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  1. aquacata

    X-Brace or Diagonal Brace?

    I prefer diagonal brace since it has much less connections and reduces a lot labors. But X-Brace gives more stability and redundency. I want to know what you prefer to use in design. Please vote. Thanks!
  2. aquacata

    Steel column block-out at post-tension slab-on-grade

    The base shear is high. 70 kips at one column. I am using the L dowel from the footing to the slab, instead of the hairpin from the blockout to the slab. I like the hairpin better cause it transfers shear directly. But since the slab will be poured first, it looks to me that to have hairpin in...
  3. aquacata

    Steel column block-out at post-tension slab-on-grade

    Then you pour the footing first, leaving dowels from the footing to the slab, then pour the slab? Or you don't use the slab to take the base shear? So you have a column block-out with expansion joint around. The slab just has turn-downs sitting on the footing and there are no dowels from the...
  4. aquacata

    Steel column block-out at post-tension slab-on-grade

    Then you pour the footing first, leaving dowels from the footing to the slab, then pour the slab? Or you don't use the slab to take the base shear? So you have a column block-out with expansion joint around. The slab just has turn-downs sitting on the footing?
  5. aquacata

    Steel column block-out at post-tension slab-on-grade

    The largest block out is 30" by 30" (30" is the diagonal side, along column grid, it is 42" each way.). It is a good idea to layout the tendon around the block-out even though I don't know the tendon spacing yet. Thanks! The post-tensioned slab engineer wanted to pour the interior footing and...
  6. aquacata

    Steel column block-out at post-tension slab-on-grade

    The slab-on-grade is post-tensioned. It will be poured together with the column spread footing. Architect preferred the steel column has a regular block-out so the base plates, grout, and anchor bolts can be hided. But to do that, the tendon of the slab will need to cut/stop at the block-out...
  7. aquacata

    Composite Deck to hang 500 pound point load

    In my project, MEP wanted to hang their stuff from the composite deck (3" concrete over 3" deck) using Hilti anchors, cast-in-place and/or post installed. The deck will be drilled a hole so the anchor get into the slab concrete above 3/4" or more. The maximum point load reached 500 lbs. I am not...
  8. aquacata

    Composite Deck to hang MEP pipes/trays

    In my project, MEP wanted to hang their stuff from the composite deck (3" concrete over 3" deck) using Hilti anchors, cast-in-place and/or post installed. The deck will be drilled a hole so the anchor get into the slab concrete above 3/4" or more. The maximum point load reached 500 lbs. I am not...
  9. aquacata

    Maximum size/length of one concrete pour for elevated slab

    Actually It is the contractor who wanted to do one pour. But I am not sure if one pour for the 100'x124' size will cause cracks or not, you know, due to the shrinkage. How do you think? Thanks a lot!
  10. aquacata

    Maximum size/length of one concrete pour for elevated slab

    I have an elevated 6" thick concrete slab being supported by concrete walls at perimeter and concrete beams and columns at interior. The footprint of the slab is overall 100' x 120'. I wonder if the whole slab can be poured one time. Do I need a control joint for this size of slab? Thank you...
  11. aquacata

    zero stiffness and ill-conditioned model

    Yes that makes a lot sense. Thanks for your valuable help!
  12. aquacata

    zero stiffness and ill-conditioned model

    Thank you, slickdeals! In your way, I saw my ramp is not meshed. I will make it meshed. My ramp is straight. I assigned it as a shell since it needs to take out-of-plane gravity load. Could you please let me know to make it behave like a rigid diaphragm, what stiffness modifier need to change...
  13. aquacata

    zero stiffness and ill-conditioned model

    After I ran my ETABS building model, I got a warning message of zero stiffness at a joint. Also it specified my model is unstable and ill-conditioned. In your experience, could you tell what is the most possible reason for that? I suspect that my ramp area is not connected to its edge beams. I...
  14. aquacata

    Anchor rod minimum embedment length

    I am designing concrete spread footings of steel columns. The footing thickness is determined by the anchor rod embedment length. No moment and no uplift exist in my base plate. I wonder in this situation, what is the minimum anchor rod embedment length. Please let me know. Thanks a lot!
  15. aquacata

    Footing of corner column at property line

    DaveAtkins, I put a large eccentricity, say 70", in both directions. That is why it needs 12'x12' size footing. The footing absolutely has partial bearing. As for overturning, I used footing weight , soil weight and slab-on-grade weight over footing to counteract. If you think this is not...
  16. aquacata

    Footing of corner column at property line

    My corner column sits at property line, in both X and Y directions. The interior column in Y dir is far way and its load is negligible. So I cannot use it to do combine or strap footing with my corner column. The adjacent column in X dir is also along property line and its own footing is strap...
  17. aquacata

    Footing Step Requirement

    I wonder where I can find the footing step requirements. Thanks for letting me know.
  18. aquacata

    Sliding of footing of retaining/bearing wall

    I am designing footings of a retaining/bearing concrete wall. The sliding became an issue because the friction coefficient is low. I wonder if the slab-on-grade adjacent to the wall can be used against the sliding. Thanks for your help!
  19. aquacata

    Lap splices of different bar size for slab top bars in tension

    Question: Over slab support, the negative top bars are #7. In the mid of span, the continuous top bars are #4. For continuity, they need lap splices. I want to know if the splice length is based on larger diameter or smaller diameter of bars. ACI 318 doesn't specify this for different sizes of...
  20. aquacata

    Base Plate Design in Seismic Design Category D

    1. AISC Seismic Provision 2002 Section 8.5 doesn't specify the use of amplified seismic loads for base connection design. However, at the end of the commentary C8.5, it says, " In the case of Moment Frames, if the building system performance intends column yielding at the base plate, the...

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