预应力混凝土箱梁桥悬浇梁段竖向接缝强度研究

Concrete Strength of Vertical Joint in Cantilever-cast Segment of Prestressed Concrete Box Girder Bridge

为了分析悬臂浇注施工的预应力混凝土(PC)箱梁桥在梁段之间存在的竖向接缝对混凝土整体强度影响,通过2座实桥与室内模型梁的接缝混凝土强度测试和承载能力试验发现:在正常施工条件下,大部分接缝处混凝土强度与腹板一般位置相比存在一定折减,其主要原因在于接缝附近端部混凝土由于振捣比较困难,混凝土沉积不均匀,导致接缝处混凝土质量要比一般位置混凝土质量差;接缝处不同混凝土粗糙度对混凝土箱梁抗拉强度有影响,其开裂荷载比整体一次浇注模型梁有所降低。因此施工中必须控制其接缝质量,增加交界面混凝土粗糙度,以提高新老混凝土结合面的粘结性能。

To analyse the influence of vertical joints lied between cantilever-cast segments of prestressed concrete box girder bridge on concrete strength,the vertical joints of two actual bridges and an interior girder model were applied to test the concrete strength and load-bearing capacity.It is found that（1） the concrete strengths of most vertical joints are lower than the strength in normal position of web under normal construction condition,the main reason of which is the vibrating difficulty and non-uniform deposition of concrete in the vertical joints,resulted in the concrete quality in that position is poor than that in normal position;（2） the tensile strength of concrete at the vertical joints is affected by the roughness of concrete,and the cracking load is lower than that of the whole model of box girder.Therefore,the quality of the vertical joints must be well controlled to improve the roughness and bond of concrete in combining site of old-new concrete during construction.