Seismic study of a typical radial floodgate in a UK gravity dam

Abstract

A seismic evaluation of a typical UK radial gate design, based on the arrangement at Kilmorack Dam, was conducted for Scottish and Southern Energy. Its purpose was to assess the general seismic risk to radial gates in the UK, and to evaluate appropriate methods for their seismic analysis. The study included dynamic hammer tests on the gate, the seismic analysis of a three-dimensional finite element model, and the equivalent-static analysis of simple two-dimensional models. Natural frequencies and mode shapes from the tests correlated reasonably with the three-dimensional model, validating it for seismic analysis. A response analysis was run for the three-dimensional model using artificial accelerograms generated from a standard UK earthquake response spectrum. The demand on the gate for the seismic condition was almost double the hydrostatic demand, indicating that this and other similar non-seismically designed gates may be vulnerable to earthquakes. Generally, the equivalent-static analysis yielded higher responses than the dynamic three-dimensional analysis, but the two-dimensional models could not represent important three-dimensional effects in the gate. This study showed that the equivalent-static analysis of simple models is appropriate for preliminary seismic assessments of radial gates, while dynamic analyses of three-dimensional models should be employed for detailed analyses.