Ductility in structural steel is defined as which property?

• A. Ductility is the ability to undergo large plastic deformations before failure; essential for energy dissipation and warning before collapse in earthquakes.
• B. Ductility is the ability to resist brittle fracture at low temperatures.
• C. Ductility is the stiffness of a steel member.
• D. Ductility is the capacity to carry higher loads without deformation.

Answer: (B)

Ductility is about how much a material can plastically deform before it fails. Steel that is ductile can stretch and deform a lot under load, absorbing energy and giving warning signs (like visible yielding and large deformations) before it ultimately fails. This capability is what helps structures withstand events like earthquakes, where dissipation of energy and the ability to deform rather than snap abruptly are crucial for safety.

The statement that describes this best is the one that emphasizes large plastic deformations before failure and the associated energy dissipation and warning before collapse. Other options mix up ductility with other properties: resisting brittle fracture at low temperatures relates more to toughness or notch toughness, not ductility; stiffness refers to an elastic response and rate of deformation under load rather than permanent deformation capacity; carrying higher loads without deformation speaks to strength, not the material’s ability to deform plastically.