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Title: The use of inerters for vibration suppression in structures
Author: Lazar, Irina F.
ISNI:       0000 0004 5916 8588
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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Civil engineering structures are subject to a wide variety of loads during their life span, either due to natural hazards or everyday use. The vibrations that are generated by these actions affect the performance of the structure. In extreme cases, especially during strong wind or earthquakes, excessive vibrations may lead to structural failure, resulting in economic losses and even loss of human life. It is therefore very important to study, understand and then act towards limiting these vibrations. Various types of devices can be attached to structures to limit unwanted vibration. Traditional passive systems, that resist motion within the structure, are the most widely used due to their simplicity. More complex devices include semi-active ones which allow closed-loop variation of parameters within a device. While these devices still only resist motion, and so retain the desirable property that they are inherently stable, this control arguably allows better vibration suppression. Active devices, such as actuators, generate motion as well as resist it, allowing potentially better control, however at the cost that they require higher power. As they can feed energy into the structure, they are not inherently stable. The research presented in this thesis focuses on the use of passive control for mitigating vibration of multiple degrees of freedom systems and the development of novel passive control systems, able to ensure good structural performance. Initially, the possibility of emulating the performance of an active control system by using equivalent semi-active and passive devices is studied. Then, a novel type of passive vibration control system, based on the inerter is proposed. The principal advantage of the inerter is that a high level of vibration suppression can be achieved with low amounts of added mass. Several layouts and installation possibilities are studied, the most efficient system being the one that preserves the layout of a tuned mass damper (TMO) where the mass element is replaced by an inerter. This is named a tuned inerter damper (TIO). A design methodology for TIOs used in earthquake and wind-excited structures is developed, while showing that the new system is most efficient when installed at the bottom storey level. This feature is one advantage of the TIO when compared to a more traditional TMO. In addition, given the inerters capacity of generating high apparent mass from small devices masses through gearing, an improved level of vibration suppression can be obtained by using a reduced dimension and economical device. The application of TIOs is then extended to stay cables, where a TIO is attached transversally to the cable, similar to the use of viscous dampers. A design methodology based on contour plots, aimed at choosing the optimal viscous damper or TIO to be connected at a given location along the cable length is proposed. It is shown that the TIO represents a viable alternative to viscous dampers, being more efficient and also economical.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available