斜拉桥H形混凝土桥塔横桥向地震破坏模式研究

Study of Transverse Seismic Damage Modes of H-Shaped Concrete Pylon of Cable-Stayed Bridge

为研究斜拉桥不同方案的H形混凝土桥塔在横桥向地震作用下的破坏模式,以某双塔斜拉桥(桥塔采用H形钢筋混凝土塔)为背景,设计制作2个缩尺比为1/20的全桥模型(桥塔分别采用强柱弱梁和强梁弱柱方案)进行振动台试验,观测桥塔破坏过程,测量桥塔基本周期变化及桥塔加速度和位移响应。结果表明:随着地震激励强度的增强,强梁弱柱设计的桥塔经历弹性阶段、裂缝开展阶段、塔柱保护层混凝土剥落及塔柱混凝土压碎4个阶段,且桥塔破坏时塔顶残余位移较小;与强柱弱梁设计相比,强梁弱柱设计的桥塔可以更好地控制塑性发展位置,并充分发挥桥塔塔柱的非线性耗能能力,减小桥塔下部基础的抗震需求。

To study the transverse seismic damage modes of H-shaped concrete pylons of cable-stayed bridge designed in different schemes, a two-pylon cable-stayed bridge, of which the pylons are structured with H-shaped reinforced concrete, is taken as a background. Thereafter, two 1/20-scale full bridge models, in which a weak girder plus strong column scheme and a strong girder plus weak column scheme were adopted, respectively, were designed and prepared to carry out shake-table tests. During the shake-table tests, pylon damage process was recorded, and fundamental frequencies, acceleration and displacement responses of pylons were measured. Test results reveal that, as the excitation intensity increases, the pylon designed in the strong girder plus weak column scheme undergoes four stages, including elastic, expansion of crack, spalling of concrete for protective layer of pylon column and crushing of pylon column concrete. The residual displacement at top of pylon is small when the pylon is damaged in the tests. Compared to the pylon designed in the strong column plus weak girder scheme, the pylon designed in the strong girder plus weak column scheme can better control the locations of plastic development, and the capacity of nonlinear dissipation of energy can be significantly utilized. Hence, the seismic demands at the foundation of pylons are decreased.