Example: An exercise bike that can support 250 lb. Does the engineer find a large enough weight that deforms the bike, then take a fraction of that as the amount it can support?
In: Engineering
Generally yes. A product’s advertised maximum weight is not the weight at which is will completely collapse. How much margin is left depends on what the product is and how dangerous a failure could be. Things like lightweight hooks don’t need much of a margin since they aren’t holding anything heavy enough to be dangerous. Safety gear such as climbing ropes and rescue equipment often have a 3-to-1 margin meaning they can actually hold 3x what they are not to exceed in a safety operation. The air bottle fires fights use for example, usually get filled up to 4,500 PSI and are testing at more like 15,000 PSI.
Those calculations are made first in theory. Material strength is its own sub-field where you determine how strong something will be based on the materials used. Then once it’s built it gets tested in the real world if possible. And example of this would be a crash test for a car. In more permanent structure like a building, you can’t really test the thing until it’s built so again, a lot of margin is factored in and institutional knowledge is relied on.
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