预应力混凝土连续箱梁顶底板搭接索拉-压杆分析

Analysis of PC Continuous Box Girder Top and Bottom Overlap Tendon with Strut-and-tie Method

针对目前预应力混凝土连续箱梁腹板1/4跨附近开裂现象比较普遍,已严重影响该类桥梁的安全性和耐久性这一问题。分别以重庆石板坡长江大桥和钟祥汉江大桥为例,采用拉-压杆理论,建立拉-压杆模型,研究顶、底板纵向搭接索引起的竖向拉力对预应力混凝土连续箱梁腹板受力状态的影响。在分析顶、底板搭接索反拱石机理的基础上,对预应力混凝土连续箱梁顶、底板纵向搭接索引起的腹板竖向拉力进行了拉-压杆模型分析。研究表明预应力混凝土箱梁顶、底板纵向搭接索可在腹板内引起较大的竖向拉力,并提出了相应的设计注意事项。

The phenomenon of web cracks of continuous PC box girder at 1/4 span is fairly common and has influenced the bridge＇s safety and durability.Taken Shibanpo bridge and Zhongxiang Hanjiang bridge as examples,the strut-and-tie model was built by using strut-and-tie theory.Then the influence of vertical tensile force caused by top and bottom slabs＇ longitudinal tendons on the stress of prestressed concrete box girder web were studied.Based on the analysis of inverse key-stone mechanism of the tendons,the continuous PC box girder web＇s vertical tension force caused by longitudinal overlap tendon in top and bottom slabs was analyzed by strut-and-tie method.The research result shows that a rather vertical tensile force could be caused by top and bottom tendons at PC box girder web.Some corresponding designing attention was put forward.