The loading also known as the alternate military loading governs design of spans shorter than 40 ft. This loading is referred to as which term?

• A. Design Lane Load
• B. Live load distribution factor
• C. Wind load
• D. Tandem load

Answer: (D)

Short-span bridge design uses a special live-load pattern to capture the effect of a heavy vehicle with its axles aligned in a line, which can produce a concentrated bending effect on a small span. This pattern, used historically as an alternate military loading for spans under 40 ft, is known as the tandem load. It specifically describes two axles in tandem loading the girders, which is why it’s the best fit. The other terms refer to different load concepts: Design Lane Load is a lane-based live load, the live load distribution factor relates to how loads are shared among girders, and wind load is a separate lateral force.