![]() I do not know of any reference standards you can use. 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 use a digital target, and the accuracy is quite good at 300 feet. 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 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. ) My laser plumb bob hangs in a two axis gimball at the bottom, and the laser shines up through where the string would go. (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. 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. 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. 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 used a plumb bob with a laser in it that I bought from Northern Hydraulics, for about $80.00, and it worked fine. My client was not trying to get a fraudulent report, so he was open to a demonstration. 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). I had a similar objection by a client back in the middle 90's. 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. There is a device known as a "Bazooka", which is quite good in windy applications, but it has a limited length. As far as I can tell, the AISC Steel Manual does not reference methods, only the criteria for acceptance.Īs you say, a free hanging plumb bob in any kind of wind is not usable. I'd like to show our client some documentation that allows for a straightedge or a laser level to be used for determining plumbness, because the plumb bob is not practicable sometimes. My question is whether anybody knows of any reference standards that can be used for the determination of column plumbness. ![]() We have discussed using a can of oil at the bottom to help stabilize, but it has been determined that at the height we are checking (17' to 22') it obstructs the natural movement too much. ![]() The problem arises when the walls are not built yet, or if the columns are exterior, and winds pick up- the plumb bob (obviously) will not stabilize. Due to the contractor claiming discrepancies when using a laser level, or 4' to 10' level, our client has stipulated that we should only use a plumb bob for this testing method. The columns are between 17' and 22' in height. I work for a third party inspection firm, and my company has a client who constructs multiple single level, large commercial buildings each year, and we have recently been requested to inspect column plumbness. I know this isn't a welding question, but I figured this is the right group to ask. ![]()
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