荷载引起的温度应变对火灾后钢筋混凝土轴压构件的影响

受约束的和自由的钢筋混凝土构件在经历升温和降温的变化后其构件的应变化是不同的，这种变化称为荷载引起的温度应变（LITS），在升温阶段LITS随温度升高而增大，而且应力强度比越高，LITS越大，在降温阶段，LITS却保持不变，因此，由于存在LITS，如果混凝土构件在较高的应力水平下遭受火灾，火灾后混凝土构件会开裂或爆裂，为了研究LITS对高温后混凝土构件的影响，研究了轴压柱升降温后的应变变化，并讨论了影响LITS和混凝土爆裂的原因，分析表明，LITS对混凝土构件高温后的爆裂影响很大。

The Influence of Load Induced Thermal Strain on Axial Compressive RC Columns after Exposed to Elevated Temperature

Strain difference between constraint and free RC members will occur when concrete members experience a cycle of heating or cooling. The difference is called Load Induced Thermal Strain (LITS). LITS increases at heating phase with increasing of temperature. The higher the ratio of stress to strength, the higher the LITS is. At cooling phase, the LITS remains constant. Therefore if concrete structures are fired at high stress level, they will be cracked after cooling down and develop spalling damage due to the LITS. In order to investigate the influence of the LITS on RC members after exposure to elevated temperature, the behavior of axial compressive RC columns during heating up and cooling down process under stressed conditions has been studied. In the study, the stress-strain constitutive relationship of concrete under SE condition (specimen heated stressed, tested at elevated temperature) was used, and parameters influencing the LITS and spalling damage were discussed. Study has shown that the LITS contributes to the cracks of RC members after exposure to elevated temperature.