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Project 2012-01

Project Title:

Re-Assessment of Bend Diameters for Reinforcing Bars


North Carolina State University
Raleigh, North Carolina


Dr. Rudolf Seracino
Natasha Boger

Award Period:

2012-2013 school year




The objective of this research program is to re-assess the minimum allowable bend diameters currently specified in Section 7.2 of ACI 318-11. Consideration will be given to bending without breakage based on the bend test requirements (Table 3 in ASTM A615, ASTM A706 and ASTM A1035), the avoidance of concrete crushing inside the bend, and the avoidance of premature fracture due to loss of ductility near the bend. The experimental program will include all available bars sizes selected from several producers for bar types ASTM A615 Grades 60, 75 and 80; ASTM A706 Grades 60 and 80; and ASTM A1035 Grades 100 and 120 to allow for the effect of variable tensile stress-strain behavior (namely, yield stress and fracture capacity) with grade. The effect of bend diameter on concrete crushing inside the bend will be evaluated using hook pull-out test specimens. The outcomes of this research program will ensure that minimum bend diameters currently specified provide adequate margin against undesirable performance or failure across all bar sizes and all grades of steel.

The outcomes of this research program will form the basis of a Master of Science in Civil Engineering research thesis from which at least one refereed technical paper will be published, including a CRSI Research Report and Technical Note. This will provide the peer reviewed evidence necessary to facilitate any possible changes or recommendations in documents including ACI 318 Building Code Requirements for Structural Concrete, and AASHTO Load and Resistance Factor Design Bridge Design Specifications.