Minneapolis major interstate bridge, Interstate 35W, was jammed with rush-hour traffic when it suddenly broke into huge sections and collapsed into the Mississippi River yesterday. Authorities lowered the death toll from an interstate bridge collapse to four.

Officials have said that the eight-lane Interstate 35W bridge, a major Minneapolis artery, was in the midst of being repaired and two lanes in each direction were closed when the bridge buckled. It is being reported that the center section of the bridge dropped straight down and pancaked in the middle of the river, leaving several vehicles stranded on a broken island of wreckage. As divers plumbed the waters, other rescuers searched frantically for victims amid broken, zigzagged sections of blacktop. Some of the injured were carried up the riverbanks.

Minneapolis police chief Tim Dolan told reporters they are expecting the death toll might climb because some people were still trapped inside the vehicles that were hurled into the Mississippi river. The recovery effort might take at least three days because of the fast moving currents from the Mississippi. However, it was recently reported that the divers are not going into the water until officials are sure that the surviving structure of the Interstate 35W bridge is stable.

It is really unfortunate because Hennepin County Sheriff Rich Stanek and Minneapolis police chief Tim Dolan told reporters that there are cars are trapped beneath the water under crumpled concrete and Stanek knows bodies are there. During rescue operations Wednesday night, divers saw victims in submerged cars before darkness postponed the work.

Minnesota Governor Tim Pawlenty told a news conference that the bridge was inspected by the Minnesota Department of Transportation in 2005 and 2006 and that no structural problems were found. Traffic had been “bumper to bumper” at the time of the incident as only one lane was open in either direction on the eight-lane road because of construction work on the arched bridge.

Even though no structural problems were found in 2006, resurfacing work was taking place on the bridge. According to UK’s Institution of Structural Engineers chief, Keith Eaton, the only way a complete bridge can collapse like it did “is either because the load is too heavy, or the connections between the bridge’s structural elements are too weak.”

“The engineers will have to see where the collapse started. Clearly a failure occurred somewhere which imbalanced the whole thing,” he said.

This might be the cause, the Star Tribune reported that the former chairman of the National Transportation Safety Board, Jim Burnett, was intrigued by a 2001 University of Minnesota study that found signs of “fatigue cracking” in the bridge supports. He added that a 2005 federal study found that the bridge was “structurally deficient.”

“A structurally deficient bridge might be one not adequate for the traffic it takes, but not necessarily dangerous,” Burnett said. “But a lot of structurally deficient bridges are dangerous.”

Eaton also debunked an earlier speculation that hot weather contributed to the accident by weakening the concrete or expanding the steel framework, however that was not a likely explanation, since modern bridges are built to cope with those extremes. I can see why some people may have jumped to this conclusion considering that back in April, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) warned that North American cities should anticipate “an increased number, intensity, and duration of heat waves.” According to the National Climatic Data Center (NCDC), between 2000 and 2006, Minnesota experienced its 4th, 6th, and 8th warmest years.

The 2001 report went on to express concerns that a single crack could “theoretically” lead to the entire bridge’s collapse. However, it also said that even if there was a crack, the load could “theoretically” be redistributed along the steel trusses or the concrete deck of the bridge, keeping the bridge aloft. Truss is a type of framework - skeletal structure - that was used to construct the bridge. A truss bridge is comprised of connected rafters, posts and struts, which the trusses dissipate, or spread out, the compression and tension forces through the structure when a load is applied. The report also indicated there was weakness at the joints of the steel that held the concrete deck above the river, due to “unanticipated out of plane distortion” of the steel girders.

Eaton concluded that there is a downside to truss bridges.

“They are made of lots of complex pieces of metal, interconnected bolts or rivets,” Mr Eaton told the BBC.

“They have little corners between two pieces of steel where water can collect and cause corrosion.”

Nesting pigeons could also be an issue.

“Their droppings are very corrosive, which can be a problem,” he said.

More intriguing is how the White House is quick to toss this political hot potato back to the state, even though their own 2005 report found structural deficiencies on the bridge. White House press secretary Tony Snow said that even though the 40-year-old Interstate 35W received a rating of a 50 on a scale of 120 for structural stability, that didn’t “mean there was a risk of failure, but if an inspection report identifies deficiencies, the state is responsible for taking corrective actions.”

One does have to ask, is this tragic event another Katrina type cluster fuck, so to speak? Isn’t the Federal Highway Administration (FHWA) to ensure that our federal highways are safe to drive on? FHWA’s role

FHWA is charged with the broad responsibility of ensuring that America’s roads and highways continue to be the safest and most technologically up-to-date. Although State, local, and tribal governments own most of the Nation’s highways, we provide financial and technical support to them for constructing, improving, and preserving America’s highway system.

It is time to start asking questions as to who really has responsibility of over seeing our National roads. How many more tragedies need to occur throughout the country for people to finally open their eyes to the uncaring bureaucratic machine who only waits for needless deaths to occur before it reacts.

Update: Star Tribune just reported that structural deficiencies in the I-35W bridge were so serious that MnDOT last winter considered bolting steel plates to its supports to prevent cracking in fatigued metal but opted against making the repairs.

Update 2: You can find my updated version of this post over at Scholars and Rogues

Related posts

• No related posts.

Tags: Bridges, FHWA, Interstate 35W, Keith Eaton, Minneapolis, NTSB |  Print This Post |
functional