I think Mr. Srinivasan has referred to the spreadsheets based on the well known " Kellog Method " .
Yes, this is a time tested method based on a derivation using the concept of beam on elastic foundation.
However I have found in most of the spreadsheets I have come across , an erratic way of combining stress and comparing against allowables.
In my opinion, the stress output from "Kellog Method" should be combined and checked as per recommendations of SEC VIII DIV 2 APP 4.
A.BHATTACHARYA
STRESS ANALYST
BECHTEL CORPORATION
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Anindya Bhattacharya