AbstractThe post-earthquake seismic assessment of buildings is usually performed through numerical methods. Geometrical simplifications of the structure are often introduced. Moreover, the seismic input is evaluated following the indications of reference standards, although overestimated forces may be obtained compared with those that actually occurred. In this paper, through the case study of a single-nave church, the significant influence of the geometric modeling of the roof on the structural response and the importance of the correct definition of the seismic input in post-earthquake analyses are shown, even in the case of very simple structural organisms. A preliminary limit analysis and nonlinear static analyses, after the definition of new response spectra based on a subset of the recorded ground accelerations, have been performed. The decisive role played by the correct geometric modeling and the proposed response spectra in the simulation of the overall response and damage status is shown. Finally, the importance of the method in the design of retrofitting works is highlighted through the basic example of the numerical response of the structure reinforced with CFRP composite.