Today I faced a very strange problem in CSi SAP. When exporting a model from ETABS to SAP, two files are created; sdb file and txt file. If text file is imported in SAP, this will give different results than if you open directly the sdb file.
Value of time period of both the models were different and we found out that there is about 300kN difference in self-weight of elements. We examined text files of both models in MS Word Compare Document feature.
It was revealed that model based on importing the text file has some additional beams. Actually, there were some NULL lines in ETABS and when you export from ETABS and import in SAP as a text file, null lines are not recognized and SAP applies the first available frame section to all the null lines which in our case was 700mm deep concrete beam. That’s why we got 300kN more self weight and different time periods.
So next time you export ETABS model to SAP and send its text file for a review, to another person or firm, be informed that it might give them wrong results. Always send the SDB file!