If you look carefully at the point where the pillars of a bridge bear the structure's enormous weight, you will often find a small cylinder. This astonishing feature is known as a "bridge bearing." The purpose of the bearing is to take the weight while giving the entire structure maximum flexibility.
Bridge bearings transfer loads and movements from the deck of the bridge down to the substructure and foundations. They make it possible for the structure to withstand the vibrations of traffic and the expansion and contraction caused by temperature variations. It is also thanks to these bearings that bridges are able to withstand severe winds, tremors and earthquakes.
The bearings are designed to redirect the forces that move over, through and around the structure. Engineers study the "downward forces" that pass through the center of the bearing, the " transverse forces" that move horizontally through the bridge or alongside it, the "uplift forces" that enter the structure from the earth and "rotational forces" that can twist in any direction.
Our feet have a natural bridge-like structure, arching between the ball and heel. They, too, have the capacity to absorb and redirect forces moving in all directions. Training to use the "red triangle" (pages 84-85) takes advantage of this natural structure and greatly increases your ability to react to and redirect forces all around you.
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