自锚式悬索桥“先缆后梁”施工临时锚碇方案研究

Research on Temporary Anchorage Types for Self-Anchored Suspension Bridge with Main Cables Installed Ahead of Stiffening Girder

东莞东江南支流港湾大桥为主跨320 m的自锚式钢梁悬索桥,采用“先缆后梁”的方法施工。在上部结构安装过程中,主缆拉力通过临时拉索传递至临时锚碇,对临时锚碇的力学性能要求较高。为确保施工过程中桥梁结构受力安全、选取合适的临时锚碇方案,采用TDV RM2006软件建立施工阶段全桥模型进行力学性能分析,并采用MIDAS Civil 2017软件对独立锚碇、不增加桩径及桩数的结合锚碇、增加桩径及桩数的结合锚碇3种临时锚碇结构进行比选。结果表明:采用“先缆后梁”的总体施工方案可以满足上部结构安装要求,施工期间塔、梁、缆的强度、刚度均满足设计要求,临时拉索最大拉力24720 kN。增加桩径及桩数的结合锚碇桩基最大弯矩3394.6 kN·m,为3种方案中最小值,结构安全性较好;最大水平位移14.1 mm,比不增加桩径和桩数的结合锚碇刚度有较大提升,与独立锚碇相差不大。综合比较可知增加桩径及桩数的结合锚碇方案具有较好的安全性、经济性及施工便利性,且工期较短,因此最终选定该方案。

The Dongjiang South Tributary Bay Bridge in Dongguan is a self-anchored suspension bridge with a main span of 320 m.The main cables are installed ahead of the stiffening girder.During the construction of the superstructure,the tensile forces of the main cables were transferred to the temporary anchorage via temporary hangers,which posed great challenges to the mechanical property of the temporary anchorage.To ensure the load bearing safety of the bridge structure in the construction process and find the proper type of temporary anchorage,a model of the full bridge in the construction stage was established by TDV RM2006 for mechanical property analysis.MIDAS Civil 2017 was used to analyze three types of temporary anchorages,including the independent anchorage,composite anchorage without excessive piles and pile diameter,and composite anchorage with extra number of piles and enlarged pile diameter.The results show that the construction of the superstructure can meet the requirements when the main cables are installed ahead of the stiffening girder,and the strength and rigidity of the towers,stiffening girder and main cables can reach the required level during construction.The maximum tensile force of the temporary cable is 24720 kN.When the diameter of the piles is enlarged and the number of piles is increased.the maximum bending moment of the piles of the composite anchorage is 3394.6 kN·m,which is the smallest value of the three types of temporary anchorages,and the safety of the structure is also favorable.The maximum horizontal displacement is 14.1 mm,indicating that the rigidity is bigger than that of the composite anchorage where the pile diameter and number is kept constant,but roughly similar to that of the independent anchorage.The composite anchorage where the pile diameter is enlarged is superior to the other two alternatives in terms of safety,cost-effectiveness,ease-of-construction and construction time,which is determined as the final option.