超高轴压比区域约束混凝土柱抗震性能试验研究

Experimental research on confined concrete columns with super-high axial compression ratio under cyclic loading

对8根混凝土设计强度等级为C40,l0/b=8.8的约束混凝土柱进行了拟静力试验,其中3根为普通约束混凝土柱,5根为区域约束混凝土柱,分别采用1.10、1.25及1.35设计轴压比。区域约束的方式保证了混凝土的延性及强度的充分发挥,高轴压比有效限制了受拉裂缝的开展,提高了剪压区受荷面积及试件初始刚度。在试验轴压比范围内,区域约束试件水平承载力、延性及耗能能力随轴压增大而增大,同时,箍筋的应力也随轴压比增大而增大,且应力分布均匀,区域约束试件也较普通约束试件的刚度退化幅度小。研究结果表明:区域约束混凝土柱在超高轴压比下具有良好的力学性能及抗震性能,且轴压比越高性能越好;对于区域约束混凝土柱,可适当放宽GB 50011—2010《建筑设计抗震规范》对轴压比的限值。

Super-high axial compression ratios up to 1.10, 1.25 and 1.35 were applied in quasi-static tests. Three normal confined concrete （NCC） columns and five regional confined concrete （RCC） columns with concrete strength 40 MPa, lo/b = 8.8 were tested. Regional confinement can ensure the development of strength and ductility of concrete, and high axial compression can limit the development of cracks, resulting in increased load carrying area and initial rigidity of specimen. In the tests, the load carrying capacity, ductility and energy dissipation capacity of RCC columns were increased with the increase of axial compression ratio. Stresses of stirrups were well-distributed and also increased with the increase of axial compression ratio. The rigidity of RCC columns degenerated slowly than NCC columns. The results indieate that RCC columns have good mechanical behavior and excellent anti-seismic property under super-high axial compression ratio, the higher of axial compression ratio is, the better of mechanical behavior and the anti-seismic properties are. It is suitable and reliable for RCC structures to exceed the specifications of ＇ Code for seismic design of buildings＇ on axial compression ratios.