Experimental study and analytical evaluation on seismic performance of CECFST moment resisting frame with bolted connections

Abstract

Concrete encased concrete-filled steel tube (CECFST) column possessed better durability and fire performance compared with ordinary concrete-filled steel tube (CFST) column. In engineering practice, the CECFST column is usually connected to steel beam using welded joints. It would be better to adopt bolted joints for fast construction and to avoid welding fracture under seismic loads. However, limited research has been performed on bolted CECFST joints. In this paper, an experimental program is conducted on bolted CECFST column joints. Typical failure modes were characterized and the moment-rotation behavior was discussed. An analytical model was established by Opensees, in which the moment-rotation model was calculated based on the component method and the shear behavior of joint panel was also accounted. The analytical method was verified by the test results and could be applied to design the bolted joints in engineering practice. Afterwards, a prototype CECFST moment resisting frame was numerically analyzed to detect its seismic performance under frequently-occurred (FOE), design-based (DBE) and maximum considered earthquakes (MCE). Subsequently, the fragility of the CECFST moment resisting frame was also explored, which verified that the CECFST moment resisting frame had high robustness and superior anti-collapse capacity. The test and analytical results confirmed that the CECFST moment resisting frame using bolted joints performed satisfactory seismic behavior and could be employed in engineering practice.