This is a fairly interesting piece of design we encountered. The owner of a home near Carnation has a 50 foot long bridge crossing a stream as a part of the driveway leading to his house. It’s a private bridge, not owned by the state, and as such, has not been inspected or maintained in some time. During that time, like much else, fire trucks have become bigger and heavier. Recently the local fire department noticed the bridge, and asked the owner for documents showing that the bridge will safely support a modern fire truck, which means the structure is good for a standard HS-20 truck loading. Otherwise, if this fellow’s house caught fire, the truck would not be able to cross the bridge.
So they called us. We sent an engineer to the site to measure the bridge and to sketch details of how it is constructed. Based on this information, we made calculations that showed the bridge required both some maintenance (lots of rust, undermined bridge abutments, etc.) and some upgrades to the main steel supporting beams.