Bridge-building – Facts and Figures

Bridge-building is often associated with forward progress and exploration and since ancient times, the effective construction and destruction of bridges has been one of the primary responsibilities of engineers. Bridges provide smooth and safe crossing where it would otherwise be extremely difficult and hazardous, if not impossible.

It can be easy to take things for granted, and bridges are no exception. But bridge-building is by no means an easy task. Back before the days of steel and reinforced concrete, people used to build bridges out of wood or stone. But I’m sure you can imagine the limits these materials place on the engineer. This is why

Alcántara Bridge, Spain

longer bridges were limited to the arch types.

Well, let’s talk about what kind of options are available. Obviously, the simplest way would be to build what is called a beam bridge. This can be as basic as laying logs across a small stream. But beam bridges can only get so long before they begin needing support in some form. Columns were the earliest forms of support, but columns are not always feasible.

Even with the superior qualities of today’s steel, beam bridges rarely span more than 250 feet. Arch bridges on the other hand can span over 1800 feet provided steel and/or reinforced concrete are used. (Largest Arch Bridges.) But even arch bridges made of just stone are known to span up to 480 feet! (Danhe Bridge, Shanxi, China)

Since the development of steel, other bridge types have come into play. Namely, steel truss and suspension. Truss bridges incorporate a system of triangular bracing spreading the load evenly throughout. These truss systems can be above or below the bridge-deck – or both – and can also arch up or down toward the deck at

Akashi Kaikyo Bridge, Japan - Note the Truss System

given intervals to cut cost and weight. The longest truss bridge at present is the Ikitsuki bridge, spanning 1312 feet, located in Nagasaki, Japan. (Longest Continuous Truss Bridges)

Suspension bridges are perhaps the newest and most majestic-looking of the lot, and understandably so! Suspension bridges can span the greatest lengths – up to 7,000 feet – making them the bridge of choice for projects requiring substantial length. Suspension bridges also utilize truss systems below the deck to supplement the load-bearing capacity as well as to counter torsion.

(Akashi Kaikyo Bridge – world’s longest suspension bridge, and the 8th most expensive “thing” in the world at 5 billion dollars! Check out the Top 15 Most Expensive Things in the World!

One Response to Bridge-building – Facts and Figures

  1. Kari says:

    I like your writing. You have a talent:) They’re all very helpful ideas.