AbstractThis paper aims to investigate the seismic performance of a steel frame with an external diaphragm joint between a concrete-filled steel tube (CFST) column and H-shaped steel beam through experiments and finite-element (FE) analysis. A quasistatic test was conducted on five steel frame specimens. The parameters involved in the test were joint stiffness, beam-to-column stiffness ratio and concrete strength. Based on the experimental results, failure mode, lateral load versus displacement hysteretic curve, skeleton curve, strength and stiffness degradation effects, ductility, and energy dissipation capacity were analyzed. The experimental results show the hysteretic curves have a plump shuttle shape; the strength degradation effect and stiffness degradation effect are relatively feeble; and the ductility and energy dissipation capacity are excellent. Therefore, the tested specimens have good seismic performance. Also, this suggests that larger joint stiffness brings about superior seismic performance; a stronger column leads to higher bearing capacity as well as inferior ductility and energy dissipation capacity; and a CFST frame performs better than a hollow steel tube column frame under cyclic loads. On the basis of the experimental results, the ABAQUS software version 6.14 was adopted to establish the FE models. The applicability and accuracy of FE simulation were first verified by experimental results. Then, quantitative parametric analysis was carried out to study the effects of different parameters on seismic performance of the CFST frame with an external diaphragm joint.