Milwaukee bridge improves downtown access
Milwaukee is putting the final touches on the first vehicular cable-stayed bridge in the state. Scheduled to open next month, the Sixth Street Viaduct has been reconstructed to improve transportation between the city’s central business district and its south side.
Built in 1908, the original steel bridge was deteriorating slowly. By 2000, the Wisconsin Department of Transportation (WisDOT) had closed two of the viaduct’s four lanes and had imposed a load limit of 12 tons for vehicles crossing the bridge. Those restrictions forced commuters and heavy trucks to find alternate routes across the Menomonee River and into downtown Milwaukee.
Although WisDOT faced rising maintenance costs for the aging bridge, it restored the structure for another reason: With the planned reconstruction of a nearby interchange, the agency needed to divert traffic to the viaduct to alleviate congestion in the construction area.
WisDOT worked with the city and Milwaukee County to select a team to rebuild the bridge as the “Gateway to Downtown Milwaukee.” The governments selected the local office of Kansas City, Mo.-based HNTB to design the bridge, along with Waukesha, Wis.-based Zenith Tech and Black River Falls, Wis.-based Lunda Construction to build it.
To meet an aggressive 24-month construction schedule, WisDOT decided to use a design-build process. Because the agency had not used a design-build contract before, it sought approval for the agreement from the state legislature. The legislature approved the project in August 2000, and groundbreaking occurred at the end of October 2000.
The new structure includes two double-leaf bascule bridges over the Menomonee River and South Menomonee Canal that open to allow boats and barges to pass underneath. The structure also has two cable-stayed sections with cables linked to two inclined concrete pylons. Each pylon is 145 feet tall and serves as the anchor point for the stay cables. The overall length of the stay cables, from anchor box to bridge deck, varies from 63 feet to 205 feet.
Bi-directional, post-tensioned, concrete was used on the deck to minimize cracking and to prolong the deck’s life. The 80-foot-wide deck has four lanes for traffic, and it incorporates sidewalks and bicycle lanes. Extensive lighting treatments have been installed for safety and to enhance the structure’s aesthetic appeal.
The completion of the $50 million project will improve vehicular access to downtown. It also will alleviate traffic disruption during the reconstruction of the Marquette Interchange in 2004.