At a meeting of the International Code Council in Rochester, N.Y., on May 23, members turned thumbs down on May 23 to the proposed code provision for progressive collapse resistance. ICC's ad hoc committee on terrorism-resistant buildings had proposed the section, S-05-06/07, for the 2007 supplement to the model International Bulding Code.

The provision drew vigorous opposition from almost every professional organization, including the American Society of Civil Engineers Structural Engineering Institute, the National Council of Structural Engineers Associations, as well as major building owner and architect groups. Groups said the proposal had not been properly vetted, was not enforceable, had not quantified the impact on construction cost and was written without adequate definition of either the threat to be protected against or acceptable performance.

  • Do you think a model building code should include progressive-collapse-resistance provisions and if so, why?
  • The topic, even among practicing engineers, has been especially controversial since the 9/11 terrorist attacks, though most engineers agree that the twin towers did not collapse progressively. Both SEI and NCSEA have formed committees to explore standards on progressive collapse resistance, also known as disproportionate collapse resistance or enhanced "structural integrity." The groups may eventually come to a consensus on the dividing issues. Among these are what constitutes progressive collapse and whether there is a need to codify progressive collapse resistance.

    Those against argue that there have been no documented instances of progressive collapse in the U.S. Advocates of codifying progressive collapse resistance counter, saying that Six World Trade Center and Seven World Trade Center were cases of progressive collapse, as was the Alfred P. Murrah Building in Oklahoma City. One supporter of codifying progressive collapse resistance is Ramon Gilsanz, prinicipal of Gilsanz Murray Steficek LLP, New York City, co-chair of the New York City building code structural committee. The draft code, which will be voted on soon by the New York City Council, has new requirements for enhanced "structural integrity" against extreme events. Gilsanz maintains that buildings, and the public, would benefit by increasing structural integrity requirements.

    Many engineers support the development of a voluntary standard in cases where owners elect to increase structural integrity for certain buildings beyond the code minimum. They do not support a mandatory code.

    "The argument for progressive collapse resistance in the codes is that it's better to be better," said John G. Tawresey, vice president of KPFF Consulting Engineers, Seattle and former SEI president, at SEI's Structures Congress, May 16-19, in Long Beach, Calif. "But the issue is the allocation of resources. Aren't there better things to do than to make buildings better than they need to be?"

    At the same meeting, another prominent structural engineer from Texas, referring to the structural integrity provisions to resist "extreme events" in the draft New York City Building Code, said: "It's just plain dumb!"