Non-uniform Shrinkage Creep Effect of PC T-Beam Bridge

doi:10.3969/j.issn.1674-0696.2023.12.03

Abstract

Abstract: In order to analyze the non-uniform shrinkage creep effect of PC T-beams under dry conditions and mixed reinforcement conditions accurately, and to master the law of deformation, cross-section stress and cross-section stress redistribution of beam body, a beam element analysis method for PC beam bridges with non-uniform shrinkage creep effect was proposed. Firstly, the cross-section humidity distribution of the T-beam was analyzed through finite element program. Then, the cross-section of the PC beam with similar humidity distribution law was divided into several fiber beam elements, and the calculation of non-uniform shrinkage creep of the cross-section was simplified by the average relative humidity of the fibers. Finally, combined the fiber beam element with the micro-prestressed solidification (MPS) theory, the effects of mixed reinforcement and prestress relaxation were introduced, and the nonlinear incremental scheme finite element theory was used to solve the problem. The research results show that the PC T-beam exhibits significant non-uniform shrinkage creep effects, the average relative humidity has good representativeness, and the drying condition has a great influence on the deflection and stress distribution law of the beam body. At 1000d, the compressive stress reserve of web is lower than that of the top plate and horseshoe, and the difference in normal stress of the same cross-section in the mid span area reaches 3~4 MPa. The characteristics of vertical cracks in mid-span web of T-beam are consistent with those of the weak stress zone of web, which is an important cause of such cracks and should be considered in the design.

Key words: bridge engineering; PC T-beam bridge; non-uniform shrinkage creep; fiber beam element; MPS theory

摘要： 为准确分析干燥条件及混合配筋条件下预应力混凝土T梁非均匀收缩徐变效应，掌握梁体变形、截面应力及截面应力重分布规律，提出了一种预应力混凝土梁桥非均匀收缩徐变效应的梁单元分析方法。通过有限元程序分析了T梁截面湿度分布；将预应力混凝土梁截面具有相似湿度分布规律的区域划分成多个纤维梁单元，采用各纤维的平均相对湿度对截面非均匀收缩徐变计算进行简化；结合纤维梁单元及微预应力-固结(MPS)理论，引入混合配筋及预应力松弛影响，采用非线性增量格式有限元理论进行求解。研究结果表明：预应力混凝土T梁具有明显非均匀收缩徐变效应，平均相对湿度具有良好的代表性，干燥条件对梁体挠度及应力分布规律存在较大影响；1 000 d时腹板压应力储备低于顶板及马蹄，跨中区域同一截面法向应力差异达到3~4 MPa；T梁跨中区腹板竖向裂纹特征与腹板应力薄弱区一致，是该类裂纹产生的重要原因，应在设计中予以考虑。

关键词: 桥梁工程；预应力混凝土T梁桥；非均匀收缩徐变；纤维梁单元；MPS理论

CLC Number:

U445.7

WANG Long, WU Xiaoguang, ZHANG Liuyu, MO Di. Non-uniform Shrinkage Creep Effect of PC T-Beam Bridge[J]. Journal of Chongqing Jiaotong University(Natural Science), 2023, 42(12): 15-22.

王龙，邬晓光，张柳煜，莫迪. 预应力混凝土T梁桥非均匀收缩徐变效应分析[J]. 重庆交通大学学报（自然科学版）, 2023, 42(12): 15-22.

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