Column Verticality Check

[Bubik]

Hi everyone.
First of all I would like to say that I don’t have much experience in working on site as I am more of a Structural Engineer. However, I am tasked to check verticality (erection) deviations of steel columns with splice connections. The structure is a cement plant tension tower appr. 47m tall and has three ‘floors’ and edge beams at every 6 to 3 m from bottom to top. Pease see picture below.

1. I was advised to check deviations at every splice (three per column) with limit 1/1000 and with reference at the base of the column. Code of practice (Eurocode) says to check deviations at one storey in relation to storey below or deviations at one storey in relation to column base. Now, my structure is somehow different from a regular building and eurocode does not say anything in regard what I was advised to do ( deviation at splices from bottom of the column)
As it seems reasonable to me to check it at the splice connections , will I check deviations at the second and third splice with reference to the base of the column also with 1/1000 limit (doesn’t seem likely)??? Any idea how to approach it and what limit to use? Or maybe completely change the approach?

2. How do I allow for manufacturing imperfections? How will I ‘pluck it in’ the allowable limit?
3. I will use theodolite to check deviations. I was also advised to get coordinates of the column at the bottom and at the splice and then get the difference. But how will I convert it to millimetres ??
Thank you!!

 

[LeeGreen]

I have performed many "vertical column plumb surveys". A task that requires this type of precision must be done with a very accurate instrument and procedures. The instrument needs recent calibration. Are you prepared for this? If not, I suggest you hire a licensed land surveyor with experience in this field or at least consult with one.

Converting to millimeters is the simplest part. There are several methods depending access to the steel columns. Personally, I use a 1" seconds Robotic Total Station with magnet mounted prism on the steel. If you can not access the steel, I use prismless mode. You can plumb the steel with just the vertical cross of a theodolite, but you will need a person at the steel column hold a rule.

LeeGreen.com

 

[Bubik]

Thank you

What about deflection limits? Would you considered 1/600 between column splices?

 

[LeeGreen]

"Would you considered 1/600 between column splices?"
Yes, if that is the required tolerance.

That would equate to 78mm allowable deflection in the entire 47m.


~LeeGreen.com
Licensed Surveyor in NY
sUAS Remote Pilot

 

[dik]

Have you considered using a digital level? They should have the precision for the work you are doing.

Dik

 

[LeeGreen]

Have you considered using a digital level?

Are you thinking of a 4ft Smart Level? At ±0.2°, it is not accurate enough.

I own a Topcon DL-502 digital level. It is extremely accurate (±0.6mm), but no way to use it for the OP's intended purpose.

~LeeGreen.com
Licensed Surveyor in NY
sUAS Remote Pilot

 

[Bubik]

All I have is a Theodolite... nowhere to get anything else, we are in the middle of desert. Obtaining some other equipment is out of questions...

 

[IRstuff]

Does it come with a laser rangefinder?

A standard brute-force approach would be to level the theodolite and align with the base of a column at something like 47-m distance and then make angular measurements up the column. A 47-mm deviation at the top would be a 707 urad angular error from plumb, which should be easily detectable in most decent theodolites. This approach does not require any additional hardware or manpower.

You'd probably need to make the measurement in the early morning to minimize the scintillation effects that would get worse as the day gets hotter.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[LeeGreen]

With a good theodolite and proper procedure, it can be done.
It will take two setups per column. You will need to setup perpendicular to the column. Plumb the steel column with the vertical crosshair of the theodolite. Have a person hold a wooden rule along the side of the steel column, perpendicular to the instrument's line of site. The instrument person then reads the offset from the plumb line to the steel column.

Much faster an easier with a modern day reflectorless Total Station, than a Theodolite, but that how it's been done for many years.

PeterOdron - What country is the desert in?

You may need to do these measurements in the early morning to eliminate effects of heat waves (refraction).

~LeeGreen.com
Licensed Surveyor in NY
sUAS Remote Pilot