对某工程城市轨道交通双线变宽连续U梁进行精细化设计。该桥采用三跨连续结构，变宽幅度远超同类型其他桥梁，设计难度较大。其变宽段采用了将中腹板进行“加厚+加箱室+分岔”的系统设计方法，整体构造复杂，需进行深入研究。通过建立全桥杆系与三维有限元模型，分析全桥空间应力效应、主桥横向受力、变宽段局部受力以及支反力与多腹板剪力分配，深入地分析了结构的受力机理。通过对全桥进行优化分析，削减主梁腹板与底板厚度，进一步提升结构受力性能，提供了该类型桥梁的合理设计研究思路。

In this study, a detailed design for a double-line continuous U-beam bridge with a variable urban rail transit width is produced. This bridge has a three-span continuous structure and a variable width far greater than that of other bridges of the same type, which means that the difficulty of the design process increases rapidly. The design of the variable width segment adopts the “web thickened + box added + web forked” system design method for the mid-web. The entire bridge is complex and requires further study. Through establishment of a beam element model and three-dimensional finite element model of the entire bridge, analysis of the overall spatial stress effect, transverse stress, local stresses of the variable width segment, and support reactions and multiple web shear distributions are carried out. The stress mechanism of the bridge is then further discussed. Through optimization analysis of the entire bridge, the thicknesses of the web and bottom plate of the bridge are reduced to further improve the mechanical performance of the structure. Therefore, the method used in this study can be used to rationally research and design this type of bridge.

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