轴向约束型钢混凝土柱耐火性能试验研究

为了考察受轴向约束的型钢混凝土柱的耐火性能，以荷载比、偏心率和含钢率为参数，开展了7根轴向约束型钢混凝土柱的耐火试验。采用恒载升温模式，研究了火灾下受轴向约束的型钢混凝土柱的温度分布、位移、变形、耐火极限及破坏形态。试验结果表明：荷载比相同时，施加在轴心受压柱顶的竖向荷载大于偏心受压柱。对于轴心受压柱，高温下柱首先缓慢膨胀，然后逐渐压缩破坏；由于轴向约束分担了柱的竖向荷载，压缩变形随时间变化较为缓和，轴向约束延长了柱的耐火极限。对于偏心受压柱，高温下其膨胀变形大于轴心受压柱，且膨胀变形先增加再减小；轴向约束增加了柱的竖向荷载，缩短了柱的耐火极限。荷载比对轴向约束型钢混凝土柱耐火极限影响显著，荷载比越大，耐火极限越小。当荷载比不大于0.5时，偏心率越大，柱的耐火极限会相应增大。含钢率增加，会在一定程度上延长柱的耐火极限。

Fire performance of axially restrained steel reinforcedconcrete columns

In order to investigate the fire resistance of axially restrained steel reinforced concrete columns, fire tests on seven axially restrained steel reinforced concrete columns were carried out considering load ratio, load eccentricity and steel ratio as the varying parameters. The test adopted a constant load heating mode, and through the experiments, the temperature distribution, displacement, deformation, fire resistance and failure mode of the restrained steel reinforced concrete columns under fire were studied. The test results show that the vertical load on the top of the axial compression columns is larger than that of the eccentric compressed columns with the same load ratio. The concentrically compressed columns expand slowly at first and then shorten gradually at high temperature. Because the axial restraint shares the vertical load of the column, the compression deformation varies mildly with fire duration, and the axial restraint prolongs the fire resistance of the column. For eccentrically compressed columns, the expansion deformation at high temperature is greater than that of the concentrically compressed columns, and the expansion deformation first increases and then decreases. The axial restraint increases the vertical load of the column and shortens the fire resistance of the column. The load ratio has a significant influence on the fire resistance of the axially restrained steel reinforced concrete columns. The fire resistance decreases with the load ratio. When the load ratio is not larger than 0.5, the fire resistance increases with the eccentricity ratio of the axial load. The fire resistance increases with the steel ratio to a certain extent.