When all groups are completed, set the bridges between 2 books. If using a force gage, show the girls how to read the gage, then press down in the center of the bridge and see how much force it can take. If using weights, see how much weight each bridge can hold before bending or breaking. Have the scouts discuss results. Bridges are structures used by people and vehicles to cross areas that are obstacles to travel.
Most bridges have a concrete, steel, or wood framework with an asphalt or concrete roadway.
Most bridges are held up by at least two supports set in the ground called abutments. Some bridges have additional supports along the middle of the bridge called piers. A span is the distance between two supports, either two piers, a pier and an abutment or two abutments. Most short bridges are supported only by the abutments and are called single-span bridges. Longer bridges usually have one or more piers to support them and are known as multi-span bridges.