# Analytical Method and Analysis of Cold-Joint Interface
## 4 Validation of Analytical Method
The relative displacement values were chosen to be small enough to be automatically adjusted while performing a non-linear analysis and, at the same time, realistic. Clamping stress was determined according to Eurocode 2 [39]. All the physical parameters for three numerical models are presented in Tables 1 and 2. Figure 6: Coulomb friction model [36]. Figure 7: Concrete layer bonding stress curve for specimen S-C65L30-6D8-Ba. The interface of an experimental specimen (Figure 8) behaved plastically up to the highest shear resistance. This implies that the highest shear resistance was reached with the help of interface friction and connectors, as the interface began to crack early. The experimental analysis curve reached a maximum shear stress value of \(\tau=3.55\) MPa at a shear slip of \(s=0.59\) mm. Then, the shear stress slightly decreased and the push-off test was stopped at a shear stress value of \(\tau=3.46\) MPa, which corresponded to a slip of \(s=4.3\) mm. The analytical curve displays a different behaviour. However, the highest shear stress values were similar. The highest shear stress for the analytical curve was \(\tau=3.50\) MPa, which was \(1.4\%\) lower than that of the experimental curve. In addition, the corresponding slip was determined to be \(s=0.29\) MPa, which was lower than the experimental slip by \(103\%\). After the highest interface shear capacity, the analytical curve displayed a decrease in shear stress to \(\tau=2.62\) MPa, which meant that cohesive stress was lost and interface shear resistance consisted only of friction and the connectors' resistance. From this point, shear stress gradually decreased. By comparing the experimental and experimental results, the shear stress values were \(\tau=3.46\) MPa, which corresponded to a slip of \(s=4.3\) mm. The analytical curve displays a different behaviour. However, the highest shear stress values were similar. The highest shear stress values were similar. analytical curves, their shear stress and slippage values, it can be stated that the proposed analytical method was able to predict a similar shear interface behaviour, especially for the highest interface shear capacity. However, the values at the stage of friction and connectors' action should be much closer to the experimental values. By analysing this case and by taking into account the results presented in Figures 9 and 10, it can be stated that the proposed analytical model should be improved to predict the cases more accurately when weaker concrete and smaller interface connector ratios are used. The numerical analysis curve was similar to the experimental curve by its shape. Nonetheless, the determined shear stress values were smaller. The loss of cohesion was visible at a shear stress of \(\tau=1.63\) MPa and slip of \(s=0.08\) mm. After this point, it was assumed that concrete-to-concrete (cohesion) bonding should be neglected and that the shear resistance of the interface was mainly achieved by the interface's friction and connectors' resistance. The numerical analysis curve reached the highest shear value of \(\tau=2.28\) MPa, which was \(56\%\) lower than the experimental value. This shear stress was determined at a slippage of \(s=0.37\) mm, which was \(59\%\) lower than the experimental slip. In the case of specimen S-C65L40-6D10-Ba (Figure 9), the experimental curve displayed a very similar shape and values to the analytical one. From the start of the push-off test to the highest interface shear capacity, the experimental data indicated a plastic interface behaviour. The highest shear stress was \(\tau=5.53\) MPa, which was reached at a slip of \(s=0.58\) mm. The corresponding analytical values were \(\tau=5.43\) MPa and \(s=0.53\) mm. The differences between the experimental and analytically determined values were \(2\%\) for shear stress and \(9\%\) for shear slip. It can be considered that the values were significantly similar, bearing in mind how unpredictable shear interface behaviour can be. From the highest shear point, both curves displayed a decrease in shear stress.