EXPERIMENTAL RESEARCH ON POST-FIRE MECHANICAL BEHAVIOR OF H-STEEL COLUMNS WITH DIFFERENT RESTRAINT

Effect of restraints on post-fire mechanical property of three restrained H-steel columns was studied basedon experimental investigation of the H-steel columns after exposure to fire. The restraints applied to the top of thesteel columns considered here were symmetrical restraint to top end of the column, unsymmetrical restraint and freedeformation. The fire and post-fire experiment results show that temperature rise and cooling of the steel columns arebehind variation of furnace temperature, the H-steel column after exposure to fire has higher axial compressive bearingcapacity and the final failure of the steel column is accompanied with the local buckling of flanges and web of thecolumn, and the post-fire mechanical property of the H-steel columns after exposure to fire is obviously affected by therestraints on top of the steel columns. It is typically shown that the post-fire longitudinal strain of the cross section ofthe steel column with symmetrical restraint is evidently different from that of the column with unsymmetrical restraint,and the stiffness of the column with unsymmetrical restraint, which is prior to the column' s buckling, is much largerthan that of the column with symmetrical restraint. It is seen that the bending curve of the H-steel columns indirection of weak-axis is S-type, which is more evident for the steel column with symmetrical restraint and that withoutrestraint