A VISCOELASTIC TUNED MASS DAMPER FOR VIBRATION TREATMENT OF LARGE STRUCTURES

Viscoelastic (VE) tuned mass dampers (TMDs) using commercially available, small thickness, VE material have been used extensively in adding targeted damping to light structures. The most common approach for realizing stiffness and damping in these tuned devices has been applying VE material to strips of elastic material (mainly metal, e.g. steel) in an unconstrained or constrained layer fashion and using such assemblies, which can be viewed as a damped leaf-springs, for the suspension element of the tuned mass damper. In this work, the suitability of tuned mass dampers with visco-elastically damped leafspring suspension for treating large, massive civil engineering structures, more specifically floor systems, was studied numerically and experimentally. The effectiveness of this tuned mass damper configuration turned out to be disappointing. In parallel to the above-mentioned study, an alternative VE suspension was devised by stacking a number of 25 mm (1 inch) thick VE rings interlaced with the same number of metal constraining ring layers. By changing the number of these rings, different stiffness's are realized and thus different tuning frequencies are achieved. The material properties of the VE polymer used in both studies are defined in terms of Prony series parameters. Viewing the Prony series parameters as optimization variables, they are recovered by minimizing the mean squared error between the dynamic material properties predicted by the Prony series parameters and the frequency-dependent dynamic material properties provided by the manufacturer. Using the material properties of the VE material, the dynamic finite element model of a 100 lb TMD was constructed and its tuned damping effectiveness demonstrated, numerically. The 100 lb TMD was also built and used to a) verify the numerical model and b) experimentally demonstrate the performance of the TMD.