Originally Posted by NasserAE
Well he is right. Structural glass is "stronger" than concrete (based on mechanics of materials) since its modulus of elasticity is higher than that of concrete. . However, each material suffer weakness some how. In concrete, it is tensile strength (this is why concrete is reinforced with steel). In glass, it is imperfections in the material itself that causes stress concentration at loads close to failure. Furthermore, glass is brittle material.
About 9 years ago I met the structural engineer who designs Apple stores glass structures in a conference about transparency in tall buildings. He told amazing things about the glass as structural material. Long story short, the structure is well designed and will perform as well as any other building in earthquake or during high winds.
Well, he isn't right. Neither are you. Especially based on the mechanics of materials. In your instance, I am correcting you respectfully because you are generally respectful.
First of all, we cannot use a single parameter to compare their "strength". Some will, again, accuse me of spouting tripe. But if we are invoking mechanics of materials, we should do it correctly. Second, Young's modulus is a measure of stiffness. In a general context, it may seem intuitive to believe that stiffness is strength. But is it that simple in the context of the durability of a building? Furthermore, what is the Young's modulus for glass? What is it for concrete? That's like asking how tall are buildings? And which direction are you measuring Young's modulus in? Like the perceived brightness of the sun, direction matters.
And we haven't even gotten into yield strength, tensile strength, compressive strength, fatigue, impact ... There is a reason the field is called mechanics of materials and not simply strength of materials.
I am going to resist sneering at your mention of meeting the dude who designed the glass structures at Apple. And again I mean that respectfully. Why do people mention these things? I went to a WHO concert, but I'd never tell anyone how to play a guitar. I saw Michael Jackson but still don't have a sense of rhythm.
There is no single structural engineer who designs Apple stores. If you met the guy who gets the credit, then you probably met James O'Callaghan. But I doubt he would say "he" designed the glass structures at Apple Stores. At least, I hope he didn't say it that way. For sure, if he heard you say that he told you, "structural glass is stronger than concrete." He'd ask you to stop because that would be a careless and incorrect generalization. I am no O'Callaghan but, for your sake, I suggest you stop repeating the same generalization, and respect the complexity of engineering. What engineers can do with glass is remarkable. But advances in concrete is no less so. In fact, you'd be amazed what happens when the two are mixed.
Finally, if you are so sure structural glass is stronger than concrete, please take a picture next time you are in a skyskraper where all the load bearing columns are made of glass alone. And if you really believe glass is stronger than steel, please take a video next time you see a construction crew drive glass piles into the ground to support a new building or bridge. Please wear safety glasses when you do this :)
Edited by stelligent - 6/8/13 at 9:58am