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Diaphragm for automated wind load

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dada23

dada23

Civil/Environmental
Apr 20, 2017
13
I have encountered an issue on the portal frame model on SAP2000 when I use diaphragm to compute the wind load automatically in different wind directions. The error is as below when run the analysis, stating that numerical problems unencountered during equation assembly. I have also attached the Sap2000 model for reference



Could someone help me out

Thank you very much
 
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dada23, can you share .s2k file as I have older version of SAP2000.
 
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dada23, sadly, the import is also aborted as SAP says that version 22 file cannot be imported to version 20.
However, I believe that you can ignore the warning generated(attached result sheet) if your structure seems to behave properly with all the load cases.
Further is joint label 1 is a support?
If yes, check if properly provided.
 
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MSUK90,the structure deflects perfectly under dead load. However, when it comes to the wind load case, the structure does not deform and I believe that it is due to the use of diaphragm parameters to apply wind load automatically. maybe something is not right there, and you will see from the result sheet, it says " diag = 0 ". If I used the exposure from area objects and input the corresponding wind coefficients, the analysis works well. Therefore, I am pretty sure that there is an issue with the diaphragm settings, but can't find it.

Also, it found it weird that joint 1 is actually at coordinate 0,0,0 but according to the result sheet, it is at coordinate 15,7.5,4.72, I have checked it in my model and there is no joint at this coordinates. So, it is quite difficult to find the problem.

I have attached all the parameters I have set for the diaphragm load and geometrical model data for your reference.







 
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Could you confirm if the whole structure should be selected for diaphragm or only the roof objects? Because previously I selected all the nodes, elements and objects (included that of the wall facade one) for the diaphragm but when I have just tried to select only the roof components and associated nodes, the structure deform perfectly now.


I want to assess the roof geometry (roof form and slope) on the wind response of portal frame system, and gable roof is one of them (we will have curved roof, hip roof, monoslope roof as well). It is one part of my current research project. So, diaphragm on SAP2000 will allow me to assess the behaviour of the models in different wind directions. I have just found from the youtube ( that the diaphragm is actually not suitable for single-storey building and it says it is recommended to apply the wind load manually. Is that true?
 
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dada23 said:
Could you confirm if the whole structure should be selected for diaphragm or only the roof objects?
Click to expand...
The diaphragm should be applied only at roof.

dada23 said:
the diaphragm is actually not suitable for single-storey building and it says it is recommended to apply the wind load manually. Is that true?
Click to expand...
Haven't seen the video but in practice most of the designers calculate wind loads manually for small buildings(especially industrial structures).

dada23 said:
I want to assess the roof geometry (roof form and slope) on the wind response of portal frame system, and gable roof is one of them (we will have curved roof, hip roof, monoslope roof as well). It is one part of my current research project. So, diaphragm on SAP2000 will allow me to assess the behaviour of the models in different wind directions
Click to expand...
Would like to get a copy of your research once you complete it.[thumbsup2]
 
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No problem :D

Thank you very much for your input on my issue. Take care
 
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