大跨度桥梁耦合抖振正交组合分析方法的应用

Practice of Coupled Buffeting Complete-quadratic- combination Analysis of Long-span Bridges

结合耦合抖振分析有限元完全正交组合 (CQC)方法 ,编制了大跨度桥梁结构三维抖振分析模块 ,并选择薄平板截面简支梁结构的耦合抖振问题作为算例进行验证 .从分析中发现 ,此方法的分析结果与Scanlan方法的结果相当吻合 .还对主跨跨度 1385m的江阴长江大桥的耦合抖振问题进行了分析和研究 .分析结果表明 ,振动模态的气动耦合对系统复模态的阻尼比有较大的影响 .在大跨度悬索桥中 ,对于主梁的竖向和扭转位移抖振响应多模态效应和模态耦合效应非常显著 ,在高风速区传统的SRSS方法将低估这些抖振响应 .广义抖振力的交叉功率谱密度对大跨度桥梁结构耦合抖振响应的作用不可忽略 .此外 ,对江阴悬索桥来说 ,在设计风速下纵向和竖向脉动风速的交叉风谱对结构抖振响应有明显的影响 ,在以后研究分析中应该给予重视 .

Based on the finite-element and Complete-quadratic-combination(CQC) method in Part I of this paper, a 3-D program is developed for analyzing the coupled buffeting responses of long-span bridges.The coupled buffeting problem of a simply supported beam structure is chosen as a check example. It has been noted that the results of the present method have fairly good agreement with those of the Scanlan's. The coupled buffeting analysis of Jiangyin Yangtse River suspension bridge with 1 385 m main span is performed. The analyzing results show that the aerodynamic coupling of the vibration modes affects markedly the damping ratios of complex mode of the system. The multimode and intermode effects on the vertical and torsional buffeting responses of the bridge deck are quite remarkable in the long-span suspension bridge, and the traditional SRSS method underestimates these responses in the range of high wind velocity. The influence on the coupled buffeting responses of long-span bridges due to the CSD of generalized buffeting forces can not ignored. Moreover, the cross spectra between the longitudinal and vertical wind fluctuations have obvious effects on the buffeting responses for this suspension bridge in the wind velocity of design and should be considered in the future study.