预应力混凝土桥梁弯曲孔道接触应力研究

Research on curved duct contact stress of prestressed concrete bridge

大跨度预应力混凝土桥梁运营过程中,箱梁跨中下挠与腹板开裂现象十分普遍.从结构受力分析,混凝土箱梁徐变效应所带来的跨中下挠,客观上表明梁体处于拉应力状态,与结构设计意图大相径庭,意味着预应力混凝土结构设计理论尚存在某些弊端.为探究预应力钢束与弯曲孔道间接触应力的分布规律以及孔道相关参数的影响,基于赫兹接触理论,通过一组预应力弯曲孔道模型挤压试验,借助CT扫描技术获取试验模型的形变数据,并结合有限元分析软件ANSYS进行数值模拟.结果表明其接触应力分布呈钟形,接触应力大小与张拉力正相关,与曲率半径负相关,接触应力梯度与接触角度负相关.研究结论对预应力混凝土构件设计理论的修正具有参考意义.

The phenomenon of mid-span deflection and web cracking of box girder of long span prestressed concrete bridges in operation is very common.According to the analysis of structural stress,the mid-span deflection,caused by creep effect of concrete box girder,indicates that the beam presents a tensile stress,which is quite different from the structural design intention,meaning that several drawbacks are needed to be considered in the design theory of prestressed concrete structures.In order to explore the distribution of contact stress between prestressed reinforcement and curved duct as well as the influence of relevant parameters of curved duct,based on the Hertz contact theory,a set of extrusion tests are conducted on the prestressed curved duct model,in which the deformation data of model are recorded using CT scanning technology.Meanwhile,finite element software ANSYS is also adopted to further explore the contact stress in curved duct.The results suggest that the distribution of contact stress is bell-shaped,and the contact stress is positively correlated with the tensile force,negatively correlated with the radius of curvature,and the gradient of contact stress is negatively correlated with the contact angle.The conclusions are of significant reference for revising the design theory of prestressed concrete structures.