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Deflection Detector
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Not to sound snotty or anything, but... a string?
Pull a string tight from end to end and measure the difference between beam and string. Or do the same with a laser measurement tool - shoot it from end to end, measure between beam and laser beam wherever you need to.
Pull a string tight from end to end and measure the difference between beam and string. Or do the same with a laser measurement tool - shoot it from end to end, measure between beam and laser beam wherever you need to.
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- #3
Beams are usually above ceiling so you need to access a small opening enough for you to peek so im thinking of a device that can send 3 or 5 laser pulses that can measure and compare different length of the beam while you are holding the device (which should have an angle compensator). Maybe there is already such device for other tasks that you can use for a beam?
Run the string line under the ceiling and measure up.
You could use an auto level/transit and grade rod, rotary laser, or construction altimiter.
If you want to be really technical/expensive, there's instrumentation for measuring the settlement profile of an embankment. I don't see why it couldn't be used for a beam.
You could use an auto level/transit and grade rod, rotary laser, or construction altimiter.
If you want to be really technical/expensive, there's instrumentation for measuring the settlement profile of an embankment. I don't see why it couldn't be used for a beam.
To clarify, what are you trying to measure?
The in situ shape of the beam?
I think that you`ll have a hard time differentiating between how much movement occured due to deflection (dead load, I assume), how much was there at the time of construction (camber), and how much may have come from external sources (settlement of the columns, perhaps)
The deflection of a beam under an applied load? I`d get a dial gauge, set it up under the beam, and apply the load.
Something else?
The in situ shape of the beam?
I think that you`ll have a hard time differentiating between how much movement occured due to deflection (dead load, I assume), how much was there at the time of construction (camber), and how much may have come from external sources (settlement of the columns, perhaps)
The deflection of a beam under an applied load? I`d get a dial gauge, set it up under the beam, and apply the load.
Something else?
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- #6
You could invest in a 3D laser scanner
Run a string line down low and shoot up with a laser
No matter what method you use, you're going to have to make a ton of assumptions. Anything cheap isn't going to have enough accuracy to give you anything meaningful.
Run a string line down low and shoot up with a laser
No matter what method you use, you're going to have to make a ton of assumptions. Anything cheap isn't going to have enough accuracy to give you anything meaningful.
And, whatever you do use will be required to make detailed measurements from the get-go, i.e., the as-built structure, followed by its settlement, etc.
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TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
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I own this Stanley TLM-330 with range up to 330-feet (100m) and accuracy of +/- 1/32-inch (1mm) (I don't know if 0.1mm accuracy is required since deflection of beam is in the range of 0.1mm). It includes inclination sensor digital leveling funciton too.
However, I don't know how to include it with a string. Bobby 46, what you meant by "Run the string line under the ceiling and measure up." Can you please elaborate? Do you mean to put the string vertical or horizontal? What is the purpose of the string in conjunction with the laser measuring tool? And jittles.. "Or do the same with a laser measurement tool - shoot it from end to end, measure between beam and laser beam wherever you need to." Should I walk from end to end of beam to measure it? But it can change the distance as I walked. Please give more details. Thanks.
How are you going to turn that into column settlement though? You've got other variables in there. Camber of the beam, floor slope and deflection if you're measuring off of a floor below, if multiple columns settle, you can't pick that out, construction tolerance, etc. You're going to lose any useful information in the noise of all those possible issues.
If you're trying to figure out columns, why even check the beam deflection? Set up a laser level to hit two columns anywhere on the column height and measure on the column from the laser level to the underside of the beam or some other feature that would be theoretically level. Even that won't actually tell you how much settlement, or even differential settlement, has happened but at least you've taken some of the measurement noise out of it.
If you're trying to figure out columns, why even check the beam deflection? Set up a laser level to hit two columns anywhere on the column height and measure on the column from the laser level to the underside of the beam or some other feature that would be theoretically level. Even that won't actually tell you how much settlement, or even differential settlement, has happened but at least you've taken some of the measurement noise out of it.
You would run a string with a line level on it to get a theoretically perfect, level reference line. It can be at any arbitrary elevation (i.e. 1-2ft off the floor so you don't have to climb any columns) as long as it is constant for all measurements. Shoot the laser up at the bottom of the beam. Compare measurements.
You will have to assume everything was either installed perfectly level and plumb, according to the plans (with slopes, cambers, etc.), or according to as-builts. All construction and fabrication tolerances would have to be assumed to be zero. By the time you sum all the error in measurements and assumptions, it will probably overshadow what you are trying to measure.
You will have to assume everything was either installed perfectly level and plumb, according to the plans (with slopes, cambers, etc.), or according to as-builts. All construction and fabrication tolerances would have to be assumed to be zero. By the time you sum all the error in measurements and assumptions, it will probably overshadow what you are trying to measure.
I find it difficult that some sort of study is needed concerning settlements unless some sort of continuing settlement is present. That might show up as cracked walls, floors obviously not level, etc. Many a building has differential settlements and life continues in spite of it. As an example, I stayed in a hotel in Stockholm once where, by my guesstimate, the floors were tilted something like one foot drop in 20 feet or less. This was a building built probably in early 1800's and still actively used. However, for running an elevation survey in a building with inferior walls, a convenient method involves a long hose with clear sections at each end, filled with water. Start at one known point and run around taking height of floor to the water level at each end. The difference in these heights is elevation difference. Its sufficiently accurate to a precision of easily 1/4" for any distance. In case you are interested in columns, use the floor next to it.
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- #16
It may be a little clunky and require some crawling... you can set up a theodolite on the floor (no tripod) and take measurements from a steel rule... graduated in 1/64 and read the relative depressions between columns. You can then use a laser rangefinder... mine reads to 1/64" and take shots from the floor and correct them for the theodolite measurements...
If everything moves uniformly... the results will be the same even if the floor moves vertically a foot.
Can you do it from the outside? They are measuring the settlement of the Millennium Towers in San Francisco externally.
How important are your measurements? Litigation?
Dik
If everything moves uniformly... the results will be the same even if the floor moves vertically a foot.
Can you do it from the outside? They are measuring the settlement of the Millennium Towers in San Francisco externally.
How important are your measurements? Litigation?
Dik
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