Experimental Study on the Influence of Out-of-Plane Effects on In-Plane Performance of Composite Slabs

This study comprised an experimental investigation of the in-plane performance of composite floor slabs under out-of-plane effects. Two composite floor slabs were subjected to pure in-plane loading, and in-plane and out-of-plane coupled loading, respectively. The study analyzed crack patterns, failure modes, and load–displacement curves, and evaluated how out-of-plane effects influenced in-plane performance. The test results indicated that both specimens exhibited a typical shear-tension failure mode, forming diagonal shear cracks. The specimen with out-of-plane loading exhibited a trend for lateral development of the shear cracks. The load–displacement curves of the two specimens showed obvious strength degradation, stiffness degradation, and a pinching effect. By comparing the two specimens, it could be observed that at a small out-of-plane displacement angle, the in-plane ultimate bearing capacity of a specimen was not significantly weakened; however, as the out-of-plane displacement continued to increase, the in-plane bearing capacity of the specimen decayed more rapidly.