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

Numerical and experimental comparison between two different blade configurations of a wind generator

This paper presents a comparison between the structural behaviour of a wind generator with straight blades and a composite prototype of a wind generator with helical blades. Numerical structural analyses are performed by means of FEM models by using ANSYS MechanicalTM software package. Furthermore, laboratory dynamic experimental tests are carried out on real scale specimens of the two wind generator configurations in order to find their modal properties in terms of natural frequencies and modal shapes. The results of the experimental campaign are then used to update the numerical models by minimizing an objective function. Total stresses and deformations of the two wind generator configurations, coming from the updated numerical models, are evaluated and compared to quantitatively point out the improvement of the structural behaviour obtained by the use of composite materials