天津南仓斜拉桥索塔锚固区U形环向预应力施工控制研究

Research of Construction Control of U-Shape Loop Prestressing in Anchorage Zone in Pylon of Nancang Cable-Stayed Bridge in Tianjin

针对斜拉桥索塔锚固区大吨位、小半径U形环向预应力施工普遍存在的伸长量超标并时常伴有断丝、按照现行规范标准无法达到伸长量和张拉力双控的现象,以天津南仓斜拉桥索塔锚固区U形环向预应力施工为研究对象,采用因果分析和工艺性试验相结合的方法,找出了造成该质量问题的短束效应、环向效应、几何变形、计算差异等主要原因,采用"单束张拉预紧、整体分级张拉"的U形环向预应力穿束、张拉工艺,以应力控制为主、伸长量为辅的控制原则,取得符合工程实际的伸长量校核方法为:δ校=δ弹+δ几+δ附。

In the light of the problem of excessive elongation and concomitant breaking of prestressing strand wires commonly existing in the construction of the large tonnage and small radius U-shape loop prestressing in the anchorage zone in pylon of cable-stayed bridge and in view of the difficulty that the elongation and prestressing tensioning can not be controlled at the same time according to the present codes and standards,the construction of the U-shape loop prestressing in the anchorage zone in pylon of Nancang Cable-Stayed Bridge in Tianjin is taken as the research object,the major causes leading to the problem,such as the strand shortening effect,loop effect,geometric deformation and calculation differences,have been found out,using the combined method of cause-and-effect analysis and construction technology testing,and the checking method δcheck=δelastic＋δgeometric＋δadditional for the elongation that conforms to the actual situation of the construction is obtained,using the construction technology of threading and tensioning of the U-shape loop prestressing strands of ＂tensioning and pre-tightening a single strand and tensioning all strands in different load levels＂ according to the principle of controlling the stress mainly and the elongation subsidarily.