提高拱梁固结拱桥自振频率的有效方法

为提高拱梁固结体系拱桥的自振频率,使该类拱桥得以在大跨径、小宽跨比的高速铁路桥梁中推广应用,在此提出一种新的有效方法,具体做法是,以拱肋作为上弦杆,主梁作为下弦杆,在L/4～3L/4区域内设置腹杆,以此形成一个带柔性吊杆的大桁架结构,通过引入刚度大的桁式结构使拱桥的整体刚度得到提高,进而改善结构的动力特性。新结构既保留了拱桥的优点,又有桁架的受力特征。计算结果表明,与普通拱梁固结拱桥相比,新结构可在材料增加很少的前提下有效提高自振频率,尤以面内自振频率增幅最为明显;拱肋内倾角对新结构的影响随振型的不同而不同,其中,对面外自振频率的影响较面内自振频率明显。

An Effective Method to Improve the Natural Frequency of Arch-girder Consolidated Arch bridges

To improve the natural frequency of arch-girder consolidated arch bridges and promote their application in high-speed railway bridges with large span and small width-span ratio, a new and effective method is proposed. The method uses arch ribs as top chords and main girders as lower chords, and web members are only installed in the L/4 to 3L/4 regions to form a large truss structure with flexible suspenders. The large stiffness truss structure improves the overall stiffness of the arch bridge, and improves the dynamic performances of the structure. The new structure not only retains the advantages of the arch bridge, but also has the stress characteristics of the truss. The calculation results show that compared with the conventional arch-girder consolidated arch bridge, the new structure can effectively increase the natural frequency of the structure with less additional materials and sharpest increase of in-plane natural frequency. The influence of the leaning angle of arch ribs on the new structure varies with the different vibration mode, and the influence on the in-plane natural frequencies is more obvious.