Why is steel a stiff material?I'm doing a project on the use of steel in the construction of skyscrapers - and obviously, for the inner steel skeleton of a skyscraper the steel support beams and girders will have to be stiff so that they don't fall apart or the building doesn't shake due to wind or other natural forces.But in my research I've found that steel (mild steel to be more exact) is ductile and malleable, meaning it can be shaped fairly easily. However, how can steel ALSO be stiff - the definition of stiffness is the tendency to withstand bending and stretching - so my question is. How can this material be BOTH ductile/malleable, AND stiff? and why? :)Thank you in advance if anyone takes the time to answer this, would be appreciated - I'll give you 10 points straight away if the answers conclusive
Steel is NOT stiff. In fact it is worldly accepted metals (steel is a metal) are not rigid in mechanical terms, and rigid means stiff. Steel easy to shape, but is strong and therefore hard to break. Thermosetting polymers (hard plastic) which is stiff, is in fact easy to break (weak) and also hard to reshape without changing its state (solid to liquid). Whoever told you steel is stiff is wrong and possible meant steel is strong, or you misheard/misunderstood.
To say that steel can be bent and shaped fairly easily isn't quite true. It takes multiple tons of force to do so, requiring some very heavy machinery. I think you're confusing a couple of concepts. For example the idea of elastic modulus, versus rigidity Rigidity is the ability of a structure to resist a load. That depends not only on the elastic modulus, but on the size and design of the structure or object. You can build fairly rigid structures out of wood. For example roller coasters. Even though wood has a much lower elastic modulus than steel, meaning that it takes much less force to bend and deform a given sample of wood.
