大跨空间网格结构风振响应主要贡献模态的识别及选取

首先简单介绍静荷载参与比例的概念和基于虚拟激励法的风振响应分析原理。考虑脉动风荷载的空间相关性,推导出脉动风作用下系统背景响应总应变能的计算公式,以及模态对背景响应总应变能的贡献,从而定义了各阶模态的模态贡献系数及模态组合的累积模态贡献系数计算公式,其中模态贡献系数可以准确地识别出所有能被脉动风激振的模态,而累积模态贡献系数可以作为模态组合合理性判别的量化标准。然后介绍了一种简单的补偿模态构造方法,并提出了模态组合的选取方法和步骤。算例分析验证了模态贡献系数和累积模态贡献系数的有效性,以及低阶主要贡献模态和高阶主要贡献模态的重要性,进而指出目前通过比较前若干阶模态的相对误差或仅考虑补偿模态的模态组合选取方法并不合理。合理的模态组合应包含绝大部分主要贡献模态,以满足累积模态贡献系数大于0.9的要求。

Identification and selection of dominant vibration-modes contributory to wind-induced vibration response for large-span space lattice structures

This paper first presents a brief introduction to the concept of static load participation ratio(SLPR) and the principle for wind-induced vibration analysis based on the pseudo excitation method(PEM).In consideration of the partial correlation between wind excitations,the formulae for calculation of contribution factor of each mode to wind response and the corresponding cumulative contribution factor of mode combination are then derived.The mode contribution factor can be used to identify accurately all possible modes which may be induced by the turbulent wind,while the cumulative mode contribution factor can be taken as a criterion to justify whether the selected mode combination is sufficient for the calculation of the wind-induced vibration response.Next,a simple compensation mode is introduced,and the method of mode selection is proposed.Two numerical examples are provided to verify the effectiveness of the mode contribution factor and cumulative mode contribution factor,as well as the significance of both the low-order and high-order dominant contribution modes.Finally,it is pointed out that current methods of mode selection which depend on the comparison of relative errors of many low-order modes or involve only compensation modes are not sufficient,and that the reasonable mode combination should involve most of the dominant contribution modes and the cumulative mode contribution factor of the selected mode combination should be larger than 0.9.