## 1 Introduction
For example, the error tolerance of insertion for grouted sleeve splice is generally about 10 mm to 15 mm. The construction can be inconvenient and time-consuming due to the required high construction accuracy which slows down the construction speed. The unseen grouting defects and required high construction accuracy of grouted sleeve splice or grouted spiral-confined lap connection violate the advantages of high construction quality and speed for precast concrete structure. Considering the deficiencies of the existing connection splices and the in-situ construction situations, this paper proposes a new steel-bar connection splice named as confined headed bar connection (CHBC) as shown in Figure 1.  
Figure 1: Confined headed bar connection (CHBC). As shown in Figure 1, CHBC consists of two overlapped headed bars and confinement stirrup. With CHBC, the cast-on-site construction is adopted instead of concealed grouting. Once the headed bar and stirrup reinforcement is placed, the reinforcement connection can be achieved after the connection area is cast-on-site. The CHBC construction process can be monitored visibly while the potential construction defects are diminished, and subsequently the construction quality as well as the reliability is upgraded. Additionally, the construction error tolerance is improved since the steel bar is not needed anymore to plug into the sleeve or grouting hole. The performance of the steel bar splice in concrete is strongly related to the anchorage properties of the steel bar. The stirrup confining the concrete at lap region can improve the rebar anchorage performance and furthermore, the heads at the end of the rebars can greatly strengthen the anchorage capacities. Through push-out tests, researchers [29; 30; 31; 32; 33; 34; 35] have found that the headed bar can achieve design tensile strength with significantly less embedded length compared to straight rebars without heads. The headed bars are also effective in the beam-column joint connection which can reduce the anchorage length of beam rebars in the column region [36]. Different design codes also quantify the improvement by head. Chinese design code GB 50010-2020 [37] suggests 40% off for the anchorage length of the headed bar while American design specification ACI318-19 [38] suggests the minimum anchorage length of the headed bar can be about 0.4 times that of the straight bar with specific conditions. In addition, researchers have adopted the headed-bar overlap splice to connect the steel bars between precast concrete members such as beam and slab [39; 40; 41; 42; 43; 44]. Results show that the precast concrete members connected by headed-bar overlap splice show practical and good bearing capacities and deformation characteristics when compared to those of continuous steel bars. The headed-bar overlap splice is practical for precast reinforced concrete member assembly. Although the feasibility of the lap-headed bar has been proved, the characteristics such as ultimate strength, slip behavior between the steel bar and concrete and so on, of this kind of steel bar connector has scarcely been studied. Moreover, the improvement added by the additional stirrup has not been investigated. So, in this paper, an experimental investigation including 18 specimens with different lap lengths and head sizes has been conducted to study the mechanical performance of CHBC under tension. The discussion is focused on the failure modes, bearing capacities and stirrup strain development, etc. The bearing capacity of CHBC consists of bond behavior force and concrete compression force at the head. The distributive relationship of these two forces has been investigated. In addition, the load-slip response of CHBC is studied. Moreover, an advanced finite element model using ABAQUS has been established, providing access to the detailed investigation of the mechanisms for concrete compression at head.