基于算法复杂度理论的拟力法计算效率评价

算法复杂度理论是一种算法效率定量评价方法,该方法通过度量算法的复杂度来客观反映其执行效率,避免了计算机系统性能等因素对效率评价的影响。拟力法是一种高效的结构非线性分析方法,以往研究工作只是在非线性分析过程和运行时间上对计算效率进行了探索,并没有从理论上量化分析。本文采用算法复杂度理论对拟力法和传统变刚度非线性求解方法进行分析,给出了两种方法的时间复杂度函数,并对比了其计算效率进行定量,从数学角度解释了拟力法计算效率高的根本原因。算例对两种方法的时间复杂度和计算时间进行对比分析,直观地说明了拟力法在计算效率方面的优越性。

Axial compression physical testing of traditional and bird beak SHS T-joints

The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, failure modes of specimens, jack load-vertical displacement curves, jack load-deformation of chord and strain intensity distribution curves of joints were presented. The effects of β and connection types on axial compression property of joints were studied. The results show that the ultimate axial compression capacity of common bird beak SHS T-joints and diamond bird beak SHS T-joints is larger than that of traditional SHS T-joint specimens with big values of β. The ultimate axial compression capacity of diamond bird beak SHS T-joints is larger than that of common bird beak SHS T-joints. As β increases, the increase of the ultimate axial compression capacity of diamond bird beak SHS T-joints over that of common bird beak joints grows. The ultimate axial compression capacity and the initial axial stiffness of all kinds of joints increase as β increases, and the initial axial stiffness of the diamond bird beak SHS T-joints is the largest. The ductilities of common bird beak and diamond bird beak SHS T-joints increase as β increases, but the ductility of the traditional SHS T-joints decreases as β increases.

基于守恒协调转换方法的4UPS-PU并联机构刚度分析

为了表明在考虑外力影响下机构雅克比矩阵微分变化对整体机构刚度的影响,这里对4UPS-PU空间并联机构的刚度特性进行了分析,文中主要分析了基于守恒协调转换的4UPS-PU并联机构的刚度分布,并与传统刚度分布进行了比较。首先对4UPS-PU机构的雅克比矩阵进行求解;其次分析基于守恒协调转换的4UPS-PU机构在各个方向上的刚度分布,并分析了传统刚度模型在各个方向上的刚度分布;通过比较传统刚度模型在每个方向上的刚度分布与基于守恒协调转换刚度分布的差别,得知基于守恒协调转换的4UPS-PU机构在各个方向上的刚度分布值比传统情况下的刚度分布值大,表明不能忽略外力对机构的影响。