## 3 Results and Discussion
### Section Height  
This section explores how adjustments to the height of precast concrete wall sections impact their shear capacity, focusing on how these geometric changes interact with varying levels of axial load. Analysing section heights ranging from 1.5 m to 3 m across different normalised axial loads (v), with the concrete compressive strength fixed at fck = 35 MPa. The results showed a consistent trend: increasing the height of the section leads to a rise in the maximum shear capacity, as can be seen in Figure 7a, which provides an overview of the trends for all normalised axial load levels (v = 0.0, 0.2, 0.4, 0.6, and 0.8). The curves clearly show that shear capacity increases with section height for all values of v, although the rate of increase varies depending on the level of axial load. The relationship is nearly linear but relatively modest for low axial loads, such as v = 0.0. In contrast, for higher axial loads like v = 0.8, the increase in shear capacity is much more pronounced, suggesting a synergistic effect between section height and axial load. Figure 7b focuses on the scenario where v = 0.0. In this case, the relationship between section height and maximum shear capacity is nearly linear, demonstrating that, in the absence of axial load, shear capacity is primarily governed by geometric factors such as section height, with little contribution from axial forces. Figure 7c highlights the case where v = 0.4, showing a steeper linear trend compared to v = 0.0. This steeper slope reflects the more significant impact of section height on shear capacity under moderate axial loads. The findings suggest that axial forces interact with wall geometry to enhance shear resistance, with the contribution of the axial load becoming increasingly significant as v rises. Figure 7d examines the relationship at v = 0.8. Here, the trend between section height and shear capacity becomes nonlinear. While the overall relationship remains positive, the rate of increase diminishes at higher section heights. This indicates that the effect of axial load on shear capacity becomes less pronounced as the section height surpasses a certain threshold. To complement the information in Figure 7, Figure 8 examines the incremental increase in shear capacity as the normalised axial load is varied. Each bar represents a different concrete compressive strength, and the results show the increment in shear strength relative to the immediately lower normalised axial load. For example, in the first set of results, the increment in shear strength for models with \(\
u=0.2\) is presented relative to \(\
u=0.0\); in the second set, the increment for \(\
u=0.4\) is presented relative to \(\
u=0.2\), and so on. It can be seen that the largest increments in shear capacity occur between normalised axial loads of 0.0 and 0.2, especially for higher compressive strengths. In chart (d), from 0.0 to 0.2 axial load, the first increment shows significant increases: 464 kN for fck = 20 MPa, 828 kN for fck = 35 MPa, and 1209 kN for fck = 50 MPa. However, the subsequent increment from 0.2 to 0.4 axial load is smaller: 383 kN, 675 kN, and 963 kN for the same compressive strengths. The smallest increase occurs between 0.6 and 0.8 axial loads, with increases of 62 kN, 271 kN, and 382 kN. This diminishing rate of growth suggests that axial load has the greatest impact on shear capacity at lower levels, and its effect becomes less pronounced as the load increases. Overall, the results highlight the critical role of section height in determining the shear capacity of precast concrete walls. Taller sections consistently exhibit higher shear capacity, particularly at greater axial loads. Additionally, increasing the compressive strength of concrete enhances shear capacity significantly, especially at higher levels of axial load.