How Pushes and Pulls Act on a Structure

Hey, engineer! I'm Atlas, and today we're going to talk about something every bridge, building, and bookshelf has to deal with: loads and forces. A load is any weight or force that acts on a structure — like people, snow, or furniture. When you stand on a bridge, YOU are the load. When snow piles up on a roof, the snow is the load. Structures are built to carry loads safely. Here's the big idea: when a load acts on a structure, that load travels through the parts of the structure as two kinds of forces — compression and tension. Compression is a PUSHING force. It squeezes material together and tries to make it shorter. Imagine squeezing a sponge between your palms — that sponge is in compression. The legs of a chair feel compression every time you sit down. Tension is a PULLING force. It stretches material and tries to make it longer. Think about pulling a rubber band apart — that rubber band is in tension. When you hang a bag from a hook, the hook and the string feel tension. A single structure often has BOTH at the same time. In a simple arch bridge, the curved stones are squeezed together — compression keeps them locked in place. But in a suspension bridge, the cables are pulled tight — tension holds the deck up. Here is the hint that will never let you down: ask yourself, 'Is this part being SQUISHED or STRETCHED?' Squished = compression. Stretched = tension.