Wednesday, 23 November 2011

Tributary Areas and Variable Loading

I've finally got some final improvements made to some useful functionality that can save hours of spreadsheet processing (or the like thereof).
I've enabled functionality within Grasshopper to compute tributary areas for nodes contained within a structural grid, as well as generating node loads from varying loading phenomena such as snow drifting or wind pressure.

This algorithm was used (in a more time consuming and specific way) for the 2012 velodrome roof in applying wind pressures from wind tunnel testing advice.  At the time we were still optimizing cable spacing but still wishing to test multiple loading scenarios.  This routine can work out tributary areas for arbitrary grids (based on mid distance from adjacent nodes), grid normals (although load can be applied in a uniform direction if desired) and utilize a varying loading intensity at different locations.  This can be defined (or checked) intuitively from a surface (or polysurface) relative to a reference plane (the local z from datum defines the magnitude of loading pressure).

If you download the models below, you'll see it uses a reference plane from the structure (required for non-planar grids), and the relative position from the loading plane.  I haven't yet developed grasshopper visualization of the generated node loads (it's on my todo list along with boundary conditions, releases etc) so you'll have to visualize in the analysis software.  I also plan to implement face loading for finite elements in a similar manner, and any other suggestions that might arise from users, so don't hesitate to send them through.

Please check the results carefully, I hope you find it useful.  I'm also very happy to assist in applying or testing this with your own applications to projects.
GSA model,  SAP model (others to be added shortly).

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