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In this paper, a comprehensive procedure is developed for the optimization of a hybrid control system for tall buildings subjected to wind-induced vibrations. The control system is made of active tuned mass dampers (ATMDs) and is conceived to mitigate the flexural and torsional response in serviceability limit state conditions. The feedback information necessary to compute the control forces is provided by a limited number of accelerometers arranged over the building's height. To reduce the computational effort, subsequent optimization subprocedures are employed that take advantage of the genetic algorithm to find the solution of the nonlinear, constrained optimization problems. At first, the optimization of the ATMDs' number and positions over the top floor of the building is carried out. Then, the optimal location of the accelerometers over the building's height is obtained. The reduction of the flexural and torsional accelerations is chosen as target of the optimization problem. The technical limitations of the ATMDs, such as the actuators saturation and the limited stroke extensions, are the constraints to the problem. As an illustrative example, a control system is optimized for the response mitigation of a tall building subjected to wind load. Figure 6. Displacements in the x (a) and y (c) directions and rotations (e) at the top floor and corresponding power spectral densities (b, d, f) for the uncontrolled, passively controlled and actively controlled systems.

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Stakeholders of civil infrastructures have to usually choose among several design alternatives in order to select a final design representing the best trade-off between safety and economy, in a life-cycle perspective. In this framework, the paper proposes an automated procedure for the estimation of life-cycle repair costs of different bridge design solutions. The procedure provides the levels of safety locally guaranteed by the selected design solution and the related total life-cycle cost. The method is based on the finite element modeling of the bridge and uses design traffic models as suggested by international technical standards. Both the global behavior and the transversal cross section of the bridge are analyzed in order to provide local reliability indexes. Several parameters involved in the design, such as geometry and loads and materials’ characteristics, are considered as uncertain. Degradation models are adopted for steel carpentry and rebars. The application of the procedure to a road bridge case study shows its potential in providing local safety levels for different limit states over the entire lifetime of the bridge and the life-cycle cost of the infrastructure, highlighting the importance of the local character of the life-cycle cost analysis.