In the purest sense of the word, a bridge is a structure built to span an obstacle. Most often, that obstacle is a body of water, a valley, roadway or railroad track. Its purpose is to provide safe passage over the barrier.
When you close your eyes and think of a bridge, you might picture an iconic arched
bridge or suspension bridge. But technically a fallen tree across a stream could be
considered a bridge. It’s possible that a fallen tree is what inspired engineers to create the modern structures we find across the globe.
It’s not just those iconic modern bridges that allow people to cross obstacles. The
world’s oldest bridge is located in Izmir Turkey, and it is still in use today. This bridge
crosses the river Meles, with its origins dating back to 850 BC.
The oldest bridge in the US, the Frankford Avenue Bridge in Philadelphia, was built in the 17th century and was known then as the King’s Highway Bridge. While the 600,000 bridges in North America were built more recently than the Frankford Avenue Bridge and came thousands of years after the bridge in Turkey, they have all seen better days.
Over 54,000 US bridges have been classified as structurally deficient. Given that people cross these structurally deficient bridges 174 million times each day, there is quite a bit of work that needs to be done to provide safe passage.
However, some of the most exciting and innovative bridges that stretch our imagination are not the oldest bridges, but those being built today. The Forth Bridge of Logroño, built by Ferrovial Agroman, spanning 140 meters over the Ebro river in Spain is one such bridge. While this bridge does have an arch in the center and maintains a single straight deck, the pedestrian walkways split off from the roadway giving one the feeling that they are floating over the river.