双线铁路整体PC箱梁上拱度分析

Camber Analysis of a Whole PC Box Girder on Double-track Railway

由于混凝土的徐变效应,预应力混凝土简支箱梁桥的梁体在预应力荷载作用下的上拱变形缓慢发展,因而对桥梁设计及施工中的徐变变形分析尤为重要。如果对于徐变变形的预测不准,在运营阶段梁体徐变变形的发展将会引起桥面的立面线形不平顺,严重影响行车安全和旅客舒适度,甚至将造成梁体上拱度过大而无法使用。在高速铁路上这种影响显得尤为突出,应予以足够重视。本文针对某双线铁路就地浇筑的预应力混凝土整体箱梁,采用MIDAS/Civil结构分析软件,结合国内外几种规范中徐变系数的计算公式,计算在施工阶段的预应力张拉、落梁和铺砟后的荷载作用下梁体的变形,并将其与现场实测的数据比较。通过现场实测变形与理论分析结果的对比得出,采用我国现行铁路规范的计算值与实测值吻合良好。

Under the action of a prestressing force, the camber deformation of a PC simply supported girder develops slowly due to concrete creep effect. Creep effect analysis is a necessity for the design and construction of a simply supported girder. Any inaccurate preestimation of the concrete creep effect will lead to an unevenness of the elevation linetype of the girder,which will seriously impact traffic safety and passenger comfort. It even leads to such a paranormal camber deformation that the girder becomes unuseful at all. This effect is graver for high-speed railways. Enough attention should be paid to it. In this paper,we used a PC box girder casted-in-site on a double-track railway line to calculate the deformation of the girder under loading action of prestressing tension, girder erection and ballast covering. We adopted the program of MIDAS/Civil and other methods to calculate the creep coefficient and then compared the calculated result with the measured one. Comparison indicates that the calculated value is well matched with the measured value.