外包薄壁钢管加固受火后混凝土柱的抗震性能

通过2根未受火钢筋混凝土柱、2根受火后未加固钢筋混凝土柱和10根外包薄壁钢管加固受火后钢筋混凝土柱的拟静力试验，考察了轴压比、剪跨比、钢管厚度及加固方式等参数对外包薄壁钢管加固受火后混凝土柱抗震性能的影响情况，建议了外包薄壁钢管加固受火后混凝土柱受剪承载力的计算公式。结果表明：薄壁钢管加固可显著提高受火后混凝土柱的受剪承载力、极限变形和累计滞回耗能，且加固后试件的割线刚度与未受火试件相比相差较小。受火后剪跨比为1.78和3.0的混凝土柱加固后的承载力分别比相应的未加固柱的承载力提高了41.8%~47.0%和38.5%~74.4%。轴压比对加固后试件的受剪承载力、刚度、耗能能力和延性影响较大，对极限变形影响较小。薄壁钢管厚度对加固后试件的耗能能力影响较大，对受剪承载力影响较小。薄壁钢管根部焊接角钢并用螺栓锚固的方式可提高加固效果。

Seismic performance of concrete columns after fire and strengthened with thin-walled steel tube

Based on the pseudo static tests of two reinforced concrete (RC) columns without fire, two RC columns after fire without strengthening and ten RC columns after fire and strengthened with thin-walled steel tubes, the effects of axial load ratio, shear span ratio, steel tube thickness and strengthening modes on the seismic performance of concrete columns strengthened with thin-walled steel tubes were investigated. A calculation formula for the shear bearing capacity of concrete columns after fire and strengthened with thin-walled steel tube was developed. The results show that the reinforcement by the thin-walled steel tube can significantly improve the shear capacity, the limit deformation capacity and the cumulative energy dissipation capacity of concrete column after fire, and the secant stiffness of the strengthened specimen is similar to that of the unfired specimen. The bearing capacity of concrete columns after fire and strengthened with thin-walled steel tube is high than, about 41.8%~47.0% and 38.5%~74.4%, that without strengthening when the shear span ratios are 1.78 and 3.0, respectively. The axial load ratio has a significant influence on the shear bearing capacity, the stiffness, the energy dissipation capacity and the ductility, but has a small influence on the limit deformation of the strengthened specimens. The thickness of the thin-walled steel tube influences the energy dissipation capacity more than the shear bearing capacity of the strengthened specimens. The reinforcement mode with welding angle and bolt anchorage at the root of thin-walled steel tube can improve the strengthening effect.