Why do radially prefabricated bars tend to relax the radius originally prefabricated?

Why do radially prefabricated bars tend to relax the radius originally prefabricated?

• A. Time and normal handling
• B. Temperature changes
• C. Vibration during transport
• D. Concrete curing pressure

Answer: (A)

Radially prefabricated bars are bent to a specific radius, leaving residual bending stresses in the steel. Over time, those stresses gradually dissipate at normal temperatures, and the metal fibers can rearrange just enough to relieve the bend. This stress relaxation, helped along by routine handling and movement of the bars, lets the curved section straighten a bit, increasing the bend radius from the originally prefabricated value. Temperature changes could influence metal slightly, but at typical ambient conditions their effect on this long-term relaxation is small. Vibration during transport or pressure from concrete curing aren’t the primary drivers of this gradual geometrical change; time and normal handling are.

Radially prefabricated bars are bent to a specific radius, leaving residual bending stresses in the steel. Over time, those stresses gradually dissipate at normal temperatures, and the metal fibers can rearrange just enough to relieve the bend. This stress relaxation, helped along by routine handling and movement of the bars, lets the curved section straighten a bit, increasing the bend radius from the originally prefabricated value. Temperature changes could influence metal slightly, but at typical ambient conditions their effect on this long-term relaxation is small. Vibration during transport or pressure from concrete curing aren’t the primary drivers of this gradual geometrical change; time and normal handling are.