Solutions for the design and increasing of efficiency of viscous dampers

In last decades many strategies for seismic vulnerability mitigation of structures have been studied and experimented; in particular energy dissipation by external devices assumes a great importance for the relative simplicity and efficacy. Among all possible approaches the use of fluid viscous dampers are very interesting, because of their velocity-dependent behaviour and relatively low costs. Application on buildings requires a specific study under seismic excitation and a particular attention on structural details. Nevertheless seismic codes give only general information and in most case the design of a such protection systems results difficult; this problem is relevant also in Italy where last seismic code (NTC 2008) on one hand has increased the performance level to be attributed to buildings, especially public and strategic, on the other hand does not give a guide for the design of external dissipation devices as fluid viscous dampers or others. In this study, after a general description of fluid viscous dampers and the criteria of applying on buildings, a simplified procedure for the design of these devices is discussed also by means an application.