Two-storey pre-cast reinforced concrete structure equipped with viscous dampers: a case study

Pre-cast concrete structures are commonly assembled at construction site so that structural systems obtained are not capable of transmitting bending moments at joints. Such structural systems show a relatively large flexibility with respect to lateral seismic loads. This characteristic often hampers the satisfaction of the interstorey drift limitations imposed by most of the seismic codes. In this paper, the use of added viscous dampers is compared with the use of traditional lateral-resisting bracing systems in order to provide such structures with the necessary lateral stiffness and resistance. The comparison is here developed with reference to the executive design of a shopping mall building in Italy. Four distinct structural solutions have been taken into consideration during the design phase: precast structure without any type of bracing, precast structure equipped with steel bracing, precast structure with dampers placed so that they connect each floor to the ground, precast structure with dampers placed between adjacent storeys. The results of the numerical time-history simulations show that traditional bracing systems are capable of satisfying the deformability requirements at the expense of large forces both in the bracing system and upon the foundation. On the other hand, the insertion of viscous dampers allows at the same time to limit the drifts of the structure and to keep the forces in the bracing system at acceptable levels.