基于应变能分析的钢-混组合桥梁结构阻尼比特性研究

Study of Modal Damping Characteristics of Steel-concrete Composite Bridges Based on Strain Energy Analysis

基于应变能方法发展了一种钢-混组合桥梁的结构等效模态阻尼比计算方法。以一座钢-混组合梁悬索桥为例,基于应变能原理分析计算了大桥的竖弯模态阻尼比,并与现场试验结果进行对比,验证了所提方法的可行性;基于该方法进一步研究了组合梁悬索桥侧弯、扭转模态的阻尼比特性。结果表明:对于钢-混组合梁悬索桥的不同模态,钢主梁、桥塔、主缆等不同子结构的应变能占比差异显著,其中主缆的应变能在竖弯模态中占比最大,钢主梁和混凝土桥面板总应变能在侧弯模态中占主导,扭转模态中不同子结构的应变能占比随阶次而改变;钢-混组合梁悬索桥侧弯等效模态阻尼比最大,竖弯等效模态阻尼比最小且远小于抗风规范建议值。最后,研究了钢-混组合梁悬索桥和斜拉桥的竖弯模态、侧弯模态及扭转模态阻尼比的差异,除侧弯模态外,钢-混组合梁斜拉桥的等效模态阻尼比均大于钢-混组合梁悬索桥。所提计算方法可用于钢-混组合桥梁结构的模态阻尼比计算,计算结果可以为抗风分析提供参考。

In this study,a method based on strain energy analysis is developed to calculate the equivalent modal damping ratio of steel-concrete composite bridges.By using a steel-concrete composite girder suspension bridge as an example,the damping ratio of the vertical bending mode of the bridge was calculated based on the strain energy principle and compared with in-situ measured results to verify the feasibility of the method.Moreover,the damping characteristics of steel-concrete composite girder suspension bridges for the lateral bending and torsional modes were further studied.The results show that the strain energy ratios of the steel main girder,bridge tower and main cable are significantly different for different modes,where the strain energy of the main cable is the largest in the vertical bending mode,and the total strain energy of the steel main girder and concrete bridge deck panels is dominant in the lateral bending mode,the strain energy ratio of the torsional mode is dependent on the mode order.The equivalent modal damping ratio of the steel-concrete composite girder suspension bridge in lateral bending is the largest,and the equivalent modal damping ratio in vertical bending is the smallest,and the damping ratio of the vertical bending modal is much smaller than the recommended value of the wind-resistant design specification.Finally,the differences of vertical bending mode,lateral bending mode and torsional mode damping ratio between steel-concrete composite girder suspension bridge and cable-stayed bridge were studied,and the equivalent mode damping ratio of steel-concrete composite girder cable-stayed bridge was larger than that of steel-concrete composite girder suspension bridge except for the lateral bending mode.The proposed method can be used for the calculation of modal damping ratio of steel-concrete composite bridge,and the calculated results can provide reference for wind analysis.