One Engineer Remembers the World Trade Center



Yesterday marked the 13th anniversary of the attack on the World Trade Center, an attack that destroyed both towers, killed nearly 3,000 innocent people, decimated New York City’s first responders, and in many ways changed the world forever.  The date September 11 will always conjure up, for those who lived through it, horrible memories — of the sights, the fears, the concerns for loved ones, and above all the concern and sorrow felt for those nearly 3,000 who we did not even know.

This blog article is an inadequate place to try to honor the memory of those who lost their lives on that day, so I will not even try.  Rather I would like to celebrate the too brief existence of two buildings – two buildings which hold a significant place in my life.

2 World Trade Center (the south tower) was my professional address from 1980 to 1983 (giving me, a young engineer a few months out of college, one of New York’s most prestigious – and most visible — addresses).  I was working for Ebasco Services, and that is really where I learned how to be an engineer.  At the time we were doing almost exclusively nuclear power work, but my experiences were extremely varied due to the life stages of the different plants I worked on: retrofit projects on long operating plants at Indian Point (NY) and Millstone (CT), as-building of a newly commissioned plant at St. Lucie (FL), and greenfield projects at WPPSS (WA) and Laguna Verde (Mexico).  It seemed like there was always something new and interesting to do.

But learning about the engineering of nuclear power plants didn’t prevent me from also learning something about the engineering of sky scrapers.  My desk was on the 80th floor – yes right in the middle of the impact zone 20 years later.  I took advantage of what opportunities I had to look out of the windows across New York harbor to the Statue of Liberty.  I remember discussing the novelty of the relatively narrow windows with my colleagues – we learned that the windows were narrow due to the fact that the perimeter of the building was made up of closely-spaced tube steel columns.  This meant that the perimeter of the building, when structurally tied at intervals with the building’s services core, was used to resist all lateral wind and earthquake loads, plus weight loads from above.  An unusual design, but one with benefits:  the entire floor, aside from the services core in the center, was wide open and column free.

WTC Construction drawing, showing perimeter tubes,
services core, and open floor space

The World Trade Center had more than just professional memories for me.  The day I met my future wife, we went to the Market Bar on the first floor of 1 World Trade Center to mark the occasion.  Later, after we were married, we moved up in the world, making it all the way up to the 107th floor to celebrate a promotion in Windows on the World.

The view from up there was amazing, even better than the view from my desk, 27 floors down.  Being so high, atop what was basically a cantilever, one would expect that the motion might spoil the appetite, but no.  Later I learned that a lot of work had gone into solving just that problem: a special wind tunnel was built which could simulate the effects of New York City wind on a 110 story building, new mathematics were developed to tune that wind tunnel and develop the structural response, and finally motion simulators were built to test what types of accelerations and displacements people could handle without adverse effects.  The projected motion was ultimately tamed through a system of viscoelastic shock absorbers; the first time such as system had been used in a building.

After the September 11 tragedy it took 10 years before I was able to face going back and looking at the Ground Zero site.  First there was memory of the horror of the attack, but also there was a strong sense that something was missing from my life.  It hurts that I can’t proudly point out to people the floor of the legendary building where I worked many years ago, or that my wife and I can’t take our kids to the Market Bar (yes, they have just turned 21) or Windows on the World to relive some family history.

I’m glad that that Freedom Tower has taken the place of the World Trade Center, but it will never replace the original for me.  But I am sure there are many other young graduates, starting their careers or starting their families, in and around that building.  May they have nothing but good memories of that site forever.

For an interesting discussion of the engineering challenges behind the World Trade Center:

Copyright © 2014 CloudCalc, Inc.


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