型钢-方钢管混凝土轴压短柱非线性分析

Nonlinear analysis of axially loaded steel reinforced concrete-filled square steel tubular stub columns

采用ABAQUS有限元软件对型钢-方钢管混凝土轴压短柱的荷载-变形曲线进行了有限元分析,探讨了型钢-方钢管混凝土轴压短柱、等截面普通方钢管混凝土轴压短柱、等截面且等体积含钢率的型钢-圆钢管混凝土轴压短柱的内力变化情况。分析结果表明:三种短柱中型钢-圆钢管混凝土轴压短柱的极限承载力最大且延性最好;与等截面普通方钢管混凝土轴压短柱相比,型钢-方钢管混凝土轴压短柱中核心混凝土纵向应力有所增长,钢管屈服后纵向应力降低速率、环向应力增加速率减缓,钢管对核心混凝土的约束作用减小;与等截面且等体积含钢率的型钢-圆钢管混凝土轴压短柱相比,型钢-方钢管混凝土轴压短柱角部端点的约束效果最明显,钢管中点的约束效果最弱,型钢-圆钢管对核心混凝土的整体约束最强,型钢屈服后纵向应力略低于其屈服强度,且型钢的翼缘部分抗压强度比腹板部分的抗压强度高;等型钢含量情况下,随着翼缘长度b与腹板高度h比值的增大,轴压短柱的极限承载力越来越低,当b/h=0,即十字形钢骨-方钢管混凝土轴压短柱承载力最高;等体积含钢率下,普通方钢管混凝土柱轴压短柱承载力最低,随着型钢截面面积As与方钢管截面面积At的比值的增大,轴压短柱的极限承载力先增后降,当As/At≈0.8时,承载力达到最大值。

The finite element analysis on load-deformation curve of steel reinforced concrete-filled square steel tubular（ SR-CFST） stub columns was carried out by finite element software ABAQUS. The changes of internal forces in SR-CFST,ordinary concrete-filled square steel tubular（ CFST） stub columns with the same section and steel reinforced concrete-filled circular steel tubular（ SR-CFCT） stub columns with the same section and steel ratio were discussed. The results were listed as follows： the ultimate bearing capacity and ductility of SR-CFCT stub columns are best in the three stub columns;compared with CFST stub columns with the same section,the axial stress of concrete in SR-CFST stub columns increases slightly. After yield,both the decrease rate of axial stress and increase rate of perimeter stress of steel tube weaken slowly and the confinement effect from steel tube to concrete also weakens; compared with SR-CFST stub columns with the same section and steel ratio,the confinement effect of SR-CFST is most obvious in extreme point but weakest in steel middle point. The confinement effect from steel tube to concrete is strongest in SR-CFCT. The axial stress is slightly lower than its yield strength and the compressive strength of steel reinforced in flange is higher than that of web; under the same section steel condition,with the increase of the ratio of flange length b and web height h,the ultimate bearing capacity of stub columns under the axial compression is lower and lower. When b / h = 0,the bearing capacity of axially loaded cross SR-CFST stub columns is highest; under the same volume steel ratio,the bearing capacity of CFST stub columns is lowest and the bearing capacity first increases then decreases with the increase of ratio of cross section area Asof shape steal and cross section area Atof square steel tube. When As/ At≈0. 8,the bearing capacity reaches the maximum value.