Role of cast-in situ slabs in RC frames under low frequency cyclic load

This paper presents an investigation on the seismic behaviors of two spatial reinforced concrete (RC) frames: RC frame with slabs and RC frame without slabs. The study is focused on the effect of the cast-in situ slabs on the seismic performance of the RC frames. Based on the low frequency cyclic loading test for two spatial RC frames, the energy dissipation, bearing capacity, ductility, effect of cast in situ slabs on the flexural capacity, effective slab width, shear distribution of columns, rotation of members and joint shear force were experimentally investigated. Research findings indicated that, due to the effect of slab, the energy dissipation capacity of specimens changed slightly while the corresponding flexural moment at the beam ends increased obviously. Compared to the RC frame without slabs, the RC frame with slabs exhibited a higher bearing capacity while inferior deformation capacity. Test results also showed that the effective slab width varied with the variation of inter-story drift and joint pattern. The torsion cracks appeared in the transverse beams and the joints shear force increased due to the effect of slabs. The failure pattern of RC frame without slabs was “strong column–weak beam” while that with slabs turned into the “strong beam weak column”. The shear distribution of columns was affected by slabs.