## 1 Introduction  
The reinforcement of building structures has emerged as a significant sector within the construction industry, with several novel materials being extensively employed [1; 2]. UHPC is a cementitious composite material containing fiber reinforcement known for its outstanding impermeability, robustness, resilience, and service life [3; 4; 5; 6]. Additionally, UHPC is utilized in engineering to construct new bridges and repair and strengthen existing ones, domestically and globally [7; 8; 9; 10]. UHPC was first derived from Mr. [PERSON]'s [11] first patent application and establishment of densified with small particles (DSP) theory. In 1994, [PERSON] and [PERSON] developed reactive powder concrete (RPC) with a compressive strength of 200-800 MPa, referring to DSP and the closest packing theory. In France in the same year, [PERSON] and [PERSON] configured a mortar with a low water-to-cement ratio and a compressive strength of 236 MPa, and first proposed the concept of UHPC based on DSP theory [12]. In China, Professor [PERSON] et al. at HunanUniversity conducted the earliest research on the development of UHPC technology, in 1993, using a 6% volume content of special steel fibers to prepare UHPC with a compressive strength of 200 MPa [13]. UHPC is not applied widely enough because of the high prices of raw materials and incomplete exploration of structural theories. However, its large-scale application will become feasible as the UHPC preparation technology gradually matures and the standards and depth of structural research improve. UHPC is being increasingly applied to the main structures of actual projects. The global application of UHPC materials in bridges increased to more than 1000, mainly in Asia, North America, and Europe [14]. UHPC is mostly used for localized reinforcement or the repair of critical parts of bridge abutments. Caluk utilized UHPC to enhance the plastic hinge zone of a bridge abutment, and the test results proved that UHPC can significantly reduce the damage to a plastic hinge zone, with good deformation and energy dissipation capacity [15]. The utilization of cementitious elements in the design of UHPC promotes sustainable development by achieving slender cross-sections, resulting in reduced concrete usage (specifically, less cement). This reduction in cement leads to decreased energy consumption and lower CO\({}_{2}\) emissions [16]. According to [PERSON] and other experts, the European Green Deal aims to reach complete carbon neutrality by 2050, thereby mitigating the environmental impact of industrial activities [17]. The extensive utilization of UHPC will additionally foster the advancement of sustainable buildings. This has significant ramifications for the preservation of the environment and the promotion of sustainable development. Currently, several building structures in China have been in use for an extended period, exhibiting varying levels of degradation, inadequate load-bearing capacity, and other issues. Several research studies have been conducted both domestically and globally on specimens that have been strengthened with UHPC. These investigations primarily focused on two areas: experimental research on axially compressed columns reinforced with UHPC, and experimental research on the performance of eccentrically compressed columns using other composite materials. In 2014, [PERSON] [18] and colleagues conducted an experimental investigation on the axial compressive parameters of RC columns reinforced with UHPC. The study demonstrated considerable improvements in the ultimate bearing capacity, peak strain, cracking load, and ductility of the reinforced specimens. In 2023, [PERSON] [19] and colleagues conducted an experimental study on the axial compressive properties of UHPC-RC columns. The study demonstrated that UHPC reinforcement significantly enhanced the axial bearing capacity and ductility of the specimens and that the increase in the bearing capacity was directly proportional to the thickness of the UHPC.