The+Arch+Bridge

**__ The Arch Bridge: __** An arach bridge is another type of bridge different from the beam bridge...The interesting thing about the arch bridge is that its one of the oldest types of bridges and has been used for over thousends of years, not only that but it has great natural strengh. They were originally built of stone or brick but these days are built of reinforced concrete or steel. The introduction of these new materials allow arch bridges to be longer with lower spans. Instead of pushing straight down, the load of an arch bridge is carried outward along the curve of the arch to the supports at each end. An arch bridge is a semicircular structure with abutments on each end. The design of the arch, the semicircle, naturally diverts the weight from the bridge deck to the abutments. Arch bridges are always under compression. The force of compression is pushed outward along the curve of the arch toward the abutments. The weight is transferred to the supports at either end. These supports, called the abutments, carry the load and keep the ends of the bridge from spreading out. **Example of the load results:** In this picture the load at the top of the key stone makes each stone on the arch of the bridge press on the one next to it. This happens until the push is applied to the end supports or //abutments,// which are enbedded in the ground.

The ground around the abutments is squeezed and pushes back on the abutments.

For every action there is an equal and opposite reaction.(We learned this in class :)) The ground which pushes back on the //abutments// creates a //resistance// which is passed from stone to stone, until it is eventually pushing on the key stone which is supporting the load.

**Pictures of arch Bridges or explain them:**

