2016 – Seismic Strengthening Design for Pre-stressed Concrete Penstocks

Mohammad Okhovat, Viculp Lal, Neil Sutherland

The precast, prestressed concrete penstocks at Meridian Energy’s Benmore power station in New Zealand have attracted attention since construction about 50 years ago because of their unusual design. They are listed as the world’s first prestressed penstocks. However, their seismic capacity has been determined to be insufficient when measured against Meridian’s current asset management objectives aimed at avoiding significant damage to generating assets in a 1:2,500 year AEP earthquake. The deficiency is mainly due to the relatively narrow base width of the penstocks.

In this study, a series of linear analyses was performed to obtain an improved understanding of seismic behaviour of the penstocks. Various strengthening solutions are under consideration for the penstocks to meet the acceptance criteria. Additionally, nonlinear analysis of the penstocks was carried out to investigate the use of seismic damping devices fitted to the penstocks, similar to damping applications in seismic response control of buildings and bridges.