Seismic design of pre-cast reinforced concrete structures using additional viscous dampers

Precast concrete structures characterised by not moment-resisting frames present a relatively large flexibility (w.r.t. lateral loads). This characteristic often hampers the satisfaction of the inter-storey drift limitations imposed by most of the codes, both in terms of resistance and deformability. This paper illustrates the advantages offered by the insertion of added viscous dampers in such structures with respect to the use of traditional lateral-resisting bracing systems through the case-study of the executive design of a reinforced concrete 2-storey shopping mall building. This paper also presents details of the design process which should be undertaken for the seismic design of structures using additional viscous dampers. The design process may be mainly summarised into two steps: (step 1) preliminary analyses developed using a linear force-velocity relationship for the constitutive law of the viscous dampers and (step 2) analyses carried out with more realistic modelling of the commercially available manufactured viscous dampers. Two original procedures have been suggested and adopted in the case study: (i) the first one providing for an effective dimensioning of the damping coefficients of the linear added viscous dampers, and (ii) the second one providing for the passage from a linear (Newtonian) modelling to a non-linear (pseudo-plastic) modelling for viscous dampers constitutive law, which leads to similar performances under same inputs.