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Calif School Footings, DSA

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Thanks Bill and Mark (and others off-list) for your responses--have copied
both below, as I subscribe in digest format and cannot "include original in
reply".

Bill, it seems that you read more into my original post than I ever
meant--or maybe I was not clear enough.

The additional 1" of cover to account for caving make perfect sense--I had
not heard of that requirement before.

My understanding of the DSA requirement was that form stakes are not allowed
in footings PERIOD.  An off-list response suggests allowing form stakes in
the footings if the holes  remaining after removing them are filled with
grout or epoxy.  Unclear on whether DSA would allow this.

As for forming the footings, common practice is to dig a footing trench 12
inches wide (or more, depending on other factors) and then suspend stemwall
sideforms from form stakes.  Since the stemwall thickness is typically about
half the width of the footing, then you do have a potential clearance
problem.  I contend that clearance required to the form stake void would be
1-1/2 inches (for # 5 bars or smaller, typical low-rise footing), since the
concrete is poured against something besides "earth"--the stake.

At least one form-rental/concrete accessory supplier (Concrete-Tie Company;
Sacto, San Leandro, Compton and one other location) rents "school brackets"
that will suspend forms above the footing trenches.

Not having heard of evidence to the contrary, I find it extremely hard to
imagine that even if the footing bars were against the form stake and then
left next to an un-filled void,  a typical low-rise footing would have no
perceptible loss of performance compared to a "DSA footing".    What about
shrinkage cracks in footings?  They also allow water and oxygen to get to
the rebar....

Would keeping form stakes out of footings produce a better structure?  YES.
Is the increased performance worth the added cost?    I  doubt it.

I remember seeing a report that plywood roof and floor diaphragms perform
better if the panels are installed in a herring-bone pattern.   Would it be
worth it to require this method of installation?  (Especially on
prevailing-wage projects, where the lowest paid worker is paid more than the
structural engineer?  I'll stay off  THAT soapbox for now....)  If I find,
in a few years, that DSA has begun requiring herring-bone diaphragms because
of this "suggestion",  I will shoot myself.

I would bet that using hot-dipped galvanized rebar would be cheaper
(sorry--"less costly") than renting and using "school brackets" or filling
voids left after pulling form stakes.  It would also give what I would
consider an actual benefit.

As you are, I am very proud of the safety record of California schools, and
feel that many of DSA's requirements are good investments in our children's
safety.  Keeping form stakes out of footings just isn't one of them, in my
opinion.

Now, for a REAL safety concern, see my post regarding Pre-Engineered Metal
Buildings....

Thor


--------------------------------------------------------------------------
Dec  3  Digest                           Message:0023
23
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From: BCainse(--nospam--at)aol.com
To: seaint(--nospam--at)seaint.org
Subject: Re: California School
=?ISO-8859-1?B?oGNvbnN0cnVjdGlvbiByZXF1aXJlbWVudHM=?=


Thor-

DSA requirements used to be that footings either needed to be formed or
additional 1 inch cover of concrete added if poured neat to account for
caving of the side walls of the footing. If you don't recognize the caving
issue, it sounds like you don't do much field observation of foundation
work.

You have a curious view on establishing a criteria for the loading a footing
is supposed to take, then ignoring it.  Would not an interior stake infringe
on cover requirements?

But to the real world, normally when contractors form a footing, they place
the form stakes outside the forms so they can remove them easily.  If so
placed, they do not infringe on the footing.

As a School Board Member and a Structural Engineer, I applaud the way DSA
manages the oversight of school building construction in California to keep
our school children safe.  You can see the results by looking at the injury
and fatality statistics for school children vs. the general public in
California earthquakes to see they are doing an excellent job.

Regards,
Bill Cain, S.E.
Albany  CA

=====================================================
=====================================================

Whew, Mark, until you responded I thought I would be completely ostracized!

I feel that this requirement adds COST but not VALUE to our schools.  And
hospitals too, if this is also an OSHPD requirement.

Thor

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Dec 4  Digest                       Message:0001
1
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From: Mark Gilligan <MarkKGilligan(--nospam--at)compuserve.com>
Subject: Re: California School  construction requirements
To: "seaint(--nospam--at)seaint.org" <seaint(--nospam--at)seaint.org>

I have seen a number of buildings wher there wasn't a problem with caving
of footings so why should we have a one  size fits all mandatory
requirement?  Also remember that many of these footings are not working
very hard and thus,  there would be no problem is there was some
intermitant minor caving.  Each case should be evaluated seperately.

It is important that we continue to evaluate the effectiveness of each of
the special DSA and OSHPD provisions.  Some questions we should ask are:
--Does the provision contribute to increased safety or is the improved
performance the result of other factors.
--Are the benefits worth the cost.  Failure to ask this question can lead to
a waste of resources and greater loss of life due to other causes.

If we cannot ask these questions then we are engaged in an activity other
than engineering, possibly politics or voodoo.

Mark Gilligan
==============================================================

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Dec  3  Digest         Message:0013                           13
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From: "Thor Matteson, SE" <matteson(--nospam--at)yosemite.net>
To: <seaint(--nospam--at)seaint.org>
Subject: California School  construction requirements

California SE's and especially DSA engineers:

Apparently DSA requires, or recently required, forming concrete footings for
schools in such a way that form stakes will not penetrate the footings.

I have two-and-a-half questions regarding this:

1    Is this still a DSA requirement?

2    If so, are there any documented cases of building failure or even
footing failure due to voids left in the footings after form stakes were
removed?  (Shrinkage cracks at holes don't count as "failure"....)

2.5   Or is this just a way to waste California taxpayers' money and create
a market for renting special forming systems that some of the larger
concrete accessory suppliers provide?

Curious to hear any comments, and to see if any other state or agency has
such requirements.

Thor Matteson,
California taxpayer and parent of children who attend aging, overcrowded
schools  (can you guess my position on this issue?)





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