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混凝土桁式组合拱桥将悬臂桁架与拱桥相结合,发挥了二者的优势且施工方便,在我国大跨径拱桥中占有独特位置。同时,近年来该桥型桥面变形大并伴随开裂等问题开始出现,为研究大跨径混凝土桁式组合拱桥结构的长期变形机理及开裂原因,以一座主跨138m桁式组合拱桥为背景,对其长期变形和混凝土开裂情况进行实测和规律分析;采用有限元模型,分析收缩、徐变及温度作用引起的挠度变化,讨论了结构在不同荷载作用下的受力特征。实测及分析结果表明,桁式组合拱桥长期线形呈M形,且在年温差作用下双立柱间的桥面发生上拱和下挠的交替变化,混凝土的收缩徐变及年温差作用是影响跨中实腹段长期变形的主要因素;结构在双竖杆处的下弦杆位置、跨中位置以及空实腹段交界位置处承受的荷载作用较大,导致在使用阶段的裂缝不断发展。
The concrete truss composite arch bridge combines the cantilever truss and the arch bridge, exerts the advantages of both and is convenient for construction, occupying a unique position in the long-span arch bridge in our country. In the meantime, in recent years, the deformation of the bridge decks is large and accompanied by cracking and other problems began to appear. In order to study the long-term deformation mechanism and cracking reason of the long-span concrete trussed composite arch bridge, taking a main span 138m truss composite arch bridge as the background, The long-term deformation and concrete cracking were measured and analyzed regularly. The finite element model was used to analyze the deflection caused by shrinkage, creep and temperature. The stress characteristics of the structure under different loads were discussed. The results of measurement and analysis show that the long-term line shape of the truss-type composite arch bridge is M-shaped, and the change of the upper arch and the lower torsion of the bridge between the double-column columns changes with the annual temperature difference. The shrinkage and creep of concrete and the influence of annual temperature difference Which is the main factor of long-term deformation in the solid belly section. The load of the structure at the position of the lower chord, the mid-span and the empty solid belly section of the double-vertical bar is larger, resulting in the continuous development of cracks in the use phase.