混凝土连续箱梁中间锚固区拉—压杆设计研究

Research on Design of Strut-and-Tie Model for Central Anchoring Zone of Concrete Continuous Box Girder

目前我国预应力混凝土连续箱梁中间锚附近开裂现象比较普遍,已经严重影响了该类桥梁的安全性和耐久性。造成该问题的原因可能与我国混凝土应力非规则区域设计理论不成熟有关,我国目前混凝土设计规范多以平截面假定为基础进行设计,而中间锚区是严重的非规则区域,不符合平截面假定。以预应力混凝土连续箱梁中间锚为分析对象,首先进行局部应力分析得到局部区域主应力矢量图,在此基础上提出相应的拉—压杆设计模型,并进行中间锚固区配筋设计,该方法具有思路清晰明确,便于应用等优点。

The phenomenon of middle anchorage zone cracks of continuous PC box girder is fairly common and has influenced this kind of bridge＇s safety and durability. The cause of this phenomenon maybe related with irrationality of designing methods of concrete stress discontinuous field. Now in China the design codes of concrete are almost based on the plane postulation. But the middle anchorage zone is serious stress discontinuous field and does not accord with the plane postulation. In this paper, a continuous PC box girder＇s middle anchorage zone is taken as analyzing object, and the anchorage zone stress analysis is done and the principle stress vector diagram is obtained. And then the strut-and-tie design model is put forward to arrange the anchorage zone reinforcement. The strut-and-tie design methods＂ conception is clear and easy to apply.