基于先简支后连续的高铁道岔连续梁设计研究

Research on the Design of High-speed Railway Turnout Continuous Beam Bridges Based on Converting Simply Supported Beams into Continuous Beam

研究目的:为克服满堂支架现浇施工的缺点,首次在高铁道岔连续梁施工中应用先简支后连续工法。本文通过有限元施工模拟,以及宝兰客专工点的实际造价、工期对比,来验证先简支后连续工法的力学合理性与经济优越性,分析优化先简支后连续工法的合龙参数,给出工程应用建议。研究结论:(1)较完全简支体系,先简支后连续体系通过刚度大幅提高,能够满足桥上道岔结构的变形限值;(2)较完全连续体系,先简支后连续体系在制梁架设过程中已完成大部分的收缩徐变、不均匀沉降,体系转换后,徐变和沉降引起的附加变形、次内力大幅降低,受力性能优化;(3)采用基于移动模架、预制架设的先简支后连续工法能够避免支架施工,在造价、工期方面取得巨大效益;(4)先简支后连续工法中合龙钢束向下锚弯、先边跨后中跨对称合龙能够减小结构位移、次内力;(5)本研究可为后续大量高铁道岔连续梁的施工建造提供经验参考。

Research purposes: In order to overcome the shortcomings of the cast-in-place method with full support, the technology of converting simply supported beam into continuous beam was applied for the first time in the construction of high-speed railway turnout continuous beam bridges. By construction simulation with finite element method, and comparing actual cost, construction period of Baoji-Lanzhou High-speed Railway, this paper aimed to verify the mechanical rationality and economic superiority of the proposed construction method, optimize the closing parameters, and give the engineering application suggestions.Research conclusions:(1) Compared with completely simply supported beam system, the passing stiffness of the simply-supported-to-continuous beam system is greatly improved, which can meet the deformation limit of the turnout structure on the bridge.(2) Compared with the completely continuous beam system, the proposed system has completed most of the shrinkage and creep and uneven settlement during the beam erection process. So the additional deformation and secondary internal force caused by creep and settlement are greatly reduced after system conversion, and mechanical properties of the bridge become stronger.(3) The simply-supported-to-continuous construction method can achieve huge benefits in terms of cost and construction period, by moving moulds casting method, precast-in-factory method, and avoid cast-in-place construction.(4) In the simply-supported-to-continuous construction, it is beneficial to reduce structural displacement and secondary internal forces by anchoring the closure steel beam downwards and symmetrical closure of side span first then mid span.(5) The research results can provide an empirical reference for the construction of a large number of high-speed railway turnout continuous beam bridges in the future.