PC梁桥负弯矩区UHPC-NC结构的抗裂性能

Anti-Cracking Property of UHPC-NC Structure in the Negative Moment Zone of PC Beam Bridge

为提高装配式预应力混凝土(PC)连续梁桥负弯矩区的抗裂性能,提出了一种在负弯矩区设置UHPC层和强配筋(配筋率≥1.5%)相结合的UHPC-NC(普通混凝土)连接构造,并以昌九高速某装配式PC连续梁桥为工程原型,进行横桥向缩尺比为1∶4、顺桥向缩尺比1∶5的缩尺模型试验研究,对该连接构造的可行性进行验证;然后,基于“平截面”假定,根据模型试验结果得到了该连接构造不同受力模式下的开裂弯矩计算方法,并采用有限元法分析了UHPC层厚度和配筋率对开裂弯矩的影响规律。结果表明:采用强配筋的连续梁桥负弯矩区UHPC-NC(普通混凝土)连接构造的开裂弯矩明显提高,验证了该连接构造是可行性的,为理论及有限元分析提供了依据;文中开裂弯矩计算方法可靠性较高,可为设计及工程应用提供参考,有限元方法与文中方法开裂弯矩结果相对误差在10%以内;纯弯矩作用以及弯-剪组合作用下,UHPC-NC结构开裂弯矩随UHPC层厚度增加而增加、随配筋率增大而增大。

To improve the anti-cracking performance of the negative bending moment zone of the continuous pre-fabricated beam bridge, this paper proposed a UHPC-NC(normal concrete) structure with a high reinforcement ratio(larger than 1. 5%) in the negative bending moment zone of an assembly continuous beam bridge. Taking A PC con-tinuous beam bridge on the Nanchang to Jiujiang expressway as the engineering prototype, the study carried out thescale model tests with the scale ratio of 1∶4 in the transverse direction and 1∶5 in the longitudinal direction. Then,based on the "plane section" assumption, it developed the calculation methods formula of the cracking moment forthe connection structure under different bearing modes. The influences of the thickness of the UHPC layer and rein-forcement ratio on the cracking moment were analyzed by means of the finite element method. The results show thatthe cracking moment with the UHPC layer in the negative moment zone of the continuous girder bridge is improvedsignificantly. The feasibility of the connection structure and the validity of the finite element model were verifiedand the calculation method of cracking moment in this paper is reliable and can provide reference for design andengineering application. the relative error of the reinforcement ratio between the finite element method and themethod in this paper is within 10%. Under the action of pure moment and bending shear combination, the crackingmoment of UHPC-NC structure increases with the increase of UHPC layer thickness and reinforcement ratio.