Controlling earthquake response of multi-storey buildings with optimized configurations of seismic isolators at various elevations

Abstract eng:
The response of multi-storey structures may be controlled under earthquake actions by installing seismic isolators at various storey-levels. By vertically distributing isolation devices at various elevations, the designer is provided with numerous options to appropriately adjust the seismic performance of a building. However, introducing seismic isolators at various storey-levels is not a straightforward task, since it may lead to favorable or unfavorable structural behavior depending on the chosen isolators’ configuration, the structural and isolators characteristics, the available seismic gap size at the base of the building, the acting seismic excitation, etc. This large number of factors and their complex effect on structural behavior give rise to a rather chaotic decision space of isolation configurations, within which a favorable solution needs to be located. Such a difficult problem cannot be generally handled with standard and simple engineering thinking and tools, therefore we rely in this work on an optimization procedure to detect favorable configurations of isolators in an automatic and optimized way. The search for favorable isolators’ configurations is formulated in this work as a singleobjective optimization task. The expressions defining the objective and the constraints of the optimization procedure involve the evaluation of the main quantities of interest regarding the seismic response of an isolated building (floor accelerations, interstorey drifts and base displacements), as well as the estimation of the total isolation cost. In the formulation of the present work, the aim of the optimization process is to minimize the maximum floor acceleration of the building under consideration, while constraints are specified to control maximum interstorey drifts, maximum base displacements and the total isolation cost. A genetic algorithm is implemented to perform this optimization task, which selectively introduces seismic isolators at various elevations, in order to locate the optimal configuration for the isolators satisfying the pre-specified constraints. This way, optimized earthquake response of multi-storey buildings can be obtained. The effectiveness of the proposed optimization procedure in the design of the isolated system is demonstrated in a numerical study using time-history analyses.

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