(sigma*)=F / mm²
…and that’s all the science it takes. Steel, not quite incidentially, is usually sold by profile, ton, quality and, first of all, stiffness (sigma). So it’s pretty easy to predict when it will bend or break. Because not doing so is what it is good for.
*I am not going to find out where in the world this Greek character might be on my keyboard. It stands for tension, anyway. F by the way is force in Newton, just to have it mentioned.
