Restoring force model for steel beam to CFST/HSS column joints with a reinforced concrete slab

The seismic performance of the steel beam-column joints is significantly influenced by the composite action of the reinforced concrete (RC) slab. This paper aims to propose a restoring force model for steel beam to CFST/HSS column joints with an RC slab. Based on the test results and numerical regression, a simplified trilinear skeleton curve and hysteresis rule were proposed. Secondly, a restoring force model considering the stiffness degradation was proposed. Finally, the restoring force models were compared with the finite element models. The results show that the ratio of the predicted results of the restoring force model to the finite element model (FEM) results at the yield and plastic points ranges from 0.91 to 1.10. The coefficients of variation for the two states were around 0.05, on average. The developed restoring force model provides a reliable and accurate method for evaluating the seismic performance of building structures or members.