Thursday, September 23, 2010

Two Rivers Bridge: Progress

The Two Rivers Bridge project is moving right along. A steel arch span will bridge the 210-foot gap between the piers in the left-center of this photo. Quite a bit has been accomplished since this was taken in early September.

The steel span over the navigation channel of the bridge has proven to be a design and fabrication challenge. I have been aware of some delays, but it appears now that a schedule is in place and there will be no delays in the completion of the project. My information has come from a number of sources, but the general consensus is that the bridge construction is ahead of schedule and that Jensen Construction is doing a fine job. I'm anxious to see the span in place, as it will do much to define the appearance of the bridge, and I hope to be on site to see it lifted into place. Here are a few things of interest that I will loosely call "facts" in that I don't have the engineering or contractual data:

The span will be shipped to the site in eight sections. A truck will be required for each of the eight pieces. Those pieces will be spliced at the floor beams into four truss sections before the final assembly. I was able to obtain some fabrication shop photos of the work-in-progress:

The truss sections will be disassembled at the center joint and placed on their sides for transportation, as the assembly would otherwise be too tall for highway transport. Spanning the 210 feet required a truss over 14' deep.

The entire span will then be assembled on site. There will be some large scale Erector Set action to get this accomplished.

The camber of the arched span is apparent from this perspective.

The steel is designed to develop a patina of rust that will prevent further oxidation and eliminate the need to paint. Even with the box beam construction, plate has been added to enhance the stiffness of the structure, more for the comfort of possibly queasy bridge users than due to a need for additional strength.

The steel is scheduled to ship in mid-October and, once assembled, the span will be lifted to its final location by a crane that I have got to see, though in checking around, 100-ton cranes are not that uncommon. The weight of the assembly is slightly over 200,000 pounds. These are bridge-building professionals, but I will bet that there will be a collective sigh of relief from all involved when the span is safely resting on the piers.

Folks, the cycling life in Central Arkansas just keeps getting better!

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