You'll have to forgive me, sometimes my style of writing makes me seem smarter than I am. Could you explain this like I'm stupid?* Post-impact capabilities of the WTC towers assessed. Demand to capacity ratios—the calculations indicating whether or not structures can support the loads put on them—showed that for the floors affected by the aircraft impacts, the majority of the core and perimeter columns in both towers continued to carry their loads after the impact. The loads from damaged or severed columns were carried by nearby undamaged columns. Although the additional loads strained the load-bearing capabilities of the affected columns, the results show that the columns could have carried them. This shows that the towers withstood the initial aircraft impacts and that they would have remained standing indefinitely if not for another significant event such as the subsequent fires. NIST previously reported that the towers had significant reserve capacity after aircraft impact based on analysis of post-impact vibration data obtained from video evidence on WTC 2, the more severely damaged tower.
* Fire-induced core column shortening detected. Due to heating from fires following the aircraft impacts and subsequent buckling, there was a shortening of core columns seen in both towers on floors at or near the fire-affected impact sites. Shortening of the core columns caused the floor system to pull the perimeter columns inward—the observed inward bowing that was seen minutes prior to the collapse of each tower. Significant thermal sagging of the floor system exacerbated the inward pull on the perimeter columns in WTC 2. Vertical loads carried by shortened columns were redistributed to perimeter columns, putting additional strain on their load-bearing capabilities.
To drive my point home, Dr. Greening uses seismic data to determine total collapse time. If we are to accept this, we must accept that this energy was being dispersed and transmitted throughout the entire structure all the way to the ground.

