考虑平移—扭转耦合结构多模态静力弹塑性分析方法模态选取的研究

An Improved Modes Selection Procedure in the Nonlinear Static Analysis for Lateral-torsion Coupling Structures

由于存在平移—扭转耦合作用,结构的非主振方向的振型对地震响应量也有贡献,和非耦合结构中模态贡献一般随着频率的增加而减小不同,对不同的响应分量有可能高阶模态的贡献要大于低阶模态的贡献,这就造成了采用振型参与系数比或有效质量参与系数比判断结构模态的选取不能保证结构全部地震响应分量的计算精度,这在算例中也得到了证实.为了更好的控制模态选取,定义了振型参数"λ_(ji)",提出采用振型参数和振型参与系数比这两个参数共同控制结构模态的选取.通过变换影响模态响应对总响应贡献大小的四个因素,即周期比、基本周期、偏心率和地面运动,按正交设计法设计了16个计算模型,采用MATLAB计算软件编程对平—扭耦合结构的动力时程分析进行了精确计算,计算结果表明振型参数和各个模态的各个响应分量的相对大小有很强的相关性,从而采用振型参数可控制振型每一个响应分量的误差,振型参与系数比可控制某一振型整体对结构响应的贡献大小,通过这两个参数可更好的控制模态选取,特别是对于复杂高层结构的意义更为明显.

Due to lateral-torsion coupling action, the modes of non-main vibration direction also have some contribution to seismic response, and for different response components the contribution of high order modes may be more than that of low order modes. For this reason, the calculation accuracy may not be guaranteed through mode selection which only depends on the mode participation coefficient ratio or modal mass participation coefficient ratio. In order to select the reasonable mode, mode parameter λji is defined. The improved procedure to select mode was proposed depending on mode parameter and mode participation coefficient ratio. 16 lateral-torsion models were designed with orthogonal design methods through changing period ratio, fundamental period, ec- centricity and ground motion. Precise time history analysis was conducted with MATLAB soft- ware for these models, and the results of calculation demonstrate that the mode parameter have significant relation with the contribution of modal components. So the errors of modal compo- nents can be controlled by the mode parameter, and the contribution of modes can be controlled by the mode participation coefficient. With the two parameters, we can obtain the more reasonable modes.