Blade_Runner wrote:
The core columns and the perimeter columns were designed and constructed to SHARE THE LOAD EQUALLY. There were 47 core columns and 236 perimeter columns, a ratio of 6 perimeter columns to 1 core column. The equal sharing of the load was facilitated by the hat trusses. Therefore in terms of load bearing strength, the core support was no more "massive" than the perimeter.
Why you seem to think that the strength of the core is the key to supporting the cockamamie CD theory is baffling. Such an erroneous assumption only demonstrates that you don't really know anything about the design and construction of the twin towers.
The tube-frame design, earlier introduced by Fazlur Khan, was a new approach which allowed open floor plans rather than columns distributed throughout the interior to support building loads as had traditionally been done. The World Trade Center towers utilized high-strength, load-bearing perimeter steel columns called Vierendeel trusses that were spaced closely together to form a strong, rigid wall structure, supporting virtually all lateral loads such as wind loads, and sharing the gravity load with the core columns. The perimeter structure containing 59 columns per side was constructed with extensive use of prefabricated modular pieces each consisting of three columns, three stories tall, connected by spandrel plates. The spandrel plates were welded to the columns to create the modular pieces off-site at the fabrication shop. Adjacent modules were bolted together with the splices occurring at mid-span of the columns and spandrels. The spandrel plates were located at each floor, transmitting shear stress between columns, allowing them to work together in resisting lateral loads. The joints between modules were staggered vertically so the column splices between adjacent modules were not at the same floor.
The core of the towers housed the elevator and utility shafts, restrooms, three stairwells, and other support spaces. The core of each tower was a rectangular area 87 by 135 feet (27 by 41 m) and contained 47 steel columns running from the bedrock to the top of the tower. The large, column-free space between the perimeter and core was bridged by prefabricated floor trusses. The floors supported their own weight as well as live loads, providing lateral stability to the exterior walls and distributing wind loads among the exterior walls. The floors consisted of 4 inch (10 cm) thick lightweight concrete slabs laid on a fluted steel deck. A grid of lightweight bridging trusses and main trusses supported the floors. The trusses connected to the perimeter at alternate columns and were on 6 foot 8 inch (2.03 m) centers. The top chords of the trusses were bolted to seats welded to the spandrels on the exterior side and a channel welded to the core columns on the interior side. The floors were connected to the perimeter spandrel plates with viscoelastic dampers which helped reduce the amount of sway felt by building occupants. The trusses supported a Template:Convert thick lightweight concrete floor slab with shear connections for composite action.
The core columns and the perimeter columns were d... (
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If there was a design flaw in the twin towers, why did Silverstein use the same basic
design for the new One World Trade Center? You do remember claiming the "tube in tube" design caused the towers to collapse, don't you?