Monitoring the wind-induced response of tall buildings: GPS performance and the issue of multipath effects

The in-situ verification of structural performance under the action of wind requires monitoring technologies capable of capturing not only the resonant response features, but also the background and mean response components. This study explores the use of high-precision global positioning systems (GPS) toward that end. In this study, the performance of GPS for resonant response tracking is first validated in full scale against accelerometers, and then its ability to track both background and resonant response data is verified through controlled field tests. As the valuable low-frequency regime of this sensing technology is often compromised by long-period distortions known as multipath effects; this study then presents a means to characterize this phenomenon using Fourier and wavelet spectra and the GPS Distortion Signature. The latter diagnostic is shown to isolate multipath effects in controlled field testing. However, even when a GPS Distortion Signature is not available on-site, it is shown that multipath effects can still be removed by filtering to permit a rare comparison of the relative contributions of background and resonant responses in full scale to wind tunnel predictions.