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Apparent bug with AISC 360-16 unbraced lengths - Calculation of Cb
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Initially when I run this calc, it fails by a substantial margin. Simple moment frame but my hand calcs show it should pass. Robot has it failing by a factor of 5. So I dig in and when I click on the detailed results tab of the beam calcs, it shows the Cb factor = 0.06. No clue how it got that number. Per AISC Section F1, Cb should never be less than 1.0. So in Robot, here's the initial calcs:
So I open up the "Forces" page and get the following:
When you press the "Calculations" button, robot recalculates Cb to the correct value of 1.27. It also matches my hand calcs:
But I'm stuck because as far as the printed calcs goes, Robot says it fails...by a lot. Can we get this fixed?