Heel Drop Test: how reliable?Discussion requested
Heel Drop Test: how reliable?Discussion requested
(OP)
Pals
Are results from heel drop test always reliable?
Are there conditions when care should be excercised.
Your experience will be worth sharing w.r.t this apparently great yet simple tool.
respects
IJR
Are results from heel drop test always reliable?
Are there conditions when care should be excercised.
Your experience will be worth sharing w.r.t this apparently great yet simple tool.
respects
IJR






RE: Heel Drop Test: how reliable?Discussion requested
The heel drop is the age-old "gold standard" for vibration-inducing forcing functions. Thomas Murray has numerous publications about this, and vibration analysis in general.
For steel structures, AISC Design Guide 11 is a great resource. It poses alternative criteria to the standard heel drop test (I think chapter 4), that better represent the response of steel framed structures. This criteria is based on a lot of research and accounts for increased use of lightweight concrete and other common construction practices today. If you're analyzing a steel floor, use this guide.
We are just beginning a vibration analysis of a concrete framed structure, and we will likely revert back to the heel drop forcing functions for analysis.
That's my VERY rudimentry take on the matter.
RE: Heel Drop Test: how reliable?Discussion requested
Heeldrops are a reliable excitation for determining the natural frequencies for low frequency floors. They're usually ok for high frequency floors also.
They actually come in two varieties: unmeasured (unreferenced) and measured (referenced).
Unreferenced means that someone heeldrops on the floor and measures accelerations on the slab. The amount of force and its exact frequency content are both unknown. The frequency content is fairly uniform for low frequencies, so the acceleration spectrum will indicate natural frequencies. That is ALL unmeasured ones are good for, period.
Referenced heeldrops are performed by heeldropping on a load-measuring device. These are relatively reliable ways to do modal testing. The output is the frequency response function (floor acceleration divided by force at each frquency). Natural frequencies, acceleration response, damping, and mode shapes can be determined from the set of FRFs measured using this method. This is less reliable than using a floor shaker, but is still an acceptable way to do modal tests on a floor. The FRFs can be used to predict floor vibration due to walking, but it's not easy.
RE: Heel Drop Test: how reliable?Discussion requested
RE: Heel Drop Test: how reliable?Discussion requested
You do heel drop on the slab and not on the beam
The slab is relatively flexible but the joist isnt.
What comes out of the test?
respects
IJR
RE: Heel Drop Test: how reliable?Discussion requested
I find that hard to believe - check your span to depth ration I am sure you will find it is much lower for the slab - if not recheck the slab.
RE: Heel Drop Test: how reliable?Discussion requested
Heeldrops can be used on joist floors. It shouldn't matter if you heeldrop over a joist assuming they're closely spaced. The heeldrop can still be used to provide excitation for your tests. Like I typed before, if you're doing unreferenced tests, all you'll get are natural frequencies. You'll get no info on mode shape, FRF, damping, predicted response to walking, etc.
RE: Heel Drop Test: how reliable?Discussion requested
Dont find anything hard to believe my dear friend.
It is possible with long span structures supporting lightweight floor system, eg wood or OSB sheathing.
In that case where should a heel drop test be made, on top of sheathing or on top of long closely spaced joists. When I say joists here it could be a truss girder.
respects
IJR
RE: Heel Drop Test: how reliable?Discussion requested
If I had something VERY thing like wood, I'd heeldrop on a joist. Not sure it's totally necessary, but that's what I'd do.
RE: Heel Drop Test: how reliable?Discussion requested
That is exactly what I was after. Conventional floor has a deck and joists that talk one language. Mine is not conventional and there was no way a stiff slab could be made.
I should have mentioned this earliear in the post anyway.
thanks all pals
respects
IJR