Active Vibration Control of Seismically Excited Building Structures by Upgraded Grey Wolf Optimizer

In recent decades, active vibration control of buildings for earthquake-induced damage mitigation has been widely considered in the scientific literature. Model-free controllers using human knowledge-based fuzzy logic rules were shown to be advantageous over conventional model-based controllers as their effectiveness is not limited by the accuracy of the structural modelling of buildings. The latter becomes challenging in view of nonlinear building response under severe seismic excitations and uncertainties to the structural properties at the time of the seismic event. Nevertheless, the specification of fuzzy logic controllers (FLCs) relying only on expert knowledge may not result in optimal control response. At the same time, the pursue of optimizing fuzzy logic control rules based on excitation and structural response data, beyond human expert knowledge, is not straightforward as it increases considerably the scale of the optimal FLC design problem. To this end, this paper puts forth an enhanced version of the Upgraded Grey Wolf Optimizer (UGWO) to optimally design membership functions and rule bases of FLC to minimize seismic structural damage. The latter is defined in terms of maximum curvature ductility ratio at the ends of structural members. The potential of the UGWO is demonstrated by considering FLC-based optimal seismic active control in a 20-story steel benchmark structure with nonlinear behavior involving more than 400 design variables. The performance of the UGWO is gauged by examining nine different structural performance metrics and compared to results of 5 different widely used state-of-art metaheuristic optimization algorithms including the standard Grey Wolf Optimizer. Comparisons demonstrate the capability of UGWO to provide improved seismic performance, resulting in reduced structural responses and damages for the considered benchmark structure.