索-悬链线拱联合结构的受力机理与力学特征

Mechanism and Mechanical Characteristics of Cable-Catenary Arch Combined Structure

早期拱桥已运营多年,缺乏有效的养护,且设计荷载等级偏低;随着交通量的增加及车辆超载,其在活载作用下的力学性能已不能满足现代交通需求。为改善此类拱桥的受力性能,提出一种索-悬链线拱联合结构,在拱肋两侧对称设置索,使索和拱肋形成新的受力体系,从而改变悬链线拱结构的传力路径,进而降低拱结构的内力。在索-拱联合结构图式下,基于弹性中心法对其力法方程进行简化,采用近似曲线积分方法推导了竖向移动荷载作用下拱肋的内力解析解,并借助ANSYS有限元软件验证解析解的准确性;分析了在车道荷载作用下索约束位置、拱轴系数、矢跨比和轴向刚度比等设计参数对拱结构的影响,揭示了索-拱联合结构的受力机理和内力变化规律。研究表明,内力解析解与有限元结果的相对误差在1%以内;索的设置改变了拱结构弯矩影响线量值的正、负区间分布,而且有效地降低了拱结构弯矩影响线的峰值,从而使拱结构的整体弯矩得到较大幅度的降低,弯矩分布更均匀;沿拱脚至拱顶,拱结构弯矩的降低幅度和轴力的增长幅度均逐渐减小;轴向刚度比从0.02增加至0.10,拱脚负弯矩的减小幅度呈非线性增大,最大降幅达63.7%;索力的增长幅度与其数值大小成反比,当索设置在距拱顶0.3L(L为拱跨经)时,索力可增至轴向刚度比为0.02时的1.9倍。矢跨比对拱结构内力带来的影响不容忽视,矢跨比越大拱结构的内力变化幅度越大;拱轴系数对拱结构内力的影响可以忽略。

With the increase of traffic volume and overloading of vehicles,the mechanical properties of early arch bridges under live load can no longer satisfy the needs of modern traffic due to low design load grade,lack of effective maintenance and long term operation.To improve the mechanical performance of this kind of arch bridges,this paper proposed a cable-catenary arch combined structure.The cables were symmetrically arranged on both sides of the arch rib to form a new force system,which could change the force transmission path of the catenary arch structure and reduce the internal force of the arch structure.Under the mechanical diagram of cable-arch combined structure,the force equation of the cable-arch combined structure was established based on the elastic center method,and the analytical solution of the internal force of the arch rib was deduced by the approximate curve integration method under the vertical moving load.The reliability of the analytical solution was verified by ANSYS finite element analysis software,and the influences of design parameters such as cable constraint position,arch-axis coefficient,rise-span ratio,and axial stiffness ratio on the internal force of the arch structure under lane loading were analyzed.The mechanical properties and internal variation rules of the cable-arch combined structure were revealed.The results show that the relative error between the analytical solution of the internal force and the finite element result is within 1%.The setting of the cable changes the positive and negative interval distribution of the bending moment influence line value of the arch structure,and effectively reduces the peak value of the bending moment influence line of the arch structure,which can greatly reduce the overall bending moment of the arch structure and make the bending moment distribution more uniform.From the arch foot to the arch crown,the reduction of the bending moment and the growth of the axial force of the arch structure gradually decrease.As the axial stiffness ratio increases from 0.02 to 0.10,the negative bending moment of the arch foot decreases nonlinearly,with the maximum decrease of 63.7%;the increase of the cable force is inversely proportional to its value,and when the cables are set at 0.3L(L is the span of the arch)from the arch crown,the cable force can be increased to 1.9 times that at the axial stiffness ratio of 0.02.The influence of the rise-span ratio on the internal force of the arch structure cannot be ignored.The greater the rise-span ratio is,the greater the change in internal force of the arch structure is.The effect of arch-axis coefficient on the internal force of the arch structure can be neglected.