黄冈公铁两用长江大桥桥塔上横梁施工技术

Construction Techniques for Upper Cross Beams of Pylons of Huanggang Changjiang River Rail-cum-Road Bridge

黄冈公铁两用长江大桥主桥为主跨567m的斜拉桥。该桥桥塔上横梁为单箱单室预应力混凝土结构,长23.85m、宽8.4m、高8.0m,桥塔采用液压自爬模施工,上横梁与上塔柱采用异步施工。上横梁浇筑支架采用在两塔柱内侧设置剪力槽,安放对拉式钢牛腿作为支架受力支承点的方案。上横梁分2层浇筑,在第2层混凝土浇筑前张拉部分预应力筋。采用MIDAS Civil建模分析上横梁施工过程,结果表明,分层浇筑和分次张拉预应力钢筋可以有效减小现浇支架的荷载,且混凝土应力满足规范要求。该桥桥塔上横梁施工技术切实可行,实现了桥塔快速化施工。

The main bridge of Huanggang Changjiang River Rail-cum-Road Bridge is a cable-stayed bridge with a main span 567 m. The upper cross beams of the pylons of the bridge are the prestressed concrete single-cell single-box structures, each being 23.85 m long, 8.4 m wide and 8.0 m deep. The pylons were constructed by the hydraulic self-climbing formwork and the upper cross beams and the upper pylon columns were constructed asynchronously. A kind of the construction scheme was adopted for the casting scaffoldings of the upper cross beams, i.e. the shear groves were set in the inner sides of each two pylon columns and the counter tensioned steel brackets were installed as the supports of the scaffoldings. The concrete of the upper cross beam of a pylon was cast in two layers and before the second layer was cast, parts of the prestressing bars were tensioned. The MIDAS Civil was used to establish the model and the construction process of the upper cross beam was analyzed. The results of the analysis show that the casting of the concrete in layers and the tensioning of the prestressing bars in times can effectively reduce the loads on the scaffoldings and the stress of the concrete can satisfy the relevant requirements in the codes. The construction techniques for the upper cross beams of the pylons of the bridge are practical and feasible. With the techniques, the rapid construction of the pylons is achieved.