When The Bridge Has A 10 Ton Limit.............

Horizon170 wrote:
Non related question.
When a sign says 10 ton limit, does that mean no vehicle over ten tons or the combined weight of all vehicles on bridge may not exceed ten tons?
I think the latter.

It is a good question. I've been involved in the design of more than 25 bridges in my professional career.

The answer is, . . . . it depends. It depends on the mode of failure which can change as the bridge ages. For suspension bridges there are multiple modes of failure. You can have a failure of the main span where the whole main span collapses, or, you can have smaller but equally problematic failures like punching through the bridge deck because of an overloaded axle/wheel. You can also have a failure of the approach structure. There are others too.

Suffice to say that you can cause a failure because of excessive combined weight or because of excessive point (axle/wheel) loads. Best bet, if the sign says 10 tons, the combined weight of your vehicle should not exceed the limit sign. As you can see from the video, going significantly over the limit doesn't always cause a failure, but it doesn't help. Abuse over time adds up.

Chum lee