Punching-shear strength of reinforced concrete slabs subjected to unidirectional in-plane tensile forces

摘要

Some reinforced concrete slabs are subjected simultaneously to concentrated loads and unidirectional in-plane tensile forces. This the case of the top slab of a box girder bridge where hogging bending moments take place at the intermediate supports. Then, the in-plane tensile forces may reduce the punching-shear strength under concentrated loads. This paper describes an experimental campaign carried out to investigate the effect of unidirectional in-plane tensile forces on the punching-shear strength of RC slabs. A total of, five slabs (1,650 x 1,650 x 120 mm), subjected to different levels of in-plane tensile forces were tested under a concentrated load up to failure. As observed, the punching-shear strength diminishes almost linearly as the tensile force increases, up to a certain point associated to concrete cracking. From that point on, the reduction of punching strength is larger since the tensile force at the crack must be resisted by the reinforcement, which yields prematurely.