Bond of steel reinforcement based on detailed measurements: Results and interpretations

Abstract

Rebar-to-concrete bond is a fundamental aspect of the behavior of reinforced concrete structures. The characterization of the interface response is challenging due to the complexity of the physical phenomena and the large number of factors involved. Locally, the response is characterized by the bond–slip relationship, which is typically obtained experimentally from pull-out tests with short bonded lengths. The behavior of longer anchorages in structural members differs significantly from short tests as the bond stress distribution is not uniform. In this context, this paper presents the results of a comprehensive research aiming to establish a better relationship between the local bond–slip response from short pull-out tests and the response of medium-length anchorages. The results of an experimental program are presented, including the effect of some parameters commonly found in structural applications, such as casting conditions, clear cover, rib geometry, and rib orientation. A local bond–slip relationship for well-confined conditions is proposed on the basis of the tests performed by the authors and on the examination of a database on short pull-out tests from the literature. Based on this relationship and some mechanical considerations, the local bond–slip relationship for unconfined conditions can satisfactorily be formulated based on crack-width measurements from the concrete surface. This can be useful for the assessment of existing structures and can be seen as a step forward in the development of a consistent mechanical model for bond.