徐变对空心钢管混凝土轴压稳定承载力的影响

为了得到核心混凝土徐变对空心钢管混凝土轴心受力构件承载力性能的影响,从材料模量变化对承载力的影响角度,利用推导出的空心钢管混凝土临界承载力公式并结合有限元程序计算出空心钢管混凝土构件中素混凝土自由徐变量、核心混凝土卸载徐变及构件纵向徐变量,根据将钢与混凝土两种材料在徐变发生后的切线模量改变,计算出徐变后构件稳定承载力下降率.分析表明:空心率越大、钢管的钢材级别越高,徐变对整体构件的承载力影响越少;而恒载占设计荷载的比例越大时,徐变对整体构件的承载力影响越大.当空心钢管混凝土轴压心受压构件承受永久荷载引起的轴心压力占全部轴心力30%及以上时,应将构件承载力乘以徐变折减系数.

Effect of Concrete Creep on Axially Compressed Stable Bearing Capacity of Hollow Concrete Filled Steel Tubular Members

To get the effect of concrete creep on axial bearing capacity of hollow concrete-filled steel tubular (CFST) structures, firstly, the ultimate bearing capacity formula of H-CFST structures is deduced and the modified bearing capacity for modulus changed due to creep is analyzed. Secondly, the finite element method (FEM) ABAQUS program is debugged to get relative parameters of concrete creep. Meanwhile, this method was verified by CFST test ideally, and the free creep value of plain concrete, unloading concrete creep value and structures creep value which relate to the change of material modulus are calculated by this method. The modulus of steel and concrete changed after the creep and the bearing capacity declined, at the same time, the relationship between descending of bearing capacity and slenderness ratio was obtained. In the end, according to the modulus of steel and concrete caused by concrete creep, the reduced ratio of the bearing capacity of H-CFST structures can be obtained.