圆、八边、正方与矩形钢管混凝土轴心受压性能的连续性

The Continuity of Axial Compressive Behaviors of Concrete Filled Steel Tube (CFST)for Circular, Octagonal,Square and Rectangular Forms

按照“钢管混凝土统一理论”的推断:钢管混凝土构件性能的变化是随截面形状的改变而变化,变化是连续的,设计方法是统一的。本文介绍了采用塑性断裂理论描述三向受压混凝土的本构关系,用试校法确定三个主要系数的最优值,得到了只与混凝土性质有关的本构关系。加上钢材三向应力状态的本构关系,采用有限元法首次得到了等效截面的圆形、八边形、正方形和矩形钢管混凝土的截面上高斯点的应力分布,和平均应力与纵向应变的全过程关系曲线。由全过程关系曲线得到了各种截面构件的轴压强度指标与轴压模量,充分证明了性能随截面形状的改变而变化的连续性。同时导出了统一的计算公式。此外,还导出了和圆钢管混凝土相比,各种截面构件紧箍效应的下降率。最后给出了各种截面钢管混凝土轴压构件的强度设计公式。关于稳定承载力将另文介绍。

According to the judgement of 'The Unified Theory of CFST', the behaviors of CFST members change with the change of cross section. The change exhibits continutity, and the design method is unified. In this paper, the application of the plastic- crack theory to decide the constitutive relation of concrete under three dimensions compression is introduced. The try-and-error method is used to constitutive relation of concrete was got,which relates to the behaviors of concrete only. With the constitu- tive relation of steel under multi--axes stresses state,the finite element method is used to get the stress distribution of Gauss Point in cross sections of circular,octagonal, square and rectangular CFST menbers. And the relation between σand εare got also. From σ-ε relation curves,the strength index and compressive modulus of various cross sections are got. It proved that the behaviors of CFST are changed with the change of cross sections and the change is in continuity. At the same time,the uni- fied design formulas are derived. In addition, the descending ratios of confining effects for cross section member. Finally, the design for- mulas of strength for various cross section CFST members problem of various cross section CFST members are presented.