This monograph presents the fundamental concepts related to seismic action, the structural response of buildings, the assessment of vulnerability, risk and seismic damage. Some indices proposed by different researchers are also indicated to assess the level of damage suffered by buildings under seismic actions. It also describes the ways to define the seismic action that are appropriate to the structural analysis. Techniques are developed to generate artificial accelerograms, which are necessary to perform the evaluation of the non-linear seismic response through an analysis in time. This evaluation also allows obtaining the level of damage suffered by the structures. The seismic action is focused on the city of Barcelona, Spain, which is located in an area of moderate seismicity and, in addition, does not have seismic records. The seismic action is established by seismic design spectra and artificial accelerograms compatible with said spectra. At the end of this work, the responses spectra considered to define the seismic demand and the artificial accelerograms obtained are shown, which can be used for the evaluation of structures for different seismic intensities and for different locations in Barcelona. Finally, a methodology for assessing the vulnerability and the seismic risk of buildings is described. The methodology is applied in several steps and includes modeling and non-linear analysis of structures. It is focused on obtaining fragility curves, which can be generated both through an empirical evaluation and through an analytical evaluation. The first is based on the damage observed in the buildings of an area after an earthquake occurs, while the second is based on a numerical analysis, where the seismic response of the structure is predicted.