Abstract

In the present research work the optimization of structures and the vibration suppression are studied. First, a methodology to find the simultaneous size, geometry and topology design optimization of structures using Genetic Algorithms (GAs) is proposed. The methodology considers that the large structures are constructed from the duplication of some basic structures called bays. In order to have realistic optimal designs, the cross-sectional areas are extracted from the standard profiles and the optimization process is performed considered the AISC design standards. The second part of the work is concerned with the suppression of the vibration in structural systems. A methodology to find the characteristic parameters of the Bouc-Wen model in the attempt to better characterize the hysteresis phenomenon of MR dampers has been proposed. The methodology takes into consideration the effect of each individual term of the Bouc-Wen model over the hysteretic loop to estimate the appropriate values of the parameters. Considering the relationships of the characteristic parameters, a new model based on the Bouc-Wen model is proposed in which the current, the frequency and the amplitude excitation are incorporated as variables. Based on the proposed hysteresis model, a Finite Element Model (FEM) for the MR damper is developed and then integrated to the FEM of the entire structure. Subsequently, an efficient vibration suppression strategy using MR damper was proposed to improve the vibration performance index of the structure. Finally, the same hysteresis model is employed to investigate the application of MR dampers as translational actuator.