Cable-Stayed Bridges - North Arm Bridge (5)

A photo of Don Bergman from Buckland and Taylor standing in front of the North Arm Bridge. Although this extrados river crossing is an attractive structure I think the different supports and various transitions for the approach structures are a little awkward.

The designer was stuck with a 139 m side span in order to cross Mitchell Channel, the nearby airport restricted the height of the towers, and the shipping channel restricted the depth of the girders. This limited the length of the main span and made an extrados bridge the logical choice for this bridge site.

Cable-Stayed Bridges - North Arm Bridge (5) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - North Arm Bridge (4)

A view from under the soffit of North Arm Bridge. Each tower supports twelve cables. The cables are made up of 58 sheathed, galvanized, and waxed strands in a 9 inch HDPE pipe. The cables were installed strand by strand. Dampers were provided at the deck anchorages to reduce wind vibration and the pipes have double-helix ribs to reduce rain vibration.  A cost-benefit analysis was performed to determine if traditional tower anchors or continuous cables in saddles (like on the Maumee River Bridge) could be used, but the tradition anchorage was found to be less expensive.

Cable-Stayed Bridges - North Arm Bridge (4) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - North Arm Bridge (3)

A closer look at the towers of the North Arm Bridge. Note the steel walkway hanging from the side of the concrete box girder superstructure.

This is an extradosed bridge, which means some of the prestressing tendons have been replaced by shorter towers and cable-stays. It has a main span of 590 ft, side spans of 456 ft, and transition spans of 170 ft. The bridge is supported by two 143 ft tall towers and a pier on each side of the river (see Google Earth photo). The towers are a steel/ reinforced concrete composite structure that Buckland and Taylor seem to prefer. The bridge was completed in 2008.

Cable-Stayed Bridges - North Arm Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.