Low weight bridges

JW of Opechee Shores wrote:
Having gone to college for civil engineering I can tell you that bridges are designed with a safety factor depending on span. Design will consider how much weight could be on a span should traffic come to a stop in both directions on the span with vehicles at max load. This would be the max dead load and if traffic is m0ving then that is a live load which has less impact. A 5 ton bridge limit should support a minimum of 10 ton plus safety factor.

Having a similar engineering degree and after designing bridges for 15 years I can say that you are correct if you are talking about H-20 loading for major bridges. Short span narrow bridges (which I think the OP is talking about here) that are rated at 5 tons (max.) are not generally covered under H-20 loading where a single axle truck load would be as much as 18,000 lbs. per axle and as much as 80,000 lbs. per vehicle. (well over the 5 ton limit) Most likely the load limit sign is referring to individual vehicles. (total weight) I'm sure there is a safety factor but speaking from experience on old county bridges, they aren't regularly inspected, especially if they are in low traffic areas on or adjacent to private property. That said, it's the OP's rig. Think about where it will be if the bridge doesn't hold. Also, think about anyone else who may rely on using that bridge and how it might affect them if it becomes impassable.

Chum lee