Analytical and experimental studies in system identification and modeling for structural control and health monitoring

One of the issues complicating the reliability assessment of structural health monitoring (SHM) methodologies slated for implementation under field conditions for damage detection in conjunction with typical infrastructure systems, is the paucity of experimental measurements from such structures. This study evaluates some promising SHM methodologies based on actual vibration measurements, obtained under realistic field conditions from three different cases of full-scale civil infrastructures. The first part of this study provides a comprehensive and comparative study of three time-domain identification algorithms applied to extract the modal parameters of the New Carquinez Bridge which is a newly-constructed long-span bridge that was monitored, in its virgin state, over a relatively long period of time, with a state-of-the-art dense sensor array. The second part of this study evaluates the usefulness of some identification techniques to determine the evolution of the modal properties of a full-scale 6-story building which has recently undertaken a 6-month seismic retrofit process, and to correlate the changes in the identified structural frequencies with the time that specific structural changes were made. The third part of this study presents the results of two time-domain identification techniques applied to a full-scale 17-story building, based on ambient vibration measurements. The UCLA Factor Building was instrumented permanently with a dense array of 72-channel accelerometers. The first identification method used in this case is the NExT/ERA, which is regarded as a global (or centralized) approach, and the second method is a chain system identification technique. Since in this method the identification of each link of the chain is performed independently, it is regarded as local (or decentralized) identification methodology. To have a statistically meaningful result, 50 days of the recorded data are considered in this study. Modal parameter and the chain system identification were successfully implemented using the output-only data acquired form the Factor building. The statistical variability of the estimated parameters due to temperature fluctuations is investigated. The last part of this study deals with a structural control application involving optimum strategies for deploying multiple-unit passive/semi-active impact dampers. This study focuses on the development and evaluation of practical design strategies for maximizing the damping efficiency of multi-unit particle dampers under random excitation, both the stationary and nonstationary type.