The more recently introduced inerter fictitiously increases the mass of the system to which it is connected, creating a mass amplification effect. This property makes it particularly attractive for use in mass-dependent devices employed in structural vibration control, i.e., the prevention and mitigation of vibrations. Conceptually, the inerter can be viewed as a two-terminal device, where its internal force is directly proportional to the relative acceleration between the two terminals. The constant of proportionality, called inertance, is the apparent mass generated, which can be notably large. In practical applications, it is effectively utilized in combination with springs and dashpot dampers, giving rise to Tuned Inerter Dampers as an alternative to traditional Tuned Mass Dampers (TMDs). Among the various prototypes of inerters, fluid inerters stand out as simpler to design and develop, with less pronounced parasitic effects compared to their mechanical counterparts. However, their inherent nature makes them susceptible to nonlinearities, such as fluid viscous shear friction, pressure drops, and other tribological effects. To mitigate these undesirable nonlinearities, a proposed solution is to connect the fluid inerter to the structure through a spring-dashpot damper element, referred to as flexible connection. To evaluate the practical feasibility of this type of connection, a novel experimental test is presented, focusing on a fluid inerter used for vibration control in a cross-laminated timber panel subjected to vertical vibrations. In addition, the control performance of the fluid inerter is compared with that of a conventional TMD, providing insight into its efficiency in controlling multi-modal structures. Finally, optimization procedures are employed to identify the connection parameters of both the TMD and the inerter, aiming to improve their performance in effectively controlling the structure.

In the last decades, the topic of structural control has gained increasing attention in structural design due to the fact that structures are becoming increasingly slender and therefore more prone to vibrations. In the context of passive control, fluid inerter-based control systems represent a novel development with great potential. Their main advantage is that the apparent mass (called inertance) which is able to reduce the displacement and/or acceleration of the structure, is orders of magnitudes higher than its physical mass.

In order to fully explore and optimize the performance of the fluid inerter-based control device, a numerical model that accurately represents the structural behavior is required. In civil engineering applications, the frequency range of interest is usually low, meaning that any non-linear effects that may occur play a major role and cannot be neglected in the numerical model. The selection of model type is intrinsically related to the determination of its associated parameters such that the model predicts the measured performance. Despite the high accuracy of the established numerical model, there may still be a gap between the model and the measurement due to the presence of uncertainties in the parameters. The identification of model parameters in a stochastic setting provides a means to understand and reduce the discrepancies between model and real behavior.

In the present study, the so-called subset simulation method, which has originally been developed for reliability analysis, is used for the stochastic identification of model parameters. It is shown that in this framework, issues such as non-uniqueness of the solution can be addressed and information about the spread of parameter values can be gained to obtain a more realistic model, which represents the real structural behavior more accurately.

This work proposes periodic water-tank metabarriers for attenuation of seismic surface waves. The dispersion properties of the infinite metabarrier are investigated by means of the Bloch-Floquet theory for different dimensions and cross-section geometries of the unit tank. The surface wave modes are identified by introducing the sound cone and making use of a pertinent energy parameter. Next, dynamic analyses of a finite metabarrier are carried out in frequency and time domains, validating the proposed concept.

In this work, we propose a radically new approach for thermo-acoustic energy conversion based on the concept of Fano-based bistable systems. The proposed device, in its simplest version consists of a bilayer polymeric cylinder with harder core and softer and thinner shell. The heat source enforced at the core-shell interface induces thermo-mechanical stress fields. The stress field causes the occurrence of wrinkling patterns in the shell and the release of acoustic energy by a snap-through-buckling mechanism. We show that, when the shell is acoustically resonant at a specific frequency, the synergetic interplay of snap-through and Fano-resonances is capable of producing high amplitude and long-lasting pressure oscillations. In other words, under specifics conditions, the synergetic interaction between wrinkling instabilities and Fano resonance is able to extract mechanical energy from the heat source. The efficiency of the system in converting heat-into-work under resonant conditions is at least 6 times higher than that out of resonance. Notably, for a temperature difference of 1 K between the heat source and the surrounding water, the system may reach a conversion efficiency above 70 % of the theoretical Carnot efficiency. The so-generated mechanical oscillations can be converted in electrical energy for instance by using sound-to-energy converting systems such as conventional loudspeakers. The characteristics of the heat source have been selected to be representative of low-grade thermal sources (e.g. waste-heat, intermittent sources) abundantly available in natural, and industrial contexts. Importantly, the systems may be adapted to many different geometries spanning from the proposed core-shell cylinders in which the heat source can be either inside the tube (for instance an exhaust gas/liquid outlet) or outside the tube, to plates (like a solar panel system). This novel concept may lay the foundation of a new class of devices able to recover waste energy from a large variety of cases.