Rejection of temperature effect in subspace-based damage detection monitoring systems : application to two historical monuments

Architectural monuments are important properties of countries due to cultural and economical advantages. It is widely known that environmental effects are of special concern in structural health monitoring and for damage prevention of these monuments. In this article efficiency of a recently developed method for damage detection in presence of temperature fluctuations based on chi-squared type hypothesis testing has been tested for two historical buildings. The classical subspace-based detection algorithm has been shown to be sensitive to temperature fluctuations during experimental setups. The new technique is based on computing a reference Hankel matrix based on averaging several Hankel matrices calculated for individual experimental scenarios to be used in the detection algorithm. In spite of the simplicity of the method, it has been shown to be robust in smoothing out sensitivity of classical subspace-based method with respect to temperature perturbations while choosing different number of safe scenarios both in time or temperature range. We will show that tests are stable during time even if the reference data sets do not encompass all the safe scenarios. Moreover we have proposed a complimentary technique to handle severe excitation level changes in order to prevent possible false alarms in the detection system, for example an earthquake affecting test results that had happened during the experimental setups measurement on one of the monuments(undefined