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Survey Penetrations & Jumpform

Hi 

I'm hoping you guys can help me out regarding a couple of best practice questions in particular survey penetrations on concrete building structures and also lift/stair jumpform.

Have done setout before on concrete structures with only up to 5/6 floors by resecting from fixed control on neighbouring buildings, however on higher structures, once control is no longer visible i will be plumming up using penetrations in the floor slabs which i've not done before. I'm wondering the best way of doing this regarding the setup? (setup over one plexi glass plum point and a standard single backsight to another??)

Also how is it possible to use this method to do prepour setout once floor above has been propped up?

The other question i have is regarding setout for the jumpform on lift/stairs. Current site has corrugated tin surrounding the jumpform meaning that it is next to impossible to do any prepour checks on the ply.

So far i've been setting up on top of the jumpform (not the most stableat times) and have been setting pins out for centre line of walls.

With the edge protection being about a metre high around the jumpform, i'll once again run into problems with the higher floors with seing control on neighbouring buildings.

Any tips or ideas would be greatly appreciated guys 

Thanks.

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  • Hi James, How did you start this building. Was controls set on the first floor ,are you not using a Auto Plumb or laser, This should have been from day one,where these points are set, If purpose-made apertures are not permitted then sight lines can be made in lift shafts, service apertures, etc.. But this is extra work and not as good of controls as site targets that are square to each other. But plans should have been made where these cut outs where to be made ,around 8 " or 200mm or so to carry up the vertical and inside envelope controls, on the outside or open frame structures you have to use offset plates or brackets, but this may not be your case.I feel for you, if there was no inside envelope close to the building corners. Controls are set to be carried up to the next floor,Most of the time ,4 of these are at 90 degrees to each other when they can be ,to act as floor controls also,and this line of site is kept,around 10 floors,that's about the limit of a Auto Plumb, then new targets are set to continue up. But this is done one floor to the next,then that floor is laid out,then poured ,so on ,and so on.Sometimes if in ?, are needed a wired plumb line, with a wet bob in water or oil is used to check the Auto Plumb or Laser. Your site penetrations must be planned from day one,and these instruments,auto plumb or laser,must be in very good adjustments,Total Station have attachments, but i have always used auto plumbs or lasers. Some tall Buildings keep their Plumb Controls,where they can be seen after the building has been built.This is old tradition , many cathedrals still have brass datum marks inlaid into their floors, that signify the center of the structure . The early skyscrapers used heavy plumb-bobs hung on wire in their elevator shafts,the plumb- bobs would be in water or some kind of liquid. Hope this helps with the other reply's,most of this has already been said.

  • I can only reiterate the methods I have previously posted.

    Procedure for HiRise layout and control:

    1: Using site control or property corners, layout the primary sides of the building  on a convenient offset (envelope-in this case I will use 4 sides)

    2: Check diangles, make any adjustments.

    3: Holding angle points, measure between and prorate any error* and stake out gridline or column lines agreed with builder on the envelope line.

    4: check between all lines individually to determine tolerance.

    5: make offsets to grid lines to clear columns to be build (eg 2' o/s)

    6: set up on offsets, sight same offset on other side of building then double line back as far as practical (eg  sidewalk, buildings, field etc) and if possible set another offset to the gridline for setups.

    7: When throwing up gridlines to building, double using plate level or electronic level in gun to get 2 marks on upper floor, split the mark, and (very important) check the floor below, do not accept more then 1/4" per floor as craftsmen can detect this and it will "bite you in the ass".

    8: if floor not poured using story pole, set the center of the column. We usually use a folding ruler with a target set in joint between the folding sections on say 3' and mark 1' for 2' offset.

    9: occupy floor using a "column clamp"** and set to proper offset, sight the mark you made on the other side of the building using the same procedure, check ground, and  set offset marks for that grid line.

    Notes: For TBM (temporary bench marks) on floors, I usually set either 4' or 5' above FF (finish floor) so you can set level cross hairs on the actual "crowsfoot" or cross and scan the other TBMs and set more. To bring TBMs up, start with marks on ground floor columns and using steel chain (tape), let tape normalize to building temperature as steel and conc. has similar temp. expansion rates, then pulling 10 pounds on the tape from above, mark the upper floors. Be sure to take up at least in 3 places, which are out of the side or facing the sun.

    *I prorate error by either pulling a chain with spring balance, until it fits, or changing the PPM's on EDM (using a mini prism close to the ground, for less bubble error) until that fits the calculated distance.

     **A simple column clamp can be 3" aluminum angle plate about 3 1/2 ft. long with a grove for a 5/8"  threaded piece to hold down instrument to be able to slide along the column clamp at least 6"

    Try to throw up lines early, before sun affects building, winds kick up or tower crane (if connected to building) starts loading.  Remember Iron buildings lean away from the sun, and if you place benchmarks on the sunny side as the iron heats up and cools down, the iron will creep downward slightly, affecting your elevations. Also read the geologist report for settlement issues, and discuss with contractor what he want you to do, because as the building is built and loaded, it will settle some (maybe up to 1/2") and if you dont know whats happening it can "bite you..."

    Most of these procedures I learned from my mentors, who learned from their mentors, I only take credit for "proration by PPM's"

    I am a California LS available for consulting and QC at [email protected]

  • Land Surveyor

    Dear James,

    I have not set control for a tall multi-story building so what I write may need to be taken with a grain of salt.

    If you have penetrations between floors, are you not able to drop a long, damped plumb bob through the several floors to carry and prove control, i.e., lead ball on piano wire?

    Good luck & best wishes,

    JAC

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