竖向荷载作用下悬索桥纵向变位特征与机理

Characteristics and Mechanism of Longitudinal Displacement for Suspension Bridge under Vertical Loads

为揭示竖向荷载作用下悬索桥纵向变位特征与机理,以主缆变形理论为基础研究了其竖向荷载下的变位特征,并得出了其竖向及纵向位移解析解;在此基础上,分析了竖向荷载作用下传统悬索桥和设有中央扣悬索桥的纵向变位特征及加劲梁纵向位移,揭示了中央扣纵向约束机制,并分别推导了加劲梁在竖向荷载下的纵向位移计算公式;最后,通过算例分析验证所提位移计算公式计算精度.结果表明:由于主缆的几何非线性特征,竖向位移与纵向位移相互耦合,在非对称竖向荷载作用下,主缆发生非同步纵向位移,而加劲梁主要以类似“摆锤体”发生刚体的纵向位移;跨中处主缆、加劲梁及中央扣因中央扣的存在形成一个“刚域”区,从而导致加劲梁纵向位移减小;所提计算方法与有限元数值解法在不同竖向荷载工况下吻合良好.

In order to reveal the longitudinal deformation characteristics and mechanism of suspension bridges under vertical loads,the deformation characteristics of the cable under vertical loads were studied based on its deformation theory,and the analytical solutions of vertical and longitudinal displacement were obtained.On this basis,the longitudinal deformation characteristics and the longitudinal displacement of the stiffening girder for the traditional suspension bridge and the suspension bridge with central buckles are analyzed under vertical loads,the longitudinal restraint mechanism of the central buckles is subsequently revealed,and the simplified formulas to estimate the longitudinal displacement of the stiffening girder under vertical loads are deduced,respectively.Finally,the accuracy of the proposed displacement calculation formulas is verified by an example.The results show that the vertical and longitudinal displacement are coupled to each other due to the geometric nonlinear characteristics of the main cable.The main cable undergoes asynchronous longitudinal displacement,while the stiffening girder mainly moves longitudinally as a rigid body similar to the pendulum under the action of asymmetric vertical loads.The main cable,the stiffening girder,and the central buckles form a"rigid domain"area in the middle of the span as the existence of the central buckle.As a result,the longitudinal displacement of the stiffening girder decreases.The proposed method agrees well with the finite element numerical solution under different vertical load cases.