重庆双碑大桥主桥斜拉桥设计

Design of Cable-Stayed Bridge for Main Bridge of Shuangbei Bridge in Chongqing

重庆双碑大桥主桥为主跨330 m的高、低塔中央索面混凝土曲线斜拉桥。主梁采用单箱三室混凝土结构。桥塔采用独柱式,低塔边跨侧位于曲线上,为减少索的横向分力对结构的影响,靠曲线外侧布置竖向预应力钢绞线束。斜拉索采用高强低松弛镀锌钢绞线索。结合地质情况,高塔墩采用24根φ2.5 m钻孔灌注桩基础;低塔墩采用明挖扩大基础。高、低塔均采用塔、墩、梁固结体系。为减少塔根弯矩,下塔墩中间设20 cm的竖缝;通过优化桥塔尺寸,有效控制了主梁横向扭转角和桥塔横向位移。高塔墩基础采用双壁钢围堰法施工,低塔墩基础采用围堰或筑岛辅助施工;主梁7 m标准节段采用前支点挂篮现浇施工。

The main bridge of the Shuangbei Bridge in Chongqing is a central cable plane concrete curved girder cable-stayed bridge with a main span 330 m and with unequal height pylons.The main girder of the bridge is a 3-cell single box concrete structure.The pylons are the single column ones,of which the part of the low pylon on the side span is on curved line.To minimize the influence of transverse component of stay cables on the structure,on the outer side of the curved line,the vertical prestressing strands are arranged.The stay cables are used with the low-relaxation high strength galvanized steel strands.In view of the geologic conditions at the bridge site,the foundation for the high pylon pier is provided with 24 nos.of φ2.5 m bored piles while that for the low pylon pier with the open-excavated spread foundation and both the high and low pylons are designed as a rigid fixity system of pylon,girder and pier.To reduce the bending moment in a pylon footing,the 20 cm long vertical joint is set in the middle of the lower part of the pylon and through optimization of dimensions of the pylon,the transverse torsional angle of the main girder and the transverse displacement of the pylon are effectively controlled.The foundation for the high pylon is constructed by the double-wall steel cofferdam while that for the low pylon is constructed by the aid of the cofferdam or the artificial island.The 7 m long standard segments of the main girder is constructed by the cast-in-situ method by the front support form travelers.