大跨斜拉输水管桥水锤冲击响应研究

大跨斜拉输水管桥管道内水锤效应往往对桥梁结构安全产生重要影响。建立了某斜拉输水管桥有限元模型，对比分析水-管-桥结构的动力特性，进行了管-桥共振复核。通过特征线法求解水锤基本方程，计算了输水工况转换过程中不同阀门关闭历时产生的水锤压力，分析了水锤冲击作用下管桥主要构件的动力响应，对比研究了水锤荷载不同加载方式及不同关阀历时对管桥构件响应的影响规律。结果表明：管道空管及充水满管情况下的自振频率与桥梁结构的固有频率错开度较大，二者没有发生共振的可能；非均匀加载方式使得管桥各构件动力响应相对均匀加载显著增大，位移和应力的增幅大都超过50%，但不会引起构件的失稳或破坏；随着阀门关闭历时的增加，水锤冲击作用减弱，管桥主要构件的动力响应降低，钢桁梁组件中K型支撑杆、横梁、腹杆的响应下降幅度相对较大，桥塔的响应下降幅度较小。

Response of long-span water conveyance cable-stayed pipeline bridge to water hammer impact

The water hammer effect in the pipeline of long span cable-stayed pipeline bridges often has an great adverse influence on the bridge structure safety. The finite element model of a cable-stayed pipeline bridge was established to comparatively analyze the dynamic characteristics of water-pipe-bridge structure, and the pipe-bridge resonance check was carried out. The basic equation of water hammer is solved by the characteristic line method, then the water hammer pressure generated by different valve closing time in the process of water conveyance condition conversion was calculated to analyze the dynamic response of the main components of the pipeline bridge under the impact of water hammer and the effects of different loading modes of water hammer load and different valve closing time on the response of the components of the pipeline bridge. The results show that the natural vibration frequencies of cable-stayed bridge and water conveyance pipeline are quite different from each other whether there is no water or full of water in the pipeline, so the pipe-bridge resonance will not occur. The non-uniform loading mode significantly increases the dynamic response of each component of the pipeline bridge, and both the increment of displacement and stress are more than 50%, but they will not cause the instability or failure of the components. With the increase of valve closing time, the impact of water hammer is weakened, and the dynamic response of the main components decreases, of which the response of the K-type support rod, beam and ventral rod in the steel truss beam assembly decreases significantly, while that of the bridge tower only decreases slightly.