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s = spacing of s t i r r u p s i n a direction p a r a l l e l to the longitudinal reinforcement = ultimate shear c a r r i e d by web reinforcement In both equations the strength reduction factor, cp, was taken equal to unity. Width of the beam, b, was taken as i n . Measured quantities were used for f J and d. The r a t i o V/M was determined from the frame a n a l y s i s for column loads. Y i e l d strength of the s t i r r u p s was assumed at 42 k s i . Shear reinforcement was very l i g h t , consisting of two closed-loop No. 3 bars spaced at 12 i n . Computed shear strengths, V^^^, at Columns E3 and Ek are l i s t e d i n Table IX. Computed values are the sum of edge beam strength at a distance, d, from the narrow faces of the columns. For both locations, E3 and Ek, strength com- puted using Eq. k and 5 more cl o s e l y predicts measiared capacity than the slab shear equations. Test to calviated r a t i o s for both E3 and E4 approach unity when analyzed as beams. This indicates that beam action predominated i n shear strength. Although the shear f a i l u r e s were conical about the columns, i t appears the diagonal cracking was precipitated by beam action. Subse- quently, s t r e s s e s were redistributed so that v e r t i c a l load was transferred through the long face of the col\imn. The extent to which the low shear strengths observed i n Test I I were caused by damage to the structure be- fore the t e s t began i s not known. Further laboratory t e s t s regarding the manner in which v e r t i c a l shear i s r e s i s t e d at edge columns are i n progress at the PCA Laboratories. Test I I I . Measured shear c a p a c i t i e s at Column C5 were l e s s than predicted. Table IX indicates that t e s t strength was only 6 0 to 6 5 percent of that c a l - cvaated by e i t h e r the ACI Code with no reduction for moment or by Moe with the moment e f f e c t determined by Eq. 2. Moment e f f e c t s analyzed by Moe were only for the condition of bending about one a x i s . From the arrangement of loading i n Test I I I , i t i s obvious that moment i s transferred to columns by bending about two axes. Thus, i t i s not surprising that strength i s underestimated using Moe's procedure. 1- k2
