HomeMy WebLinkAboutPermit Correspondence 2014-07-24Dave Shaw
From: Kevin Wilger <kevinw@structural-source.com>
Sent: Thursday, July 24, 2014 10:31 AM 2 r y' ` �✓ �/�S
To: 'Dave Shaw' SAX 2011/ moo
Cc: 'Matt Matthews'
Subject: RE: horizontal cold joint in footing
Dave,
I did some research on the horizontal cold joint question you asked about in the monolithic spread footings.
Below is a copy of a discussion from an on-line engineering forum that reviewed this condition. The final
comment in the string makes a valid point that having a cold joint just 5" from the top of the footing is a problem
impossible because the minimum development length for even a #3 hooked bar is 8" and we would only have
about 4" (5" — 1" clear cover). So, horizontal cold joint in footings is generally not a good idea.
That being said, a large number of the footings on this project are as deep as they are in order to provide
enough dead load to resist wind uplift. This condition was confirmed when I reviewed the column reactions
provided by Varco Pruden. The F4 and F8 footings specifically are much deeper than is required for the
column downward load, so you may pour these footings with a horizontal cold joint down 5" from the top and
they will not require any shear friction reinforcement. The rest of the footings either should be poured
monolithic with the slab or should be excavated an additional 5" down so that the footing can be poured to its
full depth independent of the slab on grade.
If you do pour any of the footings for the metal building columns with a horizontal cold joint, the anchor bolts
will need to be lengthened by the depth to the cold joint because they have some pretty significant uplift due to
wind loading and will require adequate development into the footing concrete.
adaerEngineer (Structural) (OP)
e often get asked by contractors if its acceptable to pour deep concrete beams in two pours. TI
e beam. (Top of slab elevation is lower than top of beam elevation) And GC wants to pour the
this something others are allowing? Typically we do not, however, this has been met by much t
you were to allow a cold joint in a concrete beam - what is the primary failure mode that you'd
Id joint may be an issue. However, if the hooks are embedded in the lower section of the bean
int. In addition, the concrete can be left rough at both faces. Concrete friction and your #3 ho.
list this load,
Another issue for exterior beams may be water penetration - it a cora joint is ren; in the beam, wal
corrode the rebar.
Does anyone have any references or deli n cf; suggestions for me on this topic? What should I b(
I greatly appreciate your input.
paueAtkins (Structural)
What you mention in your post is what should be checked --horizontal shear at the interface.
I have used such a detail on occasion with no problems.
DaveAtkins
msquared48 (Structural)
Shouldn't really be a problem if you leave a roughened concrete surface and have shear steel pro;
Mike McCann
MMC Engineering
2
civilperson (Structural)
Ask the price(' for a cold joint bulkhead between the slab and the beam in order to place the be<
make the slab,
LAE (Structural)
Keep in mind that to use shear friction across the joint, the ACI code requires the reinforcement t
need to have enough distance on either side of the joint to at least have full hook development le
not allowed in this case)
For a 4 1/2" slab or such it is impossible to provide this development and you would therefore ign
portion of beam alone.
Kevin Wilger, S.E.
Principal
- STRUCTURAL
SOURCE, LLC
86705 Pine Grove Road
Eugene, Oregon 97402
Phone: (541) 912-3958
kevi nw(a)structural-source. com
3