COMPREHENSIVE MODEL FOR STUDY OF SHEAR IN THIN-WEBBED RC AND PC BEAMS

A model developed for the study of the individual contributions to shear capacity in reinforced concrete (RC) and prestressed concrete (PC) thin-webbed beams is improved here by introducing dowel action, nonuniform distribution of crack opening and slip, and plastic-strain accumulation in the stirrups. The proposed approach is based on the truss analogy and on the diagonal-compression concept, within the context of limit analysis: the failure in shear is related to the simultaneous yielding of the stirrups and the collapse of the compressive struts in shear compression. The model, which is not devised to be an alternative to other code-oriented and simpler models, has a threefold purpose: (1) To provide a viable and open-structure tool to assess the roles of various shear-resistant mechanisms; (2) to guarantee a ductile collapse in shear through a suitable design for the stirrups; and (3) to provide a key to the truss role in shear-sensitive reinforced beams. The proposed model is checked against many test data (RC and PC beams) and its predictions turn out to be markedly closer to test results than either EC2 or ACI codes.