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Analysis of a Tragically Engineered System: The Interstate 35W Bridge Collapse
Antonio Larios
SYST 505
Professor Rochelle Jones
February 6, 2017
George Mason University
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Background
The Interstate 35 West (I-35W) Mississippi River Bridge was a steel truss bridge built by the Industrial Construction Company and Hurcon Inc. between 1964 and 1967. Located in downtown Minneapolis, the bridge spanned over 1,900 feet across the Mississippi River and had a width of eight lanes (Minnesota, 2007). As early as 1991, the I-35W Bridge had already been labelled “structurally deficient” by inspectors. Despite the deteriorating condition, it was not legally necessary to place any load restrictions on the bridge. Throughout the bridge’s 40 years of service, …show more content…
The contractor should have requested permission from the state’s project engineer to place heavy machinery on the bridge, but “lack of guidance . . . with regard to the placement of construction loads on bridges during repair” led to an overload of weight being placed on the bridge on August 1, 2007 (NTSB, 2008). There were over 100 vehicles on the bridge as it collapsed. “As a result of the bridge collapse, 13 people died, and 145 people were injured”
(NTSB, 2008).
In summary, the primary hazard, incident, and accident at the I-35W Bridge are:
Hazard: Gusset plates supporting the trusses were only half an inch thick, but should have been a full one inch thick.
Incident: A fracture in one of the gusset plates was triggered by heavy machinery and rush hour traffic positioned on the bridge.
Accident: Steel beams at the fractured gusset plate node crumpled under pressure.
The remaining nodes could not withstand the deficiency and the bridge fell.
Economic Impact
The I-35W Bridge supported over 144,000 vehicles per day, including 5,000 commercial trucks, as commuters travelled to and from downtown Minneapolis. The bridge connected the northern suburban neighborhoods directly to the industrial business regions across …show more content…
(2007, August 2). The economic cost of the bridge collapse. Retrieved from http://www.mprnews.org/story/2007/08/02/commercecosts Lilley, S. (2009, September). A Half-Inch to Failure. NASA System Failure Case Studies, 3(6).
Retrieved from https://sma.nasa.gov/docs/default-source/safety-messages/safetymessage-2009-09-01- minneapolis-bridge-collapse.pdf?sfvrsn=4
Minnesota Department of Employment and Economic Development [DEED]. (Undated).
Economic Impacts of the I-35W Bridge Collapse. Retrieved from http://www.dot.state.mn.us /i35wbridge/rebuild/pdfs/economic-impacts-from-deed.pdf
Minnesota Public Radio. (2007, August 3). I-35W bridge fact sheet. Retrieved from http://www.mprnews.org/story/2007/08/03/bridge_background National Transportation Safety Board [NTSB]. (2008, November). Highway Accident Report:
Collapse of I-35W Highway Bridge, Minneapolis, Minnesota, August 1, 2007
(NTSB/HAR-08/03). Washington, D.C. Retrieved from https://www.ntsb.gov/investigations/AccidentReports/Reports/HAR0803.pdf Xie, F., & Levinson, D. (2011). Evaluating the effects of the I-35W bridge collapse on roadusers in the twin cities metropolitan region. Transportation Planning and Technology,
34(7), 691-703.
Analysis of a Tragically Engineered System: The Interstate 35W Bridge Collapse
Antonio Larios
SYST 505
Professor Rochelle Jones
February 6, 2017
George Mason University
2
Background
The Interstate 35 West (I-35W) Mississippi River Bridge was a steel truss bridge built by the Industrial Construction Company and Hurcon Inc. between 1964 and 1967. Located in downtown Minneapolis, the bridge spanned over 1,900 feet across the Mississippi River and had a width of eight lanes (Minnesota, 2007). As early as 1991, the I-35W Bridge had already been labelled “structurally deficient” by inspectors. Despite the deteriorating condition, it was not legally necessary to place any load restrictions on the bridge. Throughout the bridge’s 40 years of service, …show more content…
The contractor should have requested permission from the state’s project engineer to place heavy machinery on the bridge, but “lack of guidance . . . with regard to the placement of construction loads on bridges during repair” led to an overload of weight being placed on the bridge on August 1, 2007 (NTSB, 2008). There were over 100 vehicles on the bridge as it collapsed. “As a result of the bridge collapse, 13 people died, and 145 people were injured”
(NTSB, 2008).
In summary, the primary hazard, incident, and accident at the I-35W Bridge are:
Hazard: Gusset plates supporting the trusses were only half an inch thick, but should have been a full one inch thick.
Incident: A fracture in one of the gusset plates was triggered by heavy machinery and rush hour traffic positioned on the bridge.
Accident: Steel beams at the fractured gusset plate node crumpled under pressure.
The remaining nodes could not withstand the deficiency and the bridge fell.
Economic Impact
The I-35W Bridge supported over 144,000 vehicles per day, including 5,000 commercial trucks, as commuters travelled to and from downtown Minneapolis. The bridge connected the northern suburban neighborhoods directly to the industrial business regions across …show more content…
(2007, August 2). The economic cost of the bridge collapse. Retrieved from http://www.mprnews.org/story/2007/08/02/commercecosts Lilley, S. (2009, September). A Half-Inch to Failure. NASA System Failure Case Studies, 3(6).
Retrieved from https://sma.nasa.gov/docs/default-source/safety-messages/safetymessage-2009-09-01- minneapolis-bridge-collapse.pdf?sfvrsn=4
Minnesota Department of Employment and Economic Development [DEED]. (Undated).
Economic Impacts of the I-35W Bridge Collapse. Retrieved from http://www.dot.state.mn.us /i35wbridge/rebuild/pdfs/economic-impacts-from-deed.pdf
Minnesota Public Radio. (2007, August 3). I-35W bridge fact sheet. Retrieved from http://www.mprnews.org/story/2007/08/03/bridge_background National Transportation Safety Board [NTSB]. (2008, November). Highway Accident Report:
Collapse of I-35W Highway Bridge, Minneapolis, Minnesota, August 1, 2007
(NTSB/HAR-08/03). Washington, D.C. Retrieved from https://www.ntsb.gov/investigations/AccidentReports/Reports/HAR0803.pdf Xie, F., & Levinson, D. (2011). Evaluating the effects of the I-35W bridge collapse on roadusers in the twin cities metropolitan region. Transportation Planning and Technology,
34(7), 691-703.