Behaviour and mechanical modeling of steel beam-to-column joints at elevated temperatures

In conventional steel structural analysis at ambient temperature, a beam-to-column joint is assumed as either .pinned. or .rigid. However, the actual behaviour of joint always lies somewhere between these two extremes. Because steel members are assembled together through joints, there is a pressing need to better understand the joint behaviour and its effect on overall behaviour of steel framed structures under fire conditions. Nevertheless, there have been only a few number of tests conducted with fairly limited types of joints at elevated temperatures, due to expensive high-temperature testing costs. This paper presents an experimental investigation of typical extended end-plate beam-to-column joints at elevated temperatures. Six beam-to-column joints have been tested, including three specimens (CR1, CR2 and CR3) tested at 400, 550 and 700 °C, respectively, and another three specimens (CR4, CR5 and CR6) tested at 700 °C with three beam axial compression levels (0%, 2.5% and 4%). Moment-rotation-temperature characteristics are summarized to investigate the degradation of such type of steel joint behaviour at elevated temperatures. It is anticipated that these results will be beneficial in verifying .Component-Based. method for steel joints in modelling steel structure under fire conditions. Such method offers the most practical and economical way of introducing a predictive capability into whole-frame modelling in fire, since it is impractical for designers to use either complex finite element analysis or expensive furnace testing.