audiothings
#1
12th September 2010
12th September 2010
#1
Lives for gear

sylomer/floating floor load calculation

This is for a semi-hypothetical situation (attached file - floor grid.jpg). just trying to wrap my head around this stuff.

the elastomer has a static and max weight spec (attached file - sylomer upload.pdf). This is in N/mm2, and I converted it to Kg/50mm x 50mm x 25mm (attached file - jpg sylomer load conversion.jpg).

By my very preliminary and approximate calculation, this room has a static load of 8000 Kg... 3500 Kg in the middle and 4500 Kg along the edges (which bear the ceiling).

No matter how I try to work it out, my max load (15000 Kg) is too close to my static load, to exert enough weight on the elastomer to actually exploit its elastic property, thereby making it a solid, coupling device.

What am I doing wrong?
Attached Thumbnails

Attached Files
sylomer upload.pdf (65.7 KB, 385 views)
#2
13th September 2010
13th September 2010
#2
Lives for gear

Jai,

Depending upon what kind of flooring you intend to put on top of this 'system' you probably do not want to put the walls on the 'floating' floor. You should isolate the walls separately.

Your static and live loads for the floor will then be reasonable and the overall load will be 'spread out' on the floor - so you can safely lay a 'predictable' grid.

Your walls will be rigid and therefore spread the load to the iso pads. The floor should be built as rigid as possible too. You can then calculate the kg/m2 or lbs/ft2 - weight of the floor or wall and match the appropriate pad to the load.

Cheers,
John
audiothings
#3
13th September 2010
13th September 2010
#3
Lives for gear

Quote:
Your static and live loads for the floor will then be reasonable and the overall load will be 'spread out' on the floor - so you can safely lay a 'predictable' grid.
Even if the walls and ceilings are isolated separately... the static load on the floor would be about 4500 Kg... and the max load would be about 12000 Kg... a ratio of about 1:3... it still doesn't work out... the published static to max ratio is upwards of 1:10, with the exception of one variant, SR1200, and even that has too high a ratio for our purposes...

besides, when we isolate the wall/ceiling separately, the static and max loads are equal for that aspect, thereby not exploiting the elastic properties of the sylomer at all.
#4
13th September 2010
13th September 2010
#4
Lives for gear

What are you doing with this room? moving trucks in and out??

If this is for a studio room.. that's too much weight in and out... I'd check my figures for static and live load again.

- John
audiothings
#5
13th September 2010
13th September 2010
#5
Lives for gear

Quote:
Originally Posted by jhbrandt
What are you doing with this room? moving trucks in and out??

If this is for a studio room.. that's too much weight in and out... I'd check my figures for static and live load again.

- John
word.

following are some rough figures from before I handed the design duties over to a pro

Floor:

* 1022.25 kg Plywood (145 sq. ft. x 2 layers 3/4" Plywood @ 2.35 Kg/Sq.ft + 3/4" plywood equivalent decorative laminated wood)
* 225 kg from 2" x 4" hardwood grid

TOTAL 1250 Kg

Ceiling:

* 565.5 kg drywall (145 sq.ft. x 3 layers @ 1.28 Kg/sq.ft.)
* 200 kg insulation
* 200 kg 3/4" x 6" plywood grid
* 75 kg decorative fabric in 3/4" frame

TOTAL 1000 Kg

Walls

* 1800 Kg Drywall (460 sq.ft. x 3 layers @ 1.28 Kg/sq.ft.)
* 750 kg plywood (3/4" x 6" frame)
* 750 kg insulation
* 200 kg decorative fabric in 3/4" frame

TOTAL 3500 Kg

If we focus on the floor for a minute, and mount the walls and ceilings outside the floor perimeter (as per your suggestion), its static weight is about 1250 Kg., and as per attached pic, it would need some 26 pads to support it... each pad should take about 50 Kg. of static weight (1250/26)... pointing to sylomer SR220, which has a static load capacity of some 58 Kgs. Heres the problem: 26 pads of SR220 have a max load potential of some 27000 kilos, and we're never going to make a dent on it with the kind of minimal loads we are likely to impose on it.

What am I doing wrong?
Attached Thumbnails

#6
13th September 2010
13th September 2010
#6
Lives for gear

Jai,

You have to add the live load to that figure..

on average, how many people are going to be in there?

I am about 90kg... so 3 of me would be 270 kg additional.. plus all the gear, console, toy racks, speakers on stands...keyboard on a stand, guitar in a case, couch, plants, producer's desk.. etc...

tally again & let me know what you come up with.

-John
#7
13th September 2010
13th September 2010
#7
Lives for gear

I forgot to mention... The grid spacing for the pads must be uniform so that each pad shares the same amount of weight.
#8
13th September 2010
13th September 2010
#8
Gear maniac

Quote:
Originally Posted by jhbrandt
Jai,

Depending upon what kind of flooring you intend to put on top of this 'system' you probably do not want to put the walls on the 'floating' floor. You should isolate the walls separately.

Your static and live loads for the floor will then be reasonable and the overall load will be 'spread out' on the floor - so you can safely lay a 'predictable' grid.
We never isolate the walls and the floor separately. They are always on top of the floating floor. We never found any advantage to not putting them on the floor, only inconvenients and structural stability problems. We build bunkers, and float the whole thing at once.

But I understand that if one is using small pads spread regularly over the whole surface there will be some load inconsistencies issues; but nothing that can't be calculated - which would then show how the pads need to be rearranged.

I don't see how not having the walls on the floor helps with load repartition. I would say that having them on the floor actually helps with load repartition as you can spread the edge & section loads on a wider surface (we just did that in The Netherlands with a building that had load capacity issues. the civil engineer spread the load over a rather wide area and avoided having to reinforce it all locally)

But we do not work with pads-like decoupling systems anyway. We usually work with long benches. The load repartition is always calculated precisely and the Sylomer / BSW Regufoam /springs are positioned at strategic points.

The floors we use are very stiff and strong (using steel deck systems etc). And I can only recommend to have the floor as stiff as possible... And make it heavy too.

@ Jai: an important point too often disregarded is also to calculate the resonant frequency of the floor structure to make sure it's not going to be a problem wrt the natural frequency of the Sylomer under the estimated load.

If you don't have a software to do that you can do it this way, by using a estimation based on Rayleigh's work.

Say you have a given steel deck section + heavy concrete with steel reinforcements floor of 16m on 1.25m which lays on it's extremities on 2x Sylomer benches and an intermediate bench in the middle, with the steel deck oriented in the lenght. Mechanically the steel deck type system will spread the load in a direction that is parallel to the waves (deck orientation) which allows us to model the floor behaviour by considering it whole beam elements of 1.25m wide on 16m.

(As a side note, for frequencies under 8Hz, the maximum acceleration cannot be of more than:
– 0,125 m/s2 :floor oscillations are noticeable
– 0,40 m/s2 :floor oscillations are problematic)
Capacity of perception is rising with the frequency.)

We use the static load (self-weight of the structure + other permanent loads) to calculate the floor's resonance frequency. It's safe to add a margin of 10 to 15% to that load.

If we have an average floor load of for ex: 4,4 kN/m2

we have:

Linear overall loads on the elements of the deck : 4,4 × 1,25 = 5,5 kN/ml
Load on the main beams (here Sylomer benches): 4,4 × 1,25 × 0,5 = 2,75 kN/ml
Load on the intermediate beam (here Sylomer bench): 4,4 × 1,25 = 5,5 kN/ml

So for a floor with locally concentrated loads like this one (on the benches) the estimated fundamental period T is given by:

T = 2π*sqrt((Σ|Pi |δi)/(gΣPiδi))

Pi is the load at point i
δi is deformation under load i ;
g is acceleration

For example if T= 0,1659 then the resonant freq of the floor will be of 1/T = 1/0,1659 = 6,0 Hz

A quick and dirty estimation you can use to get the resonant freq for bench like systems + steel deck concrete floor without intermediate bench is 18,07/δ.

Another often forgotten point: there cannot be any air trapped under the floor or the air will compress and likely influence (and even impose!) the system's natural frequency. So, vent it all...
#9
13th September 2010
13th September 2010
#9
Lives for gear

Thomas,

Excellent post. I agree with you.

I had gathered from the floor design posted that he was only wanting some increased TL and decoupling from the structure, which the double layer of plywood will do. It is not a 'proper' floating floor. That's why I suggested that it be separated. And unless the framework is extremely rigid and the pads placed properly, the walls could cause the floor to warp.

- John
audiothings
#10
14th September 2010
14th September 2010
#10
Lives for gear

Thomas, these are times when I regret that I never got myself an education. I'm arranging to sit with someone who understands the scientific language to make complete sense of your post... Thanks.

Quote:
Jai,
You have to add the live load to that figure..
on average, how many people are going to be in there?
I am about 90kg... so 3 of me would be 270 kg additional.. plus all the gear, console, toy racks, speakers on stands...keyboard on a stand, guitar in a case, couch, plants, producer's desk.. etc...
tally again & let me know what you come up with.
-John
This is for the iso booth. There will be little or nothing in it... all the space will be kept available for various recording situations which might entail a max of 8 people (will be a squeeze!) and some gear... 1000 kg max...

So, 1250 Kg static load, 2250 kg max load...

Attaching herewith manufacturer's guidelines for a system that works...
Attached Thumbnails

#11
14th September 2010
14th September 2010
#11
Lives for gear

Jai,

Why do you want to 'float' the booth? What STL are you needing? Do you have a big highway next door.. or train lines?? Are you recording classical music or a Capella?

I would suggest a noise survey first and go from there... unless you are playing rock drums on the 3rd floor... But to isolate that would take a real floating floor with mass & rigidity to bring the resonant frequency down to 10Hz or less. You're going to need reinforced concrete & you'll then need a structural engineer to approve...

- John
audiothings
#12
14th September 2010
14th September 2010
#12
Lives for gear

Quote:
Why do you want to 'float' the booth? What STL are you needing? Do you have a big highway next door.. or train lines?? Are you recording classical music or a Capella?
Its in a small apartment building with about a dozen air conditioners on the walls in near proximity, there is a ceiling fan directly under the iso booth, there is a water pump two floors below, and the floor vibrates when it is on...

Quote:
unless you are playing rock drums on the 3rd floor...
its essentially going to be for vocals and solo melodic instruments... anything more is considered a bonus.
Quote:
But to isolate that would take a real floating floor with mass & rigidity to bring the resonant frequency down to 10Hz or less. You're going to need reinforced concrete & you'll then need a structural engineer to approve...
Actually structural engineer has been consulted and he won't allow pouring of concrete. Which is why I was considering the schematic for a 'room within room' published by the manufacturers of sylomer.

given this scenario and the intended application, do we really need to place the problems created by the resonant frequency of the system over the advantages of actually floating the room? Will a 3/4" ply + 1/2" drywall + 3/4" ply sandwich plus 1/2" laminated floor yield such a high resonant frequency that it will interfere with our useful frequency range?

SR220 and SR440 have a resonant frequency of some 11Hz and 12Hz if I understand correctly... what we don't know is the resonant frequency of the whole system, correct?

I dug up some more info from the manufacturer... EDIT - please see attachment in post No. 15, for reference... Maybe this would help choose the sylomer that is suitable for this application?

Quote:
I have attached a data sheet for Sylomer SR 450. This data sheet will give a fair idea of the properties for Sylomer SR450 and the effect of shape factor on the static load carrying capacity of a specific size of pad. 1. Fix the pad size Say 50 x 50 mm
2. Find out the static load coming on a pad in terms of N/mm2. This will help to decide on the grade of material to be selected ( shown in the 1st page of the data sheet).
3. Find out the shape factor for the pad size. The shape factor is a geometric measure for the shape of an elastomeric bearing defined as the ratio of the loaded area and the area of sum of the perimeter surfaces. And is given by = (l x w)/ (2*t*(l + w)) here l =length w = width and t = thickness of the pad. The shape factor has an influence on the deflection and the static load limit of the pad. The graphs in the data sheet are given for a shape factor of 3.
4. So depending upon the shape factor you can find the max static load the pad can take referring to the graph - figure 5.
5. Based on this the natural frequency of the system( Sylomer pad and mass on it) can be determined in the graph naming “natural frequency” shown on the 2nd page.
audiothings
#13
14th September 2010
14th September 2010
#13
Lives for gear

Oh here's something I found in my mail:

Is this to be interpreted as "when load on each SR450 pad is 75 Kgs, the natural frequency attained is 11.1 Hz"?

Its not the same as what I found by converting the figures in the manufacturer's brochure from N/mm2 to Kg/50mmx50mmx25mm...

SR 450 has .45 N/mm2 static load and 5 N/mm2 max load which translates to 118 Kg/50x50x25mm static load and 1315 Kg/50x50x25mm max load.

What am I doing wrong?

Attached Thumbnails

#14
14th September 2010
14th September 2010
#14
Lives for gear

Jai,

That is the resonant frequency of the sylomer pad - not the floor structure. -- kinda like tuning a guitar or piano string but instead of stretching, you're squishing.

I can't open that last pdf for some reason...

-John
audiothings
#15
14th September 2010
14th September 2010
#15
Lives for gear

Quote:
I can't open that last pdf for some reason...
Found the missing link I think... please find attached a working version of the .pdf file...

there is a "static load" which is for .45 N/mm2 SR450
there is an "operating load" which is for .7 N/mm2 for SR450
and there is a "peak load" which is 5 N/mm2 for SR450

now the difference between static load and operating load is sufficiently small, so my room loading will actually be able to use the elastic properties of the sylomer pads.

Now to find a way to convert from N/mm2 to Kg/50mm x 50mm x 25mm... Pretty sure my previous calculation was wrong (I was converting from Kg/in2 to Kg/4 cu.in. by multiplying by 4. duh!)... surprised nobody spotted it... Any clues?
Attached Files
DB-Sylomer-SR450E_screen.pdf (476.9 KB, 1112 views)

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