ACI SP-321

Abstract

INTRODUCTION Because of constraints in space and available loading, punching of slabs is typically studied with slab-column connections (ASCE-ACI Task Committee 426, 1974). This type of test setup reflects the situation in building slabs. As a result, the available code equations are either (semi-)empirical methods derived from a statistical analysis of slabcolumn connection tests, or based on mechanical models, verified with slab-column connection tests. For the one-way shear capacity of beams, the situation is similar. Experiments are typically carried out on small, slender, heavily reinforced concrete beams tested in three- or four-point bending (Reineck et al., 2013). The available code equations are either (semi-)empirical methods derived from a statistical analysis of these tests, or based on mechanical models and verified with the available tests. When the shear capacity of reinforced concrete slab bridges is assessed, both the beam shear (one-way shear) and punching shear (two-way shear) capacity under the combination of distributed dead loads and the prescribed live loads (typically distributed lane loads and concentrated loads from the design truck or tandem) need to be verified. This loading situation is different from a slab-column connection or simplified beam shear test setup, and is an asymmetrical loading situation because of the different positions of the design trucks or tandems over the lanes. An asymmetrical loading condition that is studied for building slabs is the case of slab-column connections with unbalanced moments (Barzegar et al., 1991), reflecting the loading situation at edge and corner columns. The unbalanced moment is then considered to cause a contribution to the occurring shear stresses on the punching perimeter that needs to be summed with the direct shear stress on the punching perimeter, and the code methods reflect this approach.