中、下承式拱桥自振特性分析

Dynamic property analysis of half-through and bottom-through arch bridge

以平行式、提篮式和斜靠式3种中、下承式混凝土拱桥为工程实例,采用有限元程序MIDAS/Civil建立桥梁空间有限元计算模型,对其进行自振特性分析,比较3种不同桥型自振特性的特点,计算结果表明:中、下承式混凝土拱桥的振型主要有拱肋面外横向振动、结构整体竖向振动和扭转振动,高阶振型才出现桥面系的横向振动;3种拱桥都是首先出现拱肋的面外横向振动,低阶振型均以拱肋面外横向振动为主,拱肋的横向自振频率小于竖向自振频率;斜靠式拱桥的振型密集,横向振动基频比平行式和提篮式拱桥的横向振动基频大;3种拱桥的竖向振动都表现为桥梁结构整体竖向振动;3种拱桥的扭转振动都出现较晚。

With the background of 3 kinds of half- through and bottom - through reinforced concrete arch bridges, MIDAS/civil finite element procedure was taken to establish the spatial finite element models to carry on the dynamic property analysis, and their dynamic characteristics were compared and analyzed. The computed results indicate that the vibrations of half- through and bottom - through reinforced concrete arch bridges mainly involve three types, i. e., the arch ribs＇ transverse vibrations out of plane, the vertical vibrations of the whole bridge and torsional vibrations. The transverse vibrations of the bridge deck only appear in the higher sets of modes of vibration. The arch ribs＇ transverse vibration out of plane all happen in three kinds of bridge＇ s vibration first, and this kind of vibrations play a dominant role in the lower sets of modes of vibration, the arch ribs＇ transverse natural frequency is smaller than its＇ vertical one; The vibration modes＇ range of double X - arch bridges is much more dense, and the Double X - shaped arch bridge＇ transverse natural basic frequency is larger than the other two kinds of arch bridges＇. The vertical vibrations of the three kinds of arch bridges all appear as the whole vertical vibrations of the bridge. Three kinds of arch bridges＇ torsional vibrations all happen later.