RAM Frame Polygon intersection algorithm

You will find some detail on that here: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/4552/ram-ss-common-framing-table-errors-tn 

If it's happening in Ram Frame, prior to analysis or meshing, then it must be in the routine to determine total masses and gravity loads or exposure boundaries. 

Send the file if needed, and confirm your version. 

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File was uploaded, I am using RAM v15.11. 

That's a pretty old version, but I still see your error in Ram Frame. 

The 3D view gives some clear evidence of deck polygon problems: 

For more on laying out deck polygons on a sloped surface see: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/7207/ram-ss-3d-viewer-faq 

In this case, for example there is a transition from a sloped area to a flat area that requires two deck polygons. Try not to overlap the deck polygons in roofs like this. 

That's a pretty old version, but I still see your error in Ram Frame. 

The 3D view gives some clear evidence of deck polygon problems: 

For more on laying out deck polygons on a sloped surface see: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/7207/ram-ss-3d-viewer-faq 

In this case, for example there is a transition from a sloped area to a flat area that requires two deck polygons. Try not to overlap the deck polygons in roofs like this.