In-plane cyclic behaviour of composite floor slab diaphragm interfaces under high-shear demand

Abstract

The authors have recently described the experimental in-plane shear tests of three composite slabs under monotonic loading to failure, focusing on the interaction between the slabs acting as diaphragms and the lateral load resisting system. The tests considered rib orientations both parallel and perpendicular to the supporting beam, as well as the end-anchorage details used in New Zealand and those used in Europe. A novel pure shear test rig was developed for this purpose. It was found that all specimens exhibited similar ultimate shear strength, and that the Eurocode overestimated the design strength for the European end-anchorage detail by almost a factor of two. An improved equation for the ultimate in-plane shear strength was proposed by the authors, modifying the Easterling and Porter equation to take into account the influence of the edge rebar, showing good agreement with the experimental test results.In this paper, reversed cyclic in-plane shear tests of the same three slabs are now reported. Each test was repeated twice, resulting in six test results. The same novel pure shear test rig was adopted. In the elastic range, the reversed cyclic loading results were found to be similar to those of the monotonic tests, with the spine curve being very similar. The ultimate in-plane shear strength of all three was lower than that of the monotonic test by around 15%. Slippage of specimens was found to be insignificant in the elastic range.