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近年来,在高等级公路建设中,出现了较多“先简支后连续”的体系结构桥梁,其中组合箱梁因具有美观、经济、重量相对轻、跨径大等特点而被广泛采用,这种形式的桥梁绝大部分采用“先简支后连续的”结构体系,桥面铺装采用和路面上、中面层相同的沥青混凝土形式。因此,预应力组合箱梁和桥面铺装之间设计一层调平层,该调平层厚度一般为5c m,既起到调整与控制桥面高程的作用,又起到防水防腐的作用。但在实际施工中,调平层经常出现裂纹或裂缝,严重影响桥梁使用的耐久性和安全性,甚至造成桥面路面的损坏。产生裂缝的原因主要有:调平层厚度不均匀、调平层与箱梁黏结效果的影响、调平层中的钢筋网安放不当、调平层混凝土养生的影响、调平层混凝土的配合比不当引起混凝土的干缩裂缝、调平层混凝土碳化收缩引起混凝土表面龟裂。另外,在荷载反复作用下,调平层逐渐变为局部受压,出现应力集中、裂缝数量和宽度的增加,也会使调平层裂缝增多。
In recent years, in the construction of high-grade highways, there have been more “simple support and continuous” structural bridges, in which the composite box girders are widely used due to their characteristics of beauty, economy, light weight and large span Adopted, most of this form of bridge using “first simple support after the continuous ” structural system, deck pavement and pavement, the same surface layer of asphalt concrete form. Therefore, between the prestressed composite box girder and deck pavement design a leveling layer, the leveling layer thickness is generally 5c m, both to adjust and control the role of deck elevation, but also play a role in water and corrosion . However, in actual construction, the leveling layer often cracks or cracks, seriously affecting the durability and safety of the bridge, and even causing damage to the bridge surface. Cracks caused by the main reasons are: the thickness of the leveling layer is uneven, leveling layer and the effect of the bonding of the box girder, the leveling layer of steel mesh placed improperly, leveling layer of concrete health effects, the leveling layer of concrete mix Improperly caused by concrete shrinkage cracks, leveling concrete carbonization shrinkage caused by concrete surface cracking. In addition, under the action of repeated load, the leveling layer gradually becomes a partial pressure, stress concentration occurs, and the increase of the number and width of cracks also increases the cracks in the leveling layer.