Performance and Condition Monitoring of Structures using Discrete Strain Measurements

摘要

This paper investigates the possibility of comprehensive monitoring of structural components, covering the estimation of key deflections, bending moments, external loads, modal parameters and finally the structural condition, from spatially discrete static and dynamic strain measurements. The study covers steel frame and reinforced concrete (RC) structures. For steel structures, Euler's beam theory along with the classical slope-deflection formulations are employed to determine the desired information pertaining to structural performance* using static strain measurements. In the case of the RC structures, this is achieved by applying the limit state theory to the static strains measured on the top and the bottom reinforcement bars at specified locations, taking material non-linearity into account. The methodologies are verified on models of steel frame, steel truss bridge and an RC beam. The paper also covers the measurement of dynamic strain for extraction of structural natural frequencies for condition assessment of structures. Performance of two different sensors, electrical strain gauges (ESGs) and Lead Zirconate Titanate based piezo-electric ceramic (PZT) patches, is compared in this respect. Structural damage is located using changes in natural frequency and mode shapes of the structure. PZT patches are found to display much superior performance as compared to the ESGs for dynamic strain measurement. They are not only cost-effective but also impose minimal hardware and signal conditioning requirements.