Abstract:

In response to the significant lateral support sliding of exposed steel penstock under earthquake, the influence of displacement restrainer of sliding support on the seismic response of exposed steel penstock is studied by finite element method. The results showed that when the support was not equipped with a restrainer, the sliding distance of the support in the middle of the pipe segment was large under earthquake, and the steel pipe bent laterally, which was disadvantageous to structural stability. When a restrainer was installed, the lateral displacement of the exposed steel pipe could be controlled within the allowable range. However, during the earthquakes, the movement of the sliding support was restricted suddenly, so the sliding plate of the support collided with the restrainer greatly, resulting in an instantaneous acceleration exceeding 100m/s². The lateral force acted on the support reached 10 or even 100 times that of the static state, and the stress of the support ring increased significantly. The limit value of restrainer had a significant impact on the structural seismic response. The smaller the limit value, the greater the structural stress during earthquakes. After setting a thin cushion layer with an elastic modulus of 3MPa on the contact surface between the restrainer and the support sliding plate, the force acted on the support during the earthquake was broken, reducing the structural acceleration and stress effectively. The ratio of lateral and vertical forces of the support was basically controlled to be lower than the friction coefficient. Support restrainer is necessary for exposed steel penstock in strong seismic zones. When determining the limit value of restrainer, both displacement requirement and stress requirement should be considered. To reduce the adverse effects of collision between the support sliding plate and the restrainer during earthquakes, a thin layer of buffer material is suggested to be installed on the restrainer.

Key words: exposed steel penstock, earthquake, sliding support, restrainer, soft cushion layer