大跨度拱桥模态降阶控制中的控制模态选择

Control mode selection for modal control of a long-span arch bridge

在模态分析的基础上对大跨度拱桥进行模型降阶,以用于拱桥的减震控制设计。对大跨度拱桥模型降阶控制中控制模态的选择方法进行改进,提出按最大模态位移方法确定控制模态。该方法考虑外部激励的影响,克服了振型贡献率只考虑结构动力特性选取控制模态的缺点。以西藏尼木大桥作为算例,通过频域分析和时域分析来验证降阶模型的有效性。数值分析结果表明,对于要考虑多点地震激励的大跨度拱桥结构,采用最大模态位移的方法选择的控制模态更合理,从而得到的降阶系统也更符合原模型的性能。

For seismic control of arch bridges, a model reduction of long-span arch bridge was implemented based on modal analysis. As for the critical mode selection, an approach based on the maximum modal displacement was presented. This approach takes into consideration the effect of external seismic excitation and is more reasonable than that only considering dynamic bridge characteristics based on a modal contribution ratio. The time domain and frequency domain analysis methods were used to verify the simplified model of the Nimu arch bridge in Tibet as an example. The numerical results show that the method of maximal modal displacement better analyzes long-span arch bridges when multi-support seismic excitation must be considered. The reduced-order system also is more in line with the performance of the original model.