## 3 Results and Discussion
### Model Results, Comparison and Discussion
#### 3.5.2 Numerical Modelling Results and Analysis  
The overall response of the numerical model was consistent with the expected and observed behaviour of laboratory specimens. Specifically, it was observed that as the rebar is pulled axially, the bar elongates and slightly contracts. This displacement reduces as the distance from the loading position increased. This is because the ribs transfer the load to the grout and causes a slight dilation. This behaviour was congruent with their material properties and their interaction mechanics. It was also noted that the shorter models deformed more than the longer embedment length ones did. This was also seen in the laboratory specimens [9]. It was found that the RS2 models created by our group for the longer length specimen such as 500 mm and longer were found to be over-predictive and did not match the general trends observed in physical testing. Despite a shift in strain attenuation pattern between the short and longer lengths not being observed in the RS2 model, it was successfully seen in the ANASYS contact model. During the first stage of the model, results were very close to physical testing. For the 100 mm and the 500 mm, the model performed very well, with the largest difference being \(\sim\)15% (taken visually as original data were not available). However, generally the results were much closer. Although the 250 mm did display the correct pattern, it was over-predictive on the attenuation rate showing much greater strain departure when compared to the other models. This iteration of the model for the 750 mm standard rebar and altered bar (Stage 2.1 and Stage 3.1) did not perform as well as the smaller models (Stage 1 series models) and there was a greater difference between model and laboratory strain results. However, the global strain attenuation pattern matched much better when compared with the collected laboratory results, which can be seen below in Figure 16. The results are most similar to the specimen 750 CP and can produce very close results for 10 kN and to some  
Figure 15: Example of analytical models [11; 16] versus collected data for specimen B-1-ii.  
extent 50 kN when the front is manually debonded. The possibilities of the differences could exist within the limitation of the model but also analysis of the strain data, there could be debonding of the section in this specimen as there is the appearance of a near-zero slope front section, which if present would lead to higher strain values along the embedment length. These initial findings suggest that a ANASYS provides a closer representation than the model using RS2. Additionally, further parametric analysis, calibration, and proper grout representation could be conducted to further improve the model ability to match the laboratory data.  
It was seen that the model responded similarly to the physical results when rib spacing was increased. Increased rib spacing resulted in greater variance along the profile and a decrease in strain attenuation. The comparison between both 750 mm models (Models 2.1, 3.1) at 10 and 50 kN can be seen in Figure 17. The model also showed a greater level of dilation, which was in agreement with the literature but was not observed in this laboratory investigation. In summary, it appears that this methodology shows promise to not only capture the general response of the system but also capture the effects of parametric changes without fitting.