南沙港铁路洪奇沥特大桥主桥设计

Design of Main Bridge of Hongqili Bridge on Nanshagang Railway

南沙港铁路洪奇沥特大桥位于近海强风区,通过方案比选最终选择跨径为(138+360+360+138)m钢桁梁柔性拱桥作为桥式方案。钢桁梁采用高16m的2片主桁,桁间距15m,节间长度为13.5m和14m;采用水平向熔断型支座、纵向粘滞阻尼器、横向E型钢阻尼器的组合抗震措施;设计选用柔性吊杆;采用板式轨枕纵横梁无道砟桥面系,与传统的正交异性板有砟桥面系相比,桥面恒载由145kN/m降至70kN/m,节省了费用。为减小施工风险,在主跨设置临时支墩,并借助临时支墩悬臂拼装钢桁梁;将拱肋分成2个半拱,在钢桁梁上弦搭设支架卧拼拱肋,并借助扣塔扣索竖转拱肋。有限元计算结果表明该桥设计方案结构力学性能满足规范要求,设计合理。

The Hongqili Bridge on Nanshagang Railway is located in the offshore heavy wind area. By schemes comparison, the combined steel truss girder and flexible arch bridge was finally chosen. The bridge has four spans of 138, 360, 360, and 138 m. The steel truss girder consists of two main trusses, 16 m high each and spaced at 15 m. The panel lengths include 13.5 m and 14 m. The anti-seismic system incorporates the bearings capable of being horizontally fused, longitudinal viscous dampers and transverse E-shaped steel dampers. Flexible hangers were used. The ballastless deck system is formed of stringers and cross beams covered with plate sleepers. Compared with the conventional ballast deck system of orthotropic steel plates, the dead load on the deck is decreased from 145 to 70 kN/m, leading to the fall of the costs. To reduce the construction risk, temporary piers were added to the main spans, by the aid of which the cantilever assembly of steel truss girder was conducted. The arch rib was divided into two halves, which were assembled in the lying position on the scaffolds installed on the upper chords of the steel truss girder, and then vertically rotated with the assistance of fastening towers and stays. The results of the finite element calculation show that the mechanical property of the structure proposed can meet the code requirements, and the design is rational.