不同约束H型钢柱火灾后力学性能试验研究

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

通过对3根柱顶受不同约束的H型钢柱的火灾后力学性能的对比试验研究,讨论不同约束对H型钢柱火灾后力学性能的影响。3种约束条件分别为:柱顶对称约束、柱顶非对称约束和自由膨胀。火灾中及火灾后的试验结果显示,H型钢柱的升温和降温过程存在一定的滞后性,受火后的H型钢柱仍有较高的轴压承载力,最终破坏时伴随着翼缘和腹板的局部屈曲,约束性质对H型钢柱火灾后的力学性能有明显的影响,也即受对称约束的H型钢柱在火灾后轴压作用下的纵向应变明显不同于非对称约束的情况,而且非对称约束钢柱压曲破坏前的整体刚度明显高于对称约束。火灾后H型钢柱沿强轴方向的侧向弯曲形状呈S形变化,这一特征对于受对称约束和自由膨胀的钢柱更为明显。

Effect of restraints on post-fire mechanical property of three restrained H-steel columns was studied based on experimental investigation of the H-steel columns after exposure to fire. The restraints applied to the top of the steel columns considered here were symmetrical restraint to top end of the column, unsymmetrical restraint and free deformation. The fire and post-fire experiment results show that temperature rise and cooling of the steel columns are behind variation of furnace temperature, the H-steel column after exposure to fire has higher axial compressive bearing capacity and the final failure of the steel column is accompanied with the local buckling of flanges and web of the column, and the post-fire mechanical property of the H-steel columns after exposure to fire is obviously affected by the restraints on top of the steel columns. It is typically shown that the post-fire longitudinal strain of the cross section of the 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 larger than that of the column with symmetrical restraint. It is seen that the bending curve of the H - steel columns in direction of weak-axis is S-type, which is more evident for the steel column with symmetrical restraint and that without restraint.