What is the primary purpose of redundancy in bridge design?

• A. Providing alternate load paths so a single member failure does not precipitate collapse
• B. Increasing dead load
• C. Enhancing aesthetics
• D. Maximizing material cost

Answer: (A)

Redundancy in bridge design means building in extra capacity so loads can be redistributed if part of the structure is damaged. The goal is to ensure that a single member failure does not lead to collapse by providing alternate load paths for the forces the bridge carries. This safety net keeps the overall structure standing even when one component is compromised, which is crucial for withstanding unexpected damage, deterioration, or extreme events. For example, multiple girders and cross-bracing allow other members to take on additional load if one element fails, mitigating the risk of progressive collapse.

Increasing dead load would simply add weight without enhancing safety. Enhancing aesthetics has no direct effect on how forces are carried, and maximizing material cost runs counter to practical design goals.