Which components are part of NBIS substructure?

• A. Deck, wearing surface, and joints.
• B. Piers, abutments, and foundations.
• C. Girders and trusses.
• D. Parapets and rails.

Answer: (B)

Substructure elements are the parts of the bridge that carry loads from the deck down to the foundations. In NBIS terms, the components that fit this role are piers, which transfer loads down through the structure; abutments, which support the ends of the span and resist horizontal and vertical forces; and foundations, which anchor the entire structure to the ground. The deck, wearing surface, and joints belong to the deck system above the substructure, while girders and trusses are part of the superstructure that spans between substructure supports. Parapets and rails are edge safety features, not substructure. So the piers, abutments, and foundations are the NBIS substructure components.