非规则梁桥的振型重要性指标研究

IMPORTANCE INDEX FOR MODES OF IRREGULAR CONTINUOUS BRIDGES

针对非规则梁桥的振型重要性指标进行研究。首先,通过理论分析,确定在判断振型重要性方面,传统的振型质量参与系数存在缺点,并定义了振型位移贡献、振型位移贡献系数、振型位移贡献比例等新指标。然后,针对一座典型的非规则梁桥,通过振型质量参与系数分析和振型位移贡献系数分析的对比研究,确定采用振型位移贡献比例判断振型重要性,更加合理。最后,通过多座桥梁的参数分析,验证了振型位移贡献比例比质量参与系数更加优越。研究结果表明:振型质量参与系数仅能反映振型对于结构总体动力反应的重要性,而不能明确反映振型对于结构局部动力反应的重要性;振型位移贡献比例能弥补这一缺陷,可以作为振型重要性的指标;当前n阶振型位移贡献比例之和超过80%时,以前n阶振型为基础得到的结构位移可以满足非规则梁桥计算精度的需要。

With importance index for modes of irregular continuous bridges as the object of study, the participation mass factor is firstly theoretically analyzed, and is considered that it has defects when estimating the importance of modes. And thus, the new indexes including a contribution displacement, a contribution displacement factor and a contribution displacement ratio are defined. And then, taking one irregular continuous bridge as an example, the participation mass factor and contribution displacement factor are investigated, considering that the contribution displacement ratio is more reasonable when estimating the importance of modes. Finally, the parameter analyses based on many continuous bridges validate that contribution displacement ratio has more advantages than participation mass factor as the importance index for modes. Results show that the participation mass factor can express the importance of modes for the structural total dynamic response; however, it can not express the importance of modes for the dynamic response of a local position. Because the contribution displacement ratio can mend the defects, it is more reasonable as the importance index for modes of irregular continuous bridges. When the sum of the former n modal contribution displacement ratios is beyond 80%, the calculated structure displacement based on the former n modes can satisfy the precision demand of irregular continuous bridges.