I-35W Mississippi River bridge

44.978888888889 - 93.245Koordinaten: 44 ° 58 ' 44 "N, 93 ° 14' 42 " W

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Mississippi River

The I-35W Mississippi River bridge was a steel truss bridge in Minneapolis, United States. It was built in 1967 and led in the course of the Interstate 35W across the Mississippi River. She joined in the Minneapolis Neighborhoods Downtown East and Marcy- Holmes.

The bridge was 581 m long, 33 m wide, 19.5 m high above the river, had four lanes in each direction and is crossed, according to the Minnesota Department of Transportation from an average of 141,000 vehicles per day.

She collapsed during rush hour on August 1, 2007. By accident 13 people were killed, the last victim was recovered on the 20th of August. In the months after the disaster, built on the same site of the construction of the new ten-lane St. Anthony Falls ( 35W ) Bridge, which was released on 18 September 2008.

Historical Background

The bridge was built in an area in the east of Minneapolis, which was well developed for more than 160 years. The first commercial exploitation began in 1848 one mile north of the bridge at the Saint Anthony Falls and spread from there. Over time, therefore, developed a section of the river, which is characterized by bridges, locks and dams.

However, the progress did not come easily; the Hennepin Iceland tunnel collapses in 1869 and made ​​the concreting of a weir at the Saint Anthony Falls necessary. In 1878 it came into the grain mill Washburn "A" Mill is a momentous explosion.

The area surrounding the southern abutment of the bridge is an eight- acre site, which was used in the 90 years before the bridge by the gas works of the city of Minneapolis, which operated a coal gasification plant here. Minnegasco, which ultimately became a part of CenterPoint Energy, let demolish the factory in the 1960s, because in the meantime the use of natural gas made ​​the coal gasification unprofitable. One half of the site was sold to Continental Oil Co., camped on the site for another 20 years of oil products and processed.

Had the long industrial use, the contamination of the soil under the bridge with toxic substances result. A year long legal dispute over the cost of the disposal of these contaminated sites lasted until 1991 and 15,000 tons of contaminated soil were removed from the area under and around the bridge. The cost of disposal amounted to approximately 30 million U.S. dollars between 1993 and 1998.

Construction and maintenance

The two main pillars of reinforced concrete bridge were located on the banks of the 119 m wide river. The superstructure consisted of a 323 m long, haunched truss construction with a maximum span of 139 m. The bridge was an important road link over the Interstate 35W. Because of the cold winter in Minnesota ordered the bridge since 1999 on a deicing system. At a temperature that allowed the formation of ice on the road surface, potassium acetate was sprayed onto the road surface. A similar system was later installed on the Brooklyn Bridge in New York City.

In September 1991, the two right, northward leading tracks were closed due to maintenance works, three years later, the right leading to the north lane was temporarily suspended in order to examine the state of the bridge. In 1998, the street lighting had been repaired.

Collapse

On Wednesday, August 1, 2007 the bridge collapsed during rush hour at 18:05 local time clock ( 01:05 o `clock Thursday CEST) partially collapsed. This led at least 50 vehicles, their occupants, and several construction workers either in the river bed or on the shore. A total of 13 people lost their lives. Several vehicles caught fire. A portion of the bridge collapsed on standing under the bridge wagons which three railway cars crushed with plastic balls and a fourth were damaged. The tracks belong to an industrial port of the Minnesota Commercial Railway.

The cause of the collapse was according to the investigation report of the " National Transportation Safety Board, " a design flaw of the engineers who have the gussets of the steel girder wrong size. The lack of monitoring by the supervisory authorities is criticized in the final report further. A few weeks before the collapse began construction in front of the bridge structure, and therefore the traffic management was limited to two lanes in each direction. Shortly before the incident, the Minnesota Department of Transportation (Mn / DOT ) had announced that each of the late evenings of July 31 and August 1, the traffic would be restricted to one lane in each direction.

Mn / DOT 2001 report

In this report, it was revealed that the designers of the bridge have not shown correctly when the first fatigue failure would occur in the steel truss. Weak point were the welds that connected the individual truss members together. Further criticism was that in a fatigue fracture of one of these compounds, the entire bridge could collapse. Outcome of the investigation was that a failure of the components would not be expected and an inspection would suffice every 6 months.

The Minnesota State Highway 280 has been designated as the official detour route which he was partially converted into a freeway.