According to allcitycodes, the St. Anthony Falls Bridge is a box girder bridge in the United States, located in the state of Minnesota. The bridge spans the Mississippi River near downtown Minneapolis and is part of Interstate 35W.

Characteristics

The bridge consists of two parallel spans with a total length of 371 meters and a main span of 154 meters. The bridge is a concrete box girder bridge constructed using the free extension method. The bridge deck is a maximum of 21 meters above the river. The bridges are adjacent to each other and together they are 55 meters wide. Crossing the bridge is Interstate 35W with 2×5 lanes and left and right emergency lanes. The bridge is toll-free.

History

I-35W Mississippi River Bridge

The original bridge at this location was the I-35W Mississippi River Bridge, also known as Bridge 9340. This was a steel truss bridge with a 2×4 lane high deck. This bridge was 581.3 meters long, 34.5 meters wide and had a vertical clearance of 19.5 metres. This bridge was built between 1964 and 1967 and opened to traffic in November 1967.

Already in 1990 the bridge was labeled as “structurally deficient”, meaning that a replacement or extensive renovation is necessary. This was re-established in 2005, and a replacement new building was discussed. At the time, it was planned to replace the bridge around 2020, more than 50 years after opening.

Collapse 2007

On Wednesday, August 1, 2007 at 6:05 a.m. CDT, the main span collapsed, followed by the side spans. Almost the entire bridge collapsed into the Mississippi River. 100 vehicles were involved in the collapse. The bridge collapsed into the river, onto a railroad track and onto a waiting freight train. 13 people died in the disaster.

There were road works on the bridge during the collapse, with equipment on the main span. In addition, due to the installation of extra paving, the weight of the bridge has increased by 20%. This, in combination with a design flaw in the bearing capacity of the gusset plates that hold the beams of the truss together, led to the collapse of the bridge. More than 700 bridges of this design have been built in the United States, all of which were inspected in a short time.

The collapse sparked debate about maintenance levels and transportation financing in the United States. The term “structurally deficient” became much more widely known among the public. Thousands of bridges in the United States are structurally deficient, and in the years since the collapse, many bridges have been closed for safety to prevent collapse.

Replacement

The original bridge was a critical link in the Minneapolis highway network and is one of the busiest links in the metropolitan area. Minneapolis has a dense network of highways, but their capacity is often only 2×2 or 2×3 lanes, leaving little residual capacity to accommodate I-35W traffic. During the replacement, the parallel State Route 280 was temporarily converted to a freeway by closing intersections. However, this connection only has 2×2 lanes, so this solution was not sufficient. As a temporary measure, a number of emergency lanes have been converted into lanes on alternative highways.

In less than a year, a permanent replacement bridge was built, the I-35W Saint Anthony Falls Bridge. This was constructed between October 2007 and September 2008 and opened to traffic on September 18, 2008. The new bridge is a lot wider, with 2×5 lanes and left hard shoulder. Moreover, the new bridge is of a different type and material than the old bridge. The bridge cost $234 million and was completed ahead of schedule and under budget.

Traffic intensities

In 2012, 154,000 vehicles crossed the bridge every day.