Steel beam-to-column extended end plate joints at elevated temperature: Experimental, numerical and component-based approaches

Up till now, there are only very few tests conducted on steel beam-to-column joints under fire conditions because of the prohibitive costs associated with elevated-temperature tests. This is despite the fact that to a large extent the beam-to-column joints govern the behaviour of steel and composite framed structures. This paper presents the results of an experimental investigation of typical extended end-plate steel beam-to-column joints at elevated temperatures. Six beam-to-column cruciform joints were designed and tested to failure. They comprised three specimens tested at isothermal temperature of 400°C, 550°C and 700°C, and another three on specimens at 700°C but subjected to different axial restraints on the joints. From the test programme, a summary of moment-rotation-temperature characteristics is obtained. The second part presents a series of corresponding numerical and analytical investigations on the behaviour of these steel joints. The authors utilized a 'component-based" approach to analyze the mechanical response of these joints at elevated temperatures, incorporating the beam web shear component together with those within the tension and compression zones of the connection. Effects from thermal restraints on steel joints have also been integrated into this approach. The component-based analytical model was found to represent well the structural behaviour in the tests, including the effects of thermaJ restraint. In addition, detailed finite element simulations of the tests were also performed. Both the component-based and numerical predictions provide acceptable correlations with the test behaviour.