Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Pouring concrete piers - must pour entire Sonotube at the same time!

  • Please log in to reply
8 replies to this topic

#1 LoveChina61

LoveChina61

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1,650
  • Joined: 19 Jun 2009

Posted 19 August 2021 - 07:43 PM

I am hoping to have my observatory's foundation and piers poured soon. All of my equipment is in storage very far away so I am not able to set it up and measure the exact height of the cement pier that I will need. I wanted to pour both the cement base and cement sonotube at the same time. I was thinking of just using an extra tall sonotube to make sure that my bases are covered, but then only fill the sonotube 1/4 high with cement while doing the initial pour. After getting my equipment and being able to determine the exact sonotube height that I will need, then I could cut off the sonotube and finish filling it with cement to the right height. At that time, I would also plant my pier plate bolts (J bolts) into the top of the sonotube.

 

As long as my sonotube was well filled with rebar, wouldn't it still end up solid enough if I finished pouring the rest of the sonotube at a much later date? Or  is this just a plain old bad idea?

 

Thanks for any feedback that you can provide.

 

Mike


  • BrianThePrimate likes this

#2 TOMDEY

TOMDEY

    Voyager 1

  • *****
  • Posts: 10,348
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 19 August 2021 - 08:31 PM

I've had successful experiences with sequential pours with never a problem even many decades later. But I always lace my concrete with re-bars running the entire length and width. Without that steel in there, a column is astonishingly sensitive to catastrophic impulse failure. Just give a non-reinforced column (pier?!) a medium lateral blow with a sledge hammer and it will fracture in half and fall to the ground. Very sobering. I'm not recommending that you actually do that... but I have, just to see what would happen. Once you see that, will never again pour a column without re-bar in there! With the reinforcement, you can still bludgeon a column apart, but it will fracture off little chunks and then you need to go in there with a cutting torch to attack the steel.

 

Ummm...  I hope no one here has a tall concrete or block pier without steel reinforcement. Concrete is extremely strong in compression and extremely weak in tension. Steel bar/wire is extremely strong in tension. The combination is substantially indestructible!     Tom

Attached Thumbnails

  • 51 24-ft dome foundation N-S monuments theodolite.jpg

  • LoveChina61 likes this

#3 TomK1

TomK1

    Mariner 2

  • -----
  • Posts: 245
  • Joined: 06 Mar 2016
  • Loc: Grosse Pointe Woods, Michigan

Posted 19 August 2021 - 08:34 PM

Topic:  Messed up. Pier height is too low. Extension or new Pier?   Started by rms40 , Oct 22 2018 08:50 AM

 

One rather long read in observatory section.   Looks like you have many options where one is a second pour on top of clean rebar.    56 replies and starts like this:

 

I am building an observatory for a L-350 Planewave mount. I poured a large concrete footing with a 16" concrete pillar and a 36" MX pier on top. I calculated the height from the front on the raised observatory floor height forgetting that the ground slopes quite a bit towards the back (it doesn't look like it slopes that much but it does!). I came up about a foot too low to the top of the pier.

Could I bolt on an extension for the extra foot? Does anyone make one? Am I just going to need to buy a 48" Pier instead? Money is an issue so the best solution that doesn't cost too much is best.


  • LoveChina61 likes this

#4 Astrola72

Astrola72

    Apollo

  • *****
  • Posts: 1,180
  • Joined: 16 Feb 2014
  • Loc: Maryland, USA

Posted 19 August 2021 - 08:47 PM

It will work fine. Put 3 or 4 anchor bolts in the first pour. Before the second pour, extend those with threaded connectors. Tie rebar to those. You could just leave rebar sticking out of the first pour but this is a little neater.

 

Joe


  • LoveChina61 likes this

#5 LoveChina61

LoveChina61

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1,650
  • Joined: 19 Jun 2009

Posted 08 September 2021 - 08:11 AM

Joe,

 

Can you please give me a little more information about that? For example, if I just had about six inches of rebar sticking up from the square cement slab, would it be strong enough if I simply tied some more rebar extensions to those and ran them on up the sonotube? I mean, is it necessary for me to use threaded connectors in order to get the necessary strength, or will just tied on rebar do the trick?
 

Mike



#6 firemachine69

firemachine69

    Ranger 4

  • *****
  • Posts: 371
  • Joined: 19 May 2021

Posted 08 September 2021 - 08:24 AM

Joe,

 

Can you please give me a little more information about that? For example, if I just had about six inches of rebar sticking up from the square cement slab, would it be strong enough if I simply tied some more rebar extensions to those and ran them on up the sonotube? I mean, is it necessary for me to use threaded connectors in order to get the necessary strength, or will just tied on rebar do the trick?
 

Mike

 

 

At the very least, I'd suggest you epoxy the rebar lengthwise, while still using bale wire tightly wrapped. 


  • LoveChina61 likes this

#7 Astrola72

Astrola72

    Apollo

  • *****
  • Posts: 1,180
  • Joined: 16 Feb 2014
  • Loc: Maryland, USA

Posted 08 September 2021 - 08:52 AM

Mike -

 

Answered in PM.

 

Joe


  • LoveChina61 likes this

#8 MalVeauX

MalVeauX

    Cosmos

  • *****
  • Posts: 9,542
  • Joined: 25 Feb 2016
  • Loc: Florida

Posted 09 September 2021 - 11:48 AM

I am hoping to have my observatory's foundation and piers poured soon. All of my equipment is in storage very far away so I am not able to set it up and measure the exact height of the cement pier that I will need. I wanted to pour both the cement base and cement sonotube at the same time. I was thinking of just using an extra tall sonotube to make sure that my bases are covered, but then only fill the sonotube 1/4 high with cement while doing the initial pour. After getting my equipment and being able to determine the exact sonotube height that I will need, then I could cut off the sonotube and finish filling it with cement to the right height. At that time, I would also plant my pier plate bolts (J bolts) into the top of the sonotube.

 

As long as my sonotube was well filled with rebar, wouldn't it still end up solid enough if I finished pouring the rest of the sonotube at a much later date? Or  is this just a plain old bad idea?

 

Thanks for any feedback that you can provide.

 

Mike

 

You can pour and keep raising it as long as it has reinforcement in the concrete (steel rod, etc). I've raised piers with additions, just add rod and join the rod between the two and pour it on. Good to go. A pier isn't holding up a house or bridge. It's holding up a few pounds of mount/scope which is minutia relative to what that stuff can hold from a compression standpoint.

 

Very best,
 


  • LoveChina61 likes this

#9 speedster

speedster

    Viking 1

  • *****
  • Posts: 832
  • Joined: 13 Aug 2018
  • Loc: Abilene, Texas

Posted 09 September 2021 - 10:21 PM

Tie wire doesn't count for anything structural.  It's simply a means of holding things in place.  For the splice to have the same strength as the bar itself, lap length is 0.002 * diameter * allowable stress.  For #4 bars (1/2"), it's 24".  If you only have 6" to play with and want the full strength of the bar, there are couplings and threaded connectors that will do it.  Also epoxy systems if you want to drill some holes in the existing concrete.


  • LoveChina61 likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics