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Highways, Byways, And Bridge Photography
Martin Olav Sabo Bridge
Regional Trail Crossing At Minneapolis
Minneapolis, Minnesota

Martin Olav Sabo Bridge

• Bridge: Martin Olav Sabo Bridge
• City: Minneapolis
• State: Minnesota
• Country: USA
• Carries: Midtown Greenway Regional Trail
• Crosses: Hiawatha Ave, MN-55, Light Rail Line
• Date Opened: November 8, 2007
• Total Length: 2,200 Feet
• Longest Span: 220 Feet
• Tower Height: 100 Feet
• Deck Width:
• Number Of Spans: 1
• Height Above Highway:
The Martin Olav Sabo bridge is a signature cable stayed bridge in Minneapolis, located just north of (and parallel to) Lake Street. The bridge is 2,200 feet long with a main clear span of 220 feet, which crosses both Hiawatha Ave (MN-55) and the Hiawatha light rail line. The bridge was built to carry the Midtown Greenway, a crosstown grade-separated bicycle expressway, across the very busy Hiawatha Ave and light rail lines without a need for the bicycle riders to cross at street level. Prior to the bridge opening, crossing Hiawatha Avenue was very difficult due to the high traffic volumes and the large number of streets that converge in the area.

I went to check out the construction site on several occasions prior to the bridge opening. In mid-December, 2006, bridge piers were complete on the east end of the span. On the west end, pilings were being driven to support the main tower. The tower itself will look very much like the Reiman Bridge in Milwaukee. It will rise at an angle towards the crossing, then tip back away from the crossing, with the change in angle happening where the bridge deck meets the tower.

In early 2007, the ground-level anchors for the cables were complete. Work was starting on the pier that would connect to the embankment that leads to the west side of the bridge. As of June 2007, the piers were complete, and falsework was erected for the bridge deck to be poured in place.

With the addition of this bridge, and another bridge being built at Chicago Ave, the Midtown Greenway will run from west of Lake Calhoun to the Mississippi River. The west end connects to a trail known as the LRT trail, which is an old rail line that is being held in reserve for a future light rail project. The east end of the trail ends at the Milwaukee Road Short Line Bridge over the Mississippi River. It is hoped that rail traffic can be eliminated from that bridge, and the Midtown Greenway can be extended east of the river to connect with trails that go all the way to the Wisconsin state line.

Marty Sabo was elected to the Minnesota House of Representatives in 1960 at the age of 22. He moved onto the US House of Representatives in 1978. He retired at the end of his term which expired January 3, 2007. Sabo has been instrumental in supporting highway and transportation projects both in Minnesota and the nation as a whole.

Update—the Martin Olav Sabo Bridge suffered a serious failure sometime on the evening of February 19, 2012. A pedestrian using the bridge reported fining two cables lying on the bridge at 10:06 PM. The city of Minneapolis responded, and closed the Sabo Bridge, Hiawatha Avenue, and the Hiawatha light rail line. Light rail was closed until February 24, and Hiawatha Avenue was closed until February 27.

When the two cables failed, the bridge deck dropped slightly. That placed additional stress on the remaining cables, leaving the bridge exposed to complete failure. The city of Minneapolis rushed to shore up the east end of the suspended span. To do this, they erected towers across the northbound lanes of Hiawatha Avenue, and jacked the bridge back to its normal height. This effort was hampered by the mild winter leaving the ground soft.

The first two cables failed due to a diaphragm plate that connected to the bridge tower developing a crack. This plate has two holes in it, with the cables being connected using pins that go through these holes. The entire plate broke off, causing both cables to fall. A second diaphragm plate was found to be near failure, so two additional cables were removed. A third diaphragm plate was also found with significant cracks.

The root cause of the cracking on the diaphragm plates has not been determined as of April, 2012. Cable stayed bridges have had problems with cables vibrating, but the shorter cables on this bridge were not thought to be susceptible to those effects. Other causes that are possible include a design issue, defective steel, or improper manufacturing.

The Martin Olav Sabo Bridge was controversial due to its cost. A more routine bridge would have been only a fraction of the $5.1-million cost of this signature structure. That controversy was reignited after the bridge failure. Interestingly, the firm that designed the bridge, URS Corporation, also designed the ill-fated Interstate highway I-35W bridge that collapsed into the Mississippi River in August, 2007.

Update—the Sabo Bridge is slated to reopen by June 4, 2012. It will not be repaired when it opens. Rather, the City of Minneapolis is planning to adjust the shoring supports and release some of the cable tension to allow the bridge to be safely used by the public. A full repair will be undertaken once the failure analysis is completed and a repair plan is developed. The bridge will be closed again for a period of time when the final repairs are completed.

The photo above is a view of the structure from the commercial parking lot located just south of the bridge.

Martin Olav Sabo Bridge
The photo above is the bridge as seen from the west approach to the structure. The pavement is marked for three lanes of traffic, 2 lanes for bicycles, and one lane for pedestrians. The photo below is a view of the main bridge span.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo above is the bridge deck as it passes on both sides of the bridge tower. Benches have been installed at two locations on the bridge deck to allow pedestrians to rest and watch the world pass bye. The photo below is the main span bridge deck looking to the east.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo below is the bridge deck as it curves to the south at the east end of the structure. The photo below is a west end of the bridge deck looking to the west.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo above is the east end of the bridge as seen from north of the structure looking to the southeast. The photo below is the east abutment of the bridge.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo below is a view of one of the cable anchor blocks as seen from the bridge deck. The photo below is the connection between one of the stay cables and the bridge deck. Bridge lighting is installed in several locations on the structure, including both of these locations.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo above is a view of the bridge span from under the structure. The photo below a view of the bridge tower shortly before the bridge opened.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
These two photos are views of the bridge from late in the construction project. The photo above is a view of the bridge span, while the photo below is the west abutment.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
These two photos are views from earlier in the construction project. The photo above is the west abutment and supports for falsework that is being erected to support concrete forms. The photo below shows the falsework that has been erected for the east end of the bridge deck.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The east end of the Martin Olav Sabo Bridge is situated at an important bicycle path intersection where the Midtown Greenway crosses the Hiawatha LRT Trail. The photo above is the trail name signs, which include additional guide signs for a number of landmark destinations around Minneapolis. The photo below is the scene looking northbound on Hiawatha Avenue at 28th Street where Hiawatha was closed due to the problems with the Sabo Bridge. Traffic was diverted westbound on 28th Street, northbound on Cedar Avenue, then east on 26th Street.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo above is looking north from the edge of Hiawatha Avenue towards the south face of the Sabo Bridge. Shoring towers and jacks were blocking the northbound lanes, and the southbound lanes were unsafe in the event that additional cables fell across the highway. The photo below is an overview of the work in progress at the main bridge tower on the west side of Hiawatha Avenue.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo above is a close view of the inspection crew working to inspect the cable attachments to the main bridge tower. The nylon straps that are wrapped around the tower are safety lines that would catch these cables if they were to fail. The photo below is another view of the tower looking southwest from the parking lot of a building located east of Hiawatha and south of 26th Street.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
These two photos are views looking across Hiawatha Avenue (to the northeast) towards the work going on to install shoring towers to support the east end of the main bridge span. This end of the bridge lost some of its support when the stay cables failed, and the weight was putting additional stress on the remaining cables. It was feared that some of the remaining cables were also at risk of failing.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
These two photos are close views of the bridge deck on the east end of the main suspended span. The photo above shows a section the cables were still attached. The photo below is a section where four cables had been removed, two per side. Workers were slowing raising each of the jacks to lift the bridge deck back up to its normal level.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo above is the trail leading up to the east bridge abutment. It was blocked off to keep users off of the bridge while the work was underway. The photo below is the bridge abutment as seen from the Hiawatha LRT Trail.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
These two photos are looking northwest towards downtown along the east side of the Sabo Bridge as seen from the Hiawatha LRT Trail. The photo above shows the east bridge abutment, which actually faces south due to a large curve in the bridge on the east side of Hiawatha Avenue. The photo below shows the curve in the bridge deck.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo above is looking west across Hiawatha Avenue along the south face of the Martin Olav Sabo Bridge. The photo below is a closer view of the workers adjusting the jacks on top of the shoring towers. The black steel railing is the north end of the light rail bridge that crosses Hiawatha Avenue and Lake Street.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
These two photos are closer views of the work at the top of the easternmost of the shoring towers. Workers are using a power lift to reach the top of the towers so they can add just a little more pressure to the jacks. The goal was to very slowly lift the bridge deck. If it was lifted too fast, it could crack the concrete causing additional damage.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
These two photos are telephoto views of the work on the bridge tower as seen from the east side of Hiawatha Avenue looking northwest.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
These two photos are similar telephoto views of the work at the main bridge tower, but looking west rather than northwest. This gives a better view of how the cables are attached to the tower.

Martin Olav Sabo Bridge
Martin Olav Sabo Bridge
The photo above is looking northwest towards downtown Minneapolis. The tall building downtown are visible through the span where the light rail trains pass under the Sabo Bridge. The photo below shows a train passing through that bridge span. Trains were prohibited from passing under the bridge for nearly a week until the shoring was completed and the bridge was stabilized.

Martin Olav Sabo Bridge

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Authored by John A. Weeks III, Copyright © 1996—2016, all rights reserved.
For further information, contact: john@johnweeks.com