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Recent content by vonlueke

  1. vonlueke

    PVC pipe absolute roughness

    The absolute roughness value can make a big difference if you have, e.g., a long, straight, horizontal pipeline discharging water into atmospheric air. Imagine, e.g., long sections of pipe, and joint designs that connect the pipe perfectly flush, with no joint interior protrusion nor gap. After...
  2. vonlueke

    PVC pipe absolute roughness

    (1) Maybe I should expand my question to include polyethylene (PE) pipe, and not just polyvinyl chloride (PVC) pipe (?). Which of the two is more common for water pipe, in the diameter range I mentioned above? And is the polyethylene pipe usually PETE, HDPE, or LDPE? (2) Is there a difference in...
  3. vonlueke

    PVC pipe absolute roughness

    Yes, I should have stated, I want the typical absolute roughness, in mm, of typical, new, clean, rigid PVC pipe having an ID of, say, 15 to 75 mm. Thanks.
  4. vonlueke

    PVC pipe absolute roughness

    What is the typical absolute roughness, in mm, of typical PVC pipe having an inside diameter of, say, 15 to 75 mm? Thanks.
  5. vonlueke

    Static Force Analysis of a Seat

    Correction: My second sentence should read, "If you apply your test force to it, the linkage rods rotate upward (and the suspension upper plate stays level), which is a dynamic problem."
  6. vonlueke

    Static Force Analysis of a Seat

    davidmandis: Your structure, as currently drawn, is a mechanism and is therefore unstable. If you apply your test force to it, the linkage rods rotate upward, and the suspension upper plate rotates downward, which is a dynamic problem. In order for this structure to be static, you must fix at...
  7. vonlueke

    Nominal moment strength & plastic moment capacity

    BlastResistant: The so-called nominal flexural strength, Mn, is Fy*Z as stated in your second and third paragraphs, not Fy*S as stated in your first paragraph. And this Mn value also applies to bending about the major axis (if the member has adequate lateral bracing), not just bending about the...
  8. vonlueke

    Corner fastener calculation

    Cecile9: There are two Nxy vectors at each corner fastener, intersecting at 90 degrees. One Nxy vector is parallel to Nx, and the other Nxy vector is parallel to Ny. The parallel vectors are directly additive.
  9. vonlueke

    Corner fastener calculation

    Cecile9: Shear force on corner fastener is Ffastener = {[(Nx+Nxy)^2 + (Ny+Nxy)^2]^0.5}*pitch.
  10. vonlueke

    U-bolt Design

    licensetochill: If the U-bolt ends are simply supported, the maximum bending moment on the U-bolt occurs on the unthreaded shank at the midpoint of the leeward leg and is M = 0.62*r*F, where r = U-bolt mean radius, and F = lateral wind force on the pipe. If the U-bolt ends are fixed (clamped)...
  11. vonlueke

    CosmosWorks Results Accurate?

    PLCKing: The aspect (length-to-thickness) ratio of your elements is too large, which is an inherent problem with trying to use solid elements to mesh thin plates. Shell elements, on the other hand, are ideally suited for meshing thin plates. You can perhaps perform a reality check on your fea...
  12. vonlueke

    Sectional Properties

    prex: If you run two separate regions in an analysis program, as described in blakrapter's second post, the program has no knowledge of the composite cross section centroid location. Your formula requires this composite centroid location, whereas mine doesn't. My y1 is the distance between the...
  13. vonlueke

    Sectional Properties

    blakrapter: A2 is the cross-sectional area of the second region described in your second post. The Ix derivation is, summation of moments of inertia of the two shapes/regions (outer and inner) described in your second post (about an arbitrarily-located x axis), minus summation(Ai)*d^2, where d...
  14. vonlueke

    Sectional Properties

    blakrapter: I think your approach sounds good. If I understand correctly the way you are doing it, then working this out using parallel axis theorem in reverse, and simplifying, gives Ix = Ix1 - Ix2 - {[(A1*y1 - A2*y2)^2]/(A1-A2)}, where Ix = centroidal moment of inertia of composite cross...
  15. vonlueke

    Heel and tow effect reversed

    franc11: For load case 2, it's possible, in rare instances, that the right-hand bolt could be in "compression" (meaning zero bolt applied load) if the upper plate is very flexible compared to the lower plate, because then the upper plate might bend at, e.g., the left-hand bolt. But typically...
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