Dampening Structural Vibrations--Good Books?
Dampening Structural Vibrations--Good Books?
(OP)
Problem:
New equipment was recently added to a production plant. This causes noticeable (but not structurally worrisome) vibration in the concrete floor. This issue is that the basement is used for offices, and the noise from the vibrating concrete floor/columns (caused by the equipment) is deafening loud. Preferably, this would be addressed by using appropriate dampening pads.
I do not have any good books on the subject, but I am looking for one.
Does anyone know of a book they'd recommend to solve the above problem (and others like it)?
New equipment was recently added to a production plant. This causes noticeable (but not structurally worrisome) vibration in the concrete floor. This issue is that the basement is used for offices, and the noise from the vibrating concrete floor/columns (caused by the equipment) is deafening loud. Preferably, this would be addressed by using appropriate dampening pads.
I do not have any good books on the subject, but I am looking for one.
Does anyone know of a book they'd recommend to solve the above problem (and others like it)?






RE: Dampening Structural Vibrations--Good Books?
RE: Dampening Structural Vibrations--Good Books?
RE: Dampening Structural Vibrations--Good Books?
RE: Dampening Structural Vibrations--Good Books?
Talk to a rep from Gerb or Mason -- check out the companies online -- they specialize in this sort of thing.
RE: Dampening Structural Vibrations--Good Books?
Years ago they had a technical manual on designing foundations for vibrating equipment.
RE: Dampening Structural Vibrations--Good Books?
[1] Birkhauser, "Vibration Problems In Structures - Practical Guidelines"
[2]Chopra, "Dynamics of Structure"
The easiest way to resolve this is to set the machine on grade. Typical manufacturer requires the supporting foundation pad to be 2x or 3x mass of machine.
It is my understanding that your machine is bearing on elevated concrete slab supported off columns.
For life safety concern, the forcing frequency of the machine should be at least 2x LESS than the 1st mode natural frequency of the horizontal structure. Otherwise, you need to either: 1) stiffen the floor to achieve higher natural frequency 2) machine to bear on steel frames supported on springs. Springs to be designed to absorb the energy imposed by the machine vibration. We have to hire a vibration consultant to design the springs. The springs will reduce the forcing frequency applied to the slab.
Certainly, you still need to design the structure for amplified forces after reduction due springs. See Figure 3.5.1 in Chopra's book for coefficient to amplify the load due to forcing frequenct/natural frequency. By the figure, as your forcing frequecncy from the machine approaches the natural frequency, the forces shall be multiplied by a coefficient of almost infinity, i.e. structural will fail.
Hope this helps.
RE: Dampening Structural Vibrations--Good Books?
RE: Dampening Structural Vibrations--Good Books?
RE: Dampening Structural Vibrations--Good Books?
Lutien
The structure will not neccesarily fail. The factor only aproaches infinity for undamped structures. Buildings typically have on the order of 2-5% damping without any extra measures being taken.
You may also get away with a forcing function many times higher than the fundamental building frequency if there is low participation from the higher modes.
RE: Dampening Structural Vibrations--Good Books?
RE: Dampening Structural Vibrations--Good Books?
It is very difficult to get a sense of the problem without seeing it first-hand and taking some measurements. Typically bothersome vibrations are due to vertical excitation of the floor, and not horizontal vibration of the entire building, which respond at low-frequencies (typically below 5Hz for the first few modes).
Depending on the size (HP) and the type of equipment, equipment bases (concrete or steel) and vibration isolators (springs or neoprene pad/mounts) can work very well.
Mason is a good company, but they typically do not specify the type of system to be used. I would recommend that you hire an experienced vibration consultant to evaluate the problem; often steps in the wrong direction can create big headaches.
RE: Dampening Structural Vibrations--Good Books?
"Dampen" indeed is a word that can be used in this context, and does not always mean to "apply moisture" or make it damp. Dampen means to deaden or to reduce in amplitude.
I am not trying to start a war here, but just stating the facts.
http://dictionary.reference.com/browse/dampen
RE: Dampening Structural Vibrations--Good Books?
RE: Dampening Structural Vibrations--Good Books?
(1) Harris' Shock and Vibration Handbook (any edition) - by Cyril M. Harris and Allan G. Piersol
(2) A Practical Guide to Noise and Vibration Control for HVAC Systems - by Mark E. Schaffer
(3) Noise and Vibration Control - By Leo L. Beranek
There are many other books in this area, but this should give a start.
Andrew Gorton, MSc
Noise & Vibration Consultant
www.PapadimosGroup.com
RE: Dampening Structural Vibrations--Good Books?
I just don't think I've ever read "dampen" in the literally hundreds of vibe papers I've read. The real vibe guys never use that term. It's not as bad as "cement" vs "concrete" but I'll go with the experts.
RE: Dampening Structural Vibrations--Good Books?
Andrew Gorton, MSc
Noise & Vibration Consultant
www.PapadimosGroup.com