# The Mechanical Properties of Reinforced Concrete Columns with Longitudinal Pre-Embedded Holes
## 1 Introduction  
In recent years, with the wide spread of the concept of green building, the demolition of buildings has gradually become more environmentally friendly. Among the current methods for demolishing reinforced concrete structural members, blasting demolition is often preferred due to its high efficiency, controllable safety during operation, and cost-effectiveness [1]. To adhere to the green building concept in the blasting demolition process, green blasting technology for reinforced concrete bars using pre-buried axial pipes as blast holes is put forward [2, 3, 4]. The pre-embedded holes in this technology can not only be used as blast holes during building demolition and thus avoid drilling blasting holes but also have other functions during the building's lifespan, such as use for concrete testing, communication wiring conduits, water and electricity pipelines, gas pipelines, and equipment conduits. To fulfill these various functions in the lifetime of thebuilding, the pre-embedded holes usually have bend ends to facilitate threading and blast charging operations. While the longitudinal pre-embedded holes in reinforced concrete columns have a variety of beneficial functions improving the life cycle efficiency of buildings and reducing life cycle carbon emissions, they also have certain negative influences on the mechanical properties of the columns. Due to the presence of the embedded pipes, the cross-sectional area of a reinforced concrete column is reduced, leading to stress concentration around the holes, which may impact the mechanical properties of a reinforced concrete column. In recent years, both domestic and international scholars have conducted extensive theoretical and experimental research on the influence of the holes in reinforced concrete bars on the mechanical properties of beams and columns. [PERSON] et al. [5] conducted a study on 29 simply supported reinforced concrete beams with circular holes in the beam belly. They analyzed the effects of factors such as hole size, location, number, and concrete strength on the mechanical performance of the perforated beams. [PERSON] [6] used ABAQUS for nonlinear simulation experiments on reinforced concrete beams with holes in the beam belly, focusing on the influences of the hole ratio, hole location, and reinforcement parameters on the beam's ultimate load-bearing capacity. [PERSON] et al. [7] investigated the effects of the hole location, number of holes, hole size, and hole distance on the load-bearing capacity of reinforced concrete beams with holes. They concluded that openings in the pure bending segment significantly reduce the load-bearing capacity of the beam, and an increase in the number of holes and hole distance substantially reduces the load-bearing capacity at various stages. Meanwhile, the size of the holes has a slight impact on the load-bearing capacity of the beams. [PERSON] et al. [8] studied the influence of different sizes and numbers of transverse holes in reinforced concrete columns on the compressive load-bearing capacity of those columns. Their results indicated that the presence of the holes leads to a loss of load-bearing capacity, which is proportional to the area loss. [PERSON] et al. [9] conducted a finite element study on the impact of longitudinal holes in reinforced concrete columns on their mechanical properties, revealing that columns with longitudinal holes experience a significant reduction in load-bearing capacity, resulting in safety factors lower than the standard values specified in various codes. [PERSON] et al. [10] used ANSYS finite element software to study the effects of transverse holes with different sizes and shapes and various locations in reinforced concrete columns under axial loading and compared the results with experimental data. [PERSON] et al.