Research of restoring force model on steel-concrete composite continuous beams

Based on the test results of seismic resistant performance of eight steel-concrete composite continuous beams under low-cycle reversed concentrated loads,the shape of hysteresis loop of the load-displacement(P-Δ)is obtained,which gradually changes from shuttle to quadrangle according as the increasing of displacement.Those beams with bigger degree of shear connection and longitudinal force ratio in the negative moment zone of interior support still have good ductility.The regularity of rigidity degeneration of either loading or unloading condition accords with exponential law.Based on the experimental research,proposed formulas for calculating the skeleton curve and hysteretic rule of load-displacement,restoring force model of steel-concrete composite continuous beams are established in consideration of the degree of shear connection and lognitudinal force ratio.