铁路大跨度连续刚构收缩徐变计算分析

Calculation and Analysis of Shrinkage and Creep of Railway Long Span Continuous Rigid Frame

连续刚构由于其跨越能力强、结构整体性好、行车舒适性好、结构刚度大、抗震性能好、主墩不设支座和后期维养少等特点,在大跨度混凝土桥梁中十分具有竞争力,广泛应用于铁路桥梁工程中。由于对收缩徐变的影响考虑不充分,部分连续刚构桥梁成桥后出现较大竖向变形,并超出规范限值,严重影响了行车安全和乘坐舒适性。本文以汉巴南铁路恩阳河特大桥(72+136+72)m连续刚构为背景,采用BSAS和Midas Civil软件对6种不同规范收缩徐变变形结果进行对比分析,得出以下结论:(1)采用JTG 3362—2018规范计算收缩徐变变形与工程实际更为接近;(2)第一年收缩徐变变形占比最大,延迟铺轨时间可有效减小梁体收缩徐变变形;(3)铁路规范收缩徐变变形10年内基本完成,公路规范收缩徐变变形10年时间仅完成74%,建议收缩徐变计算时间统一按30年考虑;(4)规范中竖向变形限值为相对变形,为保证计算结果的准确性,建模时需包含桥墩;(5)BSAS和Midas Civil软件采用JTG 3362—2018规范计算结果相差不多。

Continuous rigid frame is very competitive in long-span concrete bridges because of its strong span capacity, good structural integrity, good driving comfort, large structural stiffness, good seismic performance, no support for main pier and less maintenance in later period. Due to the insufficient consideration of the influence of shrinkage and creep, some continuous rigid frame bridges have large vertical deformation after completion, which is beyond the standard limit, seriously affecting the driving safety and riding comfort. Based on the(72+136+72)m continuous rigid frame of Enyang River Bridge on Hanzhong-Bazhong-Nanchong High-speed Railway, this paper compares and analyzes the shrinkage and creep deformation results of six different specifications by using BSAS and Midas Civil software, and draws the following conclusions:(1) the calculation of shrinkage and creep deformation by using JTG 3362—2018 specification is closer to the engineering practice.(2) In the first year, the ratio of shrinkage and creep deformation is the largest, and the delay of track laying time can effectively reduce the shrinkage and creep deformation of beam.(3) The shrinkage and creep deformation in railway specification is basically completed within 10 years, while only 74% of the shrinkage and creep deformation in highway specification is completed within 10 years. It is suggested that the calculation time of shrinkage and creep should be considered as 30 years.(4) The limit value of vertical deformation in the code is relative deformation. In order to ensure the accuracy of the calculation results, the pier should be included in the modeling.(5) There is little difference between BSAS and Midas Civil software using JTG 3362—2018 specification.