某钢筋混凝土独柱伸臂桥墩开裂的加固设计及分析

Reinforcement Design and Analysis of the Typical Reinforced Concrete Single-Column Cantilever Pier

针对某桥钢筋混凝土独柱桥墩的开裂和特点,提出采用主动加固法进行加固设计,并基于空间有限元数值方法,通过精细模拟钢筋及混凝土的作用,对加固效果和施工过程进行了空间分析。结果表明,采用主动的对穿预应力束和高强螺杆的方法能够显著减小墩帽梁混凝土纵、横向的拉应力,闭合已经开裂的混凝土裂缝,同时考虑到已有的裂缝主要是由箱梁支反力较大、独柱桥墩的受力较大引起的,在加固施工时一方面要注意施工顺序和对称施工,另一方面在进行主动加固作业时要用千斤顶卸除部分支反力,待部分加固的纵横向预应力钢筋受力时再释放千斤顶的支撑力。

Aiming at special cracking and features of the reinforced concrete single-column cantilever pier in typical continuous box girder bridge,a method for retrofitting the pier by prestressing force is presented based on active reinforcement.The design details and construction sequence of strengthening the cracked cantilever pier are described.The strengthening of the cracked pier is analyzed through simulation of structure materials by the refined three-dimensional finite element numerical method.The strengthening effects and stresses conditions during the construction are evaluated.The calculation results indicate that the presented active reinforcement can obviously reduce the longitudinal and transverse stresses of strengthening the cracked pier and close the width of developed cracks.As the pier cracking is associated with large reaction force of bearing,partial reaction force of bearing should be downloaded by jack before increasing and tensioning tendons.Besides,construction sequence and symmetrical tension of tendons should be emphasized during retrofitting construction.