# Predicting Behavior of Grounded Dowel Connections Using Interfacial Cohesive Elements
## 1 Introduction and Background
Firstly, these models were one-dimensional and disregarded the radial and circumferential transfer of stresses, thus limiting their usefulness to the micro-scale of the connection. Secondly, they relied on phenomenological models developed with a unique specimen form. Due to the sensitivity of bond to several factors including the experimental form of the test set-up, analytical models derived thereof cannot be generalized. This is also reflected in the fact that most of the corroborative efforts of such models are confined to the experimental findings of their respective authors. Moreover, these efforts were not sufficiently detailed to allow for their extension and implementation into a generic 3D model that can be used to model full-scale structures. Modeling the bond--slip between a reinforcing bar and the surrounding concrete is of special importance in jointed regions, where the effects of slip and strain penetration can be detrimental to the rotational capacity of the joint. Several methodologies with varying degrees of complexity are currently available in the literature to model such bond-slip interactions [16; 17; 18; 19; 20; 21]. Some authors presented a  
Figure 1: (a) Typical grouted corrugated duct connection; (b) schematic diagram of grouted connections in precast walls (reused with permission [3]). fiber-section frame element model that takes into account slippage of the bar and subsequent bond degradations [16; 17]. [PERSON] and [PERSON] [18] used rotational springs to model the rotation of column joints due to slippage of bars in column splices and used the model to calculate the required lap splice length to sufficiently develop the bars. Others presented detailed non-linear 3D continuum models that explicitly modeled the geometry of the deformations and its bearing on the concrete keys [19; 20; 21]. The merit of such detailed models is that they can be used to conduct investigative studies on bond interactions between reinforcing bars and concrete, provided that adequate damage parameters are included in the model. However, considering their high computational cost, detailed non-linear 3D continuum models of complete reinforced concrete structures are deemed unpractical. In most recent efforts to model bond-slip, researchers resorted to interfacial elements that can be defined between the reinforcing bar and the concrete [22; 23; 24; 25; 26]. These interfacial elements have constitutive relationships through which the characteristics of the bond-slip relationship of the assembly can be implemented. Input to such interface models would be the bond-slip relationship represented in interfacial elements through equivalent stress vs. displacement of the bar in the longitudinal direction. In most recent efforts, several researchers proposed interfacial elements for use in a finite element (FE) platform. [PERSON] and [PERSON] [22] were amongst the earliest researchers who presented an element that utilizes an elastoplastic treatment for the bond stress-displacement relationship at the bar-concrete interface. This treatment modeled the effect of the normal stress on the bond stress via a yield function, while the shear dilatation caused by the bar ribs was accounted for using a non-associated flow rule. The validation of the model was carried out using a series of pull-out tests, which highlighted the accuracy and computational efficiency of the model [23]. A similar model was published by [PERSON] and [PERSON] [24], who proposed 3D interfacial elements with a different elastoplastic constitutive law to model the bond-slip behavior in FE simulations. The studies by [PERSON] et al. [25] and [PERSON] and [PERSON] [26] are different from those discussed above, in the sense that they utilized a phenomenological bond-slip law in their element formulations. Such phenomenological models were based on experimental observations, similar to that developed by [PERSON] et al.