波形钢与混凝土混合多箱室斜拉桥的剪力滞效应

Shear Lag Effect of Corrugated Steel-Concrete Composite Multi-Box Cable-Stayed Bridge

国内外多箱室的波形钢腹板矮塔斜拉桥已建造较多,但是波形钢与混凝土组合腹板的单箱多室的矮塔斜拉桥还很少见,这种新型的组合箱型截面的剪力滞效应有待深入探讨。目前,设计上分析剪力滞效应的常用分析方法多采用平面梁格模型、单梁模型、实体模型等,这些计算模型在分析剪力滞效应的各项应力指标时缺乏精细化,而空间网格分析模型可弥补这些分析方法的缺陷;因此,本文采用空间网格分析方法来探讨分析矮塔斜拉桥剪力滞效应。首先,详述了剪力滞效应的原理、空间网格分析方法及验证波形钢腹板空间网格分析方法的可行性,然后以一座波形钢与混凝土组合腹板的单箱多室的矮塔斜拉桥为典型案例,通过空间网格模型来分析其剪力滞效应。结果表明:此类箱梁的顶板表现出明显的正剪力滞、底板表现出较小的正剪力滞,混凝土腹板处的正剪力滞效应明显大于波形钢腹板处,各个工况的剪力滞系数表现出一定的变化规律。通过案例分析得出了此类钢混组合结构关键截面的剪力滞系数沿横向和纵向的分布规律,可为同类型工程提供参考。同时也由此验证了空间网格分析方法的有效性和准确性,弥补了常规分析手段的不足,为桥梁的精细化设计开拓新的思路和方向。

Many multi-box corrugated steel web low tower cable-stayed bridges have been built across the world,but single-box multi-chamber low tower cable-stayed bridges with corrugated steel and concrete composite webs are still rare.The shear lag effects of this new combined box profile sections need to be further explored.At present,the commonly used analytical methods for designing the analysis of shear lag effect mostly adopt plane beam model,single beam model,solid model,etc.But these calculation models lack refinement when analyzing various stress indexes of shear lag effect.The spatial grid analysis model can make up for the shortcomings of these analysis methods.Therefore,the spatial grid analysis method was adopted to discuss the shear lag effect of low tower cable-stayed bridges with low towers in this paper.Firstly,the principle of shear lag effect,the method of spatial grid analysis and the feasibility of the method verifying the space grid analysis of corrugated steel webs were analyzed in detail.Then a single-box multi-chamber low tower cable-stayed bridge with corrugated steel and concrete composite webs was taken as a typical case,and its shear lag effect was analyzed by a spatial grid model.The results show that,firstly,the top slab of this type of box girder shows obvious positive shear lag,and the bottom slab shows small positive shear lag;secondly,the effect of positive shear lag at the concrete web is significantly greater than that at the corrugated steel web;thirdly,the shear lag coefficients show a certain change law.Through case analysis,the distribution law of shear lag coefficients in key sections of this type of steel-concrete composite structure along the horizontal and vertical directions was obtained,which can provide a reference for similar projects.At the same time,the validity and accuracy of the spatial grid analysis method is verified.The spatial grid analysis model makes up for the shortcomings of conventional analysis methods and brings new ideas and directions for the refined design of bridges.