The strain rate effect of engineering materials should be considered in the assessment of the performance of reinforced concrete (RC) structures under extreme dynamic loads such as blast and impact. However, the strain rate behavior of 500 MPa-grade anti-earthquake hot-rolled high-strength ribbed bar (HRB500E), used in critical RC members to improve the anti-earthquake performance, has not been investigated and reported in the open literature. That restricts its application in RC structures subjected to extreme dynamic loads. In this paper, dynamic tensile tests of HRB500E steel were conducted using an electromechanical universal testing machine and a servo-hydraulic high-speed testing machine. The stress–strain curves at strain rates ranging from 0.00025 to 550 s⁻¹ were obtained where HRB500E steel was found significantly sensitive to strain rate. Existing formulations to evaluate the dynamic increase factor for yield stress (DIF_y) are found to be not suitable for HRB500E steel, thus the widely used Cowper–Symonds and Malvar models for predicting the DIF_y were modified based on the test results. Furthermore, the parameter of the Mander material model for describing engineering stress–strain relationship was also calibrated. Finally, the Johnson-Cook and proposed constitutive models for the true stress–strain relationship were examined. The proposed constitutive model can provide better prediction accuracy for yield stress than the Johnson-Cook model.

High-strength steel has been increasingly applied to engineering structures and inevitably faces fire risks. The equivalent stress-plastic strain (${\sigma }_{\mathrm{eq}}$− ${\epsilon }_{\mathrm{eqp}}$) curves of steel at elevated temperatures are indispensable if a refined finite element model is used to investigate the response of steel members and structures under fire. If the tensile deformation of steel is considerable, the ${\sigma }_{\mathrm{eq}}$− ${\epsilon }_{\mathrm{eqp}}$ curves at elevated temperatures are required to consider the strain-hardening behavior during the post-necking phase. However, there is little research on the topic. Based on the engineering stress-strain curves of Q890 high-strength steel in a uniaxial tension experiment at elevated temperatures, the ${\sigma }_{\mathrm{eq}}-{\epsilon }_{\mathrm{eqp}}$ curves before necking are determined using theoretical formulations. An inverse method based on finite element analysis is used to determine the ${\sigma }_{\mathrm{eq}}$− ${\epsilon }_{\mathrm{eqp}}$ curves during the post-necking phase. The characteristics of ${\sigma }_{\mathrm{eq}}$−${\epsilon }_{\mathrm{eqp}}$ curves, including the full-range strain hardening behavior at different temperatures, are discussed. An equivalent stress-plastic strain model of Q890 steel at elevated temperature is proposed, which is consistent with the ${\sigma }_{\mathrm{eq}}-{\epsilon }_{\mathrm{eqp}}$ curves. The constitutive model is further verified by comparing the finite element analysis and test results.

To study the lateral performance of a cold-formed steel–concrete insulation sandwich panel composite wall, two full-scale specimens with different arrangements were designed. The specimens underwent cyclic loading tests to examine the failure characteristics of the composite wall, and lateral performance aspects such as the experimental hysteresis curve, skeleton curve, and characteristic value of the whole loading process were acquired. The experimental results indicate that the failure of the composite wall system was primarily caused by the failure of the connection; the overall lateral performance of composite walls with one wall panel at the bottom and two wall panels at the top (W1) was superior to that of composite walls with two wall panels at the bottom and one wall panel at the top (W2). When loaded to an inter-story drift ratio of 1/300, the composite wall did not exhibit any significant damage. A finite element (FE) model was developed and validated by the experiments. Factors affecting the shear bearing capacity were analyzed based on the FE model, including the yield strength of diagonal braces, the thickness of the diagonal braces, the arrangement pattern of the wall panels, the dimensions of the wall panels, and the strength of the connection of the L-shaped connector and the flat connector. The FE results show that all these factors can influence the lateral performance of the composite wall.