## 2 Experimental Investigations
### Test Results
This effect can be identified by comparing series IORC-4 with IMR-22 or IORC-5 with IMR-17 in Table 2. The two pairs consist of test specimens with identical load direction and dowel reinforcement eccentricity. In both cases the concrete's condition is varied, which was undamaged in case of IORC-x, and damaged by means of approx. 0.5 mm wide cracks in case of IMR-x (Table 2). While all specimens failed due to the steel dowel being pulled out of the concrete, the mean load-bearing capacity was lower in the cracked concrete. Additionally, IMR-20 was the only test series with a load direction of 22.5\({}^{\circ}\) in which pull-out failure occurred (Figure 8, IMR-20.2). This indicates that the anchoring effect of the steel dowels was sufficient in case of IOR-2 (22.5\({}^{\circ}\); undamaged concrete, \(e_{r}\) = 16 mm) but not in case of IMR-20 (22.5\({}^{\circ}\), \(w_{r}\) = 0.5 mm, \(e_{r}\) = 16 mm). The tensile force leading to the transverse cracks in the concrete reduced the anchoring capability of the steel dowel in the concrete and led to pull-out failure at lower load levels. Figure 9 includes an overview of all results. Diagram (a) contains only specimens in uncracked concrete with varying concrete dowel reinforcement eccentricity \(e_{r}\) between 0 and 16 mm. As long as the unfavourable pull-out failure is avoided and pry-out failure occurs, the maximum force reached lied within the range defined by the shear and tensile load-bearing capacity. Pry-out failure can be assumed to be the decisive failure mode regardless of the load direction as long as the reinforcement bar in the concrete dowel remains within the steel dowels' recess as demonstrated in diagram (a), \(e_{r}\) = 0 mm. This favourable position of the reinforcement bars is presented in the lower part of Figure 9, red. If the reinforcement bars in the concrete dowel are positioned outside the steel dowel's recess, pull-out failure becomes decisive as soon as a significant tensile force is applied  
Figure 8: Overview of the failure modes (IMR-x, cracked concrete). (load direction \(\geq\) 22.5\({}^{\circ}\)) and occurs at a constant tensile force plateau as demonstrated in Figure 9, diagram a). The load-bearing capacity of the dowels in case of pull-out failure is approx. 46 kN. For shear-tension interaction and concrete dowel reinforcement positioned outside the steel dowel's recess, pull-out occurs as soon as the force's tensile component reaches this upper limit. The interaction of the tensile and shear forces can be considered using Equation (1). Here, the combined acting shear and tensile loads (\(P_{S}\) and \(P_{T}\)) are related to their associated ultimate load-bearing capacities in case of concrete pry-out failure (\(P_{S,R}\) and \(P_{T,R}\)). The load-bearing capacity, both for tensile and shear loading, shall be calculated by means of valid regulations, currently [17]. The form of the interaction's relationship can be specified  
Figure 9: Results overview and design approach: (**a**) influence of reinforcement eccentricity \(e_{r}\) and (**b**) of the concrete’s condition on the shear-tensile interaction; (**c**) linear shear-tensile-interaction curve in case of reinforcement eccentricity \(e_{r}\) = 8 mm; (**d**) influence of crack width on load bearing capacity. by the exponent \(k\). In previous research, limits 1 and 2 have been proposed for the choice of \(k\), while the exact value should be calculated in dependence on the position and amount of the concrete dowel's reinforcement. According to the findings presented here, since the exact position of the reinforcement bars is difficult to set on the construction site a simpler approach is suggested.