Which limit state provides a set of material toughness requirements based on the AASHTO Materials Specifications?

• A. Fatigue limit state
• B. Fracture limit state
• C. Fatigue I
• D. Fatigue II

Answer: (B)

Material toughness is about a material’s ability to resist crack initiation and unstable fracture, especially when flaws are present or temperatures are low. The fracture limit state is the one that explicitly requires those toughness properties to be specified and met, so that the structure won’t fail catastrophically if a crack exists or develops. In AASHTO Materials Specifications, toughness requirements are provided to guarantee this fracture behavior, often through minimum fracture toughness measures or related criteria for materials and welds. Fatigue limit states, by contrast, address how long a member can endure repeated loading and crack growth under cyclic stresses, not the inherent toughness against fracture, so they’re not describing the toughness requirements referenced by AASHTO.