施工初应力与长期荷载作用下内配型钢的方钢管混凝土轴压柱受力性能研究

Compressive behavior of square CFST column with encased profiled steel under preload and sustained load

为研究内配型钢的方形钢管混凝土构件在施工初应力和长期荷载作用下的力学性能,基于合理的材料本构,采用有限元软件ABAQUS建立了考虑这两种荷载作用的有限元模型,通过相关试验验证了模型的有效性。在此基础上,对典型内配型钢的方形钢管混凝土柱分析了该类构件各部件间受力机理和破坏形态,并分别与其一次加载时以及方钢管混凝土考虑初应力和长期荷载作用时的承载力变化进行了对比。结果表明:考虑施工初应力和长期荷载后,构件在施工初应力和长期加载阶段产生了初变形;在长期持荷阶段,主要由钢管和型钢受力,构件整体徐变率较小;而再加载阶段,主要由混凝土受力。与一次加载相比,初应力和长期荷载作用下构件承载力增大不显著,但与未配型钢的钢管混凝土相比,承载力增大明显;型钢的存在有效约束了混凝土横向的膨胀变形。

In order to study the mechanical behavior of square concrete filled steel tubular(CFST) members with encased profiled steel under preload and sustained load, based on the rational material constitutive model, the finite element model considering two loads was established with software ABAQUS. The validity of the finite element model was verified by relevant tests. On this basis, the mechanical mechanism and failure modes of typical square CFST stub column with encased profiled steel are analyzed. In addition, the bearing capacity of the member is respectively compared with the member of instant loading and square CFST stub column considering preload and sustained load. The results show that after considering the preload and sustained load, deformation of the member occurs already in the preload and long-term loading stage;in the long-term load-keeping stage, steel tube and profiled steel mainly bear load, and the creep rate is small in this stage. In the reloading stage, concrete mainly undertakes load. Compared with the instant loading, the increase of ultimate strength of the specimen is not significant, but the ultimate strength of the specimen increases obviously compared with the concrete filled steel tube. The existence of profiled steel effectively restrains the transverse expansion of concrete.