Rotational capacity of steel I-beams under fire conditions Part I: Experimental study

An extensive experimental programme has been conducted to investigate the rotational capacity of steel I-beams under fire conditions. Two main objectives are to study the effects of temperature on the rotational capacity and to identify key parameters which affect the rotational capacity. Parameters including temperature, flange slenderness, web slenderness and effective length were varied in the test programme. The test set-up was designed to represent the internal joint of a continuous beam. The segments between the plastic hinge and adjacent point of inflection where hogging moment occurs were represented by each half of a simply supported beam subjected to a mid-span point load. The specimens were heated to the desired temperature before they were subjected to an increasing point load up to failure (isothermal test). The results showed considerable reduction in the rotational capacity at elevated temperatures. In addition, the effects of flange and web slenderness, together with effective length, on the rotational capacity were clearly observed. These tests probably represent the first of its kind in the world in the experimental investigation of ductility of beams under fire conditions. Moreover, these test results were very useful to investigate the feasibility of applying finite element method to study the moment–rotation relationship of steel I-beams at elevated temperature, as described in the companion paper.