Ricerc@Sapienza

The objective of this project is to theoretically and experimentally advance the field of vibration mitigation employing novel engineered devices and materials to achieve seismic and shock protection in buildings and sound-proof barriers for railways and flutter control in bridges.
To this end, hysteretic tuned mass dampers (TMD) made of wire ropes of different materials (steel, shape memory material, carbon nanotube nanocomposite) and shock absorbers will be employed using a unique combination of analytical, numerical and experimental tools coupled with genetic-type optimization algorithms to drive the search of the optimal TMD design parameters while resorting to nonlinear mechanical models subject to various excitation scenarios. A new TMD architecture for bridges will be developed proposing a metamaterial deck concept which integrates multiple arrays of TMDs. Contrary to conventional architectures making use of a few TMDs, the metamaterial bridge deck concept aims to strategically distribute a large number of TMDs away from the torsional center in order to exert point-wise distributed forces and moments counteracting the negative damping effects of aerodynamic lift forces and moments which cause flutter or other self-excited oscillations and instabilities. To this end, a new concept of nanocomposite TMD is proposed leveraging on the exploitation of the hysteretic properties of carbon nanotube (CNT) nanocomposite materials investigated by this group in previous projects. The softening stick-slip interfacial dissipation that takes place at the interfaces between CNTs and polymer chains combined with geometric nonlinearities allow tuning of the TMD nonlinear frequency to the frequency of the bridge/structure as well as tuning of the device damping to optimally control the TMD phase relative to the bridge oscillations. The constitutive parameters of the nanostructured materials will be identified via a new technique based on nonlinear guided wave propagation.