The report was written by UC Berkeley structural engineering professor Hassan Astaneh, an internationally recognized authority on steel bridges.
Astaneh concluded that 300 tons of material on the bridge at the time of the collapse, and an additional two inches of pavement added to the bridge years before, led to the bridge disaster.
He also concluded that MnDOT and its consulting firm, URS, should have examined the 35W bridge's gusset plates under Federal Highway Administration standards. The report was the keynote address at the International Conference on Steel Bridges in Portugal.
Minnesota Public Radio News received a copy of the report, and provided the National Transportation Safety Board with a copy.
NTSB spokesman Peter Knudson says the agency had not had time to evaluate the report. But he said investigators studying the cause of the 35W bridge disaster will consider the report in their investigation.
"Anything we believe has value as providing information, we certainly want to see it. So we will be looking it over, yes," said Knudson.
Before you keep reading ...
MPR News is made by Members. Gifts from individuals fuel the programs that you and your neighbors rely on. Donate today to power news, analysis, and community conversations for all.
Astaneh's report was especially critical of MnDOT, its bridge contractor URS, and PCI Construction, the firm that was repaving the bridge at the time of the collapse.
As for its reaction to the report, MnDOT's Deputy Commissioner Khani Sahebjam said through a spokesperson that this report is only one among many reports by many intelligent people.
"Sometimes when these things come out, it just kind of devalues what NTSB is trying to do."
The agency said while this report may have something to offer, the NTSB's analysis is the agency's "definitive report." Those findings are likely to come before the end of the year.
PCI Construction and URS Corp. did not respond to requests for comment on the Astaneh report.
An engineer at the American Association of State Highway Transportation Officials did dispute some of the findings.
AASHTO writes manuals and guides on transportation projects, like bridge building. It works closely with the Federal Highway Administration, and state DOT officials are representatives of the organization. MnDOT's chief bridge engineer Dan Dorgan is the state's bridge representative in AASHTO.
AASHTO's Kelley Rehm was not able to respond specifically to the report, but said she is well aware of the collapse investigation. Rehm is the program manager for bridges and structures.
She disagrees with Astaneh's assessment that bridge engineers are required to look at gusset plates when they evaluate a bridge.
"I think it's giving the engineers and the states the ability to use their engineering judgment to decide what they feel is going to govern the load rating," said Rehm. "I don't know about the URS consultant report. Obviously they didn't feel that was going to govern the load rating, so they didn't do it."
Rehm says AASHTO has put out additional standards and guidelines on evaluating gusset plates, but typically gusset plates haven't been involved in evaluations.
"Overall, gusset plates have not been the deciding factor in load ratings," said Rehm. "A lot of times the load rating is depending on the steel member sections, the deck deterioration, things like that."
Rehm says she respects Astaneh's findings, but she says other academic reports on the 35W bridge collapse have been issued in recent months.
"Sometimes when these things come out, it just kind of devalues what NTSB is trying to do and their research," said Rehm. "It sounds like he's a lawyer for some of the people who are involved in the collapse, and you just have to wonder what his motives are in releasing this paper."
Astaneh has been hired as a consultant by Jim Schwebel, a lawyer representing some victims of the disaster.
Schwebel says Astaneh's paper is by no means comprehensive, but it does show that construction company PCI and consulting firm URS were culpable in the disaster.