## 8 Conclusions  
Current structural design regulations for the construction of buildings in seismic zones specify that a non-linear seismic analysis could be performed. Depending on the type of structure, it can be a non-linear static seismic analysis (pushover) or a non-linear dynamic seismic analysis. An important difference between both methods is that generally different acceptance levels result for the same structure, becoming more critical when performing a dynamic seismic analysis. Taking this into account, in this work a non-linear dynamic seismic analysis was carried out where both the horizontal component and the vertical component of several seismic records occurred in Mexico are considered. Two hypothetical and one realistic (code-designed) steel frames are considered. It was found that the dynamic analysis considering the horizontal and the vertical components simultaneously (as compared to using only the horizontal component), does not always lead to the largest rotation. This does not occur in most cases and could be attributed to the counteracting effect of the vertical component for certain ground motions and considered structure. In addition, it is found that there are higher levels of acceptance (i.e., larger plastic rotations) when both seismic components (horizontal and vertical acting simultaneously) are considered than when only the horizontal component is considered, as happens in most practical cases. It is recommended to include the vertical seismic component in future earthquake assessment and design of buildings since the extra calculation effort is minimal (compared to a dynamic analysis by considering only the horizontal component). This study contributes to the understanding of structural behavior by considering the effect of both components of ground motions from a specific tectonic environment, since Mexican earthquakes are used. A simple quantitative expression to correlate the non-linear response (in terms of plastic rotations) and a ground motion intensity measure (pseudo-spectral acceleration) is proposed. In the proposed equation the three modes with the highest modal participation, which are not necessarily the first three, are used. Since other combinations of the response do not lead to this consistent trend, the proposed expression is considered as a contribution of the present study. It is acknowledged that in order to formulate more robust conclusions, further studies are required by extending the analysis to other structures and by using many other recorded near-fault ground motions, while also incorporating more refined modelling assumptions for the elements and connections of realistic structures. Other aspects which are recommended for further research are to explore a probabilistic rather than a deterministic approach (for instance to obtain median values of the response using two components, while also determining the variability in quantitative terms), as well as the use of scaled records to guarantee that many members of realistic structures undergo into the inelastic range consistent with future extraordinary seismic scenarios. **Author Contributions:** Conceptualization, J.-G.-V.-, A.D.G.-S. and M.A.J. ; methodology, J.-G.-V.-, A.D.G.-S. and M.A.J. ; software, J.-G.V.-V., A.D.G.-S. and M.A.J. ; validation, J.-G.-V.-V., A.D.G.-S. and M.A.J. ; formal analysis, J.-G.-V.-, A.D.G.-S. and M.A.J. ; investigation, J.-G.-V.-, A.D.G.-S. and M.A.J. ; resources, J.-G.V.-V., A.D.G.-S. and M.A.J. ; data curation, [PERSON]-, [PERSON] and [PERSON]; writing--original draft preparation, [PERSON], [PERSON] and [PERSON]; writing--review and editing, [PERSON], [PERSON] and [PERSON]; visualization, [PERSON], [PERSON] and M.A.J. ; supervision, [PERSON], [PERSON] and M.A.J. ; project administration, [PERSON] and [PERSON]; funding acquisition, [PERSON]. All authors have read and agreed to the published version of the manuscript. The financial support from Universidad de Guanajuato (Division de Ingenierias and Campus Guanajuato) is gratefully acknowledged.