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Recent content by Sawbux

  1. Sawbux

    Wire Rope Factor of Safety

    Critical factor is how you are going to fasten the cable and pretension it. Hard to get enough blots into wood to develop the strength of the cable and turnbuckles have limited working load compared to the cable. I have done this a couple of times by using a bracket to bear on the end of the...
  2. Sawbux

    10x10 Timber Beam Sagging in century old home

    Looks to me like this is the old timber frame connection where a slot was cut partially into the main beam to provide the "beam hanger". The joists do not run through the beam. Looks like crack in beam is located at the bottom of the notched end joist beam seat. Is the second photo of the...
  3. Sawbux

    Zee purlins

    Only bracing is the through fastened roof sheeting. My main question is - Why no readily available internet sources of info on this topic? How do I discuss this as a concern with Owner? It's stood for 30 years argument...........
  4. Sawbux

    Zee purlins

    Just round out from photos that the roof Zee purlins in a 30 Y.O. building were installed with the top flanges pointing down hill. Remembering from 50 years ago Structures class that loads should pass through the shear center to prevent torsion buckling. With Zee section on 2:12 pitched roof, it...
  5. Sawbux

    Are process structures exempt from IBC code?

    I have always provided a healthy factor of safety on industrial structures to account for deflections/vibrations, future additions and possible corrosion over the life of the facility. For chemical areas, always used steel members 3/8" or greater in thickness - for corrosion allowance.
  6. Sawbux

    Bowstring Truss - Reinforcing Bottom Chord

    I've had success in cable reinforcing bowstring trusses, prestressing them to reduce the dead load stresses. 80% as you mention seems like a reasonable number. In the building I did, the ends of the trusses were accessible by cutting out a bit of siding. I put a bearing plate across the ends...
  7. Sawbux

    Old Bowstring Wood Truss Bottom Chord Split. Worried.

    The stress levels used that long ago were much higher than is allowed now days, probably 1500 psi with duration of load factor of 1.25 on top of that. So you'll likely find the bottom chords highly stressed. Looks to me that the chord may have slightly more than the allowable slope of grain...
  8. Sawbux

    Lamella roof beam repairs

    Don't see any tie-rods across the gym. Are there big concrete buttresses keeping the arch from spreading? If these have been modified or removed, it would allow the arch to spread, causing bending failure in the segments. I would repair with screws and epoxy. There is a lot of redundancy, so...
  9. Sawbux

    Industrial Stack repair

    There is a section in Gaylord & Gaylord Structural Engineering Handbook. I have 1968 edition, don't know if it is in later editions. Chapter 26 is a section on chimneys and has a smaller section on concrete about 5 pages. It refers to ACI 505-54, which may be an earlier version of ACI 307...
  10. Sawbux

    Industrial Stack repair

    Probably added bands after cracks appeared and someone got worried! Differential temperature on inner and outer wall of a thick walled stack could cause vertical cracks.
  11. Sawbux

    How to strengthen a bulged brick wall

    Looks like it may be a long term repair process. Last time I was involved in one of those we had an expert (Custodis) check it out. Rebuilt one stack by installing a fiberglass temporary stack (Ershigs in Bellingham, WA) then with stack out of operation, did a relining.
  12. Sawbux

    Glulam Macalloy Roof Truss

    Not sure what a macalloy bar is, but I would design the end connections to have the tensile forces taken in end bearing on the wood beams. You could pass the bar between the beams and pass the end through a plate and then tighten with a nut on a threaded rod end. Bolted connections will slip...
  13. Sawbux

    Specs for Weyerhaeuser Timberlam?

    I believe they were manufactured from 3 1/2" standard glulams that were resawn vertically to get the narrow width.
  14. Sawbux

    Looking for General "Rules to Remember" for Engineering Students

    A structure is smarter than you think, it will investigate all alternatives before falling down.
  15. Sawbux

    Is manual calculation still needed nowadays in structural design?

    I have a solar powered calculator. Will work during daytime with the lights out.
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