西安绕城高速上跨西安北客站转体斜拉桥设计

Design of a Rotation-Constructed Cable-Stayed Bridge Carrying Part of Xi′an Ring Expressway over Xi′an North Railway Station

西安绕城高速上跨西安北客站桥梁主桥采用跨径布置(100+240+100)m的双塔混凝土斜拉桥,桥面全宽31.4 m,双向6车道。该桥采用连续梁支承体系,并设置摩擦摆支座和阻尼器的抗震构造。主梁采用C60混凝土双边纵梁结构形式,每根斜拉索对应设置1道横梁。桥塔采用榴锦造型,外形为弧形曲线,采用C60混凝土,横向由2个塔柱组成,下设整体式承台及钻孔灌注桩基础。该桥采用转体法施工,转体系统采用钢球铰支座,分上、下两片,设计竖向承载力为385000 kN。斜拉索采用∅s 15.2 mm、标准抗拉强度1860 MPa的环氧涂层钢绞线。边墩采用三柱式框架墩,墩顶设盖梁,墩底下设承台及钻孔灌注桩基础。对结构进行静力、动力分析,各项指标均满足规范要求;对转体过程的混凝土上、下转盘进行局部受力分析,扣除局部加载的影响范围,各点的拉、压应力均满足规范要求。桥塔采用“支架法+爬模法”现浇施工;主梁采用“支架现浇+牵索挂篮悬浇”施工,平面转体跨越既有铁路。

The main bridge of the cable-stayed bridge carrying part of the Xi′an Ring Expressway over the Xi′an North Railway Station was constructed by the rotation method.The bridge has two pylons that create three continuous spans of 100,240 and 100 m and carries 6 vehicle lanes,with full deck width reaching 31.4 m.Friction pendulum bearings and dampers are installed for seismic protection.The superstructure consists of two edge longitudinal girders(C60 concrete)and the in-between floor beams that are spaced to coincide with the stay cable anchorage points.Mounted on integral pile caps supported by bored pile foundation,the pylons are designed to echo the pomegranate flower,consisting of two curved-line pylon columns made of C60 concrete.The swivel system of the bridge incorporates the steel spherical hinge which has an upper and a lower halves,capable of carrying vertical loads of 385000 kN.The stay cables consist of epoxy-coated steel strands,each composed of∅s15.2 mm steel wires with a nominal tensile strength of 1860 MPa.Each side pier,also supported by integral pile caps and bored pile foundation,has three columns,over which a cap beam is laid.The static and dynamic analysis demonstrated that all the indexes of the bridge met the code requirements.The local load bearing behaviors of the upper and lower halves of the spherical hinge during rotation construction were analyzed,deducting the influential scope of local load application,the tensile and compressive stresses at each support reached the required level.The pylons were cast in situ using scaffolds and climbing formwork.The girders were cast in situ using scaffolds and guyed form travelers and swivelled to cross the existing railways.