Performance evaluation of piezo sensors with respect to accelerometers for 3D modal analysis of structures

Strain modal analysis, as a new domain in the health monitoring field, needs to be studied in depth for experimental modal testing. Towards this purpose, this paper experimentally investigates the efficacy of piezo sensors for structural identification for structural health monitoring under different excitations applicable to large-scale structures. The piezo sensors are evaluated against industry-standard accelerometers by experimental modal testing of a scaled-down model of a pedestrian foot over bridge. The model is excited under the impact hammer, electro-dynamic shaker-based sweep and random excitations, and pedestrian motion (PM)-based low-amplitude excitations. Piezo sensors are found to be capable of capturing the modal parameters (modal frequencies, damping ratios and mode shape vector) under all the excitations with excellent correlation with respect to accelerometer-based parameters. However, some modes are missed under the shaker and PM-based excitations compared to the impact hammer-based excitations for both accelerometers and piezo sensors. Modal parameters of lower modes are successfully extracted under low-level pedestrian excitations, the most efficient type of excitation acting in operational conditions. High modal assurance criteria values between the strain and the displacement mode shapes establish the piezo sensors as effective for strain-based vibration testing and structural identification.