# Comparison of Prediction Methods for Axial Strength of Ground Connections with Shear Keys
## 5 Conclusions  
The distinctions between shear strength calculated by different codes for the same grouted connection are presented in this paper. The overall calculation result from the API (2007) code is the lowest, followed by DNV GL (2016), and HSE (2002) is the highest. According to the analysis results, the prediction method of DNV GL (2016) is reasonable, that of API is the most conservative, and that of HSE is the most radical, which is unsafe from the perspective of design.  
Compared with the experimental results, the theoretical results of different codes are significantly different, generally more than 10%. The prediction method of axial strength of grouted connections still needs further research. At present, the results of grouted connection strength in the standards still have certain limitations, mainly because the test results are not rich enough, so there is still a lot of research work to be carried out. Moreover, the research work cannot be confined to static structures; ocean engineering must also pay attention to structure fatigue performance.  
The calculation formula from HSE (2002) has obvious limitations due to the obvious simple superimposing effect, especially in the case of long grouted connections and great numbers of shear keys, so the strength is often overestimated, resulting in insecure design outcome of structures. By contrast, when there are fewer shear keys, good applicability can be guaranteed. The reliability of the calculation formula from DNV (2013) has been improved in terms of more shear keys. However, the calculated results by DNV (2013) deviate from actual capacity in some parameter combinations, which may lead to serious overestimation of the strength of specimens.  
In the absence of specific parameters of specimens, the fitting formula in the API (2007) code can credibly predict the axial strength of grouted joints. However, the formula seriously undervalues the bearing performance of grouted joints, leading to relatively uneconomic design results. The formula in the DNV-GL (2016) code for axial strength of grouted joints is safe and reliable. In some cases, the axial strength calculated by DNV-GL (2016) may undervalue the actual capacity, but its prediction method has wider applicability, which is safe, reliable, and economical in the current situation.  
Conceptualization, Y.X. and W.Z.; Investigation, Y.X., C.Z., and W.Z.; Data curation, Y.X. and C.Z.; Conceived and designed the experiments, Y.X. and W.Z.; Performed the experiments, C.Z. and Y.X.; Analyzed the data, Y.X. and C.Z.; Contributed reagents/materials/analysis tools, W.Z.; Writing, Y.X. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Natural Science Foundation of Fujian Province of China grant number 2017J01697.  
This research was supported financially by the China Three Gorges Corporation and China Fujian Provincial Department of Science and Technology of China, which are gratefully acknowledged. The authors would also like to acknowledge Fujian Provincial Key Laboratory on Multi-Disasters Prevention and Mitigation in Civil Engineering, for laboratory help.  
The authors declare no conflict of interest.