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Subject: ACI 318 -Construction Joint

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regarding construction joints to ACI-318....

i do not think it is an MANDATORY requirement - you can "engineer" a CJ to
work at almost any location. sure - there are engineering preferences for
the locations, but it is common to "engineer" a joint to assist certain
construction staging/sequencing etc.

also, it is common for CJ's in post-tensioned concrete construction to be
located outside the "middle third" - does that mean they do not comply with
ACI-318? i do not think so! also, think about precast joints etc etc....

if the joint was located "by the contractor without approval from the
engineer" and you need to check/verify its integrity/acceptance you will
need to know the actual construction details (shear key size/depth, T & B
rebar, etc), then from your structural analysis you can determine the
maximum shear and moment actions (including lateral effect if applicable) at
the actual joint location, from these actions you then calculate the joint

Para-phrasing from T.Y. not "...blindly follow the
codes-of-practice, but seek to apply the laws of nature...".

what are you going to do if the joint is rejected - demolish the concrete?
PLEASE DON'T - sure contractor's make errors (and engineers goof-up too, on
occasions)- but jointly (engineer and contractor) (pun intended) can
re-establish the joint capacity, if it is indeed calculated to be


Mark Geoghegan BE (Hons.-Structural)

S T R U C T U R A L   T E C H

I don't think you have to "evaluate the integrity" if it is, as you say, =
"mandatory requirement." If the contractor locates the construction joint=
the wrong place, then he goofed, as simple as that.
William L. Polhemus, Jr., P.E.
Polhemus Engineering Company
Katy, Texas
Phone 281-492-2251
Fax 281-492-8203

  -----Original Message-----
  From: =B1=E8=BE=E7=BC=F6 [mailto:kimslove(--nospam--at)]
  Sent: Sunday, June 17, 2001 9:58 PM
  To: seaint(--nospam--at)
  Subject: ACI 318 -Construction Joint

  Hello everyone

  ACI 318-99 Code 6.4.4 described for construction joint as follows;

  " Construction joints in floors shall be located within the middle thir=
of spans
    of slabs, beams, amd girders."

  1. Code dose not provide any exception for this requirements?
     ("shall be" - mandatory requirements)

  2. If construction joint  was not located within the middile third of
    of slabs, beams, and girders, how can I evaluate the structural
    integrity and acceptance of construction joint location ?

  Thanks in advance,
  Yangsoo Kim

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