Shear Strength of Reinforced Concrete Frame Members Without Web Reinforcement
JoDean Morrow and I. M. Viest
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Experimental and analytical studies reported in this paper havt: shown conclusively that the strength of a reinforced concrete frame member wit,h-out web reinforcement is affected by shear through the formation of diagonal tension cracks. If the percentage of longitudinal reinforcement is small the shear span is very long, a member without web reinforcement fails in flexure without prior formation of diagonal tension cracks; in such case, strength of the member is unaffected by shear. If, however, a diagonal tension crack forms, the strength of the beam is usually lower than that corresponding to flexural failure. Depending on its make-up, such member may fail either simultaneously with the formation of the diagonal tension crack or it may fail at a higher load. The first type of failure is designated as diagonal tension failure; the second is designated as shear compression failure. The relationship between flexural, diagonal tension, and shear compression failures is discussed in detail in this paper. The tests included 33 knee frames subjected to combination of axial com-pression, shear, and moment, and 38 stub beams subjected to moment, and shear. In all knee frames the axial load was equal to the estcrnal shear. The major variables were the length of shear span, the strength of concrete, and the percentage of reinforcement. Analytical expressions are presented for predicting the diagonal tension cracking load and shear compression strength. The diagonal tension cracking load is expressed in terms of the nominal shearing stress, and the shear com-pression strength is expressed in terms of the shear moment capacity.