## 1 Introduction  
At present, new construction materials are being designed to meet the development needs of building disaster prevention and mitigation and these materials are experiencing rapid investment. Notably, steel-fiber-reinforced concrete (SFRC) is becoming increasingly popular in engineering projects [1, 2]. It is used in various fields, including foundation, bridge and tunnel engineering [3, 4, 5]. Steel fibers have good tensile properties [6], which can compensate for the deficiencies of normal concrete (NC) with respect to tensile and shear properties [7], demonstrating the superiority of SFRC. As a result, SFRC members have greater strength [8], flexural toughness [9], impact resistance [10] and wear resistance [3] than NC members.  
The bond behavior between rebar and concrete is the basis for the design of structural members [11, 12]. Many scholars have used pull-out testing to study the behavior and influencing factors of the bond behavior between rebar and SFRC. Key indicators of the bond-slip characteristics between rebar and SFRC include the bond strength, bond-slip curve and bond stress distribution. [PERSON] [13] investigated the effects of various factors on bond strength and toughness (concrete compressive strength, rebar diameter,concrete cover thickness, fraction of steel fiber by volume, fiber length and aspect ratio). Pull-out tests revealed that the concrete compressive strength is the most critical factor of the bond strength, while the fraction of steel fiber by volume only has a minor effect. [PERSON] [14; 15] found that the volume fraction and aspect ratio of steel fiber affect the bond stress slip relationship, strength, stiffness and toughness. [PERSON] then used this information to create a new rebar bond model that includes the finite initial bond stiffness, based on the existing rebar bond model, that provides bond strength, stiffness and toughness prediction equations for NC and SFRC. [PERSON] [16] analyzed the bond stress distribution between rebar and SFRC for different volume fractions of steel fibers using pull-out tests of local bond specimens of SFRC. The midpoint stress interpolation method was proposed as part of a new bond stress prediction model. It was shown that the incorporation of steel fibers increases the inhomogeneity of bond stress between rebar and SFRC. As the volume fraction of steel fibers is increased, the slip near the loading end decreases and the corresponding bond stiffness greatly increases. [PERSON] [17] found that steel fibers have a dual effect on the bond strength. Steel fibers increase the concrete strength and decrease the mobility. The recommended steel fiber volume fraction was proposed to be approximately 0.25-0.75% in the structure.  
The bond behavior between rebar and SFRC deteriorates at high temperature due to fire. [PERSON] [18] proposed a new method for evaluating the effectiveness of steel fibers with respect to bond strength. It was noted that the post-peak behavior of the bond-slip curve could be considered an effect of reinforcing the bond strength between rebar and concrete. [PERSON]'s [19] study showed that incorporating mixed steel fibers with high aspect ratios increases the peak bond strength at a maximum test temperature of 825 \({}^{\circ}\)C. A reliable bond between rebar and SFRC is the basis for ensuring the safety of SFRC structural members under fire. Therefore, it is especially critical to study the bond-slip performance between rebar and SFRC at high temperatures. In this study, the bond failure process and bond-slip performance of rebar and SFRC at high temperatures are investigated. The effects of temperature and the fraction of steel fiber by volume on the bond strength between rebar and SFRC are analyzed by introducing a fiber reinforcement coefficient and a temperature reduction coefficient. Based on the impact parameters of temperature and steel fiber volume fraction, a bond-slip relationship model between rebar and SFRC at high temperature is established.