On 1st August, 2007, an eight-lane, three-span section of the I-35W bridge over the Mississippi River in Minneapolis, Minnesota, suddenly collapsed. 145 people were injured, and thirteen died.
This case study is based on an investigation of material evidence provided by the NASA Safety Center(NSC), National Aeronautics and Space administration (NASA), National Transportation Safety Board (NTSB), and a full-scale load rating of the bridge superstructure. Proximate (Direct) Cause:
Gusset plates finally fractured by the former bridge heavy construction and renovations materials, and peak hour traffic weight. Before
After
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According to the NTSB, the failing gusset plates at the nodes were only half as thick as they should be.
Except being …show more content…
Inspectors during inspections assumed the plates had no possibilities to fail so they did not pay attention to them.
The concentrated placement of massive renovations and heavy construction materials, and peak hour traffic finally stressed the bridge to disclose the deficiency on the day of the collapse “The diagonal steel beams within the failed nodes shifted to the west and fractured the gusset plates around the ends of the diagonals. Once the diagonal beams separated, the rest of the truss fell.” Underlying Problems: ❖
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Defective gusset plate design and inadequate review process.
Lack of attention to gusset plates in load ratings and inquiry.
Added weight from traffic, construction and renovations materials.
Communication problems between the State and the construction contractor. ❖
The cause of the collapse has been identified due to a critical design flaw: The U10 and L11 gusset plates (shown below), should have been 25 mm thick, but they were only 13 mm thick.
During the time of collapse, the bridge had heavy construction equipment and stockpiled materials on the site.
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❖ …show more content…
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There are many elements that cause the bridge collapse.
The original designers might have forgotten to test quality control that ensure the correctly calculations for the gusset plates.
The State didn’t communicate to contractors clearly.
“Whenever planned modifications may significantly increase stresses.” ❖
Scaling fallacy: did not pay attention on the load assumptions. Miscalculations, lack of system tests, and inappropriate safety factors.
Factor of safety: the structure's ability to carry load was not determined to a reasonable accuracy.
Cost-Benefit: it can use on product design but I do not recommend use this principle on bridge design, which they clearly used it when working on the I-35W bridge.
Structural forms: truss bridge is not as strong as other bridge types, did not use enough strong materials or solid pieces.
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Design-related Factors Re-design Suggestions ❖ ❖ ❖ ❖ ❖ ❖
Barriers
Drainage
Abutment Maintenance Proportion and form Headstocks and piers ❖
❖
Control: Implement design review, verification, and change control to ensure design
This case study is based on an investigation of material evidence provided by the NASA Safety Center(NSC), National Aeronautics and Space administration (NASA), National Transportation Safety Board (NTSB), and a full-scale load rating of the bridge superstructure. Proximate (Direct) Cause:
Gusset plates finally fractured by the former bridge heavy construction and renovations materials, and peak hour traffic weight. Before
After
❖
❖
According to the NTSB, the failing gusset plates at the nodes were only half as thick as they should be.
Except being …show more content…
Inspectors during inspections assumed the plates had no possibilities to fail so they did not pay attention to them.
The concentrated placement of massive renovations and heavy construction materials, and peak hour traffic finally stressed the bridge to disclose the deficiency on the day of the collapse “The diagonal steel beams within the failed nodes shifted to the west and fractured the gusset plates around the ends of the diagonals. Once the diagonal beams separated, the rest of the truss fell.” Underlying Problems: ❖
❖
❖
❖
Defective gusset plate design and inadequate review process.
Lack of attention to gusset plates in load ratings and inquiry.
Added weight from traffic, construction and renovations materials.
Communication problems between the State and the construction contractor. ❖
The cause of the collapse has been identified due to a critical design flaw: The U10 and L11 gusset plates (shown below), should have been 25 mm thick, but they were only 13 mm thick.
During the time of collapse, the bridge had heavy construction equipment and stockpiled materials on the site.
❖
❖
❖ …show more content…
❖ ❖
❖ ❖
There are many elements that cause the bridge collapse.
The original designers might have forgotten to test quality control that ensure the correctly calculations for the gusset plates.
The State didn’t communicate to contractors clearly.
“Whenever planned modifications may significantly increase stresses.” ❖
Scaling fallacy: did not pay attention on the load assumptions. Miscalculations, lack of system tests, and inappropriate safety factors.
Factor of safety: the structure's ability to carry load was not determined to a reasonable accuracy.
Cost-Benefit: it can use on product design but I do not recommend use this principle on bridge design, which they clearly used it when working on the I-35W bridge.
Structural forms: truss bridge is not as strong as other bridge types, did not use enough strong materials or solid pieces.
❖
❖
❖
Design-related Factors Re-design Suggestions ❖ ❖ ❖ ❖ ❖ ❖
Barriers
Drainage
Abutment Maintenance Proportion and form Headstocks and piers ❖
❖
Control: Implement design review, verification, and change control to ensure design