On bond-slip response and development length of steel bars in pre-cracked concrete

• Published in: Construction & building materials Vol. 199; pp. 560 - 573
• Main Authors: Mousavi, Seyed Sina, Guizani, Lotfi, Ouellet-Plamondon, Claudiane M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 28.02.2019; Reed Business Information, Inc. (US)
• Subjects: Analysis; Bond model; Bond strength; Concrete cracking; Concretes; Development length; Mechanical properties; Pre-cracked concrete; Slip; Steel products; Canada; Pre-cracked concrete; Development length; Bond model; Slip
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2018.12.039

•A comprehensive study on bond properties of steel bar/pre-cracked concrete interface.•Pre-cracking phenomenon has considerable effect on local bond-slip curve.•An efficient local bond-slip envelope is introduced for steel bar in pre-cracked concrete.•Large crack widths (more than 0.15 mm) result in considerably lower energy dissipated by the bond mechanism.•A new predictive equation is proposed for development length in pre-cracked concrete. Previous research on steel bar-concrete bond behaviour has been concentrated mostly on the intact concrete without considering initial cracks induced by transverse tensile loading called pre-cracking phenomenon. There is no accurate model for evaluating bond behaviour and development length of steel bar in pre-cracked concrete. This paper aims to characterise the bond-slip behaviour of steel bars in pre-cracked concrete by direct pull-out tests, and proposes a constitutive law as a function of the crack width. Results show that induced cracks, notably cracks wider than 0.15 mm, cause a significant reduction in maximum and residual bond strength. Also, results indicate that larger crack widths result in considerably lower dissipated energy by the bond mechanism. The results obtained from both the experimental tests and referenced database demonstrate that the pre-cracking phenomenon has a higher impact on the residual bond strength compared to the maximum bond strength. Unlike existing equations, the proposed model accurately considers cracking effects on the steel bar-concrete bond properties and shows a satisfactory fit with the experimental database. A predictive equation is also proposed for calculation of the development length in pre-cracked concrete, which is more conservative and prudent compared to existing regulations in design codes.