多塔悬索桥结构变形的实用计算方法

Practical Calculation Method for Structural Deformation of Multi-span Suspension Bridge

为解决利用有限元法求解活载作用下多塔悬索桥结构变形时工作量大、不便于参数影响分析的问题,基于结构内力按刚度分配的原理,建立了一种新的实用计算方法。首先添加各桥塔塔顶纵桥向位移约束,利用梁比拟法导出活载作用下缆索竖向位移表达式,并用能量守恒原理建立补充方程,分别求解各跨缆索结构的竖向位移和水平力;其次,依次解除前一步中添加的约束,对已求得的各桥塔两侧缆索水平力,将其力差按刚度分配给桥塔和相邻跨,得到多塔悬索桥活载作用下的最终位移;最后,以一座两主跨均为1 080m的三塔悬索桥为例与有限元计算结果进行了对比。研究结果表明:所建立的方法与有限元法相比,缆索竖向位移及各桥塔纵桥向位移计算相对误差一般在5%以内,能够为多塔悬索桥初步设计提供快速解算方法,并为有限元计算结果的校核提供参考。

In order to solve the problems of heavy workload and inconvenience in analysis of its parameters when solving the structural deformation of multi-span suspension bridge under live loading by FEM,a novel and practical calculation method was established based on the principle that structural internal force distribution relates to rigidity.Firstly,longitudinal displacement constraints were added at the top of each pylon,and vertical displacement expression of cable structure under live loading was derived by using the analogy beam method.Through the principle of energy conservation,additional equation was established. Thus the vertical displacements and horizontal forces of the cable structures in each span were calculated respectively.Secondly,the previous additional constraints were released in sequence.For the obtained horizontal forces of the cable in each pylon,by distributing the unbalanced forces of the cables into the each pylon and adjacent span according to the rigidity,the final displacements under live loading were obtained.Finally,by employing a three pylon suspension bridge with two main spans of 1 080 m,the results of proposed method were compared with those of finite element method.The results show that vertical displacement error of cable and longitudinal displacement error of each pylon are generally less than 5%.The proposed method providesaquick calculation approach for the preliminary design of multi-span suspension bridges and references for the verification of finite element calculation results.