With the recent release of the Sandia 100m blade model (energy.sandia.gov/?page_id=7334) there have been questions about the modifications we made to the PreComp code at Sandia. The changes were driven by incorrect analysis results on a simple verification problem that we had done. The problems were in representation of the shear web. The example verification was a simple, isotropic thin wall circular section with, and without a mid chord shear web.
The following changes were made to PreComp v1.00.02 source code:
Line 1196 – Finding the center of a shear web segment lamina stack
old: y0 = y0 - tbar/2. - y_sc
modified: y0 = ysg - tbar/2. - y_sc
Lines 1212-1213 – This change seems to fix the problems caused by shear webs
old: ipp = iepz - iemzc2ths
old: iqq = iepz + iemzc2ths
modified: ipp = iepz + iemzc2ths
modified: iqq = iepz - iemzc2ths
Hope this is helpful!