The current dissertation aims to introduce a new interaction model between concrete and reinforcement to effectively address the inner mechanism of Reinforced Concrete (RC) structures. For investigating the concrete-reinforcement interaction, traditional methods have typically dealt with a constant bonding relationship or a perfect interaction between two materials. This can further lead to numerous models that lack consistency and compatibility with one another. However, current research advocates for implementing the stress transfer methodology, which suggests the presence of force exchange between the reinforcement bars and the surrounding concrete, in other words, the bond stress. The present study develops a new model that establishes the ascending part of a bond–slip model. It is an essential step towards a constitutive bond–slip model in future, which will be able to accurately predict the serviceability performance of RC members, such as deflection, crack spacing/width etc. The first chapter reviews the mechanism of the reinforcement–concrete interface under the tensile load. Multiple approaches have been discussed to investigate the serviceability performance of RC structures. A major part of this chapter is dedicated to reviewing the existing bond stress and bond–slip models with their respective backgrounds. The last part of the chapter reviews various strain monitoring tools and techniques to extract strains from the core of the reinforcement bars encased within the concrete. The second chapter represents three experimental campaigns which consist of double pull-out tests of 14 short RC ties equipped with three distinct bar diameters (16.20 and 25 mm). The results of the mentioned tests, in terms of reinforcement strain distribution along the specimen lengths, have been displayed. A mathematical algorithm programmed in MatLab has been introduced, capable of deriving bond–slip relationships from the experimental strain output. Lastly, the obtained bond–slip relationships of all 14 specimens have been portrayed at multiple load levels. The third chapter demonstrates the formation of a novel bond–slip model based on the experimental dataset. In the latter part, the newly proposed model has been validated with the experimental results of 14 (in-sample) specimens and eight independent (out-of-sample) specimens. Furthermore, a novel validation tool has been demonstrated, which is capable of predicting reinforcement strains from a given bond–slip model. Based on the tool, another layer of validation has been performed with independent data through reinforcement strain distribution. The chapter ends with a thorough statistical analysis for assessing the existing bond–slip models in terms of their strain prediction capability.