I'm still waiting for the day Legos become a viable building material. Back then the biggest question was "should I use a round or square 2x2?" Usually more colorful too.
I'm having trouble visualizing this. They say the arches are "preformed from carbon fiber composite" and "inflated on site" and "cure within hours". Elsewhere (mainly in the news article), they say the arches are "filled with concrete" - which led me to wonder how the heck they got the concrete inside the tubes. I guess you could inflate an arch and then coat it with epoxy resin (or have it precoated), leaving it inflated for the resin to cure. But, then how do you fill the tube with concrete without compromising the composite tube's strength? Or is the concrete simply backfill over the top of the tube arch and sheet panels? I think the latter, but the "filled with concrete" verbiage is misleading in that case.
I'm figuring you have to put an elbow and a standpipe on one end of the arch tube, and dump the concrete in at the top of the standpipe. You need the gravity head to inflate the arch tube and provide enough internal pressure to make it self-supporting.
Yeah, saying 'bridge in >a< backpack' is misleading.
But, then you'd need a crane to put the concrete-filled arch into place, which they implied was not required. And I'm not sure a concrete-filled carbon fiber sleeve (as opposed to hardened/cured carbon/epoxy tube) would be stable enough to hold the arch shape while the concrete cured. Dunno, I may have to research it some more...
Hmm. Careful re-reading of the article, and similar on the U of Maine composite center's site, the arches are shipped to site, then inflated and formed to arch shape in situ, and then rigidized (cured). Subsequently they are filled with concrete (doesn't say how, and I can't see any external fittings at the top of the arches to allow for gravity feed, so I guess they pump it thru...how do they keep from having a void at the top of the arch I dunno...one more of life's mysteries...)
The arches were manufactured from 12-inch diameter rigidized inflatable hollow carbon fiber composite tubular arches spaced at approximately 2-feet on center, erected into place and filled with concrete.
Damage is a good point. I'm sure they could grout, get a fiber patch, epoxy? Seems like the epoxy step could be problematic, getting the old to bond with the new... sounds similar to fixing my Coleman raft, I usually just ditch it and get a new one. Heck at $500K a pop I might get one for my back yard... the bridge to nowhere...
I have some of the same misgivings about the exposed fiber tubes, but more due to debris impact from gully-washer floods and limbs/stumps/trees being washed down.
Kenat, yes, I read that too, but it wasn't clear at first whether the tubes were truly filled with concrete, or just backfilled/overburdened with concrete (i.e. left air-filled or hollow). The photos and text in the original article weren't very clear on the sequence.
Then again, yes, I'm sometimes guilty of overthinking, and over-posting. Debated red flagging my whole string of posts. Then decided, nah, I'll add more noise with a reply to your post instead...
My post was originally in the middle of your diatribe ;-) but I screwed up the /quote and asked 'the management' to fix my typo. However there was an issue and I was asked to repost, but now it's not in order ...
Still, seems pretty neat to me but I'd be interested to know about the durability issues.
KENAT,
Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:
I read it as another possibly cheaper way of doing formwork before the concrete is poured in. The composite will fall to bits over time leaving the circular arches unconnected to anything. These will in turn fall off sideways leaving a piece of corrugated steel dangling by hope alone to the concrete. The metal will then fall off leaving a wierd corrugated arch profile on the bridge. Water will get into the pores and inevitable voids in th corrugated profile and if there is any freeye thaw action at all the corrugations will fall off in chunks.
Looks like a design which saves money on construction and generates a whole load of maintenance problems 30-50 years on.
IMHO - Rubbish.
Can´t wait to see their new take on the wheel........
