Manual Mesh and Auto Mesh

[skyscraper]

Could someone to explain for me auto mesh in Etabs caused problem with with mass of the building and building modes? Is that right?

Thank you

[DonMehdi]

Dear skyscraper
yeah, that's right. it is better to mesh the slabs with integration third software like, ADAPT, RAM Concept, MIDAS, Robot and also CAD,... then import that to the ETABS. this is my experience in design of the most structure in DUBAI

[visu]

Dear DonMehdi,

Could you describe in detail , how to do meshing in ROBOT and import in to ETABS?
Regards,
Visu

[DonMehdi]

Dear visu
first of all you should be prepare your plan in autocad (DXF File usually) and then import in 3rd software like RAM-Concept and ROBOT ( it is available commonly in file menu import/export menu)
then after meshing the surface ( usually you have to define the column location and support and also the joint you need get corresponds) save mesh as per DXF file and then import the mesh in to the ETABS. just be careful the origin should be same

Regards
M.E.S

[PanosP]

The above mentioned dxf import can be done directly in etabs via file/import/dxf 3d. You just need to make sure that (if I remember correctly) beams should be lines and areas regions. However by manual meshing you may encounter connectivity problems between beams and areas. This can be solved by the use of automatic meshing over which though you dont have much input (black box pretty much).

[skyscraper]

Dear Donmehdi

I am not sure whether you have applied mesh from ram concept to Etabs. I think it causes a lot of messy. Even I try import one simple drawing in dxf file to etabs , it is somehow to shift away my point (even it is really small but very annoy to modify it again). I think the best way to manual mesh is draw the big square or rectangle to connect 4 columns then divide it to small elements. then use shrink point to match with close other proximity points . Any suggestion.

Regards

[michenerpark]

I have done quite a lot of FEM analysis and below are points which I think they may be valuable to you. Examples below are based on STAAD Pro and it applies to other software like SAP2000, RISA similarly. Only thing difference is SAP2000/RISA may use a different CAD element for plate/shell in CAD. For STAAD Pro it uses 3DFACE element in AutoCAD for Shell/Plate element

1. For complicated model with lots of connectities between shells/plates and beam/column, manual meshing in CAD like AutoCAD, save as DXF, and import to STADD Pro is the most efficient way.

2. To avoid the connectivities problem after import into STADD Pro, you can

1) Export the STAAD model need meshing as DXF

2) Open that DXF in CAD lioke AutoCAD

3) Start meshing in AutoCAD using the exported model. For Plate/Shell element in STAAD, just draw 3DFACE

4) AutoCAD has powerfull 3D Orbit and manipulate tool for you to copy, mirro, array set UCS view, to get the meshing done easily, none of th Structural Software has such integratel tool for you to do that

5) Do the cleanup before import back, delete all grid line etc for helping meshing otherwise they will be imported back as beam

6) Save the finehed model in AutoCAD as 3D DXF file

7) Import the DXF back to STADD

8) Due to floating point tolerance, some nodes X,Y,Z value like 0.0 it will imported in STADD as 1E-015. To make eleminate issues like this, in STADD you can set tolerance as 0.001m, check duplicate nodes and merge them, similar check like check orphan node, duplicate plates, colinear member, plate/beam connectity , warping plate etc

9) After all above checking and correct findings, now you get a perfect model!