具有刚性中央扣的大跨度悬索桥随机地震响应研究

摘要

To analyze the influence of the rigid central buckle on the seismic response of suspension bridge, a long-span suspension bridge with rigid central buckle was cited as an example for the study.The spatial finite element model of the long-span suspension bridge was established.The random vibration method was used to contrastively analyze the influence of the rigid central buckle on the dynamic performance of the suspension bridge, the influence of different ground motion power spectral density functions on the seismic response and the seismic response of the suspension bridge under three-directional earthquake excitation.The results indicate that the rigid central buckle alleviates the longitudinal floating of the stiffening girder and the occurrence of the vibration modes related to main cables vibration and enlarges the related frequencies.Under the action of longitudinal earthquakes, the central buckle suppresses the displacement of the stiffening girder, but distinctively causes the increase of the internal forces of the stiffening girder.When the Clough Penzien model was used as the model of the ground power motion spectral density function, the stochastic seismic response gained was greater than that gained by the Du xiuli model, and the results calculated by these two models were greater than those gained by using the response spectrum in the codes.Under the three-directional earthquake excitation, internal force concentration was observed at the location of the central buckle in the stiffening girder, and the seismic response was more unfavorable.The maximum longitudinal bending moment occurred in the base of the bridge towers, while, the maximum transverse bending moment were found at the intersection of the tower legs and the cross beams as well as the tower base.%为分析刚性中央扣对悬索桥地震响应的影响,以一座具有刚性中央扣的大跨度悬索桥为例,建立大跨度悬索桥的空间有限元模型,基于随机振动法对比分析刚性中央扣对悬索桥动力特性的影响、地震动功率谱密度函数的选择对地震响应的影响以及悬索桥在三向地震作用下的地震响应.结果表明:刚性中央扣减少了加劲梁纵飘及与主缆振动相关振型出现的次数并增大了相应的频率;在纵向地震作用下,中央扣减小了加劲梁的位移,但是明显增大了加劲梁的内力;地震动功率谱密度函数模型采用Clough-Penzien模型时所得到的随机地震响应要较杜修力模型大,且两者的计算结果均大于采用规范反应谱的计算结果;在三向地震作用下,导致加劲梁在中央扣位置处形成内力集中,地震响应也更为不利,桥塔最大纵向弯矩位于塔底,最大横向弯矩位于横梁交界处和塔底.