A low-cost approach to monitoring the structural health of pedestrian bridges

Abstract

Changes in dynamic properties of structures, such as damping ratios and natural frequencies can be detected by periodic monitoring (e.g. one time by year). These changes are often indications of structural damage thereby, the maintenance or demolition of the structure can be doing in due time. In the case of pedestrian bridges, people’s movements may produce a resonance state, which leads to excessive deflection that accelerates the deterioration of these structures. Typically, these dynamic properties are detected by using high-cost vibration measurement equipment to achieve high levels of precision (i.e. a very low noise levels). This article studies the measurement of dynamic properties in pedestrian bridges using a tri-axial accelerometer integrated into a mobile phone as a low-cost and alternative practice. Accelerations were recorded on a steel pedestrian bridge (flexible) and on a post-tensioned concrete pedestrian bridge (rigid) located in Barranquilla City (Colombia). Vibrations were induced by a person (e.g., by jumping). Previous studies based on traditional measuring techniques show that two dominant frequencies in both types of bridges can be identified. However, in this study a reliable damping ratio could only be established for the steel bridge that it is associated with the flexibility and the low amplitude of the induced vibrations by a single pedestrian user.