Abstract

Tuned mass dampers (TMDs) are the simplest example of primary-secondary interaction used to mitigate the effects of dynamic actions in a range of engineering structures. Typically, a SDoF (single-degree-of-freedom) secondary oscillator is attached to a MDoF (multi-degree-of-freedom) primary structure, at a position where its amplitude of vibration is expected to be relatively large, and is tuned in such a way that a significant proportion of the mechanical energy is transferred from the primary structure to the secondary oscillator. Linear and nonlinear TMDs have been shown to provide very efficient solutions in the design of new structures and the retrofitting of existing ones. More generally, primary-secondary dynamic interaction can be exploited in more complex scenarios to enhance the performance of building structures against wind and seismic excitations. This seminar will present the results of two research projects currently under development at Loughborough University. First, the possibility of using nonlinear viscousfluid dampers connecting a primary building with secondary reaction towers will be demonstrated as a viable retrofitting strategy, able to overcome some of the limitations of more traditional approaches. The effects of the key design parameters will be quantified, including the nonlinearity of the dampers, their relative size and location, the primary/secondary stiffness ratio, the ductility of both primary and secondary structures, the intensity of the seismic hazard. Second, it will be shown that double-skin façades can be optimally designed to minimise the effects of seismic forces on mid-rise building structures. The efficiency of this design solution will be confirmed using both recorded and artificially generated accelerograms and applying different optimisation tools. The combination of these two studies highlights the tremendous potential of primary-secondary dynamic interaction when trying to minimise the seismic demand in existing and new structures.