# Comparison of Prediction Methods for Axial Strength of Ground Connections with Shear Keys
## 4 Comparison between Calculation and Test Results  
### Data Acquisition and Verification  
In order to further study the accuracy and effectiveness of the formula in different codes, the axial test results of 270 grouted connections with shear keys were collected in the study [8; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. Then the code calculation process was applied to compare the results with the experimental ones. However, due to the incomplete information of some specimens given in the documents, only 64 sets of test data were available for analysis; 13 sets involving specimens that did not meet the application range of DNV-GL were excluded, and the data of the remaining 51 sets of specimens could be calculated, analyzed, and compared. In order to ensure the reliability of the collected data, the verification work was carried out by the axial compression test and finite element analysis of grouted connections. A total of seven grouted-connection specimens were tested. The specimen dimensions are shown in Table 3. A 10,000 kN electro-hydraulic servo-controlled long column pressure tester was employed to apply uniform loading under the control of a computer. The loading equipment and monitoring points are shown in Figures 8 and 9. Displacement was measured using displacement transducers (DTs), and the DT arrangements in specimens are illustrated in Figure 10a. DA1 and DA2 were adsorbed on the outer surface of the outer tube by the magnetic base, and were used to measure the relative vertical displacement of the inner and outer tubes during the test; DB1 was used to measure the overall displacement of the lower end plate of the test machine; and DB2 was used to measure the vertical displacement of the upper bearing plate. Strain gauges were glued to the outer surface of the outer tube and inner surface of the inner tube. The positions and coordinates of the strain gauges for specimens are presented in Figure 10b. The positions of the strain gauges on the outer surface of the outer tube corresponded to the positions of the shear keys on the inner surface of the outer tube; four groups of strain gauges were symmetrically arranged on each shear key; each group of strain gauges included one longitudinal and one circumferential strain gauge, which were used to test the longitudinal and circumferential strain of the steel tube during the test loading process. The positions of the strain gauges on the inner surface of the inner tube corresponded to the positions of the shear keys on the outer surface of the inner tube; two groups of strain gauges were symmetrically arranged on each shear key; each group of strain gauges included one longitudinal strain gauge, which was used to test the longitudinal strain of the inner tube during the test loading. In order to protect the strain gauges glued to the inner surface of the inner tube from damage during grouting and curing, their surface was coated with epoxy resin. Figure 7: Relationship between radial stiffness factor (\(k\)) and \(D_{\rm p}/t_{\rm p},D_{\rm s}/t_{\rm s}\), \(E/E_{\rm g}\), and \(D_{\rm g}/t_{\rm g}\) ratios. Figure 8: Schematic diagram of specimen loading in grouted connection. Figure 9: Schematic diagram of test points arrangement of grouted connection. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**No.** & \(\mathbf{D_{\text{s}}}\) **(mm)** & \(\mathbf{t_{\text{s}}}\) **(mm)** & \(\mathbf{D_{\text{p}}}\) **(mm)** & \(\mathbf{t_{\text{p}}}\) **(mm)** & \(\mathbf{L_{\text{g}}}\) **(mm)** & \(\mathbf{h}\) **(mm)** & \(\mathbf{W}\) **(mm)** & \(\mathbf{s}\) **(mm)** \\ \hline GC-N2 & 600 & 12 & 480 & 12 & 350 & 5 & 10 & 75 \\ GC-S75 & 600 & 12 & 480 & 12 & 500 & 5 & 10 & 75 \\ GC-S50 & 600 & 12 & 480 & 12 & 400 & 5 & 10 & 50 \\ GC-S100 & 600 & 12 & 480 & 12 & 600 & 5 & 10 & 100 \\ GC-H2.5 & 600 & 12 & 480 & 12 & 500 & 2.5 & 5 & 75 \\ GC-T38 & 580 & 12 & 480 & 12 & 500 & 5 & 10 & 75 \\ GC-T63 & 630 & 12 & 480 & 12 & 500 & 5 & 10 & 75 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Dimensions of test specimens.