Effects of winding and straightening of medium and large diameter reinforcing bars manufactured in coils in their mechanical properties
Keywords:Coiled rebars, ductility, residual stresses, mixed-hardening
Reinforcing bars produced in coils offer important logistic and environmental advantages, for this reason there is a tendency to produce them in medium and larger diameters. Fabrication introduces complex load and temperature histories producing residual stresses. This paper presents an experimental and theoretical study of the incidence in the mechanical properties of reinforcing bars manufactured in coils, mainly in terms of ductility. Experimentation included phases of characterization of the core and crown regions of the bar, and comparison of straight bars and identical rolled bars straightened in laboratory conditions. Numerical study is based in a mixed-hardening constitutive model and allows considering the actual geometry of the bar as well as the high temperatures involved. The model identifies the origin and distribution of residual stresses and the main effects in the mechanical properties of the bars. Finally, recommendations are given regarding coil radius in order to control bar ductility.
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