Sabo Bridge may reopen soon

Minneapolis considers opening the bridge back up before a permanent repair is completed.

by Tesha M. Christensen

The Martin Olav Sabo Bridge may soon open back up to pedestrian and bike traffic.

Experts are investigating whether Minnesota’s only cable-stayed suspension  bridge could be opened to users before a permanent fix is made, according to Minneapolis Public Works deputy director Heidi Hamilton.

The five-year-old bridge has been closed since Feb. 19, 2012 when a pair of cables was found lying on the bridge deck. The Chicago-based firm Wiss, Janney and Elstner (WJE) is currently investigating why the anchor plates holding the cables fractured. Minneapolis and Hennepin County are splitting the $150,000 fee.

In order to reopen the Sabo Bridge, one major question needs to be answered. “We need to know if the shoring in place is adequate to support a live load of bicyclists and pedestrians,” said Hamilton. The original design engineering firm, URS, will answer that question in early May.

Meanwhile, the search for answers as to why the anchor plates fractured continues. Several instruments were installed by city workers and WJE staff the week of April 16 that will provide experts with important data about how the bridge handles weather and wind conditions.

According to Minneapolis Bridge Engineer Jack Yunza, anemometers were installed to track wind speed, duration of wind and temperature during wind events. Strain gauges, displacement transducers and accelerometers will provide actual stress range movement, amplitude and frequency of cable vibrations experienced by the bridge during wind events. These instruments will be monitored 24 hours a day.

Together, these two pieces of data will be correlated to provide a complete picture of what’s happening to the bridge in all kinds of weather, explained Yunza.

The data from these instruments will then be reviewed alongside the report of why the plates broke. The metalurgical analysis of the broken plates is being done by Lehigh University in Pennsylvania.

Yunza stated, “The the information gathered will become the basis for the repair plan.”

This story printed in the May edition of the Longfellow/Nokomis Messenger.