Experimental and numerical investigations on cyclic behavior of U-shaped dissipative devices

U-Shaped Dissipative Devices (USDDs) are seismic devices consisting of U-Shaped Flexural Plates (USFPs) applied in seismic design for dissipating energy by means of hysteresis due to the steel cyclical yielding. They may be used in practice since are simple to be assembled, installed and substituted after the design seismic event. For these reasons, it becomes essential to properly predict the USDDs seismic behavior, taking into account all the fundamental parameters determining their dissipative capacity. In this study experimental and numerical investigations are carried out in order to investigate the cyclic behavior of a USDD, consisting of two pairs of USFPs in order to increase the device dissipative capacity. Moreover, the USDD investigated has significant dimensions so that it is particularly devoted for constructions (such as buildings and bridges) of large dimensions. At first, the main results of an experimental campaign are illustrated and commented. Then, a refined numerical model is implemented and validated in order to properly predict the cyclic response under the displacements imposed, taking into account the USFPs construction stages. Additionally, numerical analyses are performed with the aim of investigating the interaction among the device elements. Finally, a simplified formulation is also proposed in order to be applied in practice for seismic design of construction that are provided with the device investigated. The investigations carried out highlight that the USDD behavior is strongly influenced by the elements interaction, and by the connecting plates stiffness. Consequently, a design optimization as a function of the design displacement may be obtained in order to reduce steel amount involved, realizing cheaper devices having also a satisfactory dissipative capacity.