Why do we always use beams which have a cross-sectional shape of I, in constructions? Let's explore this intuitively in this video Created by Mahesh Shenoy
“so there is no resistance in the center, no stress in the center, why we want to put material on the center”, this is the reason why we create "I" beam. It is wonderful explanation
but as we know the thickness of steel is higher than square tube.. and it becomes heavier than square tube.. and we get an another issue "torsion and buckling" to resist than we had to add stiffeners and braces means more material more weight and more manual labor work... so practically rectangular and square tube structures are better than i beams but just because of workability and easy manufacturing I beams are used.
The steel section that you display (at 0:08) in the centre of your first compound photograph is not an 'I'-beam. In fact it is not a 'beam' at all! It is a section of Universal Column, specifically designed to take load when placed vertically. You can see this by the fact that its width is similar to its height. A section of Universal Beam (clearly shown at the top left of your photograph) is deeper in height than width. This is because it is designed to be used horizontally (as a beam). Remember: beams are for horizontal use; columns are for vertical use. It is unsafe to confuse the two.
Why can't we use hourglass beam like as he said the compression and tension gradually increases all the way to top so wouldn't it be better to make this way to ensure a bit more safety? Can you help explaining that?
This is a great explanation video describing the practicity and forces involved with a well delivered example. Thank you! A great way to complement it afterwards, with a more math based approach, is to introduce the concept of second moment of area.
