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RE: EMPIRICAL RELATIONS FOR THICKNESSES.

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Syed,

The first step in tank walls, and in slabs is to calculate the shear.  The
shear will often times determine the wall or slab thickness.

Concrete design is one of those areas that requires a lot of experience.
What we have to weigh is economy (perceived and real) and serviceability.
Part of the analysis is to determine what the practice is in the area the
project is to be constructed, what indigenous materials are available, and
what the construction practices are.

As an example, if labor is expensive relative to material, you may want to
avoid drops which will increase forming costs and rebar placement costs.  If
the project is architectural, and the cladding is costly, and floor to floor
heights must be minimized you may want to consider post tensioning a 2 way
flat plate.

As for resources, contact a reputable contractor in the area to see what his
history has been for a particular type of construction.

As for books:
I like is "Structural Design Guide to the ACI Building Code", by Rice,
Hoffman, Gustafson, and Gouwens.  The book contains a lot of design aids
that will get you to a solution quickly.

Another is "Simplified Design", by the Portland Cement Association.

The PCA also has several books on tanks.  The thickness depends on if they
are rectangular or round, what type of base restraint and roof restraint you
are considering, and if you are going to post tension the walls.  Often
times local practice and the service will dictate the wall thickness.

I also like to look at Means Cost Estimating.  It gets you to an economical
answer quickly.

Regards,
Harold O. Sprague

> -----Original Message-----
> From:	syed faiz ahmad [SMTP:syedfaiz23(--nospam--at)hotmail.com]
> Sent:	Sunday, January 27, 2002 1:15 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	EMPIRICAL RELATIONS FOR THICKNESSES.
>
> Hi there!
>
> PROBLEM:
>
>   - Empirical relations for establishing preliminary
>     thicknesses of:
>
>             - walls
>
>             - bottom/floor slab
>
>
>    in the design of water retaining structures,
>    sanitary structures, swimming pools, etc is
>    required.
>
> AVAILABLE REFERENCES:
>
>   - ACI 350  is silent on the subject, except it
>     suggests a minimum wall thickness of 300 mm
>     (12-in) should be used for depths 3 m
>     (9.84 ft) & above. The reasons forwarded are
>     related to detailing problem due to rebars on
>     both the faces including concrete cover.
>
>   - for slabs, it is silent completely.
>
>   - B.S (British code of practice) in a reference
>     DESIGN OF LIQUID RETAINING CONCRETE STRUCTURE
>     bY: R.D. Anchor, stipulates:
>
>         -  wall thickness = depth/10
>
>         - for slabs, however, it is silent.
>
>   - In yet another reference HANDBOOK OF CONCRETE
>     ENGINEERING by: Mark Fintel, the following is
>     suggested:
>
>         - wall thickness = depth/16
>
>         - slab thickness = span/16
>
>   - In case of wall thickness it looks to be on
>     a lower side as compared to B.S
>     recommendations for the same.
>
>   - But this recommendation in the above
>     reference is not supported by any related
>     documents of ACI.
>
> CONCLUSION:
>
>   - based on others experiences on the subject
>     the following is solicited:
>
>         - the usual empirical relations
>           practised by others.
>
>         - citation of any related references on
>           the subject.
>
> Thanx in advance. Regards,
>
> SYED FAIZ AHMAD; MENGG, MASCE
> SENIOR STRUCTURAL ENGINEER
> SAUDI OGER LTD
> RIYADH, SAUDI ARABIA.
>
>
> _________________________________________________________________
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>

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