FYI - composite beam deflections and RAM SS
FYI - composite beam deflections and RAM SS
(OP)
This is tangential to the recent thread on composite action. The green book uses an Ieff for deflection checks (which accounts for partial composite action). The new black book calls this same equation Iequ and recommends multiplying this by 0.75 for deflection (based on testing). RAM did not recognize this. I called them last week and they were unaware of this change, but will incorporate it into the next version. In the meantime, anyone using RAM should bump up the deflection criteria for composite beams to account for this (e.g. L/360 will want to be L/480).






RE: FYI - composite beam deflections and RAM SS
RE: FYI - composite beam deflections and RAM SS
RE: FYI - composite beam deflections and RAM SS
1. The 0.75 reduction is not new to the 13th edition manual - it first appeared in the 3rd edition commentary (see 16.1-220). It just got screwed up and had to be fixed in the 13th because the nomenclature changed (in the 3rd edition it was written as Ieff = 0.75Ieff which isn't very clear so it was revised to Ieff = 0.75Iequiv. except the nomenclature for the equation for Iequiv wasn't changed in the first printing).
2. Note that Commentary is just that, Commentary - and therefore not required. You could just as easily be arguing that RAM should be using the lower bound moment of inertia which is another approved commentary method. If you feel that the 0.75 etc. is not necessary and L/360 with Ieff has been performing fine then I would continue to use that.
RE: FYI - composite beam deflections and RAM SS
RE: FYI - composite beam deflections and RAM SS
Is I(equiv) simply the calculated I(eff) prior to multiplying by 0.75?
RE: FYI - composite beam deflections and RAM SS
RE: FYI - composite beam deflections and RAM SS
See thread507-235021: Ieff for composite steel beam.