Restoring force model of a modular steel-concrete composite column

The restoring force model (RFM) is the basis of elasto-plastic time-history analysis and forms a critical part of the seismic response analysis of structures. Based on the previous research results of a novel modular steel-concrete composite column, this paper qualitatively processed the test data through dimensionless and regression analyses. A three-fold line skeleton curve model (SCM) suitable for modular steel-concrete composite columns was proposed, and the stiffness degradation and hysteretic rule of the novel modular steel-concrete composite column were presented. Based on these results, a three-fold line RFM considering the stiffness degradation was established. Comparing the calculated results of the resilience model with the test results showed that the yield point moment obtained from the test was 0.84−1.34 times the calculated moment of the RFM, with an average value (AVG) of 1.01 and a coefficient of variation (COV) of 0.02. The peak moment obtained from the test was 0.96−1.01 times the calculated moment of the RFM, with an AVG of 0.99 and a COV of 0.00. Thus, the reliability of the RFM of the novel modular steel-concrete composite column was verified.