Dear Friends,
I'm trying to check the results of floor vibration from STAAD pro, I've modeled very simple floor system with the following properties:
Joist Type : IPE 270
Joist Span: 6.0m
Joist Spacing: 2.0m
Joist Deflection: 4.142 mm
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Girder Type : IPE 550
Girder Span: 12.0m
Girder Spacing: 6.0m
Girder Deflection: 20.3 mm
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Loads : 7.5 kN/m2
Results are shown in the attachment figure, I used the relations in Design guide 11 but I can't varify the following values:
Ds, Dj, Bj, Wj,acceleration.>>> and I don't know how does STAAD assume the value of Damping and Acceleration limit. I mean based on what ?
you can find my model in the attachment too.
Floor Vibration.std
The damping and the acceleration limits are based on the table 4.1 of the design guide 11. Typical damping varies between 2% to 5%. STAAD.Pro uses a 3% damping. The 0.5% acceleration is also typical as the other values correspond to specific structures like malls or footbridges.
- I noticed that STAAP uses different values of Damping and Acceleration Limit but I don't know what's in the inputs or outputs controls this selection. for example in the attached model STAAD is using a value of 0.002 for Damping and 1.5% for Acceleration Limit instead of 0.5%
- I'm trying to verify the value of peak acceleration for the attached simple model in STAAD pro using Equation 4.1 in the design guide 11 and STAAD outputs (Fn, W, Beta) but I can't get the same value as shown in STAAD report.
Regards,
7245.Structure1.std
I went over the floor vibration implementation in detail with a developer this morning and found that all of the four conditions outlined in the table 4.1 was not implemented. Only the first two are currently there but the logic behind when to use which one, is not properly implemented. So I have recommended an option to be introduced in the software so that users can directly specify the condition ( all 4 options will be made available in a combo box ). This will be implemented in the next version.
In the current implementation, the software calculates the results for the combined mode considering the first beam/joist and the first girder only. There is no way for the user to influence that. I have recommended averaging the results for the joist mode and the girder mode in the future implementation.
So based on the current data you posted, Fn = 0.18 sqrt [ 9806/(6.9+3.6)] = 5.5 Hz …equation 3.3
W=6.9/(6.9+3.6) x 72.0692 + 3.6/(6.9+3.6) x 139.7403 = 95.3 … equation 4.4
The other thing that I noted is that the value of Po is not changed appropriately for calculations when using metric units. For example instead of using 0.29 ( in KN) as the value for Po, the software is just using a value of 0.065 ( which is the right value for English units - Kips ). So this will be changed too. So for now, I would suggest that you use the base unit as English if you are using the floor vibration report. You do not need to make any changes to your input. You just need to set the base unit to metric and generate the floor vibration report as you normally do.
Answer Verified By: Khawaldah
Sye,
Have these changes been implemented. If they have which version of Staad Pro were they implemented in?