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  • Users: WmacG
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  1. WmacG

    Catch Basin Structural Design

    There is a ASTM spec (C 1433-06), "Standard Specification for Precast Reinforced Concrete Box Sections for Culverts, Storm Drains, and Sewers". Also, California DOT has a section for underground structures in their "Bridge Design Practice Manual".
  2. WmacG

    Concrete Beam - Horizontal Cold Joint

    Would this situation not be the similar to a beam with a composite slab?
  3. WmacG

    All These Crane Collapses

    graybeach - I agree with that.
  4. WmacG

    All These Crane Collapses

    A 30yr old crane operator could have 10+ years experience, seems adequate to me (depending on the situation). A PE only is only required to have 4 years experience to be responsible for the design of the crane (or tens of identical cranes) right?
  5. WmacG

    Rope tension

    In Blodgett's "Design of Weldments", there is an example of calculating the pressure on the drum of a winch. In his example, he uses only the pressure from the first two layers of cable around the drum. The subsequent layers tend to force the preceding layers into a smaller diameter and reduce...
  6. WmacG

    54' 1 piece rig of pipe

    If the pipe is laying flat before you pick up one end, it will have bending stresses on it until it is upright. I would check the bending stresses during erection and the attachemt method. You can pick up the pipe from somewhere other than the end to reduce the bending stress, but then it wont...
  7. WmacG

    4 leg sling

    You may be able to add or remove weight to the lifted item to get the CG where you need it. You may be able to use a spreader frame to allow the slings to clear an obstruction over the CG. You may be able to use two cranes. You may be able to tolerate lifting the object in a tilted postion...
  8. WmacG

    4 leg sling

    It will tilt to a position where the CG will be directly below the hook.
  9. WmacG

    Effect of pre-load on shear strehgth

    The AISC LRFD code I believe has a section on combined shear and tension on bearing type connections. If the applied shear stress is over a particular value, the "allowable" tension stress is reduced. I guess you could look at it the other way too (for a given tension, shear may be reduced)...
  10. WmacG

    Beam made of back-to-back channels

    I read some threads about spreader bars made with wide flanges where it was not appropriate to use the unbraced lenght as the length of the beam. This is due to the ends of the beam not being torsionally restrained. Search for "spreader bar lateral torsional buckling".
  11. WmacG

    fabricated pipe

    Try searching for "plate rolling", or "steel plate rolling", etc.
  12. WmacG

    Could Engineering Houses Affect Insurance?

    Texas has a program for counties along the coast called windstorm insurance (for hurricanes). To get the insurance, the house has to be inspected by an engineer who fills out some forms. The inspection is paid for by the homeowner who can shop around for inspectors. Without the inspection...
  13. WmacG

    Sizing of overboard water lines

    Structuraly, the lines should be sized for bending stress based on the span between their supports and loading (wave, wind, current). Vortex induced vibration may control for smaller diameters (6"&8"). 8" pipe is not uncommon for 15' spans near the waterline. Check the lines at the supports...
  14. WmacG

    wood rafter thrust problem

    Agreed
  15. WmacG

    wood rafter thrust problem

    StructuralEIT For a real roller support, the vertical reaction at each end of a sloped beam would not be in line with the center of the roller axis. The horizontal distance would cause a moment and would cause the roller to rotate untill the beam fell off the rollers.
  16. WmacG

    Effectivness of retaining wall key?

    When checking sliding for a cantilever retaining wall with a footing key, 1) Is it correct to include active pressure behind the wall down to the bottom of the key or only down to the base of the footing. 2) Does this depend on if the key is at the front, middle, or back of the footing? In...
  17. WmacG

    J tube

    On the platforms that I work with, a J tube houses an umbilical or flexible flowline from the bottom part of our hull up to the topsides. In my case the platform is a Tension Leg Platform in deep water. For installation, the umbilical or flowline is connected to a "pull head" that is used to...
  18. WmacG

    Adding a 2x8 flange to 6x10 wood beam

    I went to the house and saw the beams after modification. I't looks great in my opinion, approximately .5" deflection over the 17' span with 90% of the dead loads applied. The new members are supported at the wall. There is no sheetrock installed (so it didn't crack), the joist don't seem to...
  19. WmacG

    Adding a 2x8 flange to 6x10 wood beam

    I am planning on extending the new members over the supports if it is not unreasonably difficult. The way I think of the connection requirements of the new members to the old is to imagine that the old beam is hanging their with a deflected shape. Now place the new members so that their center...
  20. WmacG

    Adding a 2x8 flange to 6x10 wood beam

    Thanks for your replies. The reason that I did not want to add steel or wood to the sides of the beam was that the joist were not sitting on top of the beam, but possibly joined into the sides of the beam. This would have allowed only a 4" tall board on each side of the beam, even with steel...

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