The construction of residential buildings with light-weight steel strctures has largely increased in the last years, mainly due to shorter building times and reduction of the costs. The structural characteristics of these buildings greatly differ from the most common constructions, and so will do their dynamic response. Thus, a detailed study on the seismic design should be done, since seismic actions can not be neglected. This study is performed by means of the FEM and the response spectrum analysis, a particular method for seismic calculations. This thesis deals with different structural systems, beginning with cantilever, wich is useful to set the common characteristics of all seismic analyses, and concluding with the design of the x-bracing elements in a complete 3D structure. Middle steps are the analyses of a frame and façade in 2D. Finally, the possible reduction of 3D models to 2D is analysed.