Traditional and viscous dissipative steel braced top addition strategies for a R/C building

A study concerning a double-storey extension on top of an existing reinforced concrete (R/C) apartment building is carried out for two different steel structural solutions. A traditional bracing configuration, and a dissipative bracing technology incorporating pressurised fluid viscous spring-dampers, are selected for the two hypotheses. The gravity load-bearing system is assumed to be coincident, in order to directly compare the seismic response capacities of the bracing systems. Furthermore, the following mutual design objectives are fixed: attaining operational, and immediate occupancy non-structural performance levels at frequent design earthquake and serviceability design earthquake levels, respectively; and limiting strengthening interventions on the R/C structure to jacketing maximum 20% of columns, and adding a thin R/C slab over the foundations. These objectives are reached at virtually coinciding costs. On the other hand, the viscous-dissipative bracing design shows substantially higher seismic performance at basic design and maximum considered earthquake levels, as well as lower architectural intrusion, as compared to the traditional bracing solution.