基于三维实体元的预应力混凝土变截面桥梁长期性能分析

Long-Term Performance Analysis of Prestressed Concrete Variable-Depth Girder Bridge Based on Three-Dimensional Solid Element

预应力混凝土变截面梁桥空间效应较为突出,顶、底板和腹板理论厚度差异较大,杆系模型很难揭示结构成桥后收缩徐变作用下的时变效应。本文对比分析了ACI209、CEB-FIP(1990)和B4三种收缩徐变模型差异,采用Fortran语言编写ACI209、CEB-FIP(1990)和B4收缩徐变子程序,采用三维实体单元对比分析并揭示了PC变截面梁桥在不同收缩徐变模型作用下中跨跨中挠度、中跨跨中底板压应力和腹板主拉应力变化,B4模型下结构长期挠度呈不收敛的发展趋势,中跨1/4至中跨1/2区域内主拉应力相对于其他区域对竖向预应力损失更为敏感。计算分析表明,桥梁截面应力处于合理成桥状态,能有效抑制结构长期下挠。

The spatial effect of prestressed concrete(PC)variable-depth girder is prominent.And the theoretical thickness of top,bottom plate and web is quite different,so it is difficult to reveal the time-varying effect under the action of shrinkage and creep after the structure is completed.This paper compares and analyzes the differences between ACI209,CEB-FIP(1990)and B4 shrinkage and creep models.Combined with FORTRAN language shrinkage-creep subroutine,the three-dimensional solid element is used to analyze and reveal the changes of mid span deflection,mid span middle floor compressive stress and web principal tensile stress of PC variable section beam bridge under different shrinkage and creep models.Under B4 model,the long-term deflection of the structure does not converge,and the principal tensile stress in the area from 1/4to 1/2 of the midspan is more sensitive to the loss of vertical prestress than in other areas.The calculation and analysis show that the section stress of the bridge is in a reasonable state of completion,which can effectively restrain the long-term downward deflection of the structure.