CONCLUSIONS

The research presented here was based on the use of experimental tests from the research group and also on those found in the literature, as well as adequately validated numerical models with the purpose of expanding the knowledge about the behavior of structural masonry shear walls, especially for partially grouted walls with grout and reinforcement at their ends. The specific conclusions from the analyses carried out throughout the different chapters of the thesis and suggestions for future work are presented below.

a) Chapter 2: Parametric study

The study presented in Chapter 2 aimed to investigate, using finite element modeling, the influence of various parameters on the behavior of partially grouted multi-story masonry shear walls with openings. The numerical model was used to analyze the different variations of the walls as a function of the load capacity, displacement preceding the maximum load, and initial lateral stiffness. The results allow concluding that:

• The wall load capacity was significantly impacted by changes in the strengths of the ungrouted and grouted masonry, in the mortar shear strength, in the vertical reinforcement ratio, and in the aspect ratio. Around 10% of the wall load capacity varied as a consequence of a variation of about 120% in the axial stress. Except for the aspect ratio, all of these parameters had a positive correlation with the wall load capacity. The wall capacity was not affected significantly by the opening size, reinforcement spacing, or horizontal reinforcement ratio;

• The deflection of the walls positively correlated with the strengths of the ungrouted and grouted masonry, the aspect ratio, and the opening width, and negatively with the vertical reinforcement ratio and the axial stress. Changes in the mortar shear strength, horizontal reinforcement ratio, and spacing between reinforcements did not significantly impact the displacements. The opening height and deflection of the walls did not exhibit a clear relationship;

• There is a limit where increasing the ungrouted and grouted masonry's strengths have no further impact on the walls' capacity and deflection, which in this case were around 65% and 40% of the strength of the base model, respectively;

• The initial stiffness of the walls was susceptible to changes in the strengths of the ungrouted and grouted masonry, in the joint mortar shear strength, and especially in the axial stress and aspect ratio. The modifications in the opening size and the spacing and size of the reinforcement had a smaller impact on the initial stiffness;

• The load capacity and initial stiffness were positively correlated to the axial stress while the displacement was negatively correlated with it; the aspect ratio had the inverse effect. The failure mode was altered by both factors: an increase in the axial load made the failure shear-dominated, while an increase in the aspect ratio made the failure flexural-dominated;

• As the alterations imposed on the opening dimensions in this analysis reflected a reduction of, at most, 12.5% in the effective cross-sectional area and with a failure mode dominated by shear, the results addressing the opening dimensions should not be taken as absolute. More investigations are required to confirm the effect of significant changes in the opening size.

b) Chapter 3: Shear load capacity prediction

The FEM developed previously in Chapter 2 was recalibrated and revalidated to be used in the study of Chapter 3. The accuracy of expressions to predict the SLC of unperforated PGMW was evaluated by comparing a new proposed shear equation with some relevant already existing ones. Additionally, different approaches were investigated to find the best reliable strategy for estimating the SLC of single and multi-story PGMW with openings. The following conclusions can be made in light of the findings:

• The simulated scenarios could demonstrate that certain accurate predictions made with the existing shear equations are actually false positives. The absence of a term for the contribution of the vertical reinforcement and/or the underestimation of the masonry contribution caused by restrictions on the aspect ratio frequently served to balance off the overestimation of the contribution of the horizontal reinforcement and vice versa;

• Among all the equations examined, the ones from TMS 402/602 (2016) and CSA S304 (2014) delivered the most inaccurate estimations of the shear load capacity of the unperforated PGMW for both the computational and experimental datasets. The SLC of walls with horizontal reinforcement tended to be overpredicted insecurely using the TMS 402/602 (2016) equation and with a high variability using the CSA

S304 (2014) equation. The code equations tended to overestimate and underestimate, respectively, the SLC of walls with large and small horizontal spacing between grouted cells, particularly because these equations were developed for FGMW and further adjusted for PGMW using a simple constant reduction factor;

• Among the evaluated existing shear equations, that one of Dillon and Fonseca (2015) performed the best predictions for the walls of the numerical dataset, whereas the equations of Izquierdo et al. (2021), and Seif ElDin et al. (2019a) were the most accurate for the walls of the experimental dataset;

• The new proposed equation included the effects of the aspect ratio, vertical and horizontal grouting and reinforcement, and axial loading to ensure a suitable level of accuracy in estimating the SLC of the walls. Thus, the proposed equation provided the best statistical indicators among all the shear equations studied for unperforated PGMW of both the numerical and experimental datasets;

• The reduction of the effective horizontal cross-sectional area can be associated with the significant decrease in SLC of the single-story walls caused by the presence of openings. Even in a smaller proportion, the SLC of the walls also decreased when the window openings were replaced with door openings. Since the lateral load was applied at the top of the highest story, the diagonal struts found more areas of masonry between the stories to pass through, reducing the impact of the openings on walls with more stories. More research is needed to assess the impact of openings in multi-story PGMW when lateral loads are applied at each story level;

• The approach of predicting the SLC of perforated PGMW by only reducing the effective horizontal cross-sectional area in the shear equation did not yield appropriate results since this approach ignores the opening height. The approach which considered the strength of the wall as the sum of the strengths of the wall piers with dimensions limited by the diagonal shear crack forming from the upper corner of the opening to the lower diagonally opposite corner of the opening of the same story produced the most accurate predictions. The applicability of this strategy employing the newly presented shear equation for walls with openings positioned asymmetrically requires further investigation.

Finally, besides proposing a new accurate and complete shear equation for PGMW, this study indicates the need of updating the shear expression of the TMS 402/602 (2016) and CSA