火灾后平面及空间混凝土梁柱节点抗震性能试验研究

对1个平面和1个空间钢筋混凝土梁柱节点在ISO834标准升温曲线作用下的抗火性能进行了试验,然后对4个构件(上述2个火灾后试件,2个常温对比试件)进行了低周往复荷载下的试验。研究了平面和空间节点火灾后的残余抗震性能,分析了节点的裂缝发展、破坏模式、滞回曲线、骨架曲线、承载力、延性系数、刚度退化和耗能能力等。结果表明,除火灾后的平面节点发生核心区破坏外,其余节点均为梁端弯曲破坏。经历火灾后,试件的承载力、延性系数以及耗能能力降低,变形增大。火灾后混凝土的损伤削弱了现浇楼板和直交次梁对空间节点承载力的贡献,因此空间节点火灾前后性能变化更加显著。

Experimental Study on Seismic Behavior of Plane and Spatial Concrete Beam-column Joints After Exposure to Fire

The fire behavior of one plane and one spatial beam-column concrete joints was investigated under the fire according to the standard ISO834 temperature time curve, and then four specimens (the two fire-damaged specimens, two comparison specimens under room temperature) were tested under low cycle reciprocating loadings. Thus their post-fire residual seismic performances were studied. Furthermore, the cracks, failure modes, hysteretic loops, envelope curves, load bearing capacity, ductility coefficient, stiffness degradation, and energy dissipation were studied and compared in detail. The experimental results show that shear failure happens only in the joint zone of the fire-damaged plane beam-column joint, and the rest three specimens exhibit bending failure in beam ends. It is also demonstrated that the load bearing capacity, ductility coefficient and energy dissipation of the specimens is reduced, and the deformation is increased, after exposure to fire. However, the contribution of slab and orthogonal beams is weakened due to the damage of concrete after fire, which results in a more significant change in the performance of the space beam-column joint specimens before and after fire exposure.