Design News for Mechanical and Design Engineers

Failures are our own

Robert Feliciano, San Antonio, TX

AMEN!!!

When the media gave the history of the towers during the aftermath of the tragedy, I stood proud as a mechanical engineer. Knowing that the engineers who designed the building were underappreciated for their efforts, thanks for reminding us of the difference we as engineers make.

Shiryl T. White, Mechanical Engineer

I disagree with Karen Field's editorial claiming that the marvelous engineering of the World Trade Center towers slowed their collapse and allowed so many to escape.

These buildings may be remembered as examples of great structural efficiency achieved at the expense of structural redundancy and safety. Their failure mode corresponds to the scenario in early trains where wooden passenger cars had strong outer shells. In a wreck, these would telescope, one car inside another, inside another, and so on. In buildings with a structural shell like the World Trade Center, we see that should a couple of floors collapse, the weight and inertia of the falling material will telescope the remaining floors into the basement. Buildings that possess an old fashioned network of distributed columns provide redundant load paths that are needed when disaster strikes. Structures such as New York City's Empire State Building might fair better in a suicide aircraft attack because of such redundant load paths.

James C. McLane III, P.E., Houston TX

Are we so sure that the twin towers were as well designed and built as you suggest?

Talk around is that:

a) There was much consternation about the design as they were going up,

b) That there were problems with the construction as they were being built, and

c) That some are saying that if they had been built to the common, ordinary standard to which most other skyscrapers were built, they might still be standing.

My point is not to pick on you, but rather to suggest that your magazine might run an in-depth analytical article to show us the different types of skyscraper designs and give us some valid engineering data that will allow for comparative analysis of the various types of design and construction.

Perry Arnett, Cedar City, UT

Editor's note: MIT's Technology Review has published an excellent article delving into the specifics of the design of the World Trade Center. Readers can access it at http://www.techreview.com/web/special/roush.asp

I appreciated your thoughts on the collapse of the twin towers. I think I was too much in shock to think of the engineering that went into that design.

But that is not what motivated me to write this morning. It was the letters from engineers complaining about being paid less and working harder than other professions. It caused me to reflect on my choice of entering the engineering field some 33 years ago. It is plain and simple, I love what I do. I love to think up new ideas and to experiment with new products and to find ways to manufacture those products in a cost-effective way. I love the challenges we face and the unique abilities we as engineers have to make things work. I have been around long enough to know that making money is important, but also long enough to know that no amount of money can make up for not enjoying what one does for a living.

John Bunting

As an alumnus of the University of Missouri—Rolla (BSME '89), I must take issue with your article entitled "Engineers race for solar power" (DN 10.01.01) This year's second place team (last year's champions) was from the University of Missouri—Rolla—not the University of Missouri—Columbia as reported. Although UMC is a nationally known university in several areas of study, UMR is Missouri's "technical university" and nationally known as a premier engineering school. I work with engineers who went to school at both UMR and UMC so a lot of good natured ribbing goes on. The UMR guys will take great joy in a correction. The UMC guys won't say a word—they know better!

John Chalupny, Watlow Co.