Seismic Behaviour of an Irregular Old RC Dual-System Building in Lisbon

In this paper, the seismic performance of a reinforced concrete dual-system building with vertical irregularities, built in the 60s in Lisbon, is addressed. The seismic behaviour and the torsional effects of the building are investigated by means of nonlinear static (pushover) analyses and extended N2 method. Then the results are compared with the nonlinear dynamic Time-History analysis, the latter considered as the reference solution. A three-dimensional numerical model of the case-study building is developed to account for torsion in the building. The evaluation of the seismic vulnerability of structure is based on performance-based assessment procedures and on the structural safety requirements proposed in Part 3 of Eurocode 8. The main targets of this study are (i) to detect and quantify the main deficiency of this typology of old existing RC buildings, which were not designed to resist the forces induced by torsional vibrations; (ii) to propose suitable retrofitting intervention for this category of buildings.