构件承担倾覆力矩的计算方法

Calculation methods for overturning moment carried by member

基于楼层构件的弯矩平衡方程,推导了抗规框架部分承担倾覆力矩的计算公式(简称抗规公式)。给出了抗规公式的解释,把抗规公式拓展到有斜杆的结构和坡楼(屋)面的结构。有斜杆的结构,抗规公式中的剪力取斜杆的水平分力;坡楼(屋)面结构,抗规公式的楼层高度取相邻楼层水平荷载合力作用点高度的差值。文献中基于轴力的框架部分承担倾覆力矩计算方法(简称轴力法),采用的是不同于抗规公式的结构承担倾覆力矩定义,举例说明了轴力法常见确定取矩轴方法存在的问题。带有斜杆、坡楼层、坡屋面的6层框架-剪力墙结构的算例,说明了构件承担倾覆力矩抗规公式的应用,阐明了轴力法确定的取矩轴与规范公式暗含的轴力取矩轴不一致是轴力法与规范公式计算结果不同的原因。

Based on the equilibrium equations of moments for all the vertical members of a story,the formula of overturning moment carried by frame parts in Code for seismic design of building(the seismic code’formula for short)was deduced.An interpretation of the seismic code’formula was presented,and the seismic code’formula was extended to suit a structure with inclined members and a structure with pitched roofs/floors.For a structure with inclined members,the shears of the seismic code’formula were modified as the horizontal component forces of inclined members;for a structure with pitched floors/roofs,the story heights of the seismic code’formula were the differences of the heights of the resultants of the lateral loads at adjacent floors.The concept of overturning moment carried by frame parts determined directly by the axial forces of the columns(the axial force method for short)in the literature was different from the concept of the seismic code’formula,and the flaw of the axis for moment about which was determined by the usual method in the axial force method was pointed out by an example.A numerical example of a 6⁃story frame⁃shearwall structure with inclined members,pitched floor and pitched roof illustrated the application of the seismic code’formula,and interpretated the reason of the different results that the axis for calculating moment by the axial force method was different from the implicit axis by the seismic code’formula.