受火后加固钢筋混凝土偏压格构柱受力性能试验研究

为研究受火后加固钢筋混凝土格构柱的受力性能，通过5根钢筋混凝土格构柱的偏心受压试验，分析了受火时间和填实加固对钢筋混凝土格构柱的破坏形态和承载力的影响。基于条带法提出了受火后未加固及受火后加固修复格构柱的受压承载力计算方法。结果表明：未受火对比格构柱和受火后未加固格构柱均发生柱肢混凝土压溃破坏，受火后填实加固格构柱发生小偏心受压破坏。ISO 834等效受火60min和90min格构柱受压承载力分别较对比未受火格构柱降低41.2%和63.8%；ISO 834等效受火60min和90min后采用混凝土填实加固格构柱的受压承载力较未受火对比格构柱分别提高73.8%和66.6%。与未受火格构柱相比，受火后未加固格构柱的初始刚度明显下降，而受火后填实加固格构柱的初始刚度显著提高。未受火格构柱和受火后未加固格构柱柱中横梁的横截面应变不符合平截面假定，而单个柱肢横截面应变基本相同，可近似认为单个柱肢轴心受力。基于条带法计算受火后未加固及受火后加固修复格构柱的受压承载力与试验结果的相对误差为-14.8%~12.7%，符合工程计算的精度要求。

Experimental research on eccentric compression performance of fire-damaged RC lattice columns strengthened with filling concrete

To study the mechanical performance of reinforced concrete( RC) lattice columns strengthened after fire,the influence of fire exposure duration and strengthening on failure modes and load bearing capacities of RC lattice columns was studied through an experimental study on five RC lattice columns under eccentrically compression. A calculation method based on the strip method was developed to predict the ultimate bearing capacity of lattice columns after fire or strengthening after fire. The results show that both the original and fire exposed unstrengthened lattice columns exhibit concrete crushing failure at the limb,while the strengthened lattice columns exhibit small eccentric compression failure. The ultimate bearing capacity of lattice columns after exposed to ISO 834 equivalent fire for60 min and 90 min is reduced by 41. 2% and 63. 8%,respectively,compared with that of the original lattice column.After exposed to ISO 834 equivalent fire for 60 min and 90 min,the ultimate bearing capacity of the lattice columns which are strengthened with filling concrete is increased by 73. 8% and 66. 6%,respectively,compared with that of the original lattice column. Compared with the original column,the initial stiffness of the unstrengthened lattice column after fire decreases greatly,while the initial stiffness of the strengthened lattice columns with filling concrete after fire is significantly increased. The mid-section strain of both original and fire exposed unstrengthened columns does not conform to the plane section assumption,and the cross-section strain of the single column limb is basically the same,so it can be approximately treated as axial compression in single column limb. The calculation method based on the strip method is used to calculate the ultimate bearing capacity of lattice columns after fire,with an error between-14. 8% and 12. 7%,which meets the accuracy requirements of engineering calculation.