大跨度无砟轨道连续梁桥后期徐变变形研究

Study on Post Creep Deformation of Long-span Concrete Continuous Bridge with Ballastless Tracks

无砟轨道能适应高速铁路高平顺性和高稳定性的要求,但可调性很小。预应力混凝土的后期徐变变形会引起桥梁的上拱和下挠,造成轨道不平顺。本文研究混凝土桥梁徐变变形的原理和计算方法,对现行中国铁路规范、中国公路规范和欧洲混凝土规范中的混凝土徐变系数与试验值作了比较。结果表明。3个规范的徐变系数都较实测值大,中国现行铁路规范的混凝土徐变系数又较另2个规范大,比较保守。对一座85 m+135 m+85 m的高速铁路预应力混凝土桥梁,模拟施工全过程,按成桥后10 d和90 d两种时间铺轨,计算分析铺轨后20年间由混凝土收缩、徐变、预应力损失引起的徐变变形。结果表明,按现行铁路规范计算所得的上拱值最大可达20 mm,比按现行公路规范计算大得多;徐变变形对铺轨时间较敏感,成桥后等待90 d再铺轨,后期徐变变形上拱度可显著下降。

The ballastless track can fit the demands of high smoothness and high stability of high speed railways,but it can be adjusted little. The post creep deformation of pre-stressed concrete will cause hogging and sagging of a bridge, then cause non-smoothness of the track. The principle and calculation method of concrete bridge creep deformation are studied. The concrete creep parameters of the current China Railway Code, China Highway Code and Euro Concrete Code are compared with the results of tests. The results show that the concrete creep parameters of the three Codes are all larger than the test results. Moreover, the concrete creep pa- rameter of the current China Railway Code is much larger than those of the two others, which is too conserva- tive. Simulating the whole construction process of a （85 ＋ 135 ＋ 85） m high speed railway pre-stressed concrete bridge and making two different arrangements of the track laying time（10 days and 90days after erection）, the post creep deformations caused by concrete shrinkage, creep and loss of pre-stresses during 20 years are ana- lysed. The results show that the largest hogging value can reach 20 mm according to the current China Railway Code and is much larger than that of the current China Highway Code; the creep deformation is sensitive to the track laying time and the post creep deformation hogging can be decreased notably if laying tracks 90 days after the erection of the bridge.