Study of Health of Structure using GPS Measurements

Abstract

Structural Health Monitoring deals with determining the health of structure in terms of damage sensitive structural parameters. The need for SHM arises due to forever increasing no of large civil engineering structure which cater to the need of large no people every day. Hence for the safety requirement it becomes necessary to have a monitoring system that can warn against critical deterioration in the structural health. Operational Modal analysis has been a widely used technique for monitoring large scale structures where artificial excitation is not a practical approach. In this study GPS has been used to identify the modal parameters for which the default instrument has been accelerometer since its origin. The vibration readings were taken on three bridges, the first being the steel foot bridge near IRI Roorkee and the other two were Ram Jhula and Laxman Jhula bridges in Rishikesh Uttarakhand. The vibration data were processed and filtered to minimise the inherent GPS noise. It was found that GPS could measure dominant frequencies in the vibration spectrum but due to hardware limitations the measured frequencies corresponds to semi static movements, with small peaks in the higher frequency range. Comparing vibration data for the same structure taken at different times showed very slight change in dominant peaks which was expected due to small time interval between observations.