中承式斜拱曲梁组合桥动力特性参数研究

Study on Parameters of Dynamic Characteristics of Half-through Skew Arch Curved Beam Composite Bridge

摘要:

中承式斜拱曲梁组合桥国内类似工程不多，但随着对桥梁景观性的追求，在实际设计中越来越多地被采用，但是关于这一桥型动力特性的研究较少。基于这一现状，以海丝人行景观天桥（26+36+55+22）m为工程背景，采用Midas Civil 建立全桥空间有限元模型对其基本动力特性进行分析，研究了二期恒载集度、构件刚度、几何参数和边界条件等关键结构参数对桥跨结构动力特性的影响规律。结果表明：该桥基频为1.53 Hz，对应振型为一阶正对称拱肋侧倾；前10阶自振频率随二期恒载集度增大而减小；主梁刚度对各阶振型频率的影响明显大于拱肋刚度；减小矢跨比可显著提高拱肋侧倾与拱肋弯扭振型频率；拱肋倾角（10°~30°）与曲梁曲率半径（40~80 m）对结构各自振频率影响有限，相应频率变化率不超过5%；主梁与主墩之间弯扭耦合约束可显著提高前5阶振型频率。

Abstract:

There are few similar projects of half-through skew arch curved beam composite bridge in China. But with the pursuit of bridge landscape, it is used more and more in bridge design. However, there are few studies on the dynamic characteristics of this bridge. Based on the present situation, taking a (26+36+55+22)-m landscape footbridge - Haishi Bridge as the engineering background, the spatial finite element model of the whole bridge is established by using the software Midas Civil to analyze its basic dynamic characteristics. And the effect law of the key structural parameters such as the secondary dead load intensity, the stiffness of structural members, the geometric parameters and the boundary conditions on the dynamic characteristics of span structure is studied. The results indicate that the fundamental frequency of this bridge is 1.53 Hz and the corresponding vibration mode is the first-order positive symmetric arch rib tilting. The first 10-order natural vibration frequency decreases with the increase of the secondary dead load intensity. The effect of the stiffness of the main girder on vibration frequencies of various orders is obviously greater than that of the stiffness of the arch rib. The decrease of the rise-span ratio can remarkably improve the vibration frequency of arch rib tilting and arch rib bending. The effects of the dip angle (10°~30°) of arc rib and the curvature radius (40 m~80 m) of curved beam are limited on each natural frequency of structure. The relevant change rate of frequency is not more than 5%. The first 5-order vibration frequency can be improved remarkably by the bending-torsional coupling constraints between the main girder and the main pier.