control joints elevated slabs
control joints elevated slabs
(OP)
there seems to be a consensus that control joints are not needed/required in elevated concrete floor slabs (composite floor, non-composite floor etc.). is there any written article about this subject to defend myself from an engineer's report that the cracks in the floor is due to the absence of control joints. mannypons





RE: control joints elevated slabs
In other words, could you turn the tables on the engineer and ask him/her to produce documentation that shows that control joints are needed in structural slabs? I don't think they'd find any.
RE: control joints elevated slabs
However, if you are talking about saw cut contraction joints in slabs on composite metal deck, then these constraction joints become "highly desired" to control cracking in the slab. I have personal experience where the contractor did not put in the saw cut joints as specified, and the slab had extensive uncontroled cracking due to shrinkage, and negative moments over girder supports.
RE: control joints elevated slabs
The final finish on the slab should dictate whether the cracks are acceptable or not. Their presence alone does not necessarily indicate a problem. As strucuresguy alluded to, negative moment or variable loading conditions could have an affect.
What additional information do you have on slab geometry, loading, etc.? Perhaps you want to post this message in the concrete forum too...
RE: control joints elevated slabs
The cracks you experienced in your past project were of course not desired, but can be controlled with proper mix design and keeping the contractor from adding water to increase workability of the concrete for finishing. Cracks over negative moment areas should be controlled by proper reinforcing in the slab.
But sawed joints in an elevated slab?? I've never used them.
RE: control joints elevated slabs
What the asking party is demanding is to say the least weird, if the interpretation above is the correct one. Crack control in the reinforced structures that are elevated floors or slabs is gained by different means, and it is quite likely that any unsightly shrinkage cracks there are the product of the classicals in the game: heat, wind, bad cure, high diameter rebar, irregular layout of the rebar, concreting against too stiff hardened parts without consideration of shrinkage etc
Other question if you have followed some specified layout in the concreting process. To diminish shrinkage effects, closing bands or checkered concreting and akin procedures are established, and not proceeding in accord with the instructions of the director of the works or specifications, in more than being criticable and cause of liability may lead to some bad results, this could be the case.
RE: control joints elevated slabs