Return to index: [Subject] [Thread] [Date] [Author]

RE: EMPIRICAL RELATIONS FOR THICKNESSES.

[Subject Prev][Subject Next][Thread Prev][Thread Next]
The 1974 edition of Fintel's Handbook suggested thickness to span ratios of
1/12 for cantilever elements and 1/16 for propped cantilever elements. ACI
350 has drafted a document for "Design Considerations for Environmental
Engineering Concrete Structures" which will likely note these as reasonable
rules of thumb to start with. (This document is still in the committee
voting process.) The new ACI 350 code due out "any time now" will require a
minimum thickness of 12-inches for walls 10 ft or greater in height and in
contact with liquids (Section 14.6.2). You aren't likely to find "empirical
relationships" for design in ACI codes and standards since they are intended
to address minimum final design requirements rather than preliminary or
approximate methods.

I generally check minimum thickness required for shear first and then
required area of steel at point of maximum moment. I try to avoid bar sizes
greater than #8 bars in uniformly reinforced slabs and walls. Fintel's'
Handbook also suggests that a 1% reinforcement ratio generally provides
economical structures.

> -----Original Message-----
> From: syed faiz ahmad [mailto:syedfaiz23(--nospam--at)hotmail.com]
> Sent: Sunday, January 27, 2002 12:15 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.
>
>
> _________________________________________________________________
> MSN Photos is the easiest way to share and print your photos:
> http://photos.msn.com/support/worldwide.aspx
>
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   without your permission. Make sure you visit our web
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
>

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********