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  1. grantstructure

    Analyzing an existing steel column encased with concrete

    I've not tried this approach, but it seems to me you could treat the concrete as a continuous brace system for the steel column. You'd have to decide if it's cracked and what the Icr is going to be, and then prove that the concrete portion of the column alone can provide the strength to resist...
  2. grantstructure

    HELP!!! Forces in cable for safety rigging

    Well, if he takes it straight down, that's true. And even if he continues the cable in the same plane, there's some horizontal component applied to the support as the cable deflects, but it's going to be much more manageable. When I said "downward" I was thinking laterally and downward, such...
  3. grantstructure

    What type of construction is this?

    Aren't the S beams supporting the tiles already on their bottom flanges--and if those lines in between the tiles are the end of a steel tee, wouldn't the tee orientation be the opposite of what you'd expect? Maybe it was obvious that those 'lines' are steel when you visited the site, but if I...
  4. grantstructure

    HELP!!! Forces in cable for safety rigging

    The cable won't be deflected 2" in the final position, so the loads will be closer to those in the 24" position, as you noted in your original post. I believe you can use the principles of cable barrier design to get what you're after...
  5. grantstructure

    Concrete vs Grout in a Retaining Wall

    Make sure you get a separate mix design submittal for the 3/8" mix--you need concrete with 3/8" agg that meets your specs for A/E and such, not whatever masonry grout mix the local plant is turning out. Also, I'd make sure he's not going to backcharge the project for the difference--with the...
  6. grantstructure

    ACI Minimum Flexural Reinforcement for Structural Slabs and Footings

    Well, y'all did yeoman's work on that other thread.
  7. grantstructure

    ACI Minimum Flexural Reinforcement for Structural Slabs and Footings

    Good Lord. The entertainment value has pretty much vaporized now, hasn't it? I went to grad school with Robert Frosch. I'm sure he'd love to know he had a walk-on role in that thread. I've been too distracted (read: cheap) to buy the new 08 code. What does 15.10.4 say? The updated (to 08) PCA...
  8. grantstructure

    ACI Minimum Flexural Reinforcement for Structural Slabs and Footings

    That linked thread was actually entertaining. 10.5.3 specifically references 10.5.1 and 10.5.2. It would appear, based on the language, to be a stretch to apply it to 10.5.4. But really, how much lower than .0018 do you want to go?
  9. grantstructure

    Chord Buckling in an Oval Truss

    In the past, I have checked buckling of pony trusses by providing some fixity at the base of the vertical web members, and counting on them to cantilever up to brace the top chord. You then have a discrete brace system where the stiffness of the cantilevered web member is critical, including the...
  10. grantstructure

    Static tension on embedded anchors

    If the column shortens along the length of the rod, but the rod does not shorten, or not as much--it wont' creep, but if it's tensioned will lose some of its elastic extension--, then the nut could lose bearing contact. Am I thinking about that wrong? Here's my thought process. 1. Don't want...
  11. grantstructure

    Exterior elevator shaft

    That's one ginormous elevator.
  12. grantstructure

    Joist/girder evaluation for RTU

    The curbs sit directly on the roof, and you don't need to provide anything for them above the surface of the deck.
  13. grantstructure

    Joist/girder evaluation for RTU

    Yes, you'll want an angle frame under the deck to take the curb loads. I generally then treat the load to be taken completely by the angle frame, which delivers point loads to your joists. Without the angle frame, a concentrated load on the deck could cause it to deflect and pull the...
  14. grantstructure

    Static tension on embedded anchors

    Kootk, the creep I'd expect is just the concrete "relaxing" under the load, and the only thing I don't want to happen is for a snug-tight nut on the top of the anchor rod to be able to work loose over time. The beam is cantilevered at a roof condition, so uplift on the underside of the...
  15. grantstructure

    Static tension on embedded anchors

    You've basically got it. It's not shear being applied but pure tension, as the steel beam will sit on top of the column. Unless you're simply referring to the bond stress along the anchor as a shear stress. My question is really one of what methods are employed to develop pretension in embedded...
  16. grantstructure

    Concrete cracking in basment wall corners

    I'm going to vote shrinkage cracks, and theorize that the lack of reinforcement is what makes this crack location look odd to us. Corner bars and horizontal steel is probably what keeps all our walls from cracking right there.
  17. grantstructure

    Static tension on embedded anchors

    The backspan of a cantilevered roof beam is going to place tension on some anchor rods I'm placing the in top of a concrete column. Anyone have some tried and true pretensioning methods/notes for anchor rods they'd like to share? I just want enough to compensate for creep.
  18. grantstructure

    Designing basement floor of a multi-storey building

    I have had to hold the slab down exactly once--it's not cheap. Provide an active drain to a sump under the slab, and have the sump be separate from the perimeter drain such that the owner can monitor water coming up under the slab separately from water behind the walls. If the floor is not...
  19. grantstructure

    Handrail post connection detail

    I would put the client's opinion of the type of connection that should be used a distant second to your own in this case. I don't mind embedded handrail bases for, say concrete stairs on grade, but if you're talking a condominium balcony, no way. Provide an embed and weld off to it. They can...
  20. grantstructure

    One-way slab or steel on metal deck?

    Cast in place. You may also want to consider the possibility of losing soil support on one side, in which case the box will have to work as a frame to resist lateral loads, and your corner zones would then be detailed for both opening and closing moments. Also crown the slab slightly to promote...

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