Minnesota tragedy sparks review.
This bridge was the busiest in Minneapolis, typically used by over 140,000 vehicles daily. The sudden collapse immediately sent the country into a worry, with national politicians calling for inspections of their jurisdiction's bridges, including New York, Arizona, Michigan, New Jersey, and New Mexico. Governor Tim Pawlenty of Minnesota called for inspections of his own state as well, especially all those of similar designs and those falling into the same category on the assessment scale.
The assessment scale for bridges across the country includes classification categories such as "Structurally Deficient," "Functionally Obsolete," and the more typical categories like "Fair," "Good" and "Very Good." The 1-35 Bridge, which was erected in 1967, had been declared structurally deficient by a number of assessments, starting with a report done by federal investigators at the Minnesota Department of Transportation in 1990 in which the investigators warned that the bridge had sustained significant corrosion in its bearings. Minor repairs were made in response, but the grade did not improve. Regulators also mandated that the bridge was to be inspected every two years, which is more frequent than the typical schedule.
During the 1990s, other inspections found fatigue cracks and corrosion within the joints of the bridge. Further repairs were made, and the state instituted an annual inspection requirement. A federal inspection that followed in 2005 rated the bridge as just 50 out of 100 for structural stability.
These ratings sound alarmist. Yet, a structural deficiency status does not generally equate to imminent danger. In fact, studies show that more than 73,000 bridges nationwide are or have been classified as "structurally deficient," which is meant to denote that the deck, substructure or superstructure is in poor condition or that the bridge has been determined to have a low load capacity.
By comparison, a bridge becomes structurally obsolete if it has some sort of clearance, maximum capacity or roadway alignment that no longer handles traffic sufficiently. If all the bridges that possess the deficient status were to be repaired to reach a higher grade, engineers estimate that the process would take at least a generation and cost over $188 billion, according to the Associated Press.
The collapse in Minnesota immediately moved New York Governor Eliot Spitzer to increase inspections of 49 similar bridges in the state, eight of which are located within New York City. Barely 15% of New York City's 800 bridges are considered to be in "very good" condition, while 77.2% of them are graded "functionally obsolete" or "structurally deficient," according to Newsday.
Safety experts within New York say that budget cuts are ultimately endangering the bridges, as they restrict amounts that are used for repair and replacement, not to mention inspection. Despite the high number of bridges labeled deficient, however, state and city transportation officials maintain that the possibility of a similar tragedy occurring in the metropolitan area should be dismissed. "We have experts we pay to worry about our bridges," Carol Breen, a spokeswoman for the state Department of Transportation, told Newsday. "If we thought a bridge was going to collapse, we close it and you can't use it."
To be sure, all inspectors of transportation systems state that if at any point they deem a bridge to be in serious danger of collapse or catastrophe, they immediately close it to the public. But nobody deemed the 1-35 bridge in immediate need of overhaul, in fact reset-ring its ultimate replacement until 2020.
When asked for a statement on how this incident might affect the future of bridge and other infrastructure insurance, Mark Kulda, vice president of Public Affairs for the Insurance Federation of Minnesota, said that the first priority in putting the pieces of the incident back together is finding out what factors caused the collapse. He said that this particular factor is very important, because if it is found that something about the design of the bridge played a role in its instability, this might lead to a blanket overhaul of similar bridge designs.
The particular design of the 1-35 Bridge is fairly unique. The bridge was a truss bridge, with no underwater pylons, which effectively means the entire structural support is focused on the two ends of the bridge, with no redundancies existing-meaning that if there were any sort of stress exerted on a source in the bridge, the entire thing would collapse. "If the bridge has one source and that one source fails, then you have a catastrophic failure, which now is exactly what happened," says Kulda.
A study performed in 2001 by the Center for Transportation Studies at the University of Minnesota, which is ironically just a few blocks away from the fallen bridge, pronounced that the 1-35 Bridge possessed this particular risk. But the study concluded that "fatigue cracking of the deck truss is not likely" and that replacement of the bridge "may be deferred."
Since the report made the design of the bridge and its potential collapse a known risk ahead of time, the particular type of design plays a role in the potential liability associated with the collapse; "you have to wonder about other bridges of this type," says Kulda, "[and] whether we have to start replacing those types of bridges."
Kulda also extended the faulty de sign debate by saying that if the overall design is found to be at fault, there lies a possibility that the private company responsible for designing the bridge could be liable. If such is the case, bridge and infrastructure insurers would need to re-evaluate their strategies for insuring structures in the future.
Within a week of the collapse, investigators had found what may be considered a design flaw in the steel parts that connect girders. The discovery raised safety concerns for other bridges around the country, prompting the Federal Highway Administration to urge all states to pay extra attention to how much weight they allow to be placed on bridge designs using so-called gusset plates, which are not limited to truss bridges.
Safety boards concerned with the bridge collapse evaluations are in the process of verifying the stresses and loads that the plates in question endured on a daily basis. The results of the official report to the cause of the Minneapolis bridge collapse are not expected for at least a year.
Despite the availability of more stable designs with redundancies for damage factored in, the 1-35 bridge was built without pylons for a specific reason--to allow for safe and non-interrupted waterway movement of barges, which frequently traverse that area of the Mississippi River. Truss bridges of similar design stand throughout much of the United States, especially across large, trade-facilitating waterways. If the design of this sort of bridge is deemed unsafe and in need of replacement, the municipalities and private holders of the recalled infrastructure could face billions of dollars in expensive and lengthy repairs.
While glacial repair schedules are a common efficiency hindrance for municipally owned infrastructure, the same usually is not true for privately held structures. For example, since the Chicago Skyway was sold to private investors in 2005, Juan Rodriguez, a maintenance worker for the Skyway, told BusinessWeek that owners are taking the highway to a "whole new level." He elaborated, stating investors mandate that repairs are made on a very specific time schedule-sometimes down to the hour. By contract, potholes, for example, must be filled within 24 hours, and squirrel carcasses must be removed within eight hours of being found.
According to Rodriguez, these type of simple daily improvements formerly had to be logged onto a list of problems that would take days and longer to address under the municipality. Yet, for private investors, it is in their best interest to maintain strict guidelines for order and maintenance, as this is often stipulated in the contracts initially agreed upon with the municipalities that held the infrastructure be fore the buyout.
Though tragic, the unexpected collapse of the 1-35 bridge alerted officials and the public that current national infrastructure is not fail safe, and that reports of damage and stress need to be taken seriously. 1-35 is a federal highway and, thus, government possesses sovereign immunity and the ability to cap its liability, but hopefully this accident will influence both private and public bridge owners into being more careful with their structures and the inspections that they undergo. Then, there is at least some silver lining to be found.
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|Title Annotation:||FOREFRONT; Minneapolis Bridge Collapse, 2007|
|Comment:||Minnesota tragedy sparks review.(FOREFRONT)(Minneapolis Bridge Collapse, 2007)|
|Date:||Oct 1, 2007|
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