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Re: Concrete Movement Joints

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As you mentioned certain measures could be taken to reduce slab cracking due
to drying shrinkage. However, in my opinion , these measures do not help in
reducing flexural stresses in edge columns/shear walls resulting from
temperature changes.Those flexural stresses could be quite high depending on
building length, edge column stiffnesses, ... ,etc.

My question engineers in seismic areas, does a 100mm wide expansion joint
suffice to prevent pounding, taking into consideration the allowable drift
for high-rise buildings.

Hasan Hindawi

----- Original Message -----
From: La Count, Curt <Curt.LaCount(--nospam--at)Jacobs.com>
To: 'seaint' <seaint(--nospam--at)seaint.org>
Sent: Thursday, 02 September, 1999 5:57 PM
Subject: Concrete Movement Joints


> On our projects, we've been more concerned about drying shrinkage than
> temperature movements.  Typical drying shrinkage movements are .06 %,
while
> temperature movements are typically .1% per 100 degrees C.   It takes
about
> 60 degrees C to equal drying shrinkage.  Control of the design mix,
> distributed steel reinforcing, fiber reinforcing and pour sequencing are
> methods we've used to pour plates as large as 80m, with only minor
cracking.
>
>
> I have found it common practice, in non-seismic regions, to provide
> expansion joints in buildings with very small joints.  The effects of
> pounding were apparently never investigated or the probability of
occurrence
> thought to be remote enough to ignore.  On the West coast of the US,
> engineers would typically think 100mm joints as minimum separations to
> prevent pounding.
>
> Curt La Count
> Jacobs Engineering
> Portland, OR
>
>
>  ----------
> From: Rex Donahey
> To: seaint(--nospam--at)seaint.org
> Subject: RE: SEISMIC DESIGN to UBC'97
> Date: Thursday, September 02, 1999 6:28AM
>
> A major factor in cracking of large structures is shrinkage of the
concrete
> during the construction phase.  Although it can require a great deal of
> coordination, it is possible to detail closure strips in the building.  If
> the strips are left open for at least 30 days, they will allow most of the
> shrinkage to occur with less constraint.
>
>  -----Original Message-----
> From: Hasan Hindawi [mailto:hasanh(--nospam--at)go.com.jo]
> Sent: Thursday, September 02, 1999 6:01 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: SEISMIC DESIGN to UBC'97
>
>
> Greetings,
>
> 1- In Kuwait the temperature may reach 55 degrees celcius during the
summer
> days and may drop to 20 during summer nights.  And may even drop below 10
> during the winter. So the actual temperature  change is actually greater
> than 30-35 degrees celcius. But nevertheless the drop occurs. And special
> measures should be adopted when casting during the summer.
> 2- It is true that heating and air-conditioning systems reduce the effect
of
> temperature variations, however most cracking problems occur during
> construction stage. The duration between pouring a slab and operating
> heating or a.c. is a minimum of 1 year in these parts of the world.
> 3- Yes I agree that critical stresses occur in the bottom floors due to
the
> fixity of the columns to the footings. Therefore, regardless of the number
> of floors of a building, it is sufficient to analyze up to 6-7 floors for
> temperature variations
>
> Regards
>
> Hasan Hindawi
>
>
>
>