Innovative Network Tied Arch Solution to Spanning the Mississippi River

摘要

The new Mississippi River Bridge at Hastings, Minnesota is a $US 120M design-build project withrna 166 m main span network tied arch to create a community icon for this scenic recreation area.rnThe solution calls for a unique pair of free standing steel box arch ribs with no upper wind bracingrnthat utilizes post-tensioned concrete tie girders. It is a record span in North America for this type ofrnstructure. The arch is integrally connected to its piers to eliminate large bearings and is founded onrnnearly 60m long 107cm diameter driven pipe piles at one pier and closely spaced 1.5m diameterrndrilled shafts at the other pier to account for the differing geology.In addition to the unique structure type, the project is mandated to meet a rigorous structurernredundancy and a 100 year service life. A unique steel floor system with both longitudinal andrntransverse main girders was developed to meet the redundancy requirements with strict limits inrnboth service and strength conditions. The 100 year service life results in the use of stainless deckrnreinforcement, special coatings for the cable hangers and other innovative materials and details.rnThe steel system for the arch was erected on land, transferred onto barges using Self PropelledrnModular Transporters (SPMTs), floated down river, transferred onto a rail system beneath the piersrnusing SPMTs, and lifted 20m into place using strand jacks.