预应力混凝土连续梁拱组合桥吊杆成桥索力计算及影响因素分析

Calculation of the Final Cable Force of the Hangers of PC Continuous Beam-Arch Combination Bridge and Analysis of Its Influence Factors

根据预应力混凝土连续梁拱组合桥的结构特点,充分考虑主梁的承载能力,提出基于指定截面应力法的吊杆成桥索力分步算法。根据主梁截面的应力控制条件,以总的吊杆索力最小为目标函数,采用数学规划方法初定吊杆索力,然后采用最小二乘法进行吊杆索力调匀,从而得到较为合理的吊杆成桥索力。应用该方法对宿淮铁路京杭运河特大桥主桥(62+132+62)m连续梁拱组合结构进行吊杆成桥索力分析,研究主梁截面尺寸、施工方法等对吊杆成桥索力、主梁预应力布置的影响。结果表明:随着梁高的增大,主梁参与全桥受力的程度随之增大,吊杆索力减小,拱肋负担的荷载也减小;施工方法不同,吊杆成桥索力和主梁内的预应力布置也不同,当主梁由悬臂浇注法改为支架现浇法施工时,吊杆的成桥索力增大,主梁在中支点截面处需配置的预应力钢绞线数量减小,在中跨跨中截面处需配置的预应力钢绞线数量增大。

According to the structural characteristics of PC continuous beam-arch combination bridge and fully considering the carrying capacity of the girder,the step-by-step algorithm for calculating the final cable force of hangers was proposed based on specified section stress method.According to the stress control conditions of the girder sections,with the minimum total cable force of the hangers as the objective function,the cable force of the hangers was determined preliminary by adopting mathematical programming method and then was evenly adjusted using least square method.Accordingly,the reasonable final cable force of hangers was obtained.This method was applied to analyze the final cable force of the hangers of(62+132+62) m continuous beam-arch combination structure,the main bridge of Beijing-Hangzhou Canal of Su-Huai Railway.The effects of girder sectional dimension and construction methods on the final cable force of the hangers and the prestressed layout of girder were studied.The results show that,with the increase of beam height,the degree of the girder involved in the whole bridge force increases,the cable force of the hangers reduces and the load of arch rib decreases.With different construction methods,the final cable force of the hangers and the prestressed layout in the girder are also different.When cast-in-place cantilever balance method is substituted by cast-in-situ support method for girder construction,the final cable force of the hangers increases,the number of prestressed steel strand for the girder reduces at the section of the middle support point whereas increases at the section of midspan.