Adaptive Tuned Mass Damper (ATMD) based in shape-memory alloy (SMA) elements

• Autor(a) principal: Nunes, João Miguel Matos
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/18294
• topic: Shape memory alloys; Elastic modulus; Vibration control systems; Suppressor; Tuned mass damper; Variable stiffness; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Civil

The unique features of shape memory alloys (SMA) gives them an unmatched ability to be implemented in several fields of engineering. Considering their phase shift capacity, when thermoelectrically driven, SMAs assume an elastic modulus variation predicated upon two key parameters - stress and temperature. Based on the above statement, the present dissertation aims to develop a new vibration control system, which makes use of SMAs in order to extend and improve its operational domain. Initially, an experimental campaign is developed in order to design a mapping of the elastic modulus of a FLEXINOL R SMA sample.This mapping seeks to explore and an optimize the inclusion of shape memory alloys in vibration control systems. In a second step, two types of ATMDs (Suppressor and TMD) are mathematically studied in order to comprise the insertion of a SMA element in the control system. Considering the main purpose of this thesis, a particular case study structure was chosen to carry out the implementation of the new vibration control system. The selected structure consists in a footbridge built over an important highway located in the Lisbon city center, Portugal. At this stage, both the design of the SMA element and the subsequent operational limits are presented. Afterwards, a numerical model computed in MATLAB (The Mathworks, 2014) is developed to simulate the behavior of a two degrees of freedom (TDOF) system. This one provides the system’s behavior (structure + ATMD) towards a predefined harmonic request, evaluating the effects of the implementation of the new vibration control system. Using the above mentioned numerical model, an influence analysis of both control systems was carried out. Several comparisons between the variants of each ATMD (Suppressor and TMD) where drawn, showing the positive and negative aspects of their action. In the end, a single numerical model, with the ability to excite the structure, read its behavior, identify the vibration frequencies and properly tune the control system in real time, performed a complete structural analysis. Finally, a concluding chapter is presented, where the obtained results are discussed. This chapter also mentions the main future development prospects, that may be considered in studies conducted by other researchers.