Recent content by KimWT

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...

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

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

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.

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

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'...

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...

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...

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...

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...

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!

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...

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...

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...

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...