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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

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...

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...

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...

Hi! I copied two load bearing spandrels from different projects of parking structure. Longer spandrel does not have baring plate at both ends though short one has. Apparently, some precast design engineers do not add bearing plates for precast concrete load bearing spandrels. Is this industry...

Hi! I read this in the paper: The ACI 318-99 required using a lower shear strength factor and a larger minimum transverse spacing of topping wire (10 in.) to ensure more deformation capacity across the joints in the diaphragm. [precast concrete double tee flange joint] Is this 10" spacing...

Hello! When 2" or 3" wide gap between fire door frame and precast concrete wall happens, how can I fill up this gap? I heard 2 or 3 hour fire-rated door needs special treatment. Thanks! Wolly.

Hi! We have been using W24x131 to lift precast concrete products in the yard. Recently we found a line (crack?) only underside surface of bottom flange. But, when we checked the top surface of bottom flange, we could not find any crack or line. What is this line (crack)? What caused this one...

Hi! I wonder how this double tee stem can be repaired. I have to cut 12 inches at the bearing area. Also, how can I repair if I need to cut 2 inches? This is a typical 12ft wide, 60ft long precast double tee for parking structure. In the past, I reproduced it whenever this problem happened...

Hi! What are the reasons to use coils rods instead of rebars? Here is an example. Thanks!

Hi! Generally, a minimum 7ft is needed for the clearance of passenger vehicles in the parking garage. Can this minimum clearance height be interpreted as "The Vehicle Clearance (A)" shown in the picture? I think IBC code should be interpreted as "Floor to Ceiling (B)." I am looking forward to...

Hi! These questions are mainly related with precast concrete industry. 1. I wonder why DBAs are used instead of mild rebars,especially for connection hardware design. If a welding gun is not used or minor help with Fy, I think there is no advantage to use DBAs. 2. Does ASTM cover coil rods...

Hi! The following figure shows an example. According to AWS D1.4, E80 should be used to weld both A706 Gr. 60 rebars. Is E80 needed because of strength or metallurgical reason? If E90 is used in this case, can I adjust/reduce the weld size shown in ACI318? (I wonder how ACI decide this welding...