Two-way shear strength of reinforced concrete slab-column connections : influence of testing conditions in isolated specimens

To assess the two-way shear resistance, or punching shear strength, of reinforced concrete slabs, code provisions fitted from experimental data are typically employed. The experimental data forming the bases of these provisions have generally consisted of isolated slab-column connection tests that seek to represent the negative moment region of a flat plate slab. This research is focused on exploring the variation in the punching performance of slab-column connections when the typical testing conditions used to investigate isolated slab specimen are varied in a manner that produces alternative sectional loading conditions within the column connection region. To accomplish this, an innovative testing apparatus is introduced that permits alternative combinations of slab bending moment to out-of-plane shear force ratios to be applied to the slab-column connection. Results are presented from an experimental program conducted at the Ferguson Structural Engineering Laboratory (FSEL) of The University of Texas at Austin and an analysis is presented comparing the results from the tests with estimations made from current standards, the Critical Crack Shear Theory (CSCT), and also from numerical models. The data obtained from the experimental program are used to scrutinize current design and analysis procedures, and to shed light on the significance of the sectional loading conditions in the light of flat plate connection shear resisting performance.