Punching strength of continuous concrete slabs

摘要

Punching tests on continuous concrete slabs are very expensive and elaborate. As a consequence, the majority of the existing punching tests have been performed on isolated specimens representing only the hogging moment region around the considered slab-column connection. Isolated punching tests are valuable in order to analyse the punching shear behaviour systematically. Nevertheless, beneficial effects of slabs' continuity (e.g. moment redistributions and membrane actions) may not occur in these tests. To investigate the punching shear behaviour of continuous concrete slabs, in this paper the existing two-parameter kinematic theory for punching shear in reinforced and prestressed concrete slabs is applied. The beneficial effects of slab continuity on punching strength are estimated based on a theoretical model described in the literature. The kinematic theory is applied to evaluate punching tests on a continuous slab, revealing good agreement between predictions and experimental results. As only few punching tests on continuous slabs are available, further parametric studies are performed to analyse the effects of slab continuity on punching strength in more detail. The results suggest higher punching shear capacities for continuous slabs than for isolated slabs. Nevertheless, the beneficial influences of slab continuity on punching strength strongly depend on the slab stiffness and flexural cracking.