混凝土桥梁加宽改造的结构可靠度分析

发布时间：2018-08-27 07:17

【摘要】：目前关于加宽改造后桥梁的可靠性分析很少,有必要对加宽改造后桥梁的可靠性进行深入的研究,本文结合国家自然科学基金“既有混凝土桥梁拓宽改造设计的基础理论研究(51278182)”,依托实际工程项目,基于可靠性理论对一座四跨连续预应力T梁桥的加宽改造进行了研究,主要内容如下:(1)采用《公路钢筋混凝土及预应力混凝土桥涵设计规范》的收缩徐变模型进行分析,计算收缩徐变差和基础沉降差在结构内产生的附加内力。结果表明:收缩徐变差在旧桥外边梁和新桥主梁梁内产生轴拉力而旧桥中梁及内边梁则产生轴压力,且越靠近拼接缝的主梁轴力值越大;收缩徐变差在桥墩内产生的轴力较小,横向弯矩较大;基础沉降差在主梁内产生的附加内力较小,在主梁连接面处产生的剪力较大,且在横隔板附近剪力变化较剧烈,在不同桥墩内产生的轴力差别很大,内边梁侧的桥墩是外边梁侧的3.37~4.38倍,墩内产生的横向弯矩最大值为310k N·m;(2)根据等超越概率原则确定加宽改造基准期和设计荷载的取值,并求得不同设计使用年限的汽车荷载折减系数,考虑混凝土经时强度变化、钢筋锈蚀建立结构抗力时变模型;(3)根据加宽改造后结构受到的附加内力计算主梁的抗弯承载力和桥墩的抗压承载力。结果表明:在收缩徐变差及基础沉降差的影响下,6#梁的抗弯承载力提高了13.6%,7#梁的抗弯承载力下降了7.19%;1#-2墩的抗压承载力降低了18.79%,1#-3墩的抗压承载力降低了36.27%;(4)基于JC法和串联体系可靠指标计算方法对加宽桥梁进行时变可靠性分析,结果表明:加宽改造后到旧桥运营至100年时,考虑收缩徐变差和基础沉降差的影响后,上部结构的可靠指标提高了15.66%,下部结构则下降了29.8%,组合结构整体可靠指标则下降了2.20%;不加宽时,旧桥运营至30年后,可靠指标开始小于4.2,加宽后,旧桥运营至85年时可靠指标才开始小于4.2。
[Abstract]:At present, there is little analysis on the reliability of the bridge after widening and reconstruction, so it is necessary to carry out in-depth research on the reliability of the bridge after widening and reforming. Based on the National Natural Science Foundation of China "basic theoretical study on widening and rebuilding of existing concrete Bridges (51278182)", based on the reliability theory, the widening and rebuilding of a four-span continuous prestressed T-beam bridge is studied based on the actual engineering project. The main contents are as follows: (1) the shrinkage and creep model of highway reinforced concrete and prestressed concrete bridge and culvert design code is used to calculate the additional internal forces caused by shrinkage creep and foundation settlement difference in the structure. The results show that the axial tension is produced by the shrinkage and creep variation in the outer girder of the old bridge and the main beam of the new bridge, while the axial pressure is produced in the middle beam and the inner side beam of the old bridge, and the greater the axial force value of the main beam near the jointing joint, the smaller the axial force produced by the shrinkage and creep variation in the pier. The lateral bending moment is larger, the additional internal force produced by the foundation settlement difference in the main beam is smaller, the shear force generated at the junction surface of the main beam is larger, and the shear force changes sharply near the transverse partition, and the axial force produced in different piers is very different. The piers on the inner side of the beam are 3.37 ~ 4.38 times of the outside side, and the maximum transverse moment generated in the pier is 310k N m; (_ 2). According to the principle of equal transcendental probability, the reference period of widening and rebuilding and the value of the design load are determined. The vehicle load reduction coefficient with different design life is obtained, and the time-varying strength of concrete is taken into account. (3) the flexural bearing capacity of the main beam and the compressive capacity of the pier are calculated according to the additional internal force of the structure after widening and reforming. The results show that under the influence of shrinkage and creep variation and foundation settlement difference, the flexural bearing capacity of the beam is increased, and the flexural capacity of the beam decreases by 7.19% and 7.19% and the compressive capacity of the #-2 pier decreases by 36.27%; (4) based on the JC method, the compressive capacity of the #-2 pier decreases by 36.27; (4) based on the JC method, the flexural capacity of the #-2 pier decreases by 7.19% and that of the #-3 pier by 7.19%. And the calculation method of reliability index of series system is used to analyze the time-varying reliability of the widened bridge. The results show that the effects of shrinkage, creep and foundation settlement are taken into account when the old bridge is operated to 100 years after widening and reconstruction. The reliability index of the superstructure has increased by 15.66, the substructure has decreased by 29.8and the overall reliability index of the composite structure has decreased by 2.20.When the old bridge is not widened, the reliability index of the old bridge starts to be less than 4.2 after 30 years of operation, and the reliability index is widened. It was not until 85 years that the old bridge began to have a reliable index of less than 4. 2.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U445.6

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