Post-fire behaviour of high strength steel endplate connections — Part 1: Experimental study

• Post-fire tests were undertaken on high strength steel (HSS) endplate connections.
• Behaviour and failure mode of HSS endplate connections after fire were obtained.
• Comparison of HSS endplate connections after fire with mild steel ones was conducted.
• Eurocode 3 was validated with test results of high strength steel endplate connections.
• It offers basis for accurate post-fire evaluation of high strength steel structures.

In practice, high strength steels have been more and more popularly employed in significant structures and landmark constructions. However, in current literatures of civil engineering the very limited reports on behaviour of high strength steel structures cannot sufficiently guide the design of high strength steel structures, especially for their fire safety. The post-fire performance of steel structures is of significance in the fire-resistance design and post-fire evaluation, since the residual forces and deformations redevelop in steel structures after fire, which might be more dangerous than the fire condition. In order to reveal more information and better understanding on the behaviour and failure mechanisms of high strength steel endplate connections after fire, an experimental study has been conducted and presented in this paper. Tests on seven endplate connections were carried out after cooling down from fire temperature of 550 °C. The experimental behaviour of high strength steel endplate connections after fire was compared with that of mild steel endplate connections as well as with their original behaviour at ambient temperature without fire exposure. Moreover, the provisions of Eurocode 3 were validated with post-fire test results of high strength steel endplate connections. This experimental study indicates that a proper design of endplate connection employing a thinner high strength steel endplate can achieve the same failure mode, similar residual load-bearing capacity and comparable or even higher rotation capacity after fire, in comparison with a connection with thicker mild steel endplate.