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Was there an aluminum cladding problem with the World Trade Center towers?

From: blogOPTICA by R Henry Nigl

As I mentioned in my earlier post, (see July 18, 2008 post), in 1971 I was a design development draftsman working at Yamasaki's architectural office in Troy, Michigan...forty years ago now. I was honored to be working for such a distinguished firm bursting at the seams with talent and creativity. I am still proud to have been part of that team. It was an exciting time.

One of the assignments I had at that time was to detail the study drawings for the aluminum cladding system for one of the other projects* awarded the firm after the WTC. These projects shared many of the fenestration design features used on the WTC. The elaborate aluminum cladding system, (elaborate because it performed a three-dimensional seal between the glazing, spandrels and other finish materials that expanded at different rates based on thermal variables, while still providing weather integrity and effective moisture drainage). It was an elaborate detail, yet functionally effective and beautiful at the same time.

In retrospect, I remember questioning the direct connection detail of aluminum to steel, and aluminum to concrete, that was, apparently going to be used on these new projects. This was a detail that flew in the face of everything I knew about the reaction that occurs between disparate metals, like steel and aluminum. That is, an electro-galvanic reaction which will corrode and ultimately compromise the strength of the connection over time as oxidation takes place. I asked several of the senior architects and even brought it to the attention of the department head. My questions were not answered, really, and If I recall correctly, I was told that it would not be a problem because it had been tested in other structures and was a non-issue. Perhaps, ultimately, the aluminum-to-steel connection detail was not used on the project I was working on--I never saw the shop drawings or inspected the actual field connection. Nevertheless, I left the firm a few months after that, (not for that reason but for other personal reasons--I wanted to travel the U.S.).

Direct connection of aluminum to steel was probably used on the WTC towers to the best of my knowledge, and that connection's corrosive potential, among other problems, as I understand it, (having read the report in a variety of articles), was undoubtedly, some of the reasons the Port Authority, the City of New York, and the future developer, Larry Silverstein, wanted the buildings demolished. The WTC buildings were full of asbestos, (typical for construction at the time), and, looking back critically at the designs were obsolete structures in many other ways, not the least of which, was that they did not conform to the city's strict building and life safety codes applicable in our time. Of course, there was no way economical way the interested parties could renovate or, because of the toxicity of materials, demolish the structures. In fact, to renovate in accordance with standards in effect today would have cost more than the original project.

Although innovative designs, the WTC towers were 'white elephants' almost right after they opened. Space was difficult to lease, when it could be leased at all, it was at a loss, the plaza design caused a 'wind tunnel' effect that was most unpleasant to pedestrians entering the buildings at ground level...just a ton of problems. So I guess, ultimately 9/11 solved a lot of problems for some.

Aluminum to steel connection without a separating insulative barrier at the connection is bad fabrication design...it is still used, however, in many industries, automotive, signage, construction, and many others without the slightest hesitation.

*Century Plaza Hotel, Century City, Los Angeles, CA, Federal Reserve Bank of Richmond, Richmond, VA

R Henry Nigl