A bridge is a structure built over an obstacle to provide passage for cars, people, trains, animals and bicycles. Engineers generally design bridges in one of six types (beam, cantilever, arch, suspension, cable-stayed or truss) although bridges can be a combination of several types. Learn more at this week's roundup of engineering sites.
This Java game from Johns Hopkins University lets you design trusses in your browser! "Trusses are composed of straight members connected at their ends by hinged connections to form a stable configuration. When loads are applied to a truss only at the joints, forces are transmitted only in the direction of each of its members." Read the simple directions, then click through to the game page.
This introduction to the bridges of Allegheny County (in Pennsylvania) is a great place to start your bridge education. It illustrates simple spans, trusses, beams and arches. There is also a wonderful bridge glossary page; look for "Terminology: Bridge" in the left-hand menu. "Abutment: Part of a structure which supports the end of a span or accepts the thrust of an arch; often supports and retains the approach embankment."
The PBS television series Building Big includes bridges, as well as domes, skyscrapers, dams and tunnels. This Bridges section features Bridge Basics, a game quiz (The Bridge Challenge) and a fabulous Flash lesson on forces. "Forces act on big structures in many ways: squeezing, stretching, bending, sliding and twisting." Click on any of the forces to see real-life examples.
You've just been put in charge of deciding which type of bridge is best of each of four sites. Do your homework about four common types of bridges, and then "put on your civil engineer's hat and build some bridges." There are also an interesting interactive (and printable) feature about eight infamous bridge failures. "The August 2007 collapse of Minnesota's I-35W bridge over the Mississippi River killed 13 people. Tragic as it was, that accident and what we learn from it will help scientists and engineers foresee and act on structural problems and prevent failures of other spans."
Whether for a science fair, classroom, or home project, these engineering projects include ideas such as Can a Toilet Paper Tube Support Your Weight?, The Effect of Bridge Design on Weight Bearing Capacity, Paper Bridge for Pennies, and Bridges That Can Take a Shake!. Each project is rated for difficulty on a scale of 1 to 10 that roughly relates to grades K to 12. Some projects include complete instructions and research starters, while others are just abstracts.