The irregular buildings constitute a large part of urban infrastructure and they are currently adopted in many structures for architectural or esthetic reasons. In contrast, the behavior of these buildings during an earthquake generates a detrimental effect on their regularity in elevation which leads to the total collapse of these structures.

The objective of this work is essentially to model reinforced concrete framed buildings irregular in elevation subjected to seismic loads by the Finite Element Method (FEM). This modeling aims to evaluate several parameters: displacements, inter-storey drifts and rigidities, using two dynamic calculation methods; one modal and the other spectral modal. The latter is widely used by engineers.

For this purpose, a detailed study of the frames which have several setbacks in elevation is carried out to validate the correct functioning of our FEM calculation code in both cases of modal and modal spectral analyses. The performance, accuracy and robustness of the FEM calculation code produced in this study is shown by the good correlation of the obtained results for the treated frames with those obtained using the ETABS software.