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UBC Theses and Dissertations

Optimal placement and design of passive damper connectors for adjacent structures Bigdeli, Kasra


Passive coupling of adjacent structures is known to be an effective method to reduce undesirable vibrations and structural pounding effects. Past results have shown that reducing the number of dampers can considerably decrease implementation costs and does not significantly decrease the efficiency of the system. The main objective of this thesis is the optimal design of a limited number of dampers to minimize the inter-story drift. In this thesis, we present a bi-level optimization algorithm to find the optimal arrangement and mechanical properties of dampers placed between two adjacent buildings to minimize the maximum inter-story drift during (simulated) earthquake conditions. Under the assumption of equal damping coefficients for all dampers, the optimal damping configuration is found via five different approaches: exhaustive search, inserting dampers, inserting floors, locations of maximum relative velocity, and a genetic algorithm. Through several numerical tests, efficiency and robustness of each optimization method is examined. It is shown that the inserting damper method is the most efficient and reliable method, particularly for tall structures. It is also found that, assuming equal damping coefficients for all dampers, increasing the number of dampers can exacerbate the dynamic response of the system. Finding an efficient method to optimize dampers’ locations, we focus on the optimization of the damping coefficients. Letting the dampers have varying damping coefficients, the optimization problem of damping coefficients is an n-dimensional optimization problem, whose objective function is provided via a simulation. Therefore, we use non-gradient based techniques for the inner-loop of the algorithm. We compare three different methods: a genetic algorithm (GA), a mesh adaptive direct search (MADS) algorithm, and the robust approximate gradient sampling (RAGS) algorithm. RAGS is a derivative free optimization (DFO) method that exploits the structure of the finite minimax problem. Using these techniques, we show that there exists a threshold on the number of dampers inserted with respect to the efficiency of the retrofitting system. Furthermore, we show that using a structured internal subroutine (such as RAGS) for the inner-loop of the bi-level problem greatly increases the efficiency of the retrofitting system.

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