I am using STAAD V8i to do steel design for a building per the AISC 360-10 code. First run analyze all members have passed, second run (by another party) some members have failed (KL/R big differences, critical load is different). knowing that nothing was changed in the model, so what is the reason for that?
I guess the second run was done in some other version than what you are using. Can you please confirm the version number in 2 cases? Also, please share the STAAD file to investigate at our end.
Thanks & regards,
Global Technical Support
Thank you for your reply .I will confirm the version number in 2 cases, when I know it.
BILLET STORAGE SHED.std
Abhisek will definitely provide your more clarification on this once you confirm the version number. Still I want to point out few important reasons for this result mismatch. In 2017, first build of CONNECT Edition was released and since then 14 versions has been released. If we notice any problem with analysis or design results in any build of STAAD, that is fixed in the next version. For AISC 360 code, there are more than 50 such fixes in the V22 series only - some of which are major. For example, in Update 4, there was a major change related to single angle design --
A) 23 The AISC 360-10 design for single angles has been updated to address the minor axis moments used with the LTB calculation. The determination of the location of the part of the profile in compression due to the minor axis moment was being misinterpreted.
Also default value of CB has been modified from 0 to 1 which means latest version does not auto-calculate the CB value, rather considers it as 1. Also there are few changes related to Taper section design.
A) 30 The AISC 360-16 design code has been modified such that the default value of the CB parameter is now taken as 1.0. If it is manually set as 0.0, then a value of Cb will be calculated based on the forces applied to the analytical member. Any other value will be taken as a prescribed value for Cb to be used in the design.
I have noticed that in your model, you have used angle, taper and wide flange sections and also didn't specify any CB parameter (default value is used which was previously 0, now 1). So if you just consider the above three points, the design results will be different from the older version.
What we recommend, please go through the revision history file once which is located HERE and review the changes related to AISC code. This will provide a better understanding why the results are not same.
Also, for more information, provide us the exact build number of those two STAAD versions that you are using along with a specific member number - that will help us to track the reason.
Finally, STAAD.Pro v8i version is out of support and we don't recommend to use any results reported in this version.
Answer Verified By: Abdel H