An-Najah Staff

Restrained steel beams when exposed to fire develop significant restraint forces and often behave as beam-columns. The response of such restrained steel beams under fire depends on many factors including fire scenario, load level, degree of restraint at the supports, and high- temperature properties (including creep) of steel. A set of numerical studies, using finite element computer program ANSYS, is carried out to study the fire response of steel beam-columns under realistic fire, load and restraint scenarios. The finite element model is v alidated against experimental data, and the importance of high-temperature creep on the fire response of steel beam-columns is illustrated. The validated model is used to carry out a set of parametric studies. Results from the parametric studies indicate that fire scenario, load level, degree of end-restraint and high-temperature creep have significant influence on the behavior of restrained beams under fire conditions. Severe fires produce high axial forces at early stages of fire exposure, whereas in moderate fires, significant axial force develops only at later stages of fire exposure. Increased load level leads to higher catenary forces, resulting in lower fire resistance. Rotational restraint enhances the fire resistance of the laterally-unrestrained steel beam, while the axial restraint has detrimental effect on fire resistance. These numerical studies clearly indicate that the performance of restrained steel beams under design fire exposures is significantly different from that of "standard fire" exposure