On the Performance Optimization of Damped Space Frame Panels under Stochastic Wind Excitation

This study considers the problem of fatigue damage arising on an aluminum space frame tower subjected to wind induced vibrations during the service lifetime. In order to mitigate the fatigue damage, a passive control technique is proposed based on the implementation of a number of mechanical devices characterized by viscoelastic behavior. The performance optimization of the damped system is faced searching for both the optimal damping supply and the optimal device placement, as solution of a discrete optimization problem. A full stochastic formulation is adopted for wind loading, vibration calculation and fatigue analysis. Power spectral density of wind fluctuations derived by Solari is assumed. Among the many methods available in the literature, the Rayleigh approximation method is selected for fatigue calculations. Assuming that the occurrences of wind speed follow a Weibull distribution, the “state of wind” occurrence frequency can be obtained particularizing the probability distribution by means of available on-site meteorological data. The obtained results show that the outlined aluminum lattice tower is quite sensitive to fatigue problem. However, the introduction of damping devices suitably distributed along the height of the structural brings two major effects: the reductions of the peak stress amplitude related to dynamical vibrations and the increase of the wind fatigue life of the structure.