Skicat
Editing features need some practice. I advise the following
1)Draw the 3D gusset in autocad,using lines only. Approximate holes closely by a series of lines
2)Be as careful as you can, ensuring lines join and intersect. Otherwise it will be painful later to merge joints that dont intersect. If you use metric, then ? suggest you work in mm
3)Set a convenient point as 0,0,0 global in your cad drawing. This will help you in zooming later.
4)Make sure you assign all lines in your cad model to one layer(never layer 0) say layer 1. keep the name in mind
4)Export dxf with options to select. Type dxfout and the window shows up with options. select ASCII and set decimal digits to about 4 or 5. this matters a lot
5)Open sap2000, import the dxf file. YOu will be asked for the layer and units. Remember that layer for frame elements and use units carefully. If you drew in mm, then make sure mm is there.
6)divide all frames so that you have nodes.
7)Now draw the shell elements using those nodes. Duplicate, mirror etc.
8)Once happy with your shells, erase all frame elements.
It works fast enough for me. Hope it works for you.
respects
ijr