Which bridges are statically indeterminate structures whose spans are continuous over three or more supports?

• A. Continuous Bridges
• B. Through Bridge
• C. Deck Bridges
• D. Cantilever Bridges

Answer: (A)

Continuity across multiple supports is what makes the structure statically indeterminate. When a bridge has spans that are connected and continuous over three or more supports, the internal moments and reactions cannot be found from equilibrium equations alone. The deflection and slope at interior supports must be compatible with the rest of the member, which introduces additional equations. In practice, this means each interior support adds a redundant condition, so the distribution of forces and moments depends on the stiffness of all connected spans and cannot be solved by simple static equilibrium. This is the hallmark of a continuous bridge: multiple spans sharing interior supports create redundancy that requires compatibility-based analysis (moment distribution, slope-deflection, or finite element methods) to determine the internal moments and reactions. The other bridge types describe geometry or support arrangements, not the inherent continuity across several spans that produces the indeterminacy.