Which concept is used to investigate the position of vehicular live load, explaining why the design lane width is greater than the truck width?

• A. Lever rule
• B. Live load distribution factor
• C. Multiple presence of live load
• D. Wind load

Answer: (C)

The idea being tested is that vehicular live loads are not confined to a single line or a single vehicle position. In reality, vehicles can be located anywhere within the lane width and more than one vehicle can occupy the vicinity of a critical section at the same time. This is captured by the concept of multiple presence of live load, which acknowledges that several loads may be acting together and in different lateral positions on the deck.

Because loads can occur at various lateral locations and can overlap in time, the structural analysis uses a wider effective width to represent the range of possible loading configurations. That broader width ensures the design accommodates the worst-case distribution of live loads, so the deck and its supporting elements remain safe across real-world traffic conditions.

The other ideas are not addressing this specific variability: lever rule is just a basic statics principle about moments, wind load deals with atmospheric forces, and while a live load distribution factor helps allocate load to different girders, it doesn’t by itself explain why the load spread across the lane width should be widened to reflect multiple simultaneous loads.