Lap splice connection of new-to-existing rebars: a numerical study based on literature data

Bond between steel reinforcement and concrete is the basic and fundamental mechanism which assures load transfer between the two materials in reinforced concrete elements. Even though bond has been widely investigated during the last decades, the number of parameters involved in the mechanism, as well as the number of possible geometrical configurations of the final element, are such that both models for the local bond-slip law and for anchorages or lap splices still need further investigation. As evidence of this, design-oriented documents, such as the fib Model Code, are constantly updated. Significant modifications of the bond models and the methods for the calculation of the anchorage length are foreseen in the next generation of codes. The use of post-installed reinforcement offers a reliable solution for the connections in concrete structures, the strength and the stiffness being similar to traditional cast-in rebars. Many applications may be found in the rehabilitation and strengthening of existing structures. Nonetheless, post-installed rebars are becoming popular also in new constructions to make easier building and flexibility in design. Within this framework, structural designers often face the need of overlapping existing and new rebars, with a lack of design recommendations. This paper aims to investigate the load transfer of the new-to-existing lap splices. Numerical simulations were carried out with a commercial code, particularly an experiment from the literature was reviewed and numerically revaluated, also simulating the effects of different splice lengths, not counted in the original study. Inverse analysis was used to calibrate a local bond-slip law, which was the input for the following simulations. Failure mode and crack pattern are discussed showing that splitting is the dominant failure mode for short lap splices.