RAM SS Column Axial Load and Beam End Shears

I have 4 concrete beams that intersect at a concrete column. I would think that when you add all 4 of the Beam End Shears at the column it would = the column axial load but it does not? What else is contributing to the axial load on the column besides the shear at the beam ends? 

Thanks

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  • Thanks for sending the model. It is fairly simple, just beams and columns, no deck or loads other than self-weight. 

    Regarding self-weight of beams and columns, they are based on the center to center span length.

    9 * 1.33' * 1.33' * 5' * 0.15 = 12.0 total (1.33 k each, note column SW applied at top of story)

    Beams are all fixed, (indeterminate reactions) total weight:

    12 * 5' * 1.33' * 1.33' * .15 = 16 k total (1.33 k each)

    grand total weight = 28 k

    Sum of reactions from Ram Concrete analysis = 28 k (4 @ 2.58; 4 @ 3.38 and 1 at 4.17). So that part seems correct. 

    Beam shears are, however shown at the face of the column, so those are truncated. A typical 2-span beam line in your file has 0.45 kips at the face of one column, 0.53 at the interior support. So the slope of that shear diagram is (0.53 + 0.45)/ (5 - 1.33) = 0.267 k/ft which equals the unit weight of the beams (1.33' * 1.33 * 0.15). To know the shear at the column CL, one would have to extrapolate the last 8" at each end: 

    0.45+0.267*0.667=0.628k  and 0.53+0.267*0.667=0.708k

    I did notice one problem in the diaphragm of the shear forces. The plateau of the shear forces is incorrectly drawn as if the column dimension were twice as large. I'll report that. 



  • If one were also modeling a 2-way concrete slab, be careful in that the beam shears only represent the shear in the beams and do not include the out-of-plane shear resisted directly by the slab. We usually recommend using Ram Concept for hybrid beam and 2-way slab systems.