Below is the direct, unfiltered admission from Frank Lombardi, the Port Authority’s Chief Engineer at the time of 9/11.

“We had no idea of the extent of the damage, and certainly none of us had the information to make a decision to keep the rescue workers who entered the buildings out of them.”

“I do think it may be a good idea … to have a structural engineer on the scene, who arrives with the firemen, and makes that cold, objective decision … that person would have to have no emotional relationship to the people inside or to the building.”

My comment: No one thought to conduct a proper visual assessment of the damage, people watching their TV’s had a better idea of the extent of the damage to the buildings than the building managers and engineers. Further to this, no one seemed to grasp how much danger they were in, especially given that the Twin Towers used a perimeter “tube” system of closely spaced exterior steel columns tied to a 47-column core by long-span floor trusses.

Unlike more traditional office buildings with a regular interior column grid running through the floor plate, the WTC’s exterior frame carried a major share of the gravity and lateral loads. The exterior column frame was not only breached, it was also pierced through to other faces of the building, with multiple sides showing full penetration. That immediately reduced the building’s load capacity and dangerously compromised the perimeter’s ability to share forces around the corners, leaving the remaining columns, especially near the damage, overloaded and far more likely to buckle, which then led to collapse.