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  1. jfmann

    4" CMU on 8" CMU

    Ouch......good luck!.....appears to be high risk for long-term decay since water will find way behind edge of slab (and there is exposure to inside from under slab also)......at very least, use treated-wood. However, I find hard to believe competent masonry contractor could not simply install...
  2. jfmann

    Beam on top of beam, not connected, and of different length.

    Doug.........I continue to disagree about shape of pressure within contact zone, and doubt there is any sudden concentration of load at edge of contact zone....I have to believe pressure develops similar to "beam on elastic foundation" which has smooth transition. You seemed to be claiming...
  3. jfmann

    Hinge's effect on uniform load on beam?

    As noted above by others........relatively simple just analyze segment to left of hinge first to obtain point load to be applied to end of cantilever.........then analyze remainder of beam as separate element (to right of hinge only). Of course if you were to consider moving load on the...
  4. jfmann

    Beam on top of beam, not connected, and of different length.

    Doug......I must disagree with your assumed distribution of reaction force..........so then, by the same logic, if the load on upper beam were highly irregular.....say, with completely non-uniform shape......would you say that shape of pressure within contact area must somehow be the same...
  5. jfmann

    4" CMU on 8" CMU

    Consider concrete (with vertical bars) to replace upper block. John F Mann, PE www.structural101.com
  6. jfmann

    Steel Transfer Beam supporting Wood Bearing Walls above

    Deflection should be limited to code-specified limits.........even if only for your own (or your firms) liability. Take full advantage of live load reduction allowed by code, which will likely reduce floor live load substantially (up to 50-percent), depending on total floor area being supported...
  7. jfmann

    Beam on top of beam, not connected, and of different length.

    Doug......sounds like you are assuming uniform contact pressure, and then adding point loads (somewhat arbitrarily) to make up difference. Although I have been "tripped up" on first-pass at logic with this analysis........it appears that distributed load should not be uniform, but should taper...
  8. jfmann

    Beam on top of beam, not connected, and of different length.

    But wait!.......there's more.......oh geez........as close as I can get to "pure" contact for I-upper-24 (I-upper = 24-percent I-lower).......I end up with the following; Reaction at midspan = 21.01 percent of total load Reaction at 0.49 span (that is, one-percent of upper-beam-span to left of...
  9. jfmann

    Beam on top of beam, not connected, and of different length.

    Wrapping this up, at least to a "point".........looks like I owe Doug a beer! Using only point load reaction at midspan.......I calculate that "perfect" contact occurs only at midspan, down to I-upper-25 (that is I-upper = 25-percent of I-lower).......for which configuration the midspan...
  10. jfmann

    Beam on top of beam, not connected, and of different length.

    Just some musings on fundamentals........though have not quite fitted all pieces into this puzzle. For continuous beam.......moment for each beam segment is of course the same at interior support. Slope is also the same at end of each beam segment at this support (that is how segments are...
  11. jfmann

    Beam on top of beam, not connected, and of different length.

    For first contact, ratio of 1/2.4 is same as the 41-2/3-percent I reported, so at least we agree on starting point! However there is no obvious reason to then claim that point contact (only) continues for all I-upper values down to 25-percent of I-lower........or that distributed contact then...
  12. jfmann

    Beam on top of beam, not connected, and of different length.

    Hazards of long posts.......one important correction; There is difference between curvature and slope. Looking at this case for example.........at midspan of both beams, slope is the same (zero) yet curvature is not the same. We see this by looking at the total shape of each beam. This is one...
  13. jfmann

    Beam on top of beam, not connected, and of different length.

    Doug......see your graphs again........quite informative Upon comparing my "20-percent" solution (I-upper = 20-percent I-lower) to what is your graph of same configuration (you have ratio just expressed other way, as multiple of 5).......I get similar results, though one qualitative difference...
  14. jfmann

    Beam on top of beam, not connected, and of different length.

    Alrighty then.....my bad......updating yet again......going to get this! I-upper = 41-2/3 percent of I-lower M-upper = 50-percent of M-lower (in area of contact, at and near midspan of both beams) I-upper = 40-percent of I-lower M-upper = 47-percent of M-lower I-upper = 33-1/3 percent of...
  15. jfmann

    Beam on top of beam, not connected, and of different length.

    Ah, clicking tad too quickly through formulas..........revised moments for Case 2; I-upper = 41-2/3 percent of I-lower M-upper = 50-percent of M-lower (in area of contact, at and near midspan of both beams) I-upper = 40-percent of I-lower M-upper = 49-percent of M-lower I-upper = 33-1/3...
  16. jfmann

    Beam on top of beam, not connected, and of different length.

    Must admit my analysis went off-track ......forgetting to verify key assumption, which was (incorrectly) that end-rotation of upper beam would be obstructed before contact at midspan occurred. Initially (as seen in early posts) I was focusing on deflections (and should have stayed with that...
  17. jfmann

    Beam on top of beam, not connected, and of different length.

    Doug......the following is from end of my long post of yesterday (19:47)......this is for Case 2 (upper beam, with Length of L/2, centered within lower beam, with Length of L) "Finally.....claim that moment in each beam is proportional to relative I-values ......when beams have same slope...
  18. jfmann

    Trust Web Bracing

    Up until "new" regulations........which, as noted by medeek, resulted in BCSI-B3, which is an attempt to fill void caused by lack of responsibility by architects (due mostly to lack of knowledge than anything else)........TPI codes (referenced by building codes) had specified that "building...
  19. jfmann

    Trust Web Bracing

    To clarify......architects continue to claim they have no responsibility for design of truss bracing (either directly by them or via consultation with structural engineer).....it is just that now they can point to revised regulations that (as I believe is the case; someone correct me if...
  20. jfmann

    Trust Web Bracing

    From my experience over many years........ reading trade articles on this subject, reviewing architectural plans, reviewing truss-design submittals, inspecting roof-truss assemblies and even preparing reports for legal cases involving truss-assembly collapse and personal injury........it is...

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