Behaviour of beam-to-column high strength steel endplate connections under fire conditions – Part 1: Experimental study

•Tests were undertaken on high strength steel (HSS) endplate connections at 550 °C.•Behaviour and failure mode of HSS endplate connections in fire were obtained.•Comparison of HSS endplate connections in fire with mild steel ones were conducted.•Eurocode 3 was validated with test results of high strength steel endplate connections.•It offers basis to conduct fire-resistance design of high strength steel structures.

In order to reveal more information and understanding on behaviour and failure mechanisms of high strength steel endplate connections under fire conditions, an experimental study has been carried out and presented in this paper. Full-scale tests on beam-to-column high strength steel endplate connections were conducted at elevated temperature 550 °C under steady state fire condition and at ambient temperature as reference. Further, their behaviour was compared with that of mild steel endplate connections. Moreover, the provisions of Eurocode 3 were validated with test results of high strength steel endplate connections. It is found that a proper thinner high strength steel endplate can enhance the connection’s rotation capacity both at ambient temperature and in fire (which guarantees the safety of an entire structure), and simultaneously achieve almost the same moment resistance with a mild steel endplate connection.