Floor Vibration AISC Design Guide 11

[Arun4567777]

I was going through AISC Design Guide 11. I have some doubts to clear.
We have many methods to compute natural frequency such as Southwell-Dunkerley(lower bound), Rayleigh
(Upper Bound) and Modal Analysis using Staad.

I have a 4 storey steel building which has a Vibrating Screen installed on 2nd Floor.

I want to ask that should I be calculating the natural frequency(mode1) of the overall structure using Modal Analysis or do i need to calculate the frequency of the floor only as per AISC Design Guide 11.

Please clear my basics in this regards.

 

[HTURKAK]

Dear Sammy345 ,

AISC Design Guide 11 is for ( Floor Vibrations Due to Human Activity).. In your case the floor or total bldg vibration ( depending on the support cond. of the equipment ) due to Vibrating Screen..

If you provide more data ( for the screen , wt, frequency etc.. supporting provisions, and the steel bldg ) you may get better responds..

 

[wrxsti]

check to see if the manufacturer has something like this

you should probably do localized checks

supporting beam -> floor -> building

 

[Arun4567777]

I have all the data.
The vibrating screen is supported on ome floor only.
Yes AISC design guide is for Vibration due to Human Activity bit still the basic principle to calculate frewuency remains same.
I just want to know should i calculate frewuency for whole building or just the floor

 

[HTURKAK]

If the bldg is steel framed , ( the connections are rigid ) , you should calculate the natural frequency for the whole bldg..

However, ( based on my past experience ) , i will suggest;

- The vibrating screen should be supported on beams which are simply supported to columns ( with simple shear conn. )

- The natural frequency of simply supported beam should be at least twice the frequency of vibrating screen .

- The bldg could be composed of simply connected frames , and provide bracings for the stability and lateral loads ..

 

[ThomasH]

Hi

You probably need the correct natural frequency for the floor since it is the vibrations in the floor you are working with. If the properties for the whole building has a significant impact on the natural frequency of the floor, then you probably need to include the building. I assume that the Design Guide has some "simple" formulas for calculating the frequency. If for some reason the formulas are not valid, due to differences in boundary conditions or whatever, then you may need something else.

But I don't understand what you mean with the natural frequency for "the whole building" or "the floor". I assume that the floor is in the building but will a calculation of the floor alone be sufficient. I would say that it usually is but I don't know i this specific situation.

Thomas