I am uneasy about reading articles that appear in various newspapers on the collapse of the World Trade Center’s twin towers. As your story, "Engineers Seek Corrections," notes, expert engineers promulgate their own theories on the causes, and newspapers that are hungry for some "great" and preferably "scandalous" revelations are all too ready outlets (ENR 11/11 p. 11).

I was interviewed [by a newspaper] on the day of the collapse and have had only the benefit of the pictures seen on television. My opinion was, and still is, that first, the impact knocked off all the fireproofing material from the structure. Then, the enormous fire softened up the columns to the point where their load-carrying capacity was fatally compromised.

I am aware that some engineers tend to blame the floor trusses and/or their connections to the exterior wall. The claim is made that as the floor trusses collapsed under the fire, the exterior walls became unbraced and collapsed in a buckling mode of failure. I believe, however, that this is the argument to which there is a classical "So what?" answer. To the best of my knowledge, no one has yet suggested that if rolled steel beams were used as floor members, the structure somehow could have survived the attack.

Somewhere in this whole process, we seem to have lost sight that at the time of design and construction, the concept and its particular details all were great engineering achievements. The towers stood for several decades and would have continued to serve as mileposts for great structural engineering for many more decades, if not centuries, had they not become victims of madmen.

I would, however, like to see a symposium where the profession could discuss the issues. Not a post-mortem of what is the belief of one, or another, engineer on the collapse. It would be much better if we could get together and discuss the following proposition: "Is it possible to design a tower building that will withstand the impact of a 150 to 200-ton firebomb traveling at 400 miles per hour? Yes or no?" Then perhaps we may see some advanced thinking done not over the past, but over the future.

ROBERT M. DARVAS PE., SE
Professor Emeritus, Architectural
Structures
University of Michigan
Robert Darvas Associates, PC
Ann Arbor, Mich.

Open Competition Works Again

It came as no surprise to those of us at Associated Builders and Contractors that a bidding system promoting free and open competition resulted in a number of competitive bids on the most recent Woodrow Wilson Bridge replacement project contract (ENR 11/18 p. 13).

The article notes that Maryland officials can now breathe a sigh of relief. We can’t help but think about the lost time and delays that occurred as a direct result of Maryland Gov. Parris Glendening’s (D) attempt to have a union-only project labor agreement as part of the contract. With the threat of a PLA, only one bid was received on the superstructure [and] it was not even in the ballpark, so the process had to start over. It wasn’t until the Federal Highway Administration [acted] that the initiative was finally dismissed.

Before the state and governor spend too much time patting themselves on the back, the real thanks should go to the Bush administration for recognizing and understanding the basic economic principle that more competition brings about lower bids. Oh yeah, with Governor-elect Bob Ehrlich (R) taking office, we won’t have to deal with this problem again.

JAMES RUSS
Chairman
ABC of Metro Washington
Calverton, Md.