Optimal design of double skin façades as vibration absorbers

In this paper, several layouts of double skin façades (DSF) used as mass dampers to reduce the vibrations in structures under seismic events are discussed. Firstly, the mathematical coupled problem is studied considering a non-classically damped system excited by a set of accelerogram records. The design problem aims to determine the optimal values of four parameters, namely the flexural stiffness and damping of the DSF panel and the stiffnesses of the elements that connect the DSF to the primary structure. Secondly, four objective functions are presented. Two of these functions aim to minimise respectively the displacements and the accelerations of the primary structure for each earthquake. The remaining two, instead, minimise the average of the displacements and accelerations calculated for all the accelerograms given. Finally, numerical analysis are performed on a six-storey building and four DSF designs are proposed. The Particle Swarm Optimisation (PSO) is used to estimate the optimal parameters. Comparisons among the DSF layouts are presented in terms of minima of the objective functions and in terms of the power transfer functions. Moreover, a simplified design method for the connection elements is discussed.