## 6 Conclusions  
In this study, the experimental investigation of 18 specimens has been conducted to study the mechanical performance of CHBC under tension. Based on the results of this study, the following conclusions are made:  
1. All the specimens of CHBC develop diagonal cracks between the heads at peak load, which are caused by the concrete compression of the diagonal strut between the heads. The confined stirrups across the diagonal cracks mainly sustain tension force and function to provide with confinement to core concrete rather than bearing shear force which can contribute to the bearing capacity of CHBC directly;
2. For a head size equal to eight times the steel bar cross-sectional area, CHBC with only a 90 mm lap length, which is only 24% of the required lap length of straight bar splice and 36% of anchorage length of headed bar, can achieve the ultimate tensile strength of \(\Phi\)12 steel bar. The CHBC can reduce the lap length of deformed bars significantly;
3. The bearing capacity of CHBC consists of bond behavior force (\(F_{b}\)) and concrete compression force at the head (\(F_{h}\)). When the headed bar is yielding, the value of \(F_{b}\)/\(F_{h}\) increases linearly with the increase in lap length and decreases with the increase in head size. In addition, the increase in lap length by 50% (increasing from 72 mm to 108 mm) can increase the value of \(F_{b}\)/\(F_{h}\) by 310.0% and the increase in head size by 100% (increasing from 4 \(A_{s}\) to 8 \(A_{s}\)) can decrease the value of \(F_{b}\)/\(F_{h}\) by 20.8%. The change of \(F_{hy}\)/\(F_{h}\) by head size is less obvious than that of lap length;
4. When the headed bar is yielded, under same head size, for the lap length increasing by 50% (increasing from 72 mm to 108 mm), the average bond stress is increased by 71.9% when the bond slip is increased by 48.4%. It is recommended to use small lap length in CHBC in order to reduce the slip values;
5. Based on the superposition method and STM theory, a calculation method is proposed to determine the bearing capacity of CHBC. Compared with the test results, the deviation of predicted results is less than 10%. Moreover, the calculation of the required head thickness is suggested to prevent the head from yielding.  
Figure 39: Analytical model to determine head thickness (**a**) Load on head; (**b**) Plan view of head.  
**Author Contributions:** Conceptualization, Z.L., C.G., S.Z., and X.L.; methodology, Z.L., S.Z., and X.L.; software, Z.L.; validation, Z.L., and S.Z.; formal analysis, Z.L., C.G. and S.Z.; investigation, Z.L.; resources, Z.L.; data curation, Z.L.; writing--original draft preparation, Z.L.; writing--review and editing, C.G. and S.Z.; visualization, Z.L.; supervision, C.G., W.L. and S.Z.; project administration, C.G., W.L. and S.Z.; funding acquisition, C.G. and W.L. All authors have read and agreed to the published version of the manuscript.  
This study is funded by the Special Projects of Science and Technology of CHINA MINMETALS CORPORATION (2019 ZXB07).  
**Institutional Review Board Statement:** Ethical approval is not required.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** All data included in this study are available upon request by contact with the corresponding author.  
**Conflicts of Interest:** The authors declare no conflict of interest.