## 6 Discussion of the Results  
Nonlinear static analysis provides a good characterization of the seismic response of regular structures. In the present research, this analysis is used, considering its limitations, to capture the torsional behavior of a complete structure and to use the results as a basis for characterization before applying IDA. The results of this analysis show that the structure presents a low displacement ductility, calculated from the capacity curves determined by applying conventional and adaptive procedures. On the other hand, it is possible to observe the influence of the stiffness and resistance of the masonry infill panels on the lateral deformations of the structure. Upon reaching a global drift of the center of gravity at the roof of approximately 1%, the masonry infill panels cease to provide stiffness, and there is a sudden loss in the overall stiffness of the structure, which affects the sharp reduction in rotation as the lateral loading increases, since the structure loses much of its eccentricity. In addition, upon reaching the maximum rotation of the roof's center of gravity, additional lateral displacements are imposed on the columns farthest from it, which implies an increase in the global drift of approximately 0.3%. This increase reflects a higher concentration of rotations in the frames than in the columns (perimeter frames) and is introduced due to the displacements with a component normal to the plane, which especially affects the masonry infill panels. The IDA applied using accelerograms recorded during the Ecuador earthquake of 16 April 2016, results in curves that are not very dispersed, with very well defined points of collapse for the sections in which at least 20% of the initial stiffness has been lost. Regarding the fragility curve obtained for this type of building, it is evident that, for moderate accelerations, for example, 0.2 g, the building would reach a high probability of exceeding the collapse limit state (approximately 60%). However, if the probability of exceedance is calculated for the basic acceleration of the current design for the coastal zone of Ecuador [48], which contains the city of Portoviejo (0.5 g), the probability of exceedance of the collapse limit state is approximately 90%. If the accelerations achieved in the response spectra of the two components of the record obtained in Portoviejo are taken into account, exceedance probabilities very close to 100% are obtained. Based on the floor rotations obtained from the IDA, it can be clearly seen that, for both the negative and positive maximum rotations, the floors show an increase up to a certain value of spectral acceleration slightly higher than 0.10 g. At this threshold, the seismic action causes the collapse of the masonry infill panels, and without that contribution to the stiffness of the extreme frames, this change drastically reduces the torsional behavior of the building; all the rotations reduce to a minimum value corresponding to a spectral acceleration of approximately 0.17 g. After this, an increase in rotations is again experienced due to the increase in lateral displacements induced by the application of accelerograms with ordinates of greater amplitude and the presence of the weight of the masonry, which remains, although it no longer contributes to the lateral stiffness of the building. This  
Figure 15: Variations in the (**a**) maximum rotations and (**b**) relative rotations of the center of gravity for each floor calculated for various values of spectral acceleration and 5% critical damping. behavior is similar to that experienced by the rotations of the centers of gravity when applying the different types of pushover analyses reported in Figure 8a,b. On the other hand, the relative rotation of the centers of gravity between successive floors is considered applicable to measure the damage concentrated in a specific floor, considering a kind of local concentration of rotations similar to that observed when determining the interstory drifts based on the relative displacements.