Simulation of the Low-Cycle Fatigue Response of Dissipative Steel Devices in Retrofitted RC Frames

In recent years, several dissipative devices were developed and are currently available to be employed in steel bracing systems for designing and retrofitting purposes. Different geometrical materials, configurations and energy dissipation mechanisms, based on yielding under either shear, bending or torsion actions were taken into account for their development. Although innovative high-dissipative members are nowadays developed and commercialized by specialized factories, cost-competitive devices can be generally obtained through conventional steelwork procedures and can be employed as short link elements on Y-shaped eccentric braces (EB), widely adopted especially for seismic retrofitting of existing structures. In this paper, after a description of such devices, the key results obtained in recent tests carried out at the Laboratory Material testing and Structures of the University of Salerno are used as starting point for a sample application on an existing structure. Particularly, the steel devices under investigation are firstly modelled in OpenSEES and their local response is calibrated including the effects of the low-cycle fatigue. Then, the global response of an existing structure equipped with those conventional devices is investigated. Nonlinear Time History Analyses are performed by taking into account the performance of such hysteretic devices under cyclic loads by means of the low-cycle fatigue curve and the effects of increasing number of cycles on the overall structural response are unveiled.