1,721,002 research outputs found
Optimization criteria of TMD to reduce vibrations generated by the wind in a slender structure
No full textThis paper deals with the reduction of vibrations caused by wind load in slender structures. The structure is modeled as a Single-Degree-of-Freedom system and the wind load is estimated through the pre-filter technique: the aerodynamic force is a function of White Noise filtered by a simple oscillator. Two optimization criteria to calculate the best values of the frequency and the damping ratio of the Tuned Mass Damper (TMD) are compared here. The aim of the first criterion is the reduction of the displacement of the top end of the structure, while the aim of the second criterion is the reduction of the inertial acceleration of the top end of the structure. The comparison of the two criteria is carried out through sensitivity analyses for different environmental conditions and system configurations. The comparison shows that the acceleration criterion is more attractive only for some conditions. Moreover, it is plain that the different efficiencies of the TMD optimized through each of two criteria are related to the mass ratio. Finally, the optimization criteria are applied to estimate the TMD design parameters to reduce the vibrations due to wind load in a lighting tower
Optimization criteria for tuned mass dampers for structural vibration control under stochastic excitation
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Robust optimization of base isolation devices under uncertain parameters
No full textBase isolator devices are widely used for mitigation of vibrations induced in structures by seismic actions. In order to achieve high performances in the mitigation of seismic effects, base isolator mechanical properties should be designed by an optimum criterion. In common approaches, the nature of dynamic loads is assumed as the only source of uncertainty. In the present paper a robust optimization criterion for base isolator devices design is proposed, considering the unavoidable effects of uncertainty in structural properties and seismic action. Uncertain parameters are modeled as random variables and are represented by bounded independent probability density function, with uniform law. The structure is described by a single-degree-of-freedom model and is protected by a linear base isolator in order to reduce vibration levels induced by base acceleration, here modeled by the stationary Kanai-Tajimi stochastic process. The optimal design is formulated as a constrained minimization problem, assuming as an objective function a suitable measure of the isolator efficiency and imposing a constraint on the maximum isolator displacement. A sensitivity analysis is carried out on the robust solution in order to assess characteristics and differences with respect to the conventional deterministic solution
Stochastic optimum design of linear tuned mass dampers for seismic protection of high towers
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