334 T.P. Kernicky et al. such full-scale damage studies have been relatively infrequent. In contrast, laboratory-scale models have been routinely used to assess proposed techniques for VBDD. However, such studies are often plagued by the same challenges related to faithfully modeling real-world structural damage and are further disadvantaged by scaling effects and by the introduction of detailing simplifications routinely adopted when developing laboratory structural models. In this study, the increasingly popular hybrid simulation technique is explored as an intermediate solution between laboratory models and full-scale destructive testing for vibration-based monitoring and damage detection studies. In hybrid simulation, only a portion of the full structural system, referred to as the experimental substructure, is physically constructed and subjected to experimental testing. The remainder of the structural system is treated as a numerical model that interacts with the physical experimental substructure through a substructured form of the dynamic equation of motion. In this way, research investigating the performance of critical structural components or assemblages of components can be economically performed by only fabricating and testing the portion of the structure that experiences nonlinear, inelastic deformations that may be inadequately understood for a particular design or difficult to predict numerically [6]. Schematically, the interaction between the experimental and analytical substructure within hybrid simulation is illustrated in Fig. 31.1 using the structural model and bolted steel member used for the experimental substructure within the current study. Conventionally, hybrid simulation has largely been used to investigate the performance of members and connections providing lateral stability in buildings under seismic events, although additional applications have been demonstrated related to structural performance under fire [7] and in bridges under traffic loading [8]. The motivation for the current study is to explore whether hybrid simulation can be reliably used to first perform a simulation of a vibration test to obtain experimental modal analysis data for characterization of the dynamic properties of the hybrid structure, then generate realistic onset of damage in the experimental substructure through overloading, and subsequently perform a simulation of a vibration test in the damaged condition to facilitate VBDD research. Although the use of hybrid simulation to generate realistic structural damage has been proposed for evaluation of nondestructive evaluation (NDE) and other sensing technologies [9], the use of hybrid simulation for vibration-based methods of structural health monitoring has yet to be thoroughly explored. In this study, the damage was developed in the member by exceeding a bolted connection limit state through overloading independent of the hybrid framework, for simplicity. However, it is important to emphasize that the full benefit of the hybrid simulation technique could be achieved by introducing damage to the experimental substructure through hybrid simulation of an extreme loading, such as a seismic event. By leveraging the advantages of hybrid simulation, the general approach preliminarily explored in this study offers many of the advantages of full-scale structural experimentation without the costs and logistical challenges associated Fig. 31.1 Concept of hybrid simulation applied in the current study to vibration-based damage detection research on a three-dimensional lattice structure
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