plate Vs surface model? - Structural Analysis and Design - Forum - Structural Analysis and Design - Bentley Communities

# plate Vs surface model?

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#### plate Vs surface model?

• dear seniors

i had to model slab having more than 4 nodes.we have only  four noded plate to model slab.In that what to do?Shall we model slab using surface model?What is the difference between plate and surface model?

Thanks in advance

• You need to mesh the slab into a number of plates. Along the left side of the STAAD.Pro screen, look for the Geometry page. Under that, there is a Parametric models page through which you can generate a mesh for a slab defined through any number of nodes. Study the description of this feature in the online help (Help-Contents-GUI Manual).

In the Getting Started manual, take a look at Tutorial 3. It too shows various ways to mesh simple slabs.

In cases like this, you are taking upon yourself the responsibility of meshing the slab into plate elements. If you want to avoid the chore of meshing the slab on your own, surfaces is an option. Surfaces are objects where the meshing is done by the program behind the scenes and you hence have to deal with a limited number of entities on the screen, thus making the model smaller. Surfaces are especially useful if you are modeling a designing concrete shear walls.

However, in complex structural arrangements, this "behind the scenes" meshing may not always be free of modeling errors. You may run into poor conectivities between the slab entities and the beam entities and fixing them won't be easy. Also, if the parameters for defining the surface are not provided correctly, you can end up with a very dense plate element mesh with very small sized elements which will make the resulting analytical model very large.

So, stick to meshing the slab on your own until you are comfortable using STAAD.

• Thanks for ur attention brother.

• According to me the basic difference between plate and surface is that Plate behaves like a membrane and takes the command to resist  out of plane shear and bending moment as in case of floor slab. The inplane bending moment and shear force, the magnitude of which is quite small for plate, is left to be resisted by the frame The surface takes  the command to resist inplane shear and bending moment as in case of shear wall. Surface is a part of the moment resiting frame and helps the frame in resisting moment due to lateral load while plate helps the frame very little in resisting the moment due to lateral load that too throgh Master Slave command only. Surface does the above action automatically as a family member of the frame. Plate behaves as a guest member. I also suppose the surface has to be checked against out of plane buckling whereas it is not done for the plate.

Anybody who finds contradictions in the above clarification and can explain the difference between plate and surface in a more refined and explicit way, is requested to post his views because many users, as per my study, are not able to differentiate explicitly between plate and surface.