Bridge Engineering Practice Test

In bridge design, different loading cases are used to capture how a structure reacts to traffic and other forces. For short spans, the alternate military loading represents the effect of a heavy two-axle vehicle arranged in tandem, which concentrates load in a way that often produces higher reactions and bending moments than standard traffic loads on those short spans. This is why it’s the governing loading for spans shorter than about 40 ft. The term tandem load describes the two axles carrying the vehicle’s weight in line, and the alternate military loading is simply another name for that same two-axle, tandem arrangement. The other options don’t capture this specific, concentrated, two-axle scenario: design lane load reflects typical highway traffic on longer spans, wind load is a lateral environmental load, and construction load is temporary during construction.