Empirical Evidence and Structural Integrity: The World Trade Center and the Impact of Aircraft

Introduction

The questions surrounding the structural integrity of the World Trade Center (WTC) during the impact of aircraft on 9/11 have been widely debated. This article aims to explore the empirical evidence and the claims made by engineers regarding the WTC’s ability to withstand such an impact.

Empirical Evidence and Claims

The significance of empirical evidence, particularly in the realm of structural engineering, cannot be overstated. According to renowned examples like Einstein's theory of gravity and the bending of light during a solar eclipse, empirical evidence serves as the bedrock of solid and reliable knowledge. In the context of the WTC, the following points have been made based on various sources.

Design Intentions and Expectations

The World Trade Center was designed with the intention to withstand the impact of a large passenger aircraft. In a rare interview, an engineer stated that the WTC could be likened to a 'giant mosquito net' for such impacts. This suggests a level of confidence in the building's ability to endure such a collision.

Engineer Claims and Speculations

John Skilling, a chief engineer, claimed in 1964 that the towers were designed to withstand the impact of a fully loaded, high-speed DC-8 or 707 jet at 600 mph. Leslie Robertson, a junior engineer, told a German audience a week before 9/11 that he had designed the buildings to survive such an impact. Similarly, Skilling also stated in 1993 that the buildings would not only survive but also recover from subsequent fires.

Post-9/11 Debunking of Misinformation

Many arguments against the WTC's structural integrity are based on misinformation that originated from a NOVA episode in 2002. This episode has been widely cited but often without proper context. Mainsplainers continue to spread these unsubstantiated claims. The engineers themselves were very clear about their design intentions, clearly stating that they anticipated aircraft collisions at 600 mph.

Illustrative Debunking

Mr. Becker aligns with the post hoc ergo propter hoc fallacy, suggesting that because planes collided with the towers, the planes were responsible for their collapse. This ignores the fact that Building 7, which did not sustain a direct hit, also collapsed. Mr. Johnson speculates that the heat from kerosene brought down the towers, but FEMA reports indicate that the jet fuel burned off in less than five minutes, which is why the towers continued to stand for up to 97 minutes after impact.

Structure of Construction

The misconception that the WTC's structural support was located solely in the outside frame is inaccurate. The core bore 60% of the gravity loads. Additionally, the outer perimeter wall was load-bearing, clad with aluminum and steel columns, and not an unsupported curtain wall as often claimed. The so-called 'stainless steel facade' suggestion is a misinterpretation. The WTC did not have a conventional curtain wall, but rather a load-bearing external structure.

Evidence Against Flimsy Floor Theories

Mr. Chaudhery believed that flimsy floor clips could not withstand the domino effect of cascading floors. This theory, which gained traction in 2002, has since been disproven. NIST's investigations and reports have shown that one floor membrane can hold up to 11 floor membranes if the load is applied gradually, or up to 6 if applied suddenly. The WTC was designed to endure hurricane-force winds of 150 mph and was not constructed with dominoes.

Further Clarifications by NIST

NIST did not rely solely on the idea that the plane impact and ensuing fires caused the buildings to collapse. Core steel samples analyzed by NIST showed only heating to 250°C, which is insufficient to weaken the structural integrity of the steel. The NIST report, which cost 20 million dollars and spanned 10,000 pages, concluded that while plane impacts and fires did contribute to the collapse, the primary cause was the partial and sudden failure of the building's support systems, which led to the domino effect, much like the core structure held.

Conclusion

Empirical evidence from the design intentions and the investigations by engineers and NIST support the notion that the WTC was designed to withstand impact from large aircraft. Misconceptions and misinformation about the structural support and the collapse of the towers continue to circulate. Understanding the true nature of the WTC's design and the findings of credible investigations is crucial for a balanced and informed perspective.