Constraint Induced Fracture refers to which phenomenon?

• A. Weld failure under bending
• B. Corrosion-induced fracture
• C. Fracture of locally constrained steel under tension
• D. Impact fracture of brittle material

Answer: (C)

Constraint-induced fracture happens when a region of steel is locally restrained from deforming as freely as the surrounding material under a tensile load. That restraint raises the triaxial stress state at the crack tip and limits plastic deformation, so the material cannot blunt or redistribute stress effectively. As a result, fracture can initiate and propagate in these locally constrained areas even under relatively modest tension. This is why the phenomenon is described as the fracture of locally constrained steel under tension.

In bridges, you’ll see this where stiff connections or weld toes constrain the steel, creating high local stresses that promote cracking. The other options point to different failure modes: weld failure under bending involves bending stresses and weld quality; corrosion-induced fracture comes from environmental attack; and impact fracture of brittle material reflects dynamic, brittle failure rather than constraint effects.