## 3 Results and Discussion
### Concrete Compressive Strength and Axial Force  
This subsection investigates the influence of concrete compressive strength (fck) on the shear capacity of precast walls. Fixed parameters for this analysis include a section  
Figure 4: 3D plots: Maximum Shear as a function of concrete compressive strength (fck) and normalised axial force (v) for: (**a**) hc = 2.00 m (**b**) hc = 2.25 m (**c**) hc = 2.50 m (**d**) hc = 2.75 m (**e**) hc = 3.00 m.  
height (h c) of 3.0 m, a section thickness of 0.2 m, an overall wall height (H) of 2.67 m, and a connection with two bars of 25 mm. Figure 5 provides a detailed view of the combined effect of concrete compressive strength and normalised axial force on shear capacity. Figure 5a shows the global trends for all normalised axial load levels (v = 0.0, 0.2, 0.4, 0.6, and 0.8) with a standardised scale of 0 to 5000 kN, consistent throughout the article. In contrast, Figure 5b-d offer detailed magnified views with variable scales and linear fits for v = 0.8, v = 0.2, and v = 0.0, respectively. For the case where the normalised axial load (v) equals 0, as shown in Figure 5d, the plots indicate that increasing concrete compressive strength (fck) has a negligible impact on the wall's shear capacity. This is evident from the nearly horizontal trendline, with an extremely low correlation between concrete compressive strength (fck) and shear capacity (R\({}^{2}\) = 5 \(\times\) 10\({}^{-5}\)). However, for nonzero normalised axial loads (v > 0), Figure 5b,c demonstrate a clear and direct linear relationship between concrete compressive strength (fck) and shear capacity. As concrete compressive strength (fck) increases, shear capacity improves significantly, and the rate of this increment is proportional to the axial load level. For instance, at v = 0.2, the rate of increase in shear capacity with fck is approximately 36.43 kN/MPa (Figure 5c), while for v = 0.8, this rate nearly doubles, reaching 80.36 kN/MPa (Figure 5b). This demonstrates that higher levels of axial load enhance the sensitivity of shear capacity to changes in concrete strength. Furthermore, the coefficient of determination (R\({}^{2}\)) for the linear fits corresponding to v = 0.2 and v = 0.8 are extremely high (R\({}^{2}\) = 0.9988 and R\({}^{2}\) = 0.999, respectively), indicating that the data align almost perfectly with a linear model. This strong correlation underscores the reliability of the observed trend. Figure 5: Influence of Concrete Compressive Strength on Maximum Shear Capacity for Different Normalised Axial Loads: (**a**) Global Trends for all Levels of Axial Load, (**b**) Magnified view for v = 0.8, (**c**) Magnified view for v = 0.2, (**d**) Magnified View for v = 0.0. In summary, the data confirm that the influence of concrete compressive strength (fck) on shear capacity highly depends on the presence and magnitude of axial force. At higher levels of v, concrete compressive strength (fck) becomes a dominant factor in enhancing the shear strength of precast walls. Figure 6a plots the normalised axial load along the horizontal axis, ranging from 0.0 to 0.8, while the vertical axis represents the maximum shear capacity. Seven curves are included in each chart, corresponding to various compressive strengths of concrete. The fixed parameters in this analysis remain consistent with those in Figure 5: a section height (hc) of 3.0 m, section thickness of 0.2 m, overall wall height (H) of 2.67 m, and connection with two bars of 25 mm. Figure 6 illustrates how normalised axial load impacts the shear capacity of precast walls for different values of concrete compressive strength (fck). As the axial load increases, there is a noticeable rise in the wall's shear capacity across all values of fck. This trend is attributed to the enhanced frictional forces and improved force distribution within the wall under higher axial loads. Increased axial load enhances the contact and interaction between the wall components, contributing to greater stability and effectively allowing the wall to resist higher shear forces.