How do they KNOW the WEIGHT LIMIT of a BRIDGE?

Question

Do they make a first bridge and keep on driving heavier and heavier trucks over it until it collapses and then record the weight of the last truck and then post that weight at the entrance of another newly constructed bridge?

Answer 1

Nice Calvin and Hobbes ref!!!

Truth is they can calculate the breaking force given the construction materials and the construction layout of the bridge. Then, after taking away a safety factor, they can find the maximum tolerance of the bridge.

Answer 2

A bridge must be over-designed to support a load limit. This provides a factor of safety. Engineers (often civil engineers) produce stress diagrams for the entire bridge including all members and joints. This reveals the weakest link (which must still be acceptable). The bridge must be rated for static and dynamic loads since the force on the bridge may be greater than the weight of a vehicle as the span takes up the load. Also, the bridge may have to support several vehicles in addition to the limiting truck weight at the same time (two-way traffic?). Of course any bridge failures, especially from aging, are carefully analyzed and a history for bridge types is reflected in new designs and revised load limits.

Answer 3

They put objects on it to see the maximum capacity it can hold or they do tests to the wood and stuff and guess the limit then say a weight under that to be safe.

Answer 4

no, there are mathematical and engeneering formulas which will tell you the forces needed to make a certain structure fail.

it is a combination of concrete strength, architectural strength due to shape, material properties, and frame strength. all of which are determined before any construction can begin.

Answer 5

Math. Engineers can calculate it. The stress, material, angles,....

kathy..d above. Are you crazy ? There is no guessing involved when it comes to bridges.