .I .Table 3EPF'ECTJiVE HElBWW Fig 7.. 'Condition of supportI. I Walleffective .o .,. . heightI - " I , . .1, Adequate lateral support and partial rotaional mt- 0.75 Hraint at top and bottom-where the floor (or roof') hasa direction of span at right angles to the wdJ, srr &atthe reaction to the load of the floor or roof is rwihded by the walls or whtre the concrete floors aye w4 bearing on walls, irrespective of the dimtion of s@n.2. Adequate lateral support and partial rotational rest- 0.85 H #raint 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 concretefloor, (b) roof trusses above @I reinforced concretefloor or the like.S3. Ade uerta lateral support at top and bottom-wherethe oors (or roofs) have a direction of span parallelwith the wall, topand bottom, and do not bear on it:or fully braced construction which is itself adequatelysup orted and which incorporates roof trusses andtim r upper storey floors.&R1.00 H4. Adequate lateral support and partial rotational rest- I . 1.59 Hrainl at bottom and no lateral sup r~ OP rotationalrestraintatthetopwherethewdl g snolateralsup.. .ort at top construction not fully anchored or notF I, ully braced . I5. Free standing non-load bearing members. ' i & ~Table 4EFFECTIVE LENGTH OF THE ~hIISL @. CONDITIONS OF SUPPORT + I&&lpe ks@h 1
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