钢管约束钢筋混凝土柱抗震设计方法及塑性铰

Seismic design method and plastic hinge of square steel tube confined reinforced concrete(STRC)columns

钢管约束钢筋混凝土柱具有承载力高、延性好和施工便利等优点,满足“建筑工业化”的要求,因而被广泛应用在高层建筑中。基于混凝土的塑性-损伤模型与钢材的弹塑性混合强化模型,采用ABAQUS软件建立方钢管约束钢筋混凝土(STRC)柱的三维实体精细有限元模型进行拟静力分析。模型考虑了钢管对核心混凝土的约束作用以及合理的边界条件、加载模式,分析所得柱的破坏形态、荷载-位移滞回曲线和荷载-位移骨架曲线等有限元结果与已有拟静力试验结果吻合较好。进一步建立了136个足尺模型并进行参数分析,研究结果表明:钢管的套箍约束作用可减小混凝土压应变峰值并提高压应力峰值,延缓柱的破坏,有效提高其承载力和延性;破坏位移角和极限承载力随钢管厚度增大而增大。提出了不同轴压比时5种材料强度匹配的钢管合理厚度和套箍系数等抗震设计方法,以混凝土应变、钢管应变为依据的塑性铰判定方法以及塑性铰长度实用计算公式,可为框架柱的抗震设计提供依据和支持。

Steel tube confined reinforced concrete columns have the advantages of high bearing capacity,good ductility and convenient construction,which meet the requirements of"building industrialization",so they are widely used in high-rise buildings.Based on the plastic-damage constitutive model of concrete and elastic-plastic mixed strengthen constitutive model of steel,finite element software ABAQUS was used to build an elaborate 3D finite element solid model and perform pseudo-static analysis of square steel tube confined RC(STRC)columns.The model considered the confinement effect of the steel tube exerting on the core concrete,as well as reasonable boundary conditions and loading modes.Good agreement was achieved between the finite element analysis results and the existing quasi static experimental results regarding to the failure modes,load-displacement hysteretic curves and load-displacement skeleton curves.Based on the validated model,136 full scale model examples were established and extensive parametric analysis was conducted.The results show that the confinement of external steel tube can reduce the peak compressive strain and increase the peak compressive stress of concrete,thus delaying the failure of RC column and improving its bearing capacity and ductility effectively.Besides,the failure displacement angle and ultimate bearing capacity increase when the thickness of steel tube increases.Finally,the seismic design method including reasonable thickness and hoop index of the steel tube were proposed for 5 material strength matching and different axial compression ratios.A method to judge the plastic hinge based on concrete strain and steel tube strain was proposed,as well as a practical calculation formula of plastic hinge length.This study can provide basis and support for the seismic design of frame columns.