dear Shany.
thank you for answering question 1.
for question 3.
i can't share the staad file due to company regulation. i'm so sorry.
but i can show you my study staad for stair tower. this staad represent my problems.
i check using AISC 360-05, staad says error due to slenderness exceeds. in 360-10. staad doesn't give any error message.
for my comparison using beam no 410.
using 360-05 code, staad says FAIL (left image), and PASS in the right image (360-10 code). the kL/r value are same. but the ratio is totally different. why ?
in the left image, i think the staad is correct, because the compression member allowable slenderness is 200. if the kL/r exceed or over 200 ,the member is FAIL.
but in the right image, 360-10 code says the member is a tension member. which mean the slenderness ratio is "should be" 300. right ? so it PASSED.
however, in the output result i will show you in below image.
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staad pro using different load case for strength check and slenderness check. am i right ?
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above explanation : critical ratio, and biggest force happens due to load case 105 and the member experiencing tension. but for slenderness check, staad (using 360-10 code) check using LC 101. the actual slenderness is 228 which over than the allowable (200 for compression). but staad doesn't say this a problem. it is PASS(ed).
i do checking via Post-Process to earn the beam force. it is true, that in the LC 105 the member is tension. and the LC 101 makes the beam compress.
but, why staad using the LC 101 instead of LC 105 for slenderness check ?
what is wrong in here ?