Force reduction factor for yielding SDOF systems equipped with viscous dampers

This paper proposes a simplified methodology for the seismic design of yielding SDOF systems equipped with viscous dampers. The methodology allows to consider, at the same time, the non-linear behaviour of the structural elements and the effect of the viscous dampers through the use of a properly calibrated force reduction factor. In detail, the force reduction factor to be adopted for yielding structures equipped with viscous dampers (characterized by high values of the damping ratio, even larger than 30%) should guarantee the same safety level of the same structures without dampers (characterized only by the inherent damping). In order to reach this purpose a parametric study characterized by a large number of non-linear dynamic analyses of SDOF systems has been performed imposing the equal ductility criterion. Finally, an applicative example is presented.