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Imagine yourself down on all fours, as if you were crawling.
If someone placed one of the following things—a feather, a cat, or an elephant—on your back, which one of them would break it? It’s clearly the elephant!
The design of a beam bridge is similar to you on all fours: a horizontal beam (your back) is supported at each end by vertical posts (your arms and legs). The beam bridge is also known as a girder bridge. It is the simplest and least expensive bridge to build. Its design is perfect for crossing short distances.