Which component forms the boundary between the bridge’s superstructure and substructure?

• A. Deck
• B. Girders
• C. Substructure
• D. Bearings

Answer: (D)

Bearings form the boundary between the bridge’s superstructure and substructure. They sit between the deck/girders (the superstructure) and the piers or abutments and foundations (the substructure), transferring loads while allowing essential movement. This interface accommodates thermal expansion, shrinkage, and other movements, preventing excessive stresses at the connection. The deck and girders are parts of the upper structure, while the substructure includes supports and foundations; the actual boundary where loads are passed and movement is accommodated is the bearing system.