## 1 Introduction  
Concrete-filled steel tube (CFST) columns have been widely used in multistory and high-rise buildings in many countries, mainly due to their high structural efficiency, low cost and fast construction time [1; 2; 3; 4]. Currently, most existing CFST columns are connected to H-steel beams via welding processes, but this kind of installation is complex, time consuming and costly. Moreover, it is quite difficult to ensure the quality of the site construction, and these connections are prone to brittle welding fractures. A bolted connection between a CFST column and a steel beam can solve these problems; however, it is difficult to access the inside of the hollow section, and ordinary high-strength bolts cannot be directly used in the connections. However, this problem can be overcome with blind bolts that are installed only from one side of the steel tube wall. Currently, the most commonly used blind bolts are the Hollo-Bolt, Molabolt, Flowdrill, Ajax Oneside, and Ultra-Twist. Currently, the applications of the available blind-bolting systems are restricted to the construction of shear-resisting joints, whereas blind-bolting systems have not been developed for moment-resisting joints. This is because when the blind-bolted joint is resisting a moment, the square steel tube in the tension zone is always the weakest part due to the poor outward bending stiffnesses of the square steel tube wall; therefore, the blind bolts are unable to utilize their full strengths, which limits the performance of this type of moment-resisting joint. In a study on the flexural behavior of square CFST column joints with ordinary blind bolts, the joints typically failed due to cracking at the corner, excessive deformation of the tube face, and slippage and pull-out of the blind bolt [5; 6]. Some researchers have proposed increasing the outward stiffness of steel tubes by using constructional measures for the bolted connections between the CFST columns and H-steel beams, including strengthening the panel zone of the joint or transferring the load to the sidewalls or the back of the column [5; 7; 8; 9]. Although these measures have certain effects, they are too complicated in fabrication and are unfavourable to the construction of space connections. A more convenient and effective method is installing an anchoring device at the end of the blind bolt to improve its anchorage performance in the tension zone, thereby enhancing the flexural behaviors of CFST column joints. [PERSON] and [PERSON] [10] initially proposed welding a straight or cogged reinforcing bar to the ends of blind bolts to form a complete unit; several studies have focused on this type of modified blind bolt [11; 12; 13; 14; 15]. Thereafter, [PERSON] et al. [16] extended the blind bolt and installed a nut at the end, similar to a headed stud; this bolt is referred to as the Extended Hollo-Bolt (EHB), as shown in Figure 1. [PERSON] et al. [17] and [PERSON] et al. [18; 19] investigated the tensile behavior of a modified blind bolt with a nut on the end. Their results indicated that an anchored blind bolt could ultimately achieve the full tensile capacity of its internal bolt and could limit the local outward deformation of the column and dramatically improve the strength and stiffness. Moreover, anchorage failure could occur for short extensions, welding fractures between the bolts and the reinforcing bars. [PERSON] et al. [20; 21] investigated the rotational stiffness and hysteretic performance of a blind-bolted end-plate connection to CFST columns with EHBs. Their results indicated that the connection can offer an appropriate energy dissipation capacity and ductility for its potential use in seismic design. To date, research on anchored blind-bolted joints to CFST columns is limited, especially for cyclic loading tests, and the experimental parameters are incomplete, presenting limitations in these studies.