1927 086 Ordinance - Laserfiche WebLink

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ficient distance to insure proper bonds. Siaty (60) diameters for medium steel bars, a.nd seventy (70) diameters for,high tensile steel rods will be considered a sufficient lergth to .develop same.- -Forty (40) to fifty. (50) dianieters may be considered, f=or twis- ted or deformed bars. - ' ,. , . In all .case's, however, beams and girders v:hich are built monolithic at the supports shall have at,least twenty (20) per cent asmzch steel ii1 the top over sup- ports as at the center. For concentrated loads on continuous beams or girders, the ber_ding moment at the center shall be calculated as for a single beam andthis moment may be reduced twenty, (20) _per, cent for- intermediate ?spa.ns or ten (10) per cent for er_d -spans. VJhere a short span adjoins a long span and one-half (2) of the sh ort sp an con- sidered as a cantilever cannot produce a, bending moment which will deeelop the strength of the reinforcement over the supports the long span shall be considered as an.end span. . For simple girders, beams or slabe the span shall be taken as the clear sp an and for continuous girders, beams or slabs the span shall be taken as t he distEnce be- tween centers of supportso Sec.129. I,ITlfITING -NIDTH OF FI,ANGE I1V THE BMIS. When beams ar.e made monolithic with the floor slab a portion;.of.the .floor may-be assumed as acting in flexure in com- bination with the beam. The width of the slab so acting in flexure is to be governed by the sheariizg resistance between slab and beam,.but limit,ed to awidth equal to one-third (1/3) of the span lengtH of the beams betvteen supports and also limited to a span length ?6f three-fourths:(.3/4) of the,distance from.center, to center between beams. No part of the slab sY!all be coneidered as a portion of the rib, unless the slab and. rib a,re cast at the same time. __ . ..... . , Where reinforced concrete girders support reinforced concrete beams, the p or- tion of the floor slab actin; as flari.ge to the girder must be reinforced ?rith rods near the top, at right angles to the girder to enable it to transmit local loads dir- ectly to the girder and no# through the beams. Sec.130. tAlh]B-STRESSES. VJhere the diagonal tension exceeds 4-0 .1bs. per sq. in. additional vaeb reinforcement of approved d.esign shall be usedo Stirraps shall not be placed further apart then te+ro-thirds. (2/3) °'d'! i-L tliey are corisidered as adding to the shearing resistance, In no case'shall the'shear ex- ceed 125 lbs.. per sq. in. lVhen reinforcement is used to increase the uriit shear, the proportion of the nnit sheax taken by.the concrete sha.ll not exceed 40 lbso per sqo ins and the reingorcoment.shall be sufficient to take the rema.inder. '.If.:unattached stirrups are used they sha.ll pass under the main reinforcing bars.. _ ;. . There shall be sufficient-, anchora,;e to develop the stirrups: above tYie neutral axis of the bdams cuithout exceedi.ng:the„bond stresses specified..,If the stirru.ps are attached to the reinforcing bar,s?-thp; conncecion rmzst -be sufficient 'to develop 'the el- astic limit of the steel without causing^slipping along_the main.bars. -,, If the reinforcing rods,are.bent'to approximately 45 degrees and are spaced no further apart than "d" .or:if_-.the.bars are bent at the one-fourth`(?) points, they may be figured a's shear meinbers in providing- for the:.excess shear over 40 lbs per sq. in. If a beam is required:to carry_a series of concentrated loadsthe bending of the reiilfox•cing bars should be gove.rned-accordingly..., y . . _