# The Mechanical Properties of Reinforced Concrete Columns with Longitudinal Pre-Embedded Holes
## 5 Conclusions  
1. The inclusion of longitudinal pre-embedded holes in reinforced concrete columns leads to a reduction in their ultimate load-bearing capacity. When the diameters of the pre-embedded holes are 50 mm, 75 mm, and 90 mm, the ultimate load-bearing capacity of the specimens decreases by 1.76%, 2.22%, and 3.47%, respectively. This reduction becomes more pronounced as the diameter of the pre-embedded holes increases. The primary reason for this trend is that the presence of pre-embedded holes reduces the effective load-bearing area of the column cross-section, leaving the column more susceptible to entering failure conditions under axial loading. 2. When the diameter of the embedded hole is \(\geq\)75 mm, the presence of the hole alters the stress state of the reinforced concrete column under axial loading. The column experiences an eccentric compression effect due to the hole. However, through stress redistribution and the material's ductility, the impact of the eccentric compression gradually diminishes. Ultimately, the failure mode does not undergo a fundamental change and remains dominated by axial compression failure. This indicates that, while the embedded hole affects the stress state, the overall failure mechanism of the column does not undergo a fundamental change due to the presence of the hole. 3. When the concrete strength exceeds C30, the diameter of the embedded hole should not exceed 50 mm. However, if the hole diameter increases to 75 mm or above and the strength of the concrete reaches C35 or above, the existence of the embedded hole will cause the failure mode of the concrete column to change from axial compression failure to shear failure along the plane where the curved part of the embedded hole is located. Figure 21: Influence curves of different factors on the ductility coefficient of longitudinally pre-embedded hole reinforced concrete columns. * Increasing the stirrup ratio can effectively improve the performance of reinforced concrete columns with embedded holes. As the stirrup ratio increases, both the load-bearing capacity and ductility of the specimens are enhanced, and the stress concentration is reduced, which helps mitigate the risk of local shear failure. * With the gradual increase in slenderness ratio, both the ultimate bearing capacity and ductility of the column show a decreasing trend, but the change amplitude of the ultimate bearing capacity of the column is not significant and can be ignored. The ductility of the specimen column is more obvious with the increase in the slenderness ratio. This indicates that the slenderness ratio has limited influence on the performance of reinforced concrete columns with embedded holes in practical engineering applications, but its potential influence should still be considered in the design to ensure the safety and reliability of the structure. * In practical engineering, the technology of longitudinally pre-embedded hole reinforced concrete columns demonstrates significant advantages, supporting its use in future frame structures and temporary buildings. Optimizing the cross-sectional design reduces self-weight and saves materials, offering considerable economic benefits. Additionally, the innovative multi-functional hole design improves the utilization efficiency of the holes, significantly enhancing the building's life cycle benefits and reducing its carbon emissions over the entire lifespan. This provides an innovative solution for the development of green buildings. Conceptualization, J.Z. and J.Y. ; Methodology, J.Y. ; Software, J.Z. ; Validation, W.X. ; Formal analysis, X.L. ; Investigation, W.X. and X.L. ; Data curation, W.X. ; writing--original draft preparation, J.Z. ; writing--review and editing, J.Y. ; Visualization, W.X. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The data used in this study can be obtained from the corresponding authors.