GPS Measurement of Wind-Induced Suspension Bridge Girder Displacements

A new method using the Global Positioning System (GPS) was proposed to directly measure the suspension bridge girder displacements induced by wind forces. The field measurements were carried out using this system on an existing suspension bridge during the strong wind season. The semistatic displacements of the girders were successfully obtained, and agreed well with the numerically predicted values and the wind tunnel test results. The spectral densities of the displacements measured by GPS corresponded with the numerical results by the finite-element method analysis and the forced vibration test results. The gust response of the girder due to the turbulence of the wind flow was evaluated from the acceleration records measured by accelerometers and compared with the GPS data. The mode frequencies of both results showed good agreement in the low-frequency range and the spectral peaks estimated by the accelerometers corresponded to the GPS values with good accuracy. It is concluded that the GPS method is reliable and useful to clarify the semistatic and gust response behaviors of long-span bridges.