Abstract:

In response to significant lateral sliding of exposed steel penstocks during earthquakes, this study investigates the impact of displacement restrainers on the seismic response of exposed steel penstocks using finite element method. The results reveal that without restrainer, the sliding distance of the support at the midpoint of the pipe segment increased considerably during earthquake, leading to significant lateral bending of the steel pipe, detrimental to structural stability. Conversely, installing a restrainer controlled the lateral displacement of the exposed steel pipe within acceptable limits. However, during earthquakes, the sudden restriction of the sliding support led to substantial collisions between the sliding plate and the restrainer, causing instantaneous accelerations exceeding 100 m/s². The lateral forces on the support surged to 10 or even 100 times the static forces, significantly increasing the stress on the support ring. Lower limit value resulted in higher structural stress during earthquakes. By adding a thin cushion layer with an elastic modulus of 3 MPa between the restrainer and the support sliding plate, the forces on the support were mitigated, effectively reducing structural acceleration and stress. This adjustment kept the ratio of lateral to vertical forces on the support below the friction coefficient. Therefore, a support restrainer is essential for exposed steel penstocks in seismic zones. Meanwhile, it is crucial to consider both displacement and stress requirements when determining the restrainer’s limit value. To minimize adverse impacts of the collision between the support sliding plate and the restrainer during earthquakes, installing a thin buffer layer on the restrainer is recommended.

Key words: exposed steel penstock, earthquake response, sliding support, restrainer