不同尺寸钢筋混凝土短柱高温后抗震性能分析

为了研究不同尺寸钢筋混凝土短柱在高温和地震耦合作用下的力学行为,建立了火灾高温后钢筋混凝土(RC)短柱抗震性能研究的三维数值模型,对12个几何形状相似、尺寸大小不同的RC柱进行不同受火时间后的水平反复加载试验。在验证模型有效性的基础上,研究了受火时间和截面尺寸对RC柱温度场分布、破坏模式、低周反复荷载下的骨架曲线、位移延性、刚度退化、抗剪承载力等的影响规律和失效机制; 基于模拟数据和经典的Bazant尺寸效应思想,提出了考虑混凝土强度尺寸效应影响及受火时间、尺寸影响的双参数修正的钢筋混凝土柱抗剪承载力实用计算公式。结果表明:火灾后截面尺寸越大的RC柱温度差异越大,受热越不均匀,角筋比其他纵筋升温快,保护层有助于延缓钢筋温度的升高; 构件高温后刚度退化较常温时平缓; 高温后构件尺寸越大,刚度退化越迅速; 构件抗剪承载力随受火时间增长而降低,并受构件截面尺寸的影响; 提出的钢筋混凝土柱抗剪承载力实用计算公式可供火灾后大尺寸钢筋混凝土柱安全性鉴定作参考。

Analysis of Seismic Performance of Reinforced Concrete Short Columns with Different Sizes After High Temperature

In order to study the mechanical performance of reinforced concrete short columns with different sizes under the coupling action of high temperature and earthquake, the three-dimensional numerical model was established to study the seismic behavior of reinforced concrete(RC)short columns after high temperature fire. The horizontal repeated loading tests of 12 RC columns with similar geometry and different sizes after different fire duration were carried out. On the basis of verifying the validity of the model, the influence law and failure mechanism of fire time and cross-sectional size on RC column temperature field distribution, destruction mode, skeleton curve under low cyclic loading, displacement ductility, stiffness degradation, and shear-resistant carrying capacity were studied. Based on the simulation data and the classical idea of the size effect of Bazant, a practical calculation formula of shear bearing capacity of reinforced concrete columns was proposed by introduction of two parameters considering the size effect of concrete strength and the influence of fire duration. The results show that the larger the cross-section size of RC column is, the greater the temperature gradient and the more uneven of the temperature field are. The temperature rise of corner reinforcement is faster than that of other longitudinal reinforcements. The concrete cover can help delay the rise of steel bar temperature. The rate of stiffness degradation after high temperature is slower than that at ordinary temperature. The larger the member size is, the faster the stiffness degradation is. The shear bearing capacity of reinforced concrete columns decreases with the increase of fire duration and is affected by the cross-section size of members. The proposed practical calculation formula of shear bearing capacity of reinforced concrete columns can be used as a reference for safety determination of large-size reinforced concrete columns after fire.