If the materials are the least expensive installed cost, don't require maintenance like steel, and last longer because they are impervious to rot, chemicals, etc, then it looks to me like the total cost of ownership would be lower than steel. If the materials cost is the same as steel, or even somewhat higher, this lower COO is likely to offset that cost. The simple fact that the Army is paying for it tells me this is highly likely.
I'd be surprised if it's impervious to fire--I don't know any plastic that is.
This is a great use of recycled material. A major portion of steel bridge maintenance is the on-going sandblast / paint cycle. Using plastic for the bridge span is great. Using recycled plastic is even better.
Good story, Ann. I'm impressed. It's one thing to fill a car seat with this material, but a weight-bearing bridge is quite something else. It pretty much takes the ceiling off for this material. Imagine, infrastructure made from landfill material. Now I don't feel so bad about drinking bottled water.
All over Europe, energy is recovered by incinerating trash, generating steam for heating apartment complexes in towns and cities and/or generating electricity. This works very well, greatly reducing the volume of material that needs to be buried in landfills.
These materials have higher specific strength than mild steel, and we have a handle on the most important issue for thermoplastics- the creep issue.
As for cost, I'll let other speak. The Army has just completed a full 2 year constant study of the first takn bridge at Bargg, and came through perfectly. Listen to the video on the tank bridge opening ceremony very carefully. He says 3 important things- one referring to maintenance, one referring to degradation, and one referring to a ROI.
Thank you for the nice article. These materials are quite different from Trex in many regards, and this is recyclable after the end of life. As for static/Dynamic considerations, the tank bridges were designed to have a tank parked on the bridge for 25 years and then drive off and have the bridge recover its' shape. The Scotland bridge was a more modest 10 year loading.
I recommend a couple of videos to those interested:
The reference to the M1 ABRAMS tank crossing a bridge @ Ft. Bragg begs the question regarding static & dynamic loads. Was the tank in motion or sitting mid-span? If in motion, the calculations for acceptable load vs. deflection take on a different posture than if the tank was sitting mid-span w/ engine running while the summer sun baked down on the bridge structure. While I'm convinced that the designers did their "homework" regarding allowable loads, did they also consider ambient temperature and/or chemical decomposition from UV rays, etc.? The installation of a short-span bridge in Scotland, which see much cooler average temperatures & wetter climate conditions than many parts of the U.S. etc. also should be a factor in determining suitability of installation. The initial cost of installation should not be high on the list of priorities, given the elimination of periodic maintenance, especially in light of the fact that maintenance costs are not fixed over time. It would seem to me that they are probably more exponential in nature.
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