Improved formulation for compressive fatigue strength of concrete

This is the author accepted manuscript. The final version is available from CRC Press via https://doi.org/10.1201/b18972-139Cracks are inherent in reinforced concrete structures. The origin of cracks can be manifold. At early stages they can be caused by plastic settlement, shrinkage, drying shrinkage, etc. Typically, the most severe forms of cracking in reinforced concrete structures are those caused by the corrosion of the reinforcing bars. Corrosion products are expansive in nature and tend to generate tensile stresses in the concrete surrounding the corroding bars. As soon as these stresses exceed the tensile capacity of the concrete, cracks around and along the reinforcing bars are formed. In assessing existing structures engineers often notice severe cracking due to corrosion or longitudinal cracks due to plastic shrinkage e.g. in the anchorage zones. The section loss of these bars can easily be taken into consideration when performing load bearing capacity checks, but questions arise with respect to the remaining bond capacity of the rebars in the cracked concrete. This study aims to quantify the influence of different parameters on the bond strength of reinforcing bars in cracked concrete. Rather than performing accelerated corrosion tests, it focuses on the effect of cracking itself (in absence of corrosion products) so the results can be used for non-corrosion related cases as well. Parameters under investigation include the confinement, concrete cover, crack direction and crack extension. Results show that single cracks as narrow as 0.03 mm can have a significant influence on the obtained bond strengths.The authors would like to gratefully acknowledge the financial support of the UK Engineering and Physical Sciences Research Council (EPSRC) through the EPSRC Project ‘Reinforced concrete half-joint structures: Structural integrity implications of reinforcement detailing and deterioration’ [Grant no. EP/K016148/1]