I have a member failing the Critical Simplified deflection ratio, however the graphed D+S load combination deflection (0.613 in) does not correspond with the reported deflection of 1.1 in. I’m not sure if this is a bug or if I’m misinterpreting the program?
The steel beam only has uniform dead+snow loads on a simple span.
Thanks for the help.
Hi Maxwell! Thanks for pointing this out.
The critical deflection calculates a maximum deflection from serviceability load combinations (L, Lr, S, 0.42W)- this does not include dead load as it is not considered in IBC 2018. This is the load combination that is graphed in ClearCalcs, where the dead load has an impact on the shear and moment graphs, but is not considered in the graphed deflection envelope since it is not required by the IBC.
Although, since some local building codes require unfactored dead + live or snow combinations, we have the “critical simplified DL + (LL or SL) deflection” as an additional check. This calculation considers the dead load, so the additional deflection you see in the -1.1 in (vs -0.613 in) would be from the dead load.
Thank you for the clarification!
