Global Bridge Construction Designs from Around the World
Throughout history, humans have tried to develop new technologies for building bridges. The earliest constructions were simple logs placed over narrow ravines, but these were quickly replaced with more stable and longer-lasting structures. Modern bridge designs use fewer materials than ever before, to create longer, sturdier bridges than humanity even dreamed of just a few centuries ago.
In modern bridge building, a variety of bridge types are used today.
The most popular bridge in existence is the multiple beam bridge. Most span approximately 40-100 feet and consist of steel or prestressed concrete beams that are supported by abutments or piers. The beams can be a have a variety of shapes such as I-sections, T-sections, or box sections. Spacing of the beams can vary, and in some cases box beams may be placed side-by-side to form an adjacent box beam bridge. The beams then support a deck that provides a surface for vehicular and pedestrian traffic.
Built in 1836 as a timber bridge, the B&O Railroad Potomac River Crossing is a beam bridge in West Virginia, USA and has been added to the National Register of Historic Places. Because of the topographical, economic, and skill needed to build this bridge, it was an engineering feat to complete.
Truss bridges were very popular in the earlier years of bridge history, with many early timber bridges using truss designs. The truss is an efficient usage of material. Though not as popular now for larger spans due to construction techniques, expensive labor costs, and more recent concerns in regards to redundancy, trusses are still frequently used for shorter spans. The trusses for the bridge can exist above the deck surface (known as a thru truss) or below it (deck truss).
Some of the best-known modern bridge designs are truss bridges. The Sky Gate Bridge in Japan links more than two dozen cities to the Kansai International Airport and handles more than 25 million travelers a year. The nearly 11-mile-long Francis Scott Key Bridge in Maryland spans Baltimore Harbor as a way to take pressure off the city’s other major roadways.
Suspension bridges are used for much longer spans than other types of bridges. Though these types of bridges are often depicted, very few of these bridges exist relative to the other types of bridges. These bridges consist of tall towers that support cables from an adjacent tower or anchorage at the end of the bridge. The cables support vertical suspenders that support trusses, beams, and the deck. These bridges are often high above waterways to allow shipping to pass or to span deep, long valleys.
The Golden Gate Bridge, built in 1937, is the most recognizable suspension bridge in the world. Its two individual suspenders hold a bridge that measures 4,200 feet across the Golden Gate Strait.
Cable Stayed Bridges
Similar to suspension bridges, cable stayed bridges are used for much longer spans than other types of bridges. These bridges consist of tall towers that support cables. However, the cables in these bridges run directly to support beams and the deck. These bridges are often high above waterways to allow shipping to pass or to span deep, long valleys. One of the more popular cable stayed bridge is the Sunshine Skyway.
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Truss Bridges – https://www.tn.gov/tdot/article/bridges-historybridges
Bridges of the Future – http://journal.frontiersin.org/article/10.3389/fbuil.2015.00003/full