@dhengr…thanks! Do you know of a supplier for the system you described?
@Ron:
I’m about as literate on these kinds of products as I am about bird language. But, at least I’ve oriented the thing to keep most of the bird crap off the screen. Some electronics guy or some company which makes this kind of mech./electronic equipment sure should be able to help you. I envision a .1” or .125” gridwork on a computer screen or some such, 160 units or 128 units sq., whatever size you wish. Then, there should be a fairly simple electronic and software means of determining the x-y coordinates of the grid which is being lit up, by the laser spot, at every given second. This x-y coordinate is combined with the anemometer reading and the time clock on the data recorder. This screen/flat pl. is mounted at the corners/top of the bldg., facing down and in a horiz. position, with the laser spot at the center of the screen, or zero x-y coordinates, in the at rest position. Maybe the surveying equip. people would have something, or some ideas. They shoot at a specific target point or plane for elevations and the like.
@dhengr…Thanks, again! I’ll check with a couple of laser and NDT monitoring suppliers. I’ve done a lot with strain gages and accelerometers, but no experience with lasers.
@Ron - I’ve been thinking / reading on this challenge. I’m sure you, like me, have been through tropical storms / hurricanes. I see that you would prefer to make measurements at 55+ MPH. In my experience, all hell breaks loose fairly predictably at about 50 MPH - power outages, flying debris, wind driven rain deluge, etc.
Any system that uses external sensors (lasers) may not be working, able to “see”, or “shaking” too much (independent of building motion), when needed most. Also, GPS tends to go haywire in tropical weather.
As flawed as they are, seems like accelerometers are normally used for this type measurement. At least they are fairly small, self-contained, inside the building, and have a battery backup, I suppose.
See:
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Good point sliderule.
Then what about mounting the laser inside an elevator shaft at the bottom with a target on the ceiling of the penthouse? Might be able to discover or make a continuous line of site for the laser. Will still need battery backup though. Will also need protection from flooding/ water intrusion.
Any rotation in the foundation might not be discoverable though unless the laser was mounted independent of the building foundation.
Might be able to incorporate a gyro to always keep the beam in a vertical orientation.
@MSQUARED48 - You must be on to something about adding a gyro. I did see mention of gyros in some of the papers & articles I read, but did not notice how they are used.
I’m leaning toward accelerometers, since I have experience with those. No laser experience. Good ideas, all…but I’ve used accelerometers in amusements parks, paper mills, pile driving and other applications, usually with good results.
Yes, SRE…you are correct…this will need to be independent of any external power source and will have to be weather protected.
Ron, I think the instrument that does exactly what you want would be called a seismometer (which is just a specially packaged accelerometer with recorder).
Back to your OP: while the building will experience more sway at the top from wind, I would think that the stresses and strains in the walls should be higher in the bottom floors.
CP…Thanks
We have considered a seismograph, since we actually have one; however, for the long term of monitoring, we do not want to tie up an expensive piece of equipment for that long. It would record the movements and do it well…just can’t part with it for that long and the rental on a similar unit would be more than the cost of dedicated accelerometers.
Ron