Ok, now that you have put this in layman terms, I think I can see the light at the end of the tunnel. This brings back many  things I have heard (should have learned, but......) over the years. Even now recall the science class in high school with the bridge building. Balsa wood, stirng and glue.

 But I can now see a little bit of why attention to the flanges are so much more important than the web. Though the web is the connection between the tension and compression, and is important in what it does, it does not take all that much to be just a connection. Whereas the flanges, top and bottom, have to resist compression and tension. It's the resistance to compression on the top flange and the resistance to stretch (or tensile strength?) of the bottom flange that do the main work. The web just allows them to do the work they need to do?

 Or...........................?