Experimental study on high-strength Q460 steel extended end-plate connections at elevated temperatures

Abstract

This paper presents an experimental study on high-strength Q460 steel extended end-plate connections at ambient and elevated temperatures. Ambient temperature tests were conducted on connections with 8 and 12 mm end-plates to investigate the ambient temperature structural response, including the initial rotational stiffness, plastic flexural resistance and ultimate rotation. The results show that high-strength steel connection with 12 mm end-plates significantly improves mechanical properties compared to that with 8 mm end-plate with an increase of 22% at least while not influencing the failure modes. Then, the experimental results were compared with the theoretical predictions of Eurocode 3. There are reasonable agreements between these two methods on plastic resistance, while the calculation by Eurocode 3 on initial rotational stiffness exhibits much higher results. In addition, the temperature distribution of the connection specimens and furnace air, rotation-temperature characteristics, and failure modes of the connections in transient tests were obtained to study the influence of different end-plate thicknesses. The 12 mm end-plate effectively improves the connection's rotation capacity at elevated temperatures with an increase of 29% compared to 8 mm end-plate while influencing the critical temperature and fire endurance lightly. Besides, the fire performance results were compared and discussed between mild steel and high-strength steel connections. Finally, a rotation-temperature relationship model was proposed to predict the fire behavior of high-strength steel end-plate connections under transient conditions and validated against the experimental data with considerable accuracy.