Which loading category is primarily associated with vehicles on a bridge?

• A. Secondary Live Load
• B. Ice Pressure
• C. Primary Live Load
• D. Dead Load

Answer: (C)

When analyzing bridge loads, we separate permanent weight from variable, or moving, loads. Vehicles on a bridge create a variable load because their presence changes over time as traffic moves, so they fall under live loads.

Within live loads, the term primary live load refers to the main vehicle traffic that drives the design—think of the standard design vehicle or trucks that determine the bridge’s strength and capacity. The secondary live load covers other, less dominant moving loads (like pedestrians, maintenance equipment, or occasional non-vehicular loads), which are considered after the primary vehicular demand. Ice pressure and the dead load (the bridge’s own weight) are separate categories, not primarily about vehicle traffic.

So, the loading category most associated with vehicles on a bridge is the primary live load.