Possible PreComp bug fix

Hello Everyone,
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 + iemz
modified: ipp = iepz + iemzc2ths
modified: iqq = iepz - iemz

Hope this is helpful!

Dear Brian,

Thank you for reporting this bug and its fix! I will add your bug/fix to our design codes “to-do” list.

Unfortunately, Gunjit Bir (the developer of PreComp) no longer works at NREL. We are still trying to figure out the best path forward for future developments of PreComp.

Best regards,

Version 1.00.03 of PreComp has been released and posted at wind.nrel.gov/designcodes/preprocessors/precomp/

We are still evaluating the output of PreComp, please use with caution.