Why Should the WTC Towers Suffer Complete Collapse?, page 1

Originally posted by Richard Gizinu
Core columns? They broke at the welds.

The core columns were manufactured in 3 floor lengths - 30 ft? Then welded together as it went up. The welds were sometimes only on 2 sides, and weren't fully penetrating welds. This would have been sufficent since the core columns were never intended to take bending loads ( how's that for an accurate term?), just vertical gravity loads.

Exterior columns broke apart at the bolted connections.

Would you please post the sources of your description about how the core was constructed?

Also, your contention that the cores were only intended to bear gravity loads is misleading, as the entire building was designed to sway in response to wind loads. I can personally attest to this as I'd visited once on a windy day and stood at the corner of one tower and could actually see the building sway. Quite a sight. Here is an analysisconcerning the wind loads only in relation to the perimeter columns:

With regard to the WTC’s perimeter columns, the factor of safety fluctuated from day to day and even from hour to hour, because, in addition to supporting 47% of the WTC’s gravity load, the perimeter wall also had to withstand the lateral force of the wind, which is highly variable given the whims of Mother Nature. A single face of the WTC presented an enormous “sail” to the elements, for which reason John Skilling vastly overbuilt this part of the structure. According to the NIST report, the outer wall’s factor of safety against wind shear on 9/11 was extraordinary, i.e., in the 10-11 range.[67] Why so high? The answer is simple: On the day of the attack there was essentially no wind, only a slight breeze.[68] For this same reason nearly all of the perimeter wall’s design capacity was available to help support the gravity load. As the NIST report states, “On September 11, 2001 the wind loads were minimal, thus providing significantly more reserve for the exterior walls.”[69] When NIST crunched the numbers for a representative perimeter column in WTC-1 (column 151, between the 93rd and 98th floors), they arrived at a factor of safety of 5.7.[70] Assuming this average figure is a typical value we arrive at a reasonable estimate of the perimeter wall’s amazing reserve capacity. Even if we subtract those columns severed/damaged by the impact of Flight 175, and the lost capacity due to the alleged (but unproven) buckling along the eastern perimeter wall, there was still a wide margin of safety, more than enough by several times over to support the outer wall’s share of the gravity load, with plenty to spare.[71]

The WTC’s tremendous reserve capacity was no secret. In 1964, four years before the start of construction, an article about the planned WTC appeared in the Engineering News-Record. The article declared that “live loads on these [perimeter] columns can be increased more than 2,000 percent before failure occurs.”[72] A careful reading of the piece also gives insight into why the plane impacts were not fatal to the integrity of the outer wall. The reason is simple: the perimeter columns were designed to function together as an enormous truss, specifically, a Vierendeel truss. The wall was inherently stable. After the plane impacts it behaved like an arch, simply transferring the load to the surrounding columns.