216. SEISMIC LOADING OF WIND TURBINES
Name: Ian M Prowell
Grad Year: 2009
Using wind turbines to generate electrical power is big business. Wind turbines are currently the largest source of renewable electrical power outside of hydroelectric power. Unlike traditional building structures wind turbines have little mechanism for viscous damping and provide minimal ductility before global failure. Preliminary analysis of experimental data from full-scale tests conducted using the National Science Foundation (NSF) Large High Performance Outdoor Shake Table (LHPOST) at the University of California, San Diego (UCSD) in November 2004 suggests that existing design assumptions lead to an acceleration at the top of the turbine significantly lower than measured experimentally. The test results suggest that viscous damping of turbines is much lower than that assumed by existing building codes. In addition to low damping and low ductility, wind turbines exhibit a complicated structural response influenced by aeroelastic, centrifugal, and Coriolis effects not seen in traditional building structures. Despite this lack research, wind turbines are being actively installed in seismically active regions. In California there are three main regions that represent 95 percent of the installed wind turbines: Altamont Pass, Tehachapi, and San Gorgonio. Altamont Pass and Tehachapi are located within 25 km of mapped faults. The San Gorgonio installation is littered with fault traces. Some turbines in the San Gorgonio installation are located less than 30 meters from the fault trace of the San Andres Fault. In contrast to a city comprised of many different structures, a wind farm consists of very few types of unique structures. This homogeneity raises the problem that an earthquake with unfavorable characteristics could cause significant loss for a wind farm. A design methodology that accurately estimated earthquake loading of wind turbines would allow turbines to survive anticipated earthquake loading and provide reliable electrical power following an earthquake.