Shake Table Testing of a Radar-Based Structural Health Monitoring Method

Structural Health Monitoring (SHM) is an active field of research concerned with the development of sensors to measure structural loading and deformation as a result of external loading. This paper details the testing of a new method of SHM, which uses frequency-modulated continuous wave (FMCW) radar to measure the displacement of a structure. This method avoids the integral drift errors incurred by contemporary accelerometer-based devices. In order to determine a structures interstorey drift ratio (IDR), an FMCW radar device measures the diagonal distance between two opposite corners of two adjacent floors. This distance can then be converted to an IDR using knowledge of the dimensions of the structure. A prototype FMCW radar unit was built to verify that such a method is able to achieve the precision necessary for SHM. The device was tested using a shake table driven with ground motion data taken from the 2011 Christchurch, New Zealand earthquakes. The distance between the radar transceiver and the target reflector was compared to linear variable differential transformer (LVDT) data to determine the error in target tracking. The mean distance error was found to be 0.0308%, which corresponded to a mean IDR error for an arbitrary structure of 0.00107. This value was half the required mean error determined to be suitable for SHM purposes, meaning that the results of this experimentation justify further research into the implementation of this method.