A passive control system based on double U-shaped metal elements: applications cases, design and developments

The proposed work presents application cases use and the future development of passive-based hysteretic devices (Displacement Dependent Devices DDDs, Non-linear Devices NLDs). The technology consists of the combination of one or two pairs of U-shaped metallic elements, where substantial energy dissipation occurs. The basic configuration of the systems provides a mono-directional dissipative response, however a combination of two elements can ensure the dissipation in both directions. In the last years, several solutions have been widely adopted in practical applications thanks to the easy implementation of these elements. Their versatility has also allowed them to be used in combination with other devices. In the infrastructural field these elements have been used as longitudinal restraints or bidirectional restraints combined with pot or spherical supports or even shock transmitter units, in the building retrofit, however, as dissipative element of bracing system. The adoption of the aforementioned devices in a wide panorama of structures has given the possibility to develop and test high-performance devices. The experimental data led to the derivation of a simplified methodology that is easily applicable in the design. Furthermore, in order to obtain further optimizations of the devices and extend their use to different structural applications, the experimental results were interpreted using high-resolution digital image correlation methodologies for local strain measurement supported by refined numerical simulations.