佛山富龙西江特大桥主桥桥塔中塔柱施工控制关键技术

Key Construction Control Techniques for Intermediate Pylon Columns of Main Bridge of Fulong Xijiang River Bridge in Foshan

佛山富龙西江特大桥主桥为主跨580 m的双塔双索面混合梁斜拉桥,“白鹭”造型桥塔高194.3 m,塔柱采用液压爬模法分节段施工,中塔柱直线段内倾12.5°,布置5道主动横撑(G1~G5)。建立主桥施工全过程杆系有限元模型和中塔柱塔肢结合部位实体模型,通过计算确定主动横撑安装位置、顶推力、横撑拆除顺序及中塔柱节段横向预偏量;确保横撑顶推前后塔柱根部最大拉应力不超过1 MPa;制定先从上往下拆除G3、G2、G1横撑、再从下往上拆除G4、G5横撑的拆除顺序;加大G4、G5横撑钢管规格,并在G2横撑下方增设竖向支撑;中塔柱节段向外侧设置横向预偏,抵消自重及施工荷载作用下塔柱内倾的影响。在每道横撑顶推施工期间对横撑钢管表面应力、对顶口相对位移、塔肢顶部偏位和根部截面应力进行精细化监测,确保横撑顶推力有效施加到塔柱上。施工中桥塔线形和内力状态控制良好,符合设计要求。

The main bridge of Fulong Xijiang River Bridge in Foshan is a hybrid girder cable-stayed bridge with a main span of 580 m.The stay cables are arranged in double cable planes.The two pylons,resembling egrets,rise 194.3 m,constructed using hydraulic climbing formwork.The straight portion of the intermediate pylon columns incline inwardly at 12.5°,and five temporary cross struts(G1-G5)were used to facilitate the construction.The whole construction process of the main bridge was simulated using link elements,and the joint section of the intermediate pylon columns was simulated using solid elements in MIDAS Civil,by which multiple parameters were determined,including the installation locations of the active cross struts,thrust forces,cross struts dismantling sequence and the lateral pre-offset of the central pylon shaft segments.The maximum tensile stresses at the base of pylons should not exceed 1 MPa before and after the jacking of the active cross struts.In accordance with the global link-element modelling,a preliminary plan was to dismantle the active cross struts downwards from G3 to G1,and then followed the G4 and G5.The strengths and stability of the tubes constituting the active cross struts were verified,and it was determined to improve the specs of the steel tubes of active cross struts G4 and G5,and adding vertical supports beneath the active cross strut G2.The segments of the intermediate pylon columns were laterally cambered to counteract the inward inclination of the lower pylon columns due to the self-weight and construction loads.During the pushing of the active cross struts,detailed monitoring was performed to capture the variation of multiple parameters,including the surface stresses of the constituent steel tubes of the active cross struts,relative displacements at the butts,offsets at the top of the pylon columns,and the stresses in the pylon-bottom cross-section,to ensure that the thrust forces of the active cross struts could be effectively function on the pylon columns.The alignment and internal forces of the pylons were under sound control throughout the construction,and met the design requirements.