Creative Speculation
In reply to the discussion: North Tower Exploding... [View all]AZCat
(8,342 posts)It's scarily easy for the collapse to progress to completion once initiated, because the individual columns are loaded beyond their capacity by the failure of others. The math is pretty simple if you have the geometry laid out correctly and your materials modeled appropriately. Even the baseline loads calculated for the towers by NIST had some structural members (including both perimeter and core columns) with DCRs greater than 1.0.
Your "Physics 101" claim isn't going to do much good if you don't allow for all the relevant forces. Neglecting gravity is going to cause problems in your model, because that's the reason the falling mass doesn't just disappear. That mass has to go somewhere, and the dominant force acting on it is gravity, so it goes down.