## 5 Discussion  
The findings of this study confirm the applicability of the simplified micro-modeling approach in predicting the seismic performance of STPU-retrofitted masonry walls. While this method demonstrated strong agreement with experimental failure loads and deformation patterns, it is important to note its inherent limitations in capturing progressive damage and localized cracking. These limitations became more evident at higher PGA levels, where cumulative damage and nonlinear effects were not fully represented.  
Moreover, the simulation did not account for phenomena such as interface debonding or degradation of bonding between STPU/GFRP and the masonry substrate, which  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Thickness**} & \multicolumn{4}{c}{**Numerical Analysis Result**} \\  & **Displacement** & **Strain** & **Y-Axis Stress (MPa)** \\ \hline \multirow{2}{*}{1 mm} & Max. & 1.54 & 0.000095 & 0.26 \\  & Min. & \(-\)0.80 & \(-\)0.000187 & \(-\)0.53 \\ \hline \multirow{2}{*}{2 mm} & Max. & 1.48 & 0.000093 & 0.25 \\  & Min. & \(-\)0.70 & \(-\)0.0000174 & \(-\)0.49 \\ \hline \multirow{2}{*}{3 mm} & Max. & 1.50 & 0.000118 & 0.31 \\  & Min. & \(-\)0.81 & \(-\)0.000189 & \(-\)0.51 \\ \hline \multirow{2}{*}{4 mm} & Max. & 1.51 & 0.000119 & 0.32 \\  & Min. & \(-\)0.82 & \(-\)0.000196 & \(-\)0.54 \\ \hline \multirow{2}{*}{5 mm} & Max. & 1.51 & 0.000114 & 0.31 \\  & Min. & \(-\)0.79 & \(-\)0.000175 & \(-\)0.50 \\ \hline \multirow{2}{*}{6 mm} & Max. & 1.51 & 0.000103 & 0.28 \\  & Min. & \(-\)0.79 & \(-\)0.00016 & \(-\)0.46 \\ \hline \multirow{2}{*}{7 mm} & Max. & 1.51 & 0.000116 & 0.32 \\  & Min. & \(-\)0.79 & \(-\)0.000187 & \(-\)0.51 \\ \hline \multirow{2}{*}{8 mm} & Max. & 1.54 & 0.000111 & 0.32 \\  & Min. & \(-\)0.80 & \(-\)0.000192 & \(-\)0.52 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Parametric study results for different thicknesses of STPU.  
influenced the experimental results--particularly in the MWPF5 specimen. Incorporating interface damage models or cohesive elements in future simulations could enhance the accuracy of predicted responses.  
In addition, the study used representative material properties sourced from relevant prior research to model the equivalent masonry units. Although appropriate for the present scope, future studies should include sensitivity analyses on masonry material parameters (e.g., tensile strength, modulus) to evaluate their influence on retrofitted wall behavior. Exploring probabilistic modeling approaches may also help to address uncertainties in both material properties and seismic demand.  
From a practical perspective, the results of this study suggest that a 2 mm thick application of STPU offers a balanced solution between structural enhancement and economic feasibility. While thicker coatings provided marginal improvements in displacement and strain reduction, these gains may not justify the additional cost, material use, and curing time. Therefore, for masonry walls subjected to moderate seismic demands, a 2 mm thickness is recommended as the optimal configuration.  
Future design guidelines for STPU application could adopt a performance-based approach where the required strengthening thickness is calibrated against target displacement or strain reduction thresholds, as established through experimental or numerical analysis.