Sunday, 1 March 2009

Geometry Gym - Structural Analysis Data to/from Rhino

Geometry Gym has developed several plug-ins for Rhino that allows data to be transferred to and from Rhino from Structural Analysis programs used by Engineers to assess structural performance and strength.  This is currently released for Oasys GSA (which is used at our office at Expedition), and early versions are being worked on for other similar programs.

A lot of engineering time is spent on updating and altering structural analysis model geometry as projects and designs evolve and change.  Particularly when different design disciplines coordinate and accomodate to find efficient solutions.  By taking advantage of Rhino and using custom and default tools and commands, greater efficiency and productivity can be achieved in updating models.

You can watch this tutorial on this video link, then I'll explain the steps for you to try.

Initial GSA model here.
Initial Robot model here.
Initial SAP2000 model here.
Initial Sofistik model  here.
Initial SpaceGASS model here.
Initial Strand7 model here.

You can find the Rhino model with the a surface representing the desired shape here.

Download both these files to your computer.  Open the GSA model, but you can skip the step to export the model to GWA (text) format as the file is already supplied as such.  Note that all the nodes and elements lie on within a horizontal plane.

Open the Rhino model above, If you haven't already, install ssiGSA and then open the above rhino file.  Click on the import GWA button on the plug-in toolbar to import in the GSA model data.  Note that you can elect not to draw the 3d shapes for this example.

For this example, we want to move all the nodes in vertical location until they match the target surface.  This target surface was generated by the free Math Plug-in by Jess Maertterer.  

We can use the Rhino command project which will relocate objects perpendicular to the current cplane until they intersect with a target surface.  Only node data coordinates are sent back to GSA, so all the points can be selected by right clicking on the node layer.  Type in the Rhino command Project (ensuring you are in the Top view, or that a World Top Cplane is set in Perspective view), and select the surface as the target.  Ensure that the original data is deleted so that duplicate nodes are not present in the model.  You should see the planar nodes are now all lying on the surface.  The updated node coordinates can be obtained by clicking on the second button in the ssiGSA toolbar.  The GWA data will be copied to the clipboard, and can be imported into GSA by right clicking on the gateway and electing to paste data.  You can manually inspect the contents by pasting into WordPad (or similar text editior).  You will see the GSA nodes in their desired position.

Note this is one way of taking advantage of the advance sculpting and scripting environment of Rhino.  Upcoming blog entries will take a look at other simple but powerful ways of transforming models to efficiently change structure geometry.