L形截面部分包覆钢-混凝土组合柱轴压性能试验与承载力计算

Axial compression performance test and bearing capacity calculation of L-shaped section partially encased composite steel-concrete columns

为研究L形截面部分包覆钢-混凝土组合(LPEC)柱的轴压性能,进行了6根LPEC短柱的轴压试验,研究了含钢率、系杆间距、截面高宽比等参数对LPEC短柱轴压荷载-位移曲线、承载力、刚度、延性、承载力提高系数等的影响规律,揭示了LPEC短柱的典型破坏模式和受力机理。结果表明:LPEC柱受力性能良好,其破坏模式主要表现为柱中部混凝土压溃和型钢翼缘的局部鼓曲,部分出现柱端部混凝土压溃同时系杆被拉断;增大截面含钢率、减小系杆间距可以明显提高对混凝土的约束效应,进而提高柱截面承载力和延性,但截面高宽比对承载能力的影响不显著。此外,由于规范ACI318-14、Eurocode 4和T/CECS 719-2020《部分包覆钢-混凝土组合结构技术规程》中给出的钢-混凝土组合柱承载力计算式中未考虑混凝土约束效应,计算得到的LPEC柱轴压承载力偏于保守;考虑混凝土约束效应分区,基于叠加原理提出了LPEC柱轴压承载力简化计算方法,计算结果与试验结果吻合较好。

To study the axial compression performance of L-shaped partially encased composite steel-concrete(LPEC)columns,axial compression tests of six LPEC short columns were conducted.The influence of critical parameters,such as steel content,link spacing and section aspect ratio,on the load-displacement curve,bearing capacity,stffness,ductility coefficient and bearing capacity improvement coefficient of LPEC short columns was investigated.The typical failure mode and load-bearing mechanism of LPEC short columns were revealed.Results indicate that the LPEC column has good mechanical performance,and its failure modes are mainly concrete crushing in the middle of the column and local buckling of the section steel flange.Meanwhile,concrete collapse at the end of the column and link breaking around the weld seam also occur in some specimens.Increasing the steel content and decreasing the link spacing can obviously improve the confinement effect of concrete,and then improve the bearing capacity and ductility of the specimen,whereas the influence of the section aspect ratio on the bearing capacity is not significant.In addition,for LPEC columns,the axial compression bearing capacities calculated by the steel-concrete composite column bearing capacity formulas given in the specifications ACI318-14,Eurocode 4 and T/CECS 719—2020‘Technical specification for partially-encased composite structures of steel and concrete'are conservative due to failing to consider the concrete confinement effect.Based on the superposition principle,a simplified calculation method for the axial compression bearing capacity of LPEC columns considering the confinement effect of concrete was proposed,and the calculated results are in good agreement with the experimental results.