What bridge do you drive on?

What type of bridge is this?

Why do bridges come in all sorts of shapes and sizes?

Bridges save you a lot of travel time. Some of them can be massive and the loads they take are phenomenal. 

Engineers choose different types of bridges to span an obstacle based on its suitability under the usual environmental conditions.

Bridges span obstacles such as rivers or valleys. It has to carry its own load as well as the loads of vehicles running over them. The chosen design takes the loads and distributes them through a combination of tension and compression into a few key supports. 

The following pictures show how some typical bridges distribute their loads. 

Maybe the next time you're driving on a bridge, you'll know how it keeps you and everything else moving safely.

On a related topic, see how things can go horribly wrong when the environmental conditions are not properly considered…the Tacoma Narrows Bridge Failure. 

Suspension bridge

The Golden Gate bridge is a classic example of a suspension bridge. The load is transferred up the hangers, then diagonally to the tower, and down the pier.

Arch Bridge

Bowstring Bridge

Cable-stayed Bridge

Cantilever Bridge

 

The Glen Canyon bridge in Arizona is an example of an arch bridge. The deck is supported by the arch, which transfers the load towards the abutments in the canyon walls.

The Sydney Harbour Bridge is a good example of a Bowstring bridge. The load is distributed up through the hangers and diagonally into the abutments.

A beautiful example of a cable-stayed bridge over the Oolentangy River in Columbus, Ohio. The cables support the deck and transfer the loads into the towers and down the piers.

The Forth Bridge is an example of an old cantilever railway bridge. The trusses support the deck and transfer the loads into the piers, and then down to its anchored piles.

Attribution:

•  Sydney Harbour Bridge - Kazuhisa Togo
• Forth bridge - Roger Wollstadt
• Arch bridge - LoggaWiggler on Pixabay