Experimental control of the mechanical properties of pressurized fluid viscous dampers over twenty years after their production

The stability over time of the mechanical properties of seismic dampers is a fundamental requirement to guarantee the maintenance of their protective action on the buildings and infrastructures where they are installed. This requirement can only be checked experimentally, by repeating at a considerable interval of time the qualification tests carried out on the devices immediately after their production. This topic is addressed in the paper, focusing on Pressurized Fluid Viscous (PFV) dampers, which have been the subject of over than twenty-five years of research activities by the first two authors. During the first season of these activities, several testing campaigns have been developed on various types of PFV devices, which allowed identifying their mechanical characteristics. Some of the experimental investigations carried out in the early 2000s are currently being repeated on the same devices tested at that time. A synthesis of the new laboratory campaign completed on a first pair of PFV spring-damper is presented herein, comparing the results with those of the original qualification tests. The identification process developed on both data sets allows to assess a complete stability of the mechanical properties and response capacities of the examined devices over this significantly long-time span.