Punching Shear Capacity Related to Load Level of the Corner Columns

Abstract

The paper discussed the effect of column load on punching shear resistance of flat slabs. Previous experimental investigations demonstrated that beneficial effect of lateral expansion of joint concrete, resulting from column pressure, can lead to an increase in punching shear resistance.

To verify this issue in relation to external joints a total of six specimens, reflecting connection between slab and corner column, were tested. The test setup allowed for independent loading of columns and slabs. The main variable parameter was the column load level. The column load causing pressure exceeding the uniaxial compressive strength of the slab concrete induced additional tensile forces in the slab longitudinal reinforcement, which translated into approximately 20% higher rotations at reaching the experimental loads. The tests demonstrated that load acting on the corner column can affect punching shear capacity of the slab. However, this effect was moderate and dependent on the column location. In the case of columns flush with free edge of the slab, an increase in the column load led to a reduction in punching shear capacity by about 9%. However, for elements with overhang slabs, the opposite trend was stated and an increase in experimental load by about 10% was found.