I just watched a video on Facebook of the construction of a wind turbine. The really amazing part was when they set the first tower pedestal. There were multiple rows of anchor bolts with very close spacing. When they raised the pedestal and set it down on the base, all the bolts went through the bolt holes without having to twist,?ÿ wobble, or beat any bolt to fit.?ÿ It was picked up by the crane, raised to vertical and set on the base. The precision of the bolt placement and hole placement was phenominal.
In Belgium most WindTurbines are constructed by German companies, very well organiseer! I never went on site my self but I know the toleranties for bolt approval are very tight. For levels the planplate with micrometer was required, so we speak about some thents of a mm. Horizontal tolerante for bolts must be 1 or 2 mm I guess.
christof.
I'm guessing they have a precision jig that holds the bolts in place while the concrete sets. Level the jig and don't even measure on the bolts.
Yup. the construction folks use the term "template". Often the challenge is the orientation mark on the template. The superintendent says "yeah, the mark is for zero degrees" which to him means 90 degree azimuth, due east. And then it's not real world east it's site east based on some building grid lines two miles away.
Then there's the detail buried in the plans somewhere that shows orientation angle of 42 degrees. Grrr...
I have staked thousands of piers, and large foundations with anchor bolts and I have never seen any tolerance greater than 18th of an inch. That was 18th of an inch around the bolt so you have to be careful and as for jigs, I have seen them on occassion. The bolts are always tied and secured but once that concrete gets in their and they put the vibrator to it things move if it's not secure.
Sleeved bolts have a bit more wiggle room.
This is interesting.....
????
@flga-pls-2-2
WOW!
A time lapse on the Great Pyramids would be cool too. Of course Youtube has many guesses, but the original film appears to be lost.
Loyal
@flga-pls-2-2
...but the original film appears to be lost.
Loyal?ÿ
I saw it once when I was a school boy.?ÿ It wasn't all that spectacular...it was sub-titled, grainy and only in black and white.
@flga-pls-2-2
that was a waste of a lot of concrete that were removed at the top of each pile that were eventually covered with concrete again.
I recently read somewhere that concrete waste and rubble is being recycled. I, for one, cannot see any financial benefit by doing this as the raw materials for concrete are readily available. Maybe to lessen stress on landfills? That doesn't seem likely. ????
Did the "actors" have on black socks and sunglasses? ????
I'd like to point out how unlikely it is that the surveyors doing this work were selected from the phone book on the basis of lowest bid.?ÿ
@flga-pls-2-2
aside from the materials wasted, you are talking of manpower needed to pour the concrete then chipped away at the end.
as to the precision needed to layout each bolt, I think they have metal plates with pre-drilled holes to serve as guides (3:xx minute mark on the video). I doubt position of each bolt was determined by a surveyor. BTW, I may have missed it but I did not see any surveyor in the video?
@flga-pls-2-2
I live in an area where gravel is of abundance. This summer I visited/worked in an area where they recycled concrete because it was cheaper than purchasing gravel for a driveway or pad. Sometimes the neighborhoods we work in are not like home. Den
The "concrete" used for that is a very lean mix that chips away very easily. It's purpose is merely to protect the iron while the surrounding dirt is excavated. The same is done for shoring piles in building foundation excavations.
the pile concrete is placed from the bottom and pushes the mud etc out the top. The only way to know that you don't have any mud inclusions in the pile is to keep on overflowing it at the surface.
So the piles are always to the piling platform level. Trying to leave them low will end in tears. It's not really a lot of waste in the grand scheme of things.
There are a lot more efficient ways to remove the waste concrete though than simply chipping away at it.
?ÿ
the pile concrete will be quite a high grade. it might be a bit weaker at the top where there is a bit of mud and extra water in it, but really that should have been pushed out the top when they concreted it.
Thanks for clarifying, my language was not specific enough. It is only the portion of the pile that will later be exposed that gets the lean mix.
how does that work? i can't imagine how that would be achieved. bored piles are concreted from the bottom (by tremie pipe) generally. or at least well below the top concrete level.
and the concrete goes well above the cutoff level for reasons described above.
are you Mark Mayer as well as Norman Oklahoma?
How does it work? As simple as can be.?ÿ
- Hole is bored to desired depth.
- Pile (an I- beam in the cases I am most familiar with) is lowered into the hole and positioned. A rebar cage would work the same.?ÿ?ÿ
- Concrete (full strength mix) is poured into hole up to a desired elevation (the final bottom of excavation elevation). Vibrator heads are dropped into the mix to consolidate the concrete.?ÿ ?ÿ
- After a period of curing (a few hours) the remaining depth is topped off with a very lean and soupy mix.
Frankly, it seems to me that your method of pouring from the bottom is more mysterious.?ÿ ?ÿI would not have assumed that mud inclusions would always float on the concrete, as the two materials would normally have similar specific gravities.?ÿ ?ÿ
Yes, I am both Mark Mayer (from home, generally) and Norman Oklahoma (from work). How that happened is a long story that involves being an economic exile for a period of time, a corporate takeover, me changing jobs (and therefore email addresses) over time, and the website itself changing formats and requiring us to re-register. But never any intention to deceive.?ÿ?ÿ
