What characteristic defines secondary members in a bridge structure?

Secondary members in a bridge structure are defined by their role in assisting with load distribution. These members do not carry the primary loads of the structure but instead support the main components by helping to distribute the loads evenly across the primary members. This function is crucial for maintaining the overall stability and integrity of the bridge, as it ensures that no single member is overloaded and that the loads are managed effectively throughout the structure.

Primary members are the ones that handle the main forces and loads directly, such as beams and girders that bear the traffic load. In contrast, secondary members, such as cross-bracing or secondary beams, play a supportive role that is essential for the structural effectiveness of the bridge without being the primary contributors to overall load-bearing capacity. Therefore, they are vital in maintaining the bridge's performance and safety while enhancing the efficiency of the load distribution process.