RAM Beam Floorvibe vs DG11

I am doing a vibration analysis on a perfect bay. The girder spans 35' and the joints span 34'. I also have a spread sheet that follows DG11. I am getting different results from floorvibe. When I look at the complete report floorvibe calculates Dg =Ig/(Avg Lb), where it takes the Avg Lb as the trib width of the girder, rather than dividing it by Lj as defined in DG11. Why is it doing this?

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  • Design Guide 11 defines Dg as Ig/Lj, where Lj is the span of the joists on either side of the girder. Note that if the joists on either side of the girder have different spans, Lj should be the average of the two lengths. Also note that the trib width of the girder is one half of the joist span on each side of the girder, for a total of one joist span; therefore Avg Lb = trib width = Lj. So FloorVibe calculates Dg by taking Ig / Average joist span, which is consistent with the req't of the Design Guide.

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  • Design Guide 11 defines Dg as Ig/Lj, where Lj is the span of the joists on either side of the girder. Note that if the joists on either side of the girder have different spans, Lj should be the average of the two lengths. Also note that the trib width of the girder is one half of the joist span on each side of the girder, for a total of one joist span; therefore Avg Lb = trib width = Lj. So FloorVibe calculates Dg by taking Ig / Average joist span, which is consistent with the req't of the Design Guide.

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