Seismic behaviour of steel-concrete composite beams

Five steel-concrete composite beams are tested under low reversed cyclic loading. The failure patterns, hysteretic characteristics, hysteretic model, deformation restoring capacity, ductility, energy dissipation capacity, stiffness degradation and slips of the prestressed composite beams are discussed. Attention is paid to the effects of partial prestress ratio and degree of shear connection on the seismic performance of these beams. Studies show that the prestressed composite beams behave in a relatively ductile manner. Ductility of the composite beams decreases as the partial prestress ratio and the degree of shear connection increase. It was also observed that the applied prestressing is favourable for energy dissipation during downwards loading. Slips between concrete slabs and steel beams have adverse effects on energy dissipation in positive moment regions of composite beams. Tests also show that the effects of partial prestress ratio and the degree of shear connection are negligible to degradation of stiffness in composite beams.