Existing prefab R/C industrial buildings: Seismic assessment and supplemental damping-based retrofit

A research study on prefab reinforced concrete buildings designed with older Technical Standards is presented in this paper, where attention is focused on hall-type industrial structures. A representative case study, which includes the main sources of seismic vulnerability, is examined in detail. The possible rigid rotation of the bottom end zone of columns, which are encased in smooth socket-type foundations, and the frictional contact between the neoprene pads situated on top of the columns and the terminal zone of the roof girders are modelled in time-history assessment analyses. Initially carried out by assuming an elastic behaviour of columns, the analyses highlight unsafe response conditions under seismic action scaled at the basic design earthquake level, and near-collapse caused by the loss of support of several girders from the neoprene pads at the maximum considered earthquake level. A second step of the analyses, where plastic behaviour of columns is investigated by incorporating fiber-type plastic hinges at their bottom end sections, shows a remarkable ductility demand, as well as potential collapse induced by the complete loss of support of girders. The high lateral displacements of columns may also cause failure of the fastenings of the connected cladding panels, likely to result in their overturning-induced collapse. Based on these data, a supplemental damping-based retrofit hypothesis is suggested, consisting in the installation of dissipative braces equipped with pressurized fluid viscous spring-dampers. The protective system allows attaining a completely undamaged response of structural and non-structural members, and therefore meeting the requirements of the Immediate Occupancy limit state, up to the maximum considered earthquake level.