Back in my days of erector engineer, it was usual practice that maximum out of plumbness of structural columns was one per thousand, i.e., one millimeter per meter (you translate into feet and inches).
I don't see any reason why the plumb bob can't submerged into a can of oil. Back in my days of erector engineer, that was usual practice.
But if you definetely want to get rid of the oil can and the wind is annoying you, use a theodolite. It's easy to operate
Giovanni S. Crisi
Sao Paulo - Brasil
As you say, a free hanging plumb bob in any kind of wind is not usable. There is a device known as a "Bazooka", which is quite good in windy applications, but it has a limited length. If the customer is trying to get the "plumbness" signed off, and the column is close to the AISC Code Of Standard Practice limit, you could be being used for "inspection fraud" by the customer. I had a similar objection by a client back in the middle 90's. The client's objection was based on an incident, where the laser from a 6 inch torpedo level was used and the results were very inaccurate (because the level vial was not manufactured or installed in the level correctly). My client was not trying to get a fraudulent report, so he was open to a demonstration. I used a plumb bob with a laser in it that I bought from Northern Hydraulics, for about $80.00, and it worked fine. I met with the client at night, when the wind was not a factor, showed him my laser plumb bob, verified its accuracy with a free hanging plumb bob, and then with an optical transit. I also showed him the bazooka readings and showed him why it could not be used in this (high rise building) application An optical transit might be a better device to measure with (With my 20 second transit, I can see the difference in the thickness of the shop coat at 60 or 100 feet, which is much more accuracy than you can use to plumb a building for AISC Code of Standard Practice tolerances.), but Union Rules would not allow me to set one up, so during the day it would have to be done by a NYC Licensed Surveyor. The other limitations of using a transit is that all columns might not be visible from the right aspect angle, accuracy depends on the operator correctly leveling the instrument, and the inherent accuracy of the instrument. (your $139.00$ two minute transit will not be nearly accurate enough, and a $2400.00 twenty second transit or a $12,000.00 total station is more than you need. )
My laser plumb bob hangs in a two axis gimball at the bottom, and the laser shines up through where the string would go. It is like the laser is the string. I also use a $1600.00 two axis automatic (self Leveling) laser level, which is accurate to at least 1/32 inch at 100 feet, but again, I run afoul of Union Rules. I have used the horizontal component of the laser level to measure the sweep of bridge girders in "progressive assembly" in a bridge fabrication shop. I use a digital target, and the accuracy is quite good at 300 feet. For one and 2 story buildings (out side of the City), I use a Bazooka and a transit (usually there is no Union Rules problem with those buildings, and the union erectors even ask me to check it for them.
I do not know of any reference standards you can use. The AISC Code of Standard Practice is the controlling document under the building codes, (Except in some high rise elevator shaft steel, where more accuracy than 1 in 1000 is sometimes specified, ) If your client is open minded, perhaps he would be open to a demonstration like the one I described to you in a paragraph above.
Something else to consider:
What are the column sizes? Are they HSS (tube) or W shape columns?
The reason for that question is that sometimes plumbness (or lack thereof) arises long before the material is even fabricated. For instance, the ASTM A6, Table 24 describes permissible variations for camber and sweep. The A6 identifies four groups of steel in that table that, if the user specifies "for use as columns" in the purchase/mill order, the mills will supply them to a tighter tolerance depending on the length of the material. You will notice that the four groups begin at W8 x 31 lbs/foot and heavier; W10 x 49 #/ft and heavier; W12 x 65 #/ft and heavier and W14 x 90 #/ft and heavier. Very common column size material. Some fabricators will specify "for use as columns" on their orders even when these shapes are used for diagonal bracing, so that when the bracing goes into compression it is less likely to buckle due to the straightness of the material.
If the column material is HSS, then consider permissible variations for that as described in ASTM A-500
These ASTM tolerances are formulated to work along with the AISC Code of Standard Practice. Unfortunately, it is not the first time that column plumbness is compromised because the permissible variation of camber and/or sweep were outside the ASTM tolerances; ergo, the AISC COSP tolerances could be compromised. Yet, many fabricators, contractors, inspectors do not investigate incoming material for sweep and camber using Table 24.
This table has been around for many, many years. I have a copy of a USS table (dated 12/1978) that is verbatim to the current A6 Table 24 with one exception, the W14 group began at 78 #/ft.
If your client did their homework correctly, they might have incoming inspection reports (not the MTR's) but actual QC inspection reports as to whether or not camber and sweep passed inspection. Ask to see their purchase orders for the column material. If they did not specify "for use as columns" then it is most unlikely that they performed camber and sweep inspections at receiving. Their loss if anything goes to court.
Just a thought to add to your bank of knowledge.
ziggy
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