配置竖向无粘结预应力筋的RC桥墩残余变形研究

Residual displacement of RC bridge piers with vertical unbonded prestressing strands

为进一步讨论采用竖向无粘结预应力筋减少钢筋混凝土(Reinforced Concrete,RC)桥墩震后残余位移的可行性,建立了竖向配置预应力筋的RC桥墩动力分析模型,结合拟静力和振动台试验结果,对数值分析模型的准确性进行了验证。在此基础上讨论了无粘结预应力筋对RC桥墩震后残余位移的影响。结果表明,RC桥墩中配置竖向无粘结预应力筋能够明显减小桥墩震后残余位移;随预应力筋配筋率的增加,墩顶残余位移值明显减少;预应力筋初始应力和预应力筋位置对桥墩震后残余位移影响不大。近断层地震动是引起桥墩震后残余位移过大的主因,远场地震动下,桥墩震后残余位移与墩顶最大位移的比值在10%内;而近断层地震动下,桥墩震后残余位移与墩顶最大位移的比值可达30%以上。预应力筋最大应力值随墩顶最大变形基本呈线性增加的趋势。

To investigate the feasibility of reducing the residual displacement of reinforced concrete （ RC ） bridge piers by using unbounded prestressing strands, a dynamic analysis model for RC piers with vertical unbonded prestressing strands was built, and the accuracy of the model was verified by comparing the analysis results with those of quasistatic and shaking table tests. The influence of prestressing strands on the residual displacement of piers was studied. It is found that the residual displacement of piers can be reduced obviously by using the unbonded prestressing strands. And a larger prestressing strand ratio will lead to a smaller residual displacement. The initial stress of prestressing strands and the location of strands have little influence on the residual displacement of piers. The near fault ground motion is the main factor inducing the residual displacement of piers. The ratio of the residual displacement to maximum displacement of piers under far fault ground motion is less than 10% , while the ratio would increase to larger than 30 % for piers under near fault ground motion. The maximum strand stress increase linearlys with the maximum lateral displacement of the pier.