钢骨-圆钢管混凝土轴压短柱力学性能分析

Behavior of tubular stub columns of axially loaded steel-reinforced concrete-filled circular steel

为研究钢骨-圆管混凝土轴压短柱的相互作用关系,建立钢骨-圆管混凝土轴压短柱极限承载力计算公式,采用三维有限元法和弹塑性法对钢骨-钢管混凝土轴压短柱的荷载-变形曲线进行分析。采用有限元法分析钢骨-钢管混凝土轴压短柱和钢管混凝土轴压短柱的钢管纵向应力与横向应力、核心混凝土的纵向应力以及钢骨纵向应力的变化。基于极限平衡理论建立钢骨-圆管混凝土轴压短柱承载力计算公式。研究结果表明:由于钢骨对核心混凝土的约束,钢骨屈服后纵向应力略低于其屈服强度;与钢管混凝土相比,由于同时受钢管和型钢的约束,钢骨-钢管混凝土中核心混凝土纵向应力有所增大,钢管屈服后纵向应力降低速率、环向应力增加速率减小,钢管减少了对核心混凝土的约束作用;短柱承载力公式计算结果与有限元计算结果相近,且与试验结果相比,这2种计算结果都偏于安全。

In order to understand the mutual effects among section steel,concrete and steel tube of steel reinforced concrete-filled circular steel tubular（SR-CFST） stub columns under axial compression and to propose the formula of ultimate bearing capacity for SR-CFST stub columns,both 3D finite element model and elasto-plastic method were applied to analyze the load-deformation curve of SR-CFST stub columns.Based on the finite element method,the changes of axial stress and perimeter stress of steel tube,the axial stresses of concrete and section steel in both SR-CFST stub columns and concrete-filled circular steel tubular（CFST） stub columns were discussed.Based on the limit equilibrium method,simplified formula of ultimate bearing capacity for the axially loaded SR-CFST stub columns was proposed.The results show that at yield state,the axial stress of section steel is slightly lower than its yield stress due to the restriction effect from section steel to concrete.Compared with CFST stub columns,the axial stress of concrete in SR-CFST stub columns increases slightly for the concrete confined by both section steel and steel tube,and axial stress decreases and perimeter stress of steel tube increases after yield weakens slowly.The confinement effect from steel tube to concrete also weakens slowly.The analysis results by limit equilibrium method are close to those by finite element method,and both are in safe range compared with the experimental results from references.