Jeff Briggs (MoDOT) and
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 recently.
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 three weeks ago.
Following NTSB recommendations, MoDOT is studying all truss bridges to determine whether the weight they carry has significantly increased since their construction, 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.
"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.
As The Sentinel reported in the January 23 issue, the bridges inspected in the county are G0453 on MO 15 South over the North Fork of the Fabius River (built in 1923-located north of Edina); N0456 on Rt. E South over the South Fabius River (1958-located south of Newark); P0507 Rt. M South over the Middle Fabius River (1954-located near Rutledge); and S0952 on MO 156 East over the South Fabius River (1963-located near the Newark quarry).
The online MoDOT report shows numbers N0456, P0507, and S0952 as having been inspected and found safe. Bridge G0453 north of Edina has been designated as needing further study.
According to MoDOT sources, a traffic count in 2003 showed an average of 1,600 vehicles per day, while the count in 2006 showed over 1,800 vehicles. The counts are done on a three year rotation. That same source said that the weight study was probably done before the resurfacing in
2004, and the limit is 80,000 pounds.
The only plans for the bridge in the immediate future are to replace the two-rail treatment on the approach from both sides and on the bridge with guardrails. That is planned for sometime this summer.
MoDOT also says that about the only way the bridge can be replaced is "if the County and the City would consider chipping in, MoDOT would be glad to talk."
Representative Brian Munzlinger reported that he has spoken with MoDOT on numerous occasions as to repair, replacement or remodeling of the bridge, without success.
Dave Garrison, with Homeland Security in the Northeast Missouri Regional Planning Office suggested that those concerned with the safety of the bridge and possible replacement meet informally with elected officials, area residents, and MoDOT representatives to see what can be done.
Watch The Edina Sentinel for further updates on the bridge and for the possibility of a public meeting.