Staad(X) / Structural

We are currently modeling a building, and I am trying to transfer the geometry from Structural Modeler via Structural Synchronizer into Staad.X.

One problem is that as we usually stop our walls and columns below the slab, and start the next on top of the next slab, we will get 2 nodes in the Staad.X model.

Is this something we should do differently, or is this a known problem which we cannot expect to be without?

  • In my experience, when working with STAAD or RAM or any of the various finite element analysis applications out there, the default or expectation is that the member (column or beam) and slab centerlines should all match.  That’s how the program knows the members and slabs are connected.  From there, rigid offsets can be used to introduce eccentricities and make the analytical model more geometrically accurate, depending on how far you want to take it.

    If you are stopping your members at the face of intersecting members or shell, that model in STAAD(X) is not initially going to work because you will have two nodes rather than one leaving things unsupported.  It could probably be fixed with various tools inside the STAAD(X) or STAAAD.pro environments, but that’s a lot of extra work.



  • Ok, but what is best practice then? On one side or the other we have to address the problem.

    On the calculation side

    During import there should be an option to virtually extend walls and columns to meet slabs.

    In the model

    That requires one thing I always wanted - dynamic subtracting objects from each other. If a wall extends into a slab, the wall should be subtracted from the slab. (The wall would have to be connected to the slab, like a parent - child relationship).

  • One more thing regarding slabs.

    When transferring geometry from Structural to Staad.X via Structural Synchronizer, the reference plane for the surface elements is the bottom of the slab (would probably be the top if I created slab to extend below during creation).

    Using Structurals analytical feature usually generates the analytical members in the centre of the slab.

    New source of headache...?

  • In my tests going from Structural Modeler to ISM, I always see the Placement Surface = Bottom and the Boundary coordinates are at the elevation of the bottom of the slab.

    When the ISM model is brought into STAAD(X) it simply uses the Boundary Coordinates to define the plate nodes and uses those points for the centroid of the plate. This adjustment means that the slab plate in the STAAD(X) model is typically dropped ½ slab thickness compared to the physical model from Structural Modeler as you have noted. But all of this is good news; it should mean that the STAAD(X) model is connected to the columns and in working order. If we didn’t make an adjustment it might look right in 3D, but things would be disconnected in the analysis.

    We are investigating better ways to deal with the physical slab elevation and the requirements of analytical applications like STAAD(X) or RAM Elements, but there does not seem to be a perfect solution that maintains physical geometry perfectly while also making an analytically stable model.



  • In my opinion the analytical model should never use the base of the plate as the design plane, but always the center of the slab. All codes which I am aware of have this requirement.

    It should therefore be a part of the process between the structural software (Staad.X) and ISM to agree on how translations should be done.

    As for your comment regarding that this behaviour is good news, I have to disagree.

    As we always draw our walls between the slabs (from top of slab to base of slab above), we already have a problem - at the top of the slabs.

    I good way to fix that would be to allow how intersections between walls and slabs, and columns and slabs should be handled. In my opinion that should allow some user configurations.