Des Moines Business Record
02/20/06
From Katrina to 9/11, engineers address
structural failures
By Erin Morain
erinmorain@bpcdm.com
As a forensic investigator, Iowa State University professor Max Porter
analyzes materials and data, pores over documents and conducts interviews to
get to the bottom of a case.
No, this isn’t “CSI: Ames.”
But the increased use of forensic evidence in criminal investigations has been
paralleled by a greater reliance on forensics in engineering. A professor in Iowa
State’s department of civil, construction and environmental engineering, Porter’s
part-time job as a forensic engineer allows him to use engineering to explain the
whys and hows of structural failures caused by human error or Mother Nature.
“Each case is different and each case teaches us as professionals something
new or something different,” said Porter, who has earned a number of
professional certifications related to forensic studies. He said his real-world
experiences have also given his students better insight into practical applications
of engineering.
Forensic engineers have been called in to investigate disasters such as the
1989 DC-10 crash in Sioux City and the collapse of a bonfire at Texas A&M
University before its football game with the University of Texas in 1999, as well
as structural failures caused by weather. Porter has been involved in forensic
work related to the devastation left by Hurricane Katrina.
“We know how to design structures for this kind of wind speed,” he said. “So why
is it that so many of them are flat?”
On Sept. 11, 2001, Porter watched live footage of the smoke pouring out of the
World Trade Center towers. Considering the fire source (jet fuel), the heat the fire
would generate and the effect on the building’s internal structures, he was certain
the towers would collapse.
As then-president of the Construction Engineering Institute, Porter guided an
investigation by that organization to determine what contributed to the collapse.
The temperature of the fires – about 1,500 degrees – led to the decoupling of the
buildings’ trusses and the floors began to sag, Porter said. Once one or two
floors began to give way, he said, the entire building was likely to collapse. In
addition, the force of the airplanes knocked off the fireproofing material in those
areas of the building.
“Had that remained bonded to the structural steel members so the fireproofing
could do its job, we’d like to think maybe that building would have stood for one
heck of a lot longer period of time,” Porter said.
Investigative work into the collapse of the towers has been ongoing since the
terrorist attacks and has led to discussions about changes in design standards.
But the issue at hand is whether tougher design standards would force builders
to use unaffordable materials.
“If a building is going to fall down and kill people, we have an ethics problem,” he
said. “But the other aspect is what kind of risk people are willing to take that this
is going to happen again.”
The responsibility for preventing such accidents lies in the hands of the entire
team, from the engineers to the building owners, Porter said. He also points to
the issue of low bids and the occasional tendency to cut corners.
“They might pay a cheaper price upfront, but they’ll have to do a lot of
maintenance later on,” he said.