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  1. BAretired

    Truss Top Chord Lateral Support

  2. BAretired

    Truss Top Chord Lateral Support

    No, I will not elaborate! The information you must provide are: the required vertical clearance under the bridge to allow the passage of vehicles. the required width of road. the required separation of roads. I do not understand your last two sentences about referencing your posts. What do...
  3. BAretired

    Truss Top Chord Lateral Support

    Yes, that would be possible. Two rollers and one hinge would be possible, but a pinned support would need a stiff column below it, fixed at the base and pinned at the top. A pin can't exist by itself. The entire structure would deflect with the column in addition to temperature movement...
  4. BAretired

    sketching tool

    Looks as if he created it with either Open Office or Libre Office, but then saved it with his Snipping tool to put it in the png format..
  5. BAretired

    Truss Top Chord Lateral Support

    Your points A and B are necessary supports. So there are four supports in total. The middle truss acts like a doubly cantilevered beam with a truss reaction R at the end of each cantilever. See below.
  6. BAretired

    Truss Top Chord Lateral Support

    Yes, that works fine, but you suggested a preference for the Warren configuration in your original post. It looks better too. 1. If you design pin joints at A and B (blue to orange connection), the structure is statically determinate. 2. I like the idea of making three trusses each 60'...
  7. BAretired

    Truss Top Chord Lateral Support

    Of course one can. I would prefer to use only one frame at each end as I showed on the Bridge Elevation. One is enough and it can be X-braced or V-braced...your choice. I am not particularly keen on slender rods for X-bracing. I believe they should have an L/r of 200 minimum so they can act...
  8. BAretired

    Beam Reinforcement Calculation

    It's really not odd at all, human909. I would expect the shear stress in each side plate to follow a parabolic curve from zero top and bottom of plate to a maximum at mid height. I would expect the total shear for the height of plate to be shared by the I-beam web and the side plates. And I...
  9. BAretired

    Beam Reinforcement Calculation

    @Celt83, A-A2 is closer to what I expected, but without dimensions of beam and plates, who knows? We could check stresses for an imaginary I-beam and plates if anyone wishes.
  10. BAretired

    Beam Reinforcement Calculation

    Maybe he was...that would be unusual for Celt83. But, in any case the VQ/I which should be used is the value for the composite section, not for the reinforcement plates. No, no, no...Hell no! The shear in part of the I-beam web will be reduced. It has a pair of side plates helping it. VQ/Ib...
  11. BAretired

    Beam Reinforcement Calculation

    In agreement with whom? Even if the side plates are removed, VQ/I is not zero at that point. If VQ/I at tops of side plates is 0, there is no shear stress in the I-beam web at that point. Q is for the combined section, so at the top of side plates, Q is for the Tee section comprised of the...
  12. BAretired

    Beam Reinforcement Calculation

    Omitting the side plates would be my approach.
  13. BAretired

    Beam Reinforcement Calculation

    On the other hand, Timoshenko and MacCullough seem to be quite convincing in their text "Elements of Strength of Materials". Below is their derivation of Formula for Horizontal Shearing Stress. Perhaps human909 could point out the fallacy in their reasoning.
  14. BAretired

    Beam Reinforcement Calculation

    Shear flow between the I-beam and plates is not zero. Depending on the thickness of side plates, it may actually reduce the shear stress in the beam web for the height of side plates, but that is a questionable advantage since the shear stress in the remainder of the web remains the same as it...
  15. BAretired

    Beam Reinforcement Calculation

    Q at the neutral axis is not 0, I agree. Q is the area above or below the section where shear is to be found and y is the distance of its c.g. to the n.a. Sorry, but weld on one edge is not enough to properly engage the side plates. I also agree that Q is a geometric parameter, but it applies...
  16. BAretired

    Beam Reinforcement Calculation

    I think the practical use is to understand how shear flow works in unusual situations. Not many engineers would reinforce an I-beam with short side plates, but if they did, we could calculate the shear stress at any point. And from that, we could calculate the welds required to adequately...
  17. BAretired

    Beam Reinforcement Calculation

    The sketch below shows a beam cross section with a bulge in the middle, i.e. all one piece. No need for any welds, but the horizontal and vertical shear at several points is calculated using VQ/Ib. If instead of a bulge, we use two side plates, why should it be different, other than the fact...
  18. BAretired

    Truss Top Chord Lateral Support

    There are many ways to frame the bridge. I like the concept in the elevation below. The orange tee shape would be erected first, then the two blue trusses would be connected at both ends. In effect, each blue truss is free to move outward horizontally with two pins on exterior support.
  19. BAretired

    Beam Reinforcement Calculation

    Exactly Celt83, and similarly you can look at the vertical shear plane between the upper and lower halves of the side plates in the original post. Q is the first moment of area for the upper or lower half plate area about the centroid of the combined section. Each weld must be designed to...
  20. BAretired

    Beam Reinforcement Calculation

    I agree that there is confusion. I don't believe shear flow is zero between I-beam and the top or bottom half of each side plate, and I believe that a weld is required top and bottom of each side plate in order to consider the section composite. Otherwise, the side plates and I beam are not...

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