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预应力混凝土斜拉桥中,主梁的湿接缝往往是结构受力的薄弱部位。为揭示湿接缝的破坏机制,建立了天津永和大桥的施工阶段分析模型,计算了主跨合龙段与相邻预制节段之间的湿接缝的混凝土应力状态,分析了活载超载、拉索松弛及混凝土收缩徐变等多种因素对湿接缝混凝土应力的影响,同时也阐明了主跨合龙段的预应力钢筋、湿接缝的位置、湿接缝的施工质量等构造方面的固有缺陷。研究表明:长期超载运营是造成湿接缝破坏的最主要的因素,而运营期间拉索的松弛和混凝土的收缩徐变等因素是造成湿接缝破坏的不可忽略的原因。另外,湿接缝在桥跨中所处的位置、合龙段预应力钢筋的布置方式、新老混凝土结合面的处理方式及其普通钢筋配筋率等均是造成湿接缝破坏的内部因素。结合研究结果,从设计、施工、养护等层面上提出了相应的建议。
In prestressed concrete cable-stayed bridges, the wet joints of the girders tend to be weak parts of the structure. In order to reveal the failure mechanism of wet joints, the construction phase analysis model of Tianjin Yonghe Bridge was established. The concrete stress state of wet joints between the main span and adjacent precast sections was calculated. Cable relaxation and concrete shrinkage and creep on the stress of wet-jointed concrete, as well as the inherent structural aspects of the pre-stressed steel bar, the location of wet joints and the construction quality of wet joints in the main span closure sections defect. The results show that long-term overloading operation is the most important factor causing wet seams to sabotage. Factors such as relaxation of cables and shrinkage and creep of concrete during operation can not be neglected. In addition, the location of the wet joint in the span of the bridge, the arrangement of the prestressing reinforcement in the section, the treatment of the new and old concrete joints and the normal steel reinforcement ratio are the internal factors that cause the destruction of the wet joints. Combined with the research results, the corresponding suggestions are put forward from the aspects of design, construction and maintenance.