自复位高墩振动台模型试验

为探讨自复位桥墩的地震反应，以某简支梁桥为工程背景，设计并制作了一个缩尺的模型桥梁。通过白噪声扫频获得了自复位桥墩的动力特性及其变化规律，选取El-Centro、Mexico和Chi-Chi强震记录作为地震动输入，进行振动台模型试验。试验记录了墩顶的加速度和位移反应，考查了地震动强度、频谱特性及预应力钢筋及其初始预加力对模型桥墩动力特性及摇摆反应的影响。试验结果表明:墩顶水平加速度反应随地震动强度及初始预加力的提高而增大，墩顶位移反应受地震动的强度、频谱特性及初始预加力大小影响较大。墩底提离面轻微损伤会明显降低体系的整体水平刚度，初始预加力则能提高体系整体水平刚度，桥墩的阻尼比随体系的水平刚度增大而减小。强震下自复位桥墩发生了预期的提离摇摆，震后墩底提离面出现轻微损伤，墩身无裂缝产生，结构具有良好的抗震及自复位性能。振动台试验结果验证已有文献的数值分析结论，振动台试验数据可用于数值模型校核或修正。

Shaking table test of self-centering model bridge pier

In order to study the seismic responses of the self-centering bridge pier, a simply supported girder bridge was taken as the engineering background and a 1/25 scale model of bridge was designed. The white noise was scanned to obtain the dynamic characteristics and their evolving mechanism of the self-centering pier. The shaking table model test was conducted with the El-Centro, Mexico and Chi-Chi strong ground motion records as the input. The acceleration and displacement responses of the pier top were recorded. The effects of the earthquake intensity, frequency spectrum, prestressed steel bars and its initial prestressing force on the dynamic characteristics and rocking responses of the model pier were investigated. The experimental results indicate that the horizontal acceleration response of the pier top increases with the increase of the earthquake intensity and initial prestressing force. The displacement response of the pier top is greatly affected by the earthquake intensity, frequency spectrum characteristics and the magnitude of initial prestressing force. The damage of the uplift surface significantly reduces the overall horizontal stiffness of the system, while the initial prestressing force improves. The damping ratio of the pier decreases with the increase of the horizontal stiffness of the system. The anticipated uplift and rocking of the pier occurred under the strong ground motions. No damage was found on the pier body, while slight damage was observed at the uplift surface of the pier bottom after the earthquake. It proves that the structure has good seismic behavior and self-centering performance. The shaking table test data can be used for validating or updating the numerical model.