一致激励下的混凝土斜拉桥振动台试验

Shake Table Test of a Concrete Cable stayed Bridge Subjected to Uniform Seismic Excitation

摘要:

以某一典型中等跨径混凝土斜拉桥为研究对象，设计了1∶20大比例振动台全桥试验模型.采用Chi Chi波和场地人工波进行了纵、横桥向小幅四台阵全桥振动台试验，并对该试验模型进行了场地人工波输入下的横桥向破坏性试验.试验结果表明：纵桥向输入时，由于Chi Chi波长周期丰富，激起结构反应较大；横桥向输入时，两条波的频谱特性在结构横向周期附近基本相同，故激起结构反应相差不大；结构在场地人工波1.3g横桥向输入时，桥塔上横梁主筋断裂、混凝土大面积剥落、发生明显破坏，上横梁与塔柱之间形成的塑性铰导致桥塔的框架效应明显削弱，桥塔得到了有效保护，达到了试验预期目标.

Abstract:

A 1∶20 scale model of a typical mid span concrete cable stayed bridge was designed, constructed and tested on 4 shake tables in longitudinal and transverse directions, respectively, first with minor excitations of Chi Chi wave and then with site specific artificial wave. The destructive behavior was observed with much severe transverse shaking of site specific artificial wave. The experimental results showed that the bridge responses which were excited by the long period Chi Chi wave were larger under longitudinal earthquake input, but the structure responses which were excited by Chi Chi wave and site specific artificial wave were similar under transverse earthquake input because the two wave spectrum characteristics concerned were basically identical. Under the transverse site specific artificial wave input with PGA approaching 1.3g, the upper beams of the tower were obviously damaged including the fracture of longitudinal reinforcement and concrete spalling in a large area, which formed the plastic hinges between the upper tower column and the tower upper beam, therefore the tower base were effectively protected owing to this weakened framing effect.