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  1. 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...
  2. 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.
  3. 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...
  4. 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...
  5. BAretired

    Beam Reinforcement Calculation

    Omitting the side plates would be my approach.
  6. 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.
  7. 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...
  8. 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...
  9. 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...
  10. 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...
  11. 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.
  12. 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...
  13. 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...
  14. BAretired

    Truss Top Chord Lateral Support

    You could avoid thermal forces by designing the middle support for longitudinal forces and allowing each end to slide horizontally, in other words, an expansion joint.. If there is no stair at the end supports, there must be a ramp. Otherwise it is one big step. I won't comment on the other...
  15. BAretired

    Beam Reinforcement Calculation

    Nick6781 said: Only vertical shear transfer needs to be considered, so welds are required for vertical shear only. That is simply not true. Your own diagrams show otherwise.
  16. BAretired

    Cantilever Plate bending with UDL

    The sketch below is the case where a concentrated load P is applied at the free edge, causing a deflection 'd' at the point of application. Using Yield Line theory, the value of m, which is the plate moment per unit length turns out to be P/8. For the case of a UDL running perpendicular to the...
  17. BAretired

    Truss Top Chord Lateral Support

    Yes, I believe so. Connection should be a moment connection to laterally support the top chord. Hell no! That would be a pin joint. You need to prevent rotation of the verticals. I think you need to develop your basic concept first before going into these details. If I recall correctly...
  18. BAretired

    Beam Reinforcement Calculation

    Great! We have total agreement. Thanks human909.
  19. BAretired

    Cantilever Plate bending with UDL

    Line load perpendicular to fixed edge. 45 degrees looks okay to me.
  20. BAretired

    Beam Reinforcement Calculation

    My understanding for the weld calculation below is to find the Q value for the upper or lower green shape. The upper fillet welds must resist a shear flow of VQ/I where Q is taken for the upper green outline. Similarly, the lower welds resist VQ/I where Q is for the lower green outline.

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