无背索曲塔曲梁斜拉桥参数敏感性分析

无背索曲塔曲梁斜拉桥参数敏感性分析刘世明1,2 刘永健1 （1.长安大学 桥梁与隧道陕西省重点实验室，陕西西安 710064；2.华北水利水电学院 土木与交通学院，郑州450011；）摘 要：为研究无背索曲塔曲梁斜拉桥施工中各参数变化的影响，对桥梁施工过程进行预控和参数误差识别，确保成桥时主梁变形、塔顶位移、主梁应力、塔底应力和拉索索力达到设计状态，以无背索曲塔曲梁斜拉桥东莞水道桥为工程背景，采用MIDAS/CIVIL空间有限元分析软件，考虑结构容重、混凝土弹性模量、拉索弹性模量、温度作用等参数变化的影响，进行了各参数的敏感性分析。结果表明：主梁在y方向上变形的敏感参数为整体温度作用，主梁在z方向上变形、主梁应力、塔顶位移、塔底应力以及拉索索力的敏感参数是整体温度作用和容重；整体降温时，主梁z方向最大位移增量为-12.2mm，位于主跨1/4跨径附近，梁截面应力增量在上、下缘的左右侧相差较大，主梁的扭转明显，引起塔顶x、y、z方向的位移增量最值分别为7.4mm、3.2mm和-21.3mm，在塔底截面上、下缘均产生拉应力增量，拉应力增量最大值为7.28MPa，发生在左侧塔底部截面左下缘；整体降温和容重增加引起的索力增量最值分别为23.24kN和18.11kN，其中，整体降温时左、右侧对应拉索的索力增量表现出较大的差异，对应拉索的索力增量差值最大达6.05kN。关键词：桥梁工程；斜拉桥参数敏感性分析；有限元分析；无背索；曲塔；钢-混组合梁中图分类号：U448.22 文献标识码：A Sensitivity Analysis of Parameters for Curved-pylon and Curved-girder Cable-stayed Bridge without Back-staysLIU Shiming，LIU Yongjian（1.Key Laboratory for Bridge and Tunnel of Shaanxi Province, Changan University, Xian 710064,china;2.North China Institute of Water Conservancy and Hydroelectric Power, Zhengzhou 450011, China;）Abstract：In order to study the influence of parameters for curved-pylon and curved-girder cable-stayed bridge without back-stays during construction, to precontrol the construction process and identify the parameter error, to be sure the deformation of the beam and the top of the pylon, stress of beam and the pylon bottom, cable force of the stay cable which be corresponding to the design value at the completion of the bridge construction, according to the construction of Dongguanshuidao bridge, which is a curved-pylon and curved-girder cable-stayed bridge, the analytical model is founded through the finite element analysis software MIDAS/CIVIL, and the parameters change such as structural unit weight and concrete elasticity modulus and cable elasticity modulus and temperature action are considered, sensitivity analysis of the parameters are carried out. The results show that the sensitive parameter of the deformation of the beam at the direction of y axis is temperature, and the sensitive parameters of the deformation of the beam at the direction of z axis and stress of the beam and the deformation of the top pylon and the stress of the pylon bottom are temperature and structural self-weight; the maximum deformation increment at the direction of z axis of the beam is -12.2mm caused by temperature drop, which is located at 1/4 point of the main span; temperature drop can cause the stress increment of the upper and lower beam and the stress differences of the left side and right side of upper and lower beam section are greater, torsion is obvious, the deformation increment caused by temperature drop of the top pylon at the direction of x axis, y axis and z axis are 7.4mm, 3.2mm and -21.3mm respectively, the tensile stress is occurrence at the upper and lower edge of pylon bottom section when temperature drop, the maximum tensile stress increment is 7.78MPa at the location lower edge of left pylon bottom section; the cable force increment caused by temperature drop and unit weight increment are 23.24kN and 18.11kN respectively, the force differences of the same number cable between the left and right are lager, the maximum difference of cable force increment is 6.05kN. Key words: bridge engineering; sensitivity analysis of parameters of cable-stayed bridge; finite element analysis; without back-stays; curved-pylon; curved-girder; steel-concrete composite beam引言无背索斜拉桥通过塔柱倾角来平衡桥面恒载和活载，不设背索，结构独特，造型优美，近年来在我国得到一定程度的发展1，目前已建成10余座。斜拉桥施工过程的影响因素比较多，黄灿2等采用几何控制法的基本原理，对几何尺寸、刚度和荷载变化对超大跨径钢箱斜拉桥的影响进行了系统的分析，为施工阶段误差确定、修正、控制提供依据；何祖发3等对独柱斜塔混合梁斜拉桥的施工控制进行了研究；其他学者也对斜拉桥参数敏感性进行了相关研究 4-8，然而，尚未见无背索曲塔曲梁斜拉桥施工控制及参数敏感性研究文献，类似桥梁的建设经验和研究资料较少，为确保桥梁施工的顺利实施，鉴于桥梁施工过程中影响因素多，结合东莞水道桥的施工监测监控工作，进行桥梁结构容重、混凝土弹性模量、拉索弹性模量、温度作用等参数的敏感性分析具有重要的理论价值和工程实用价值8-10。1 桥梁结构分析建模1.1桥梁概况东莞水道桥平面位于半径为800m圆曲线上，左、右侧纵坡分别为1.68和-4.00，竖曲线半径为2000m。结构采用无背索曲塔曲梁矮塔斜拉桥，塔梁墩固结体系，跨径布置为51.5m+138m+55m。桥面宽度为29.2m37.2m，桥梁的立面、平面、主塔处横断面如图1、2、3所示。主梁采用单箱四室箱型断面，顶板横向对称于箱梁中心线设置向外2%的双向横坡，中心线处高度为2.3m4.705m，沿纵向分为混凝土部分和钢梁部分，其中混凝土部分采用C60混凝土，布置三向预应力，左右两侧长度分别为23.25m、19.25m，钢主梁部分长度为95.5m，采用Q345钢材。主塔采用钢壳混凝土曲塔结构，与水平线夹角为58，塔身截面纵桥向宽度为5m7m，横桥向3m4.5m。斜拉索采用环氧喷涂钢绞线索，共有3s15.2、25s15.2和27s15.2三种规格，斜拉索布置在中央分隔带处。桥梁中跨沿纵桥向两侧无索区长度分别为29m、28m。梁上索距为9m，塔上索距为4.742m，为确保塔身的稳定性，在两桥塔间布置2根水平拉索，全桥共有22根斜拉索。图1 桥梁立面图（单位：cm）Fig.1 Longitudinal view of the bridge (unit: cm)图2 桥梁平面图（单位：cm）Fig.2 Plan view of the bridge (unit: cm)图3 桥塔处横断面图（单位：cm）Fig.3 Transverse view at the pylon of the bridge (unit: cm)1.2施工方案混凝土部分采用满堂支架施工，钢主梁部分采用浮吊安装施工。施工的顺序为：（1）墩台桩基、承台、墩台身、下塔柱施工；（2）满堂支架的搭设和预压；（3）主塔1号节段钢壳安装，预应力管道预埋；（4）预应力混凝土段和钢混结合段主梁施工；（5）待混凝土达到设计强度等级90%且龄期不少于7天时，先张拉纵向预应力钢筋