# Analytical Method and Analysis of Cold-Joint Interface
## 4 Validation of Analytical Method
The experimental stress stopped when slip \(s=4\) mm was reached. At this point, the experimentally determined shear stress value was \(\tau=4.15\) MPa. At slip \(s=4\) mm, the analytical curve displayed a shear stress value of approximately \(\tau=4.5\) MPa. The difference between the two shear stresses was \(8\%\). As explained earlier, the analytical model seemed to depict a better correspondence when a higher interface concrete strength and connector ratio were used. The numerical curve portrays a similar behaviour from the start of the loading to the point of complete cohesion loss to the specimen in Figure 8. This time, the loss of cohesion was visible at a shear stress of \(\tau=2.21\) MPa and slip of \(s=0.12\) mm. After the previous point, the shear stress reached a value of \(\tau=4.36\) MPa, which was achieved at slip \(s=0.49\) mm. The value of shear stress was lower than the experimental value by \(27\%\). At the same time, the disparity of slip values was lower, with a difference of \(18\%\). In the case of the numerical analysis of S-C65L40-6D10-Ba, this shear stress point was not the highest shear stress that was acquired at the interface, because, after this point, the shear stress-slip curve decreased to a value of \(\tau=4.05\) MPa and then increased to a shear stress pf \(\tau=4.58\) MPa. The increase in shear stress is the result of the larger involvement of interface connectors in interface shear transfer. The diagrams for specimen S-C65L50-6D12-Ba (Figure 10) showed a considerable similarity between the analytical and experimental curves. This time, a more rigid experimental interface behaviour from the start of the loading to the highest shear resistance could be noticed. The reason for this might be the higher concrete strength used. The maximum shear stress for the experimental specimen was \(\tau=7.14\) MPa and \(\tau=7.45\) MPa for the analytical curve. The difference between these values was \(4\%\). The slippage values at this point were \(s=0.85\) mm for the experimental curve and \(s=0.62\) mm for the analytical curve. The difference between these values was \(37\%\). After the highest interface shear resistance, the stress values began to decrease. The experimental test was ended at slip \(s=4.18\) mm. The corresponding shear stress value was \(\tau=5.1\) MPa. At this point, the shear stress for the analytical curve appeared to be identical. After analysing the figures (Figures 8-10) in which experimental and analytical interface shear stress-slippage relationships are compared, it can be concluded that the proposed analytical method is suitable for predicting the behaviour of an interface subjected to shear. By analysing the numerical analysis curve, it can be noticed that the shape of the curve was similar to a curve in Figure 9; however, the values of interface shear stress were naturally higher. Just like in the curve in Figure 9, the highest shear stress value was not reached when the interface cracked. After the formation of a crack, a point is reached at which the shear stress value of \(\tau=5.84\) MPa was acquired, which was 22% lower than the experimental value. The slip corresponding to the stress was \(s=0.59\) mm, which was 44% lower than the experimentally determined value. After the point of \(\tau=5.84\) MPa, the shear stress slightly decreased and started to increase until the end of the test due to the connectors becoming tense. After three comparisons (Figures 8-10) between the experimental values and the values determined by numerical analysis, it can be stated that the finite element analysis is an appropriate tool for the analysis of shear interface behaviour. However, the performance of an interface (from the start of the loading to the point of interface connectors failure) is an intricate problem and the models which are used today should be improved to predict the interface behaviour more accurately.