Analysis of a class of nonlinear tuned mass dampers

Abstract

The main objective of this thesis is to analyze a class of nonlinear tuned mass dampers (TMDs). Specifically, we consider bi-linear softening spring dampers and their effectiveness relative to short and long duration excitations. The reason behind using a bi-linear softening spring is to provide the TMD with the capability of rapidly responding to transient excitations such as an earthquake, by having an initially stiff response while still being able to resonate with the structure by means of the final stiffness. Note that this constitutes a nonlinear TMD (NTMD) The report starts off with a brief literature review about the work done on different passive NTMDs, we then propose and analyze a bi-linear softening spring model subject to sinusoidal excitations. Afterwards, we use the power spectra method as a replacement for the response spectra in order to understand the performance of bi-linear devices. The reason for this alternative is also explained. We then tune our NTMD when subject to short and long duration sinusoidal excitations. Finally, the results are presented in terms of energy absorption plots, which indicate that the proposed bi-linear TMD shows significant improvement over the linear TMD.