交错桁架结构体系的极限承载力及其影响因素分析

Analysis of ultimate bearing capacity and its influence factors of staggered-truss building system

本文基于非线性连续介质力学理论和内力屈服面塑性流动理论,推导出计算交错桁架结构体系极限承载力的二阶弹塑性刚度方程。在该刚度方程的构造中不仅考虑了单元截面上的轴力、剪力、弯矩、扭矩以及结构剪切变形的影响,还考虑了杆端塑性铰处内力之间的相互影响。数值计算表明本文方法具有良好的计算精度。最后,本文还在此基础上就结构高宽比、荷载偏心、柱子截面形式和平面桁架的形式等因素对交错桁架结构极限承载力的影响进行了探讨,结果表明当交错桁架结构体系达到其极限承载力时,杆件的塑性铰主要集中分布在下部楼层,设计时建议适当加大下部楼层的杆件截面,以保证结构具有足够的极限承载力。此外,在偏心荷载作用下,柱子截面形状对结构极限承载力的影响较大,其工形截面的影响要比箱形截面更为显著。

Based on nonlinear continuum mechanics and stress-resultant yield surface plastic flow rule, a new type of elastoplastic stiffness matrix for calculating the ultimate bearing capacity of staggered-truss building system is presented. In this approach, not only the effects of axial force, shear force, bending moment and torsion on cross-section and structural shear deformation arc considered, but also the interaction of internal force between the plastic hinges is taken into account. Numerical solutions show that this method has high precision. In the end, the influence factors such as the ratio of structure height to width, the load eccentricity, the shape of the column section and the shape of the truss are discussed, the result indicates that the plastic hinges of the elements are concentrated on the lower floors, when the structural system reaches its ultimate bearing capacity, so that the member sections in the lower floors should be enhanced in order to ensure the ultimate bearing capacity of the structure. On the other hand, under the eccentric load, the shape of column section is another main influence factor on the structural ultimate bearing capacity, in which the 1-section is more serious than the box section.