The structural response of steel I-section members subjected to elevated temperature gradients across the section
This work is primarily concerned with the structural response of steel I-section beams and columns heated along one flange to the elevated temperatures likely to be reached in real fires in buildings or ISO 834 fire resistance tests. Experiments have employed nominally full size models, heated using high powered, ceramic insulated, electrical heating elements at temperatures up to 1000°C. The experiments have been conducted on: a non-loaded, simply supported beam; a design-loaded, simply supported beam; a non-loaded 2-span beam on simple supports; and design-loaded, pin-ended columns free to bow about both axes. Load, displacement and temperature data have been recorded and analysed for a number of heating, imposed loading and restraint conditions likely to be met in practice. One of the experiments simulates the loading and restraint conditions used in the BS 1476 : Part 8 : 1972 standard fire resistance test on beams. The data may be used as benchmarks for the validation of analytical studies. Simple theories f or the bowing displacements of non-loaded members having temperature gradients across the section have been derived and validated not only with the model experiments but also with data from full scale compartment fires in a collaborative programme of research undertaken by the British Steel Corporation Swinden Laboratories and Fire Research Station. The practical application of the theory has been demonstrated in other ways. A finite element method, using the PP.FEC program, has also been used which takes account of phase transformation - the sudden temporary shrinkage in steel as it is raised above a temperature of 720°C - but it has not proved possible to use PAFEC for plasticity analyses of beams or columns at elevated temperatures. The phenomenon of' reverse direction bowing has been observed In the model column tests and this confirms observations made by other workers.