Expansions and Contraction Joints
Expansions and Contraction Joints
(OP)
I work for a Gerneral Contractor that is currently building a denitrification building. There will be 35 filters 11.67' wide x 102' wide. The wier wall is 15.17 high. There are 17 filters on each side of the building. There are 36 filter slabs for 17 filters. All but 4 slabs are 26'x27'x5.75'. There are 8 24" pile per slab (4 rows and 2 columns). The location to the center of pile relative to the slab: 3.083' from left, .417' from right, and 3' from top and bottom. Each pile has an ultimate bearing resistance of 460 tons. The Y-Walls in the filter are centered over the columns of pile. There are only expansion and contraction joints between all of the slabs. There is a foundation keyway between all of the slabs that is .958' deep (T/6) and 1.917' wide (T/3). The expansions and contraction joints continue up between the walls. With no rebar through the joints and the slabs cantilevering over the pile it seems very unusual to have no construction joints. Our company has just finished a denitrification building that only had 2 expansions and contraction joints throughout the structure. Please provide any insight into the reason and logice for the slabs not being tied togeather. I have attached some drawings to reference.






RE: Expansions and Contraction Joints
I'd like to see the details for his contraction joint. If the bars pass though them, then I would call it a construction joint and have no problem. If they stop I would like it less, because these joints are more likely to leak, but being on piles would minimize any movement, so it shouldn't be a problem either way. And not to criticize anyone else's design, but I would delete the shear keys. They're pretty much worthless.
My question is more on the first building you built. That seems like a lot of concrete with very few joints.
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints
I still don't like it, and I think it's unnecessarily complicated with the shear keys and all, but having the whole building on piles should cure a lot of problems. I don't think it will leak unless you don't do a good job installing the waterstop.
I would put in construction joints instead of contraction joints, but besides that, I can't find a fatal flaw.
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints
Somewhere ACI mentions that shear keys are overrated. It might be in the commentary. Or maybe it's in some textbook. I'll look for it tomorrow.
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints
Knowing nothing about the qualifications and experience of the design engineer, there are nevertheless clues given by the drawings. For example, there are cases where corner bars are shown around interior corners rather than extending to the far face. This is unacceptable practice, and is likely to cause breakout in those corners.
This may be a case where you need to retain the services of an independent engineer experienced in this type work to review the drawings and plead your case.
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints
Dik
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints
There are two large structures on this project, and two different contracts. One of the contracts has not let yet. Our contract includes the pile, some grade beams and slabs for the adjacent structure. That structure was designed by a different firm. It is interesting to see how different the stuructures are designed because of different engineers. In the other project at slab to wall construction joints that include rebar there is no key and the rebar bends down to accomodate the waterstop. All of the grade beams in the structure we are building have the same expansion and contraction joints as the slabs we have been discussing. In the other structures there were no expansion or contraction joints in the 3 mudwell slabs (153'-10"x50'). The building only has 2 expnsion joints the the disrection that is 500'. Two very different designs for two similar structures. I attached the foundation for the other structure.
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints
RE: Expansions and Contraction Joints