强震下两跨斜交简支梁桥桥面旋转反应的影响因素分析

为了研究在双向地震激励下两跨斜交简支梁桥桥面的旋转效应,选取Open Sees建立考虑两跨梁体间纵向、梁体与挡块间横向碰撞的有限元模型,从模态特征与地震反应2个层面分析了斜度、横隔梁数量及布置方式、下部结构支承刚度和跨径布置对两跨斜交简支梁桥桥面旋转的影响.结果表明:斜交简支梁桥的面内旋转振型早于正交桥出现;斜度的增大加剧了桥面的旋转;非对称结构的低阶振型表现为平动与桥面内旋转的耦合振动,其结构偏心效应加剧了桥面的旋转;不设或设置过多的横隔梁、采用平行于支承边布置横隔梁均会加剧桥面的旋转;纵向碰撞对不同斜度的两跨斜交简支梁桥桥面旋转有不同的作用效果;横向挡块能有效抑制两跨斜交简支梁桥桥面的旋转.

Analysis of Influential Factors on Rotation Responses of Two-span Simply Supported Skewed Girder Bridges Under Strong Earthquake

In order to investigate the rotation response of two-span simply supported skewed girder bridges ( TSSSGB) under bi-directional earthquake excitation, the software OpenSees was selected to build finite element models that the effects of longitudinal pounding between two decks, and transverse pounding between decks and retainers were considered. The influences of skew angle, number and layout of diaphragms, supporting stiffness of substructure and span layout on the rotation of TSSSGB were analyzed from two viewpoints: the modal characteristics and the seismic responses. The results show that the rotation vibration mode of simply supported skewed girder bridges appears earlier than that of right bridges. The increase of skew angle intensifies the rotation of TSSSGB. The low order vibration modes of asymmetric structures have shown translational and rotational coupling vibration, and its structural eccentric effect intensifies the rotation of TSSSGB. The rotation of TSSSGB can be intensified without or setting too much diaphragms, or setting diaphragms oriented parallel to support skew. The effects of longitudinal pounding between two decks on the rotation of TSSSGB are different for different skew angles, and transverse retainers can effectively restrain the rotation of each deck.