01/31/08
JEFFERSON CITY – Preliminary studies of all Missouri bridges with gusset plates similar to the collapsed bridge in Minnesota are complete, with many already confirmed as safe, Missouri Department of Transportation bridge engineers announced today.
Engineers are evaluating the state’s 232 truss bridges. Truss bridges use steel beams joined together by steel gusset plates to support the structure. The Minneapolis bridge likely collapsed because of an original design error in some of its gusset plates, which couldn’t support increased loads on the bridge deck, according to National Transportation Safety Board findings released two weeks ago.
Following NTSB recommendations, MoDOT is studying all truss bridges to determine whether the weight they carry has significantly increased since they were built, which could expose any original design errors in the gusset plates.
Preliminary studies have found 156 bridges with no significant weight increase since their construction, or that are already scheduled for replacement in the near future. These bridges are safe, with no further study needed. The remaining 76 bridges have added significant weight since their construction, so further study is needed to make sure there were no errors in the original design of the gusset plates.
Bridges typically add weight when the bridge deck is replaced to add a new driving surface, or when the existing deck is resurfaced. The average age of Missouri’s truss bridges is 67 years old.
“So far we’ve found no problems, and I fully expect these studies to confirm that all bridges on Missouri state highways are safe,” said MoDOT Director Pete Rahn. “Now that we’ve narrowed down the list, we’ll study those bridges further to make absolutely sure there are no problems.”
Rahn said the detailed studies would continue as quickly as possible, with any needed improvements made immediately.
Further Study Needed No Further Study Needed
01/16/08
MoDOT Studying Minneapolis-Style Bridges; Statement from Director Pete Rahn In Response to Federal Findings
Complete listing of the 232 bridges to be studied.
10/04/07
MoDOT Completes Inspections of Minneapolis-Style Bridges; All Are Safe (10/04/07)
Deck Truss Bridge Inspection Schedule and Results (Excel, 16kb)
A deck arch truss bridge means the truss (the long metal support structure) is below the deck and supports it. This is compared to other truss bridges where the truss is on top of the deck. Arch refers to the shape of the truss. The only deck arch truss bridge in Missouri is the Hurricane Deck bridge (pictured right) at Lake of the Ozarks (Route 5 in Camden County). |
