Experimental study on seismic behavior of reinforced concrete composite T-beams

The reinforced concrete composite T-beam which is composed of precast inverted T-beam, precast slabs and cast-in-place (CIP) slab, is studied in this paper. Based on the low reversed cyclic loading tests on a full-scale composite beam and the CIP control specimen, the failure mode, hysteresis curves, displacement ductility, stiffness degradation and energy dissipation capacity etc. were investigated. The results indicated that both the composite beam and the CIP control specimen failed in bending. The measured slips between precast beam and precast slab and between precast slab and CIP slab near the web were 0.5 mm and 0.2 mm under the peak load, respectively. Both specimens exhibited a stable load-deflection hysteresis response at the low deflection levels, and slight pinching could be noticed in the hysteresis loops at higher deflection levels, however, the overall energy dissipation capacity of the specimens was good. The stiffness of composite beam degraded evidently from cracking to yielding, while the stiffness degradation became relatively slow after yielding. The positive and negative flexural strength of normal section of composite beam was about 9% and 3% lower than those of the CIP control specimen, respectively. The displacement ductility of composite beam was approximately 6% and 14% lower than those of the CIP specimen in the positive and negative directions respectively; however, the displacement ductility factor of both specimens was more than 4.8. In addition, the behavior of composite beam and the CIP control specimen under cyclic loading was compared with those of the corresponding specimens under monotonic loading.