The NBIS rating of substructure evaluates the condition of which components?

• A. Piers, abutments, foundations.
• B. Deck, girders, and bearings.
• C. Roadway approach and guardrails.
• D. Traffic signals.

Answer: (A)

Substructure refers to the parts of a bridge that are below the deck and carry loads into the ground. The NBIS rating for the substructure focuses on how well these below-deck elements are performing. The components in this category are piers, abutments, and foundations. Piers support the loads between spans, abutments sit at the ends to transfer loads to the ground and retain adjacent soil, and foundations anchor the structure to the soil and resist movement and scour. When inspecting, you’d look for signs like cracking, spalling, exposed reinforcing, settlement, or scour around the foundations, or misalignment or movement at piers or abutments. The deck, girders, and bearings are part of the superstructure, not the substructure, and roadway approaches, guardrails, or traffic signals aren’t substructure components.