October 10, 2007
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If you know someone who wants the “serious info” it is here. http://www.dot.state.mn.us/i35wbridge/rebuild/ I spent an hour on it. They have all the source material there.
They released the design info on the new !35W bridge today. It’s will be a boxed concrete pre stressed concrete shallow arch. Basically two bridges, each five lanes two piers and crossing box beams for each. I think one might be “drivable” by the time of the Republican convention but the scheduled completion date is Christmas eve 2008. There is half a million dollar a day incentive to complete it early.
Light rail potential was added at around 25% of the cost. Basically they widened the center some. Not hard since rail doesn’t need a “breakdown lane” on the side. It includes the light rail space, not the approaches. Light rail, being rail only needs a narrow space. The plan doesn’t include light rail and the approaches would be “tricky” but the bridge could handle it.
The bridge also contains provisions for a “pedestrian/bicycle” suspension bridge hung from the underside. It is not included but it seems it could be built rather cheaply. Minneapolis planning likes that kind of thing. There are observation decks under both ends of the bridge. They have a “green area” under the rest of the bridge but I suspect this will become parking. Actually it is quite “scenic”. You look west and there is a waterfall river gorge and you look East ant there is a surprisingly pristine river gorge. It seems a nice place for a picnic and can have memorials for the collapse victims. Before the collapse it was just industrial. It’s really a magnificent view with the waterfall and the mostly pristine river gorge.
As for the structural design it uses precast concrete box girders in transportable sections. They have precast a lot of precast tubes in there . The thing about the right alloy precast steel cable wire is that it has a lot of “elasticity” before metal fatigue is significantly increased . Basically, if this bridge, as I understand it is kept dry, (fairly easy) it can last almost forever. If it fails in the middle it would sag but all of the pre-stressed concrete steel cables would hold it up. They would eventually be stressed and fail but it would be a slow process.Another feature is that the “arch” can be built without falsework. For an rough idea how the bridge will look check out the Wabasha bridge in Downtown St. Paul, built by the same designers. I drove under the Wabasha bridge along the River Road and it looked very impressive and clean from below. Here is a link to an inderside view of the Wabasha Bridge.
