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  • Users: KimWT
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  1. KimWT

    Precast Double Tee Dapped End

    Thanks for your input! This question sometimes happens. For example, if you need to repair 10ft long DT with cutting stem, do you want to increase/supplement concrete volume or add additional plate/reinforcement? If you have to cut stem by 4" or 6", do you have to add Av or Ash? ... So, this...
  2. KimWT

    Precast Double Tee Dapped End

    Hi! This picture shows some reinforcements around dapped end of typical double tee like 12DT30. Is there any test data available with PLAIN concrete, no reinforcement? In this case, which failure mode happens first? Bearing? Shear? Thanks in advance! KimWT
  3. KimWT

    Map Cracking on Precast Double Tee Flange

    This is precast concrete; one double tee is only one day old... Can ASR happen within 24 hours after concrete is poured?
  4. KimWT

    Map Cracking on Precast Double Tee Flange

    Aggregates do not contain any special component causing ASR. If they do, ASR should happen everywhere and every component. This problem happens only in double tees. Slabs, walls and spandrels are clean.
  5. KimWT

    Map Cracking on Precast Double Tee Flange

    ASR? This sometimes happens, not often. It happens only in the flange, not stems. Why?
  6. KimWT

    Map Cracking on Precast Double Tee Flange

    Hi! You can see some severe cracks in the flange. These two photos show how bad they are looking. These are from typical double tees of two parking garages; one is pre-topped and the other is field-topped. I wonder what caused this problem. I am looking forward to precast engineers'...
  7. KimWT

    Rebar Development Length (with or without hook)

    Hi! I would like to hear other engineer's opinion about reinforcement development length. [Straight Rebar, P1 & P2] When concrete covers rebar well, L2 can be considered as development length, Ld. What about rebar located close to the edge, P1? If side cover S1 satisfies minimum concrete cover...
  8. KimWT

    Composite Action on Epoxy

    Hi! CONCRETE LAYER-2 (4" THK) ----EPOXY---- CONCRETE LAYER-1 (4" THK) I apply epoxy to fix cracks on concrete layer-1 and they are completely bonded. 10 days later I pour topping concrete layer-2. And then, can I expect perfect bonding between layer-1 and 2? So, can this whole section...
  9. KimWT

    Prestressed Concrete Column Design

    Hi! I am looking for PRACTICAL guideline/information regarding prestressed concrete column design. I am not sure current ACI318 can handle prestressed columns; I saw some papers and articles refer to this issue. Even PCI has not updated design guideline after mid-80s. I think prestressed...
  10. KimWT

    New Edition of PCI Design Handbook

    This question will be clear if we consider ASCE7. Though ASCE7-16 was released and now it is the latest edition, can you use new ASCE7-16 with IBC2012? I don't think ASCE7-16 can be used OFFICIALLY unless IBC2018 is adopted. Likewise, the 8th edition of PCI design handbook cannot be used with...
  11. KimWT

    New Edition of PCI Design Handbook

    Hi! PCI released the 8th edition of precast concrete design handbook in 2017. Its preface says new edition is based on IBC 2015 and ACI 318-14. Should I apply 8th edition or old 7th edition of design handbook where IBC 2012 and ACI 318-11 are currently used? Thanks!
  12. KimWT

    Water Leaking in Precast Double Tees

    Hi! It was rare to use pre-topped double tees in my region. Recently, I heard some roof double tees water leak where 2" CIP topping concrete and 4" precast concrete meet in the flange. When I worked in the North where most double tees were pre-topped, I did not hear this problem. Is this...
  13. KimWT

    "Superglue" for Concrete Repair

    Hi! I heard precasters use Superglue for crack repair. I am not sure how this will work in the concrete. When I search the internet, I cannot find good info related construction use. I guess this repair method is not popular. Is this really proper repair product? I wonder why they do not use...
  14. KimWT

    Live Load Reduction & Influence Area

    Hi! When I tried to apply live load reduction, I was not sure I understood KLL (Live Load Element Factor) correctly. It is not clear how exterior columns called as (2), edge columns (3) and corner columns (4) are defined. [I attached respective conditions with (1) to (5).] How much slab should...
  15. KimWT

    How to lift concrete slab?

    Hello! I have to lift 5 ton roof precast concrete slab of elevator shaft to repair. Isn't there any jackup tool to raise slab only 10" temporarily through 1/2" horizontal joint between this slab and elevator walls? (Crane cannot access this area.) This elevator shaft is located at the perimeter...
  16. KimWT

    Elevator Hoist Beam

    Generally, which side is against eliminating hoist beam after elevator is installed? Is it GC or elevator company? Why?
  17. KimWT

    Elevator Hoist Beam

    Thanks, JLNJ! You raised realistic problem! Elevator companies are very tough to work with. When precast members are designed, they do not sometimes provide elevator shop drawings on time. (Though Contract Drawings showed many details including specific dimensions regarding elevator shafts...
  18. KimWT

    Elevator Hoist Beam

    You can see small space between hoist beam and elevator motor. Is it big enough to absorb 9" error?
  19. KimWT

    Elevator Hoist Beam

    Hi! I have a question related with elevator shaft. This project is precast concrete parking structure, which needs passenger elevators. By mistake, precast elevator shaft was erected 9" lower than the roof height elevator shop drawings show. I was told elevator hoist beam cannot be installed...
  20. KimWT

    Concrete Bearing Strength...Precast Bearing Connection

    In the typical load bearing spandrel design in the parking structure, steel bearing plate is 6"x10" (asssumed). Using PCI design handbook formula, phi Cr (0.85f'c)A1...=0.55x(6ksi)x60in^2=200Kips (concrete bearing strength) Approximately 20Kips per DT stem and spandrel self-weight=53Kips...

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