方钢管约束钢筋混凝土柱拟静力有限元分析

采用ABAQUS软件建立5根方钢管约束钢筋混凝土(STRC)柱的三维实体精细有限元模型并进行拟静力分析,模型考虑了混凝土的塑性损伤性质和钢材的弹塑性混合强化性质以及钢管、钢筋对核心混凝土的约束作用.在破坏形态、荷载-位移滞回曲线、荷载-位移骨架曲线和刚度退化-位移曲线的有限元结果与已有拟静力试验结果吻合较好的基础上,进一步分析了各部件的应力-应变和塑性耗能特征.结果表明:①高轴压比0.8作用下,钢管的约束作用可显著减小核心混凝土、纵筋和箍筋的应变峰值,提高柱的总塑性耗能值而降低核心混凝土的塑性耗能占比,延缓核心混凝土压碎破坏,提高承载力和延性;②当轴压比由0.34增大为0.65、0.8,各部件的压应变峰值以及总塑性耗能值都增大,核心混凝土的耗能占比增大而更易压碎;③当混凝土强度等级降低,钢管作为延性材料承担了更大比例的塑性耗能,提高了柱的延性.

Finite element analysis for pseudo-static of square steel tube confined RC (STRC) columns

ABAQUS software was used to build an elaborate 3D finite element (FE) solid model and perform pseudo-static analysis of 5 square steel tube confined RC (STRC) columns. The model considers the plastic-damage of concrete, elastic-plastic mixed strengthen of steel, the confinement effect of both the steel tube and the rebar exerting on the core concrete. Good agreement was achieved between the finite element results and the existing quasi static experimental results regarding to the failure mode, load-displacement hysteretic curves, load-displacement skeleton curves and stiffness degradation-displacement curves. The stress-strain and plastic energy dissipation of each component are further analyzed. The results show that: (1) Under high axial compression ratio of 0.8, the confinement of steel tube can significantly reduce the peak strain of core concrete, longitudinal bars and stirrups, increase the total plastic energy dissipation of STRC column and reduce the plastic energy dissipation proportion of core concrete. Thus it can delay the core concrete crushing and improve the bearing capacity, the ductility. (2) When the axial compression ratio increases, peak compressive strain of each component increase and the energy dissipation proportion of the core concrete increases which tends to crush. (3) When the strength grade of the concrete decreases, the steel tube as a ductile material bears a greater proportion of plastic energy dissipation, which improves the ductility of the column.