基于无应力正装迭代法的大跨混凝土斜拉桥合理施工状态分析

Analysis of Reasonable Construction State of the Long-span Concrete Cable-stayed Bridge Based on Stress-free Forward Iteration Method

大跨混凝土斜拉桥收缩徐变效应显著,单一计算方法很难完美确定其合理施工状态。目前确定斜拉桥合理施工状态的常见计算方法有前进分析法、倒退分析法、正装迭代法、倒拆-正装交互迭代法、无应力状态法等。以一座主跨300 m的大跨混凝土斜拉桥为依托,建立Midas三维空间有限元模型,基于无应力状态法与正装迭代相结合的计算方法,确定其合理施工状态,获取考虑收缩徐变效应后无应力正装迭代收敛本质及相关迭代规律。主要结论表明:考虑混凝土材料收缩、徐变效应后,构件无应力状态量会随施工过程发生变化,收缩徐变对结构线形影响实质是对结构构件无应力状态量的影响,导致最终成桥状态与目标状态不闭合;调整无应力状态量进行正装迭代分析可实现闭合;基于无应正装迭代法,大跨混凝土斜拉桥索力、线形与设计值能够闭合,内力与设计值接近。

The shrinkage and creep effect of long-span concrete cable-stayed bridge is remarkable.It is difficult to determine its reasonable construction state perfectly by a single calculation method.The common calculation methods for determining the reasonable construction state of cable-stayed bridges include forward analysis method,backward analysis method,forward-backward iteration method,and stress-free state method.Relying on a long-span concrete cable-stayed bridge with a span of 300 m,the finite element software Midas/Civil was used to establish a three-dimensional model.Based on stress-free forward iteration method,its reasonable construction state was determined and essence of convergence and related iteration law of stress-free forward iteration considering shrinkage and creep effects were acquired.The main conclusions are as follows:after considering the shrinkage and creep effects of concrete materials,the stress-free state of components will change with the construction process.The essence of the effect of shrinkage and creep on the structural alignment is the influence on the stress-free state of structural components,resulting in the no-closure of the final bridge state and the target state.The closure can be achieved by adjusting the stress-free state variables by forward iteration analysis.With the stress-free forward iteration method,the cable forces and alignments of long-span concrete cable-stayed bridges can be consistent with the design values,and the internal forces are close to the design values.