Characteristics of restoring force of high strength reinforced concrete frame columns

A restoring force model was necessary for dynamic analysis of members under seismic action. In this paper, by analysis of the test results of low cyclic reversed loading experiments conducted on totally 19 steel reinforced high-strength concrete (HSRC) columns with different parameters (the slenderness ratio λ ≥ 3), the dimensionless skeleton curves, dimensionless hysteresis loops, and stiffness degradation rules of the HSRC columns were simulated using the experimental fitting method. Based on these simulations, a restoring force model was established for the HSRC columns. The results show that the dimensionless skeleton curves can be expressed by a four-segment polygonal line; the dimensionless hysteresis loops can be expressed by a three-segment polygonal line; after each cycle, the stiffness degradation become more serious, and the curve returns but overshoots the original unloading point; the stiffness degradation between the yield point and limit point increases with an increase in the absolute horizontal displacement.