A simplified model for seismic safety assessment of reinforced concrete buildings: framework and application to a 3-storey plan-irregular moment resisting frame

•Simplified building model for seismic assessment using dynamic analyses.•Model suitable for non-shear-type buildings as it accounts for beams flexibility.•Torsional behaviour of irregular buildings accurately captured.•Remarkable reduction of computational time.•Validation on a 3D irregular reinforced concrete moment resisting frame building.