Just need your opinion on my proposed methodology for carrying out a building/column layout for a 40 floor building.
Scenario:
1. I plan to use 3 (or more) points for resection positioning of control points as floors are erected.
2. No vacant spaces around building site to place controls that would be visible as building goes higher.
3. Plan to establish the resection points on nearby buildings by bolting 360 prisms to the walls of surrounding buildings. Got permission
from several buildings already.
4. Same problem of visibility as the building floors go higher.
Question :
1. Is my method feasible?
2. How high will the 360 prisms be before the movement due to wind shear start to have an effect on my controls measured by resection?
Thanks.
Have you considered building deflection due to the sun's diurnal cycle?
Glad this is your baby and not mine. Could be a fun challenge, though. How tall are the nearby buildings that you could tie into?
Also consider building sway. Sometimes all the new technology just NOT needed, or not the correct tool. I have seen surveyor try using using robots and even scanners to perform building column layout for high rise. Then a carpenter checks it with a tape to find the offsets that took the surveyor 3 days to layout, are 4'3" from column. When it should be 4'. Good optics, double centering and buck in.
PS: Do not use those aluminum tripod legs shown in your avatar, for column layout.
Hi,
Surrounding buildings are about ~40 floors which I think is the local zone limits. I am more worried about wind shear more than anything else as floors go up. Layout will be done using steel tape after resection computation of control points.
No tripods will be used during the survey. We will be welding in place the tribach in a specific place for the duration of the layout survey per floor or until points are visible. Plan to leave the instrument in place overnight/day if needed to remeasure again next day depending on construction activity. Layout survey will be night time so heat deformation will not be a factor. This will lessen movement (I hope) while layout on each floor is not yet completed.
Not sure why I signed on for this work. This is the type of work that will give you sleepless days until building is completed! But I also guesss this is what you will be bragging about when you retire.
FrancisH, post: 361040, member: 10211 wrote: ... We will be welding in place the tribach in a specific place for the duration of the layout survey per floor ....
You may want to google survey column clamp. http://www.surveysupplyinc.com/Seco-Heavy-Duty-Column-Clamp-4852-16/
Or, in this case Cantilever Column Pod http://www.stakemill.com/laser-scanners-c-629/cantilever-column-pod-p-5550.html
I might also suggest you study Errors and Omissions insurance.
I recall Scott Zelenak discussing how the building sinks (for lack of a better term) as the dead weight of the upper floors compress the lower portion of the structure.
Some suggestions....
If you are utilizing resection.. Strongly suggest creating a mount system to your elevator shaft conc wall.. These usually go up first..
Prefab a metal base or Some are made for sale ..
Wait I just re-read what you wrote..
Yes, do that!
Best measure at different, between shifts and lunch.. We did a lot of work at night..
Also I forget the manufacturer I used, but an industrial plumb laser to utilize on grid intersections. We made a small cylinder in and between floors that would be incorporated into the pours.. This would give us a good plumb line good for 50 feet at an 1/8" dot..then we would resect..
Also piano wire set in oil in a 5 gal bucket can do wonders..usually
In an elevator shaft..
The sun and wind will play games.. And if your floor will be stressed during the pour..
Once you get a good system with common points and tools, you'll get a "feel" for the building..
Good luck! Sounds like a good challenge!
Also talk and talk some more to your super... He'll probably have some
Suggestions along the way..
Good Luck..
Been thru a few of these, but not 40..
It's a rush after u can finally sleep!
Hey Francis
Is this a survey in Singapore, remembered before you mentioned you were in Singapore. Will be curious and would like to learn more about it, if possible.
With regards to 360 prism. I am using a sokkia robotic and at too steep a vertical angle, it just cant lock onto and focus onto the prism. This may be a consideration.
I think it is an interesting project to have.
Cheers
FrancisH, post: 361023, member: 10211 wrote: Just need your opinion on my proposed methodology for carrying out a building/column layout for a 40 floor building.
Scenario:
1. I plan to use 3 (or more) points for resection positioning of control points as floors are erected.
2. No vacant spaces around building site to place controls that would be visible as building goes higher.
3. Plan to establish the resection points on nearby buildings by bolting 360 prisms to the walls of surrounding buildings. Got permission
from several buildings already.
4. Same problem of visibility as the building floors go higher.Question :
1. Is my method feasible?
2. How high will the 360 prisms be before the movement due to wind shear start to have an effect on my controls measured by resection?Thanks.
40 storeys would normally be best achieved using either plumb bob (old school) , optical plummet or laser plummet. is there a reason why this has been discounted?
transferring control upwards by resection will add errors at every level. autolock centring error on a 360 prism for starters.
Sireath,
Yes I'm from Singapore but current project is in Hong Kong - Lantau and design consultant is based in Manila. Have not done building monitoring in Singapore yet. Steep angle of observation is always a problem but less with 360 prism. Regular prism is ok but it would be a challenge to place them in surrounding buildings so that TS could get a signal back for distance measurements. I think anything outside of 60 degrees would not reflect back to the TS.
The hole in the floor is the best method together with a steel tape. This would be ideal for box type buildings where floor layouts are more or less identical in layout. Most new building layouts today vary from floor to floor. A vacant space on the 10th floor would hit a truss on another floor, or when you are on the 20th floor a sewer pipe will need to be installed on lower floors hence covering your reference hole to the ground floor. As you go up, the lower floors become very busy & sometimes contractors for elec, water, sewer contractors etc can't hold off forever their work just so you have a clear hole to the ground.
Just a thought. What TS or software are you using. Are you able to set multiple backsights based on angles? How about setting your azimuth based on far away antennae or tower you can sight far away easily.
Can understand your problem with not able to use a plummet as this is a similar problem here now as architect likes to design more and more complicated designs.
Don't they still use a plumb bob for this? Or some variation of one, like piano wire with a weight on the end in an oil bucket to dampen the vibration and sway? If there are multiple elevator shafts of other vertical openings couldn't those be utilized to plumb down?
I don't want to pretend to know a lot about this. I have never worked on anything that tall. I stay like 8 stories or less, and it's even rare that I have gone that high.
Two tips.
1. Redundancy. Have more than one method.
2. Simplicity. Drop a bob over the edge and place on line from floor below. Great sanity check.
Here's a link (white paper) to a project done in Calgary, AB, Canada not too long ago. It's a 50+ floor building, and they used some state of the art technology to get it done. I thought it was a very interesting read. May be of help to you OP.
http://www2.canadianconsultingengineer.com/awards/pdfs/F-3_TheBow.pdf
Leica have developed a system for this , called core wall system, uses Robotics, GNSS and inclinometers and lotsa fancy software.
Interesting that the two articles above are from Canada and the Middle East, while here in the United States we still argue about plumb bobs and oil and wonder if our licensing requirements are too strict.
With regards to the Leica system, have not read the article but 1st thing that comes to mind are the buildings surrounding the construction site. On the lower floors GPS signal would have a high PDOP value I would guess with all the reflection of signals coming off the surrounding walls? It would get better as you go higher. Not sure if software can reduce multipath errors. Even if product brochures say their unit can counter MP errors, real world situations would say otherwise. I read that the latest Javad unit has better capabilities to counter multipath errors.
Hire the Wallenda family to string tightwires from nearby skyscrapers for resectioning.:woot::woot:
see my previous post on building control