A load-bearing member which distributes loads longitudinally and is principally designed to resist flexure.

• A. Secondary Member
• B. Tertiary Member
• C. Primary Member
• D. Main Span

Answer: (C)

The main idea is identifying the primary load-carrying member that transfers loads along the length of the structure and is designed to resist bending. This type of member spans between supports, carries the majority of the vertical loads (dead and live loads), and develops bending moments along its length. Its main function is to resist flexure, which is the bending due to those loads, so it must have high bending stiffness and strength.

Secondary members, by contrast, mainly provide support, bracing, or connection between the main load-carrying elements and do not carry the major bending along the span. Tertiary members are even less critical load-wise, often used for minor stiffening or detailing. The term main span describes a portion of the bridge, not a category of member. Therefore, the member described is the primary member.