Influence line

Have you ever played with a see-saw or a balance board? You probably know that if someone or something heavy sits on one end, the other end goes up into the air. That's because the weight is being balanced between the two sides.

Now imagine a long bridge instead of a see-saw. The weight of cars and trucks driving on the bridge puts a force on the different parts of the bridge. Engineers need to figure out if the bridge can handle all that weight without breaking or bending too much.

This is where influence lines come in. They help the engineers figure out where the weight on the bridge is putting its maximum force. Instead of testing the whole bridge with weights, they can just use a simple math equation and draw a diagram called an influence line.

The influence line is like a see-saw for each part of the bridge. It shows where the heaviest weight would put the most force on that part of the bridge. This way, the engineers can design the bridge stronger where it needs to be and make sure it can handle all the heavy traffic.

So a bridge engineer uses influence lines to figure out where the biggest forces will be on the bridge, just like using a balance board to figure out where the weight is on a see-saw.