Originally Posted by jhbrandt
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
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...