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Teng's curve
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trustmeasfrnd
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PostPosted: Sat Jun 20, 2009 7:15 am    Post subject: Tengs curve. Reply with quote

i guess enclosed extarct will help u from foundation design by Wyane C Teng .

with regards,
Abhisekh



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teng.pdf
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Extracts from foundation design by Wyane C Teng

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lele_raj
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PostPosted: Sat Jun 20, 2009 9:43 am    Post subject: Teng's curve Reply with quote

Hi Mr Choksi,

I'll appreciate if you could send the charts as well....


Best regards,

Rajendra (Raj) Lele


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From: jiwaji <forum@sefindia.org>
To: general@sefindia.org
Sent: Thursday, 18 June, 2009 7:10:20 PM
Subject: [SEFI] Re: Teng's curve

     Dear Mr Choksi
I will be greatly obliged if you could mail me the Teng's full charts (4-zones) to my email id jydesai@tce.co.in (jydesai@tce.co.in)
Regards
Jiwaji Y Desai
DGM (C&S)
TCE Jamshedpur


"JVCSNL"  
06/18/2009 12:47 PM Please respond to
general@sefindia.org (general@sefindia.org)

To
general@sefindia.org (general@sefindia.org) cc
Subject
[SEFI] Re: Teng's curve




Dear Mr. Gurnam Singh,

Teng's curves are very popular in foundation engineering.

The reference is W C Teng's foundation design book. (Might be out of print). Other reading material is Hansen and Peck book.

Almost all the foundations are subjected to axial force and bending moments about both the axes. You may recall from the principles of direct and bending stresses that when the application of load is within the kern of the foundation, bearing pressure (P/A+/- Mi/Zi) below footing is compressive in nature.

However, when the load is outside kern, the bearing pressure in footing is not compressive within footing and there exists negative pressure at one or more corners.

Since, there is no medium between footing pad and soil to resist this tension (called uplift) the portion in negative area can not be considered effective. In this case, the entire load shall be taken by the portion of footing in contact with soil. Since, in all conditions, the equilibrium shall occur, the bearing pressures gets modified and location of neutral axis also shifts.

Though, this concept looks simple in nature, it is very difficult to obtain modified pressure values and location of neutral axis after satisfying equilibrium conditions.

Teng's chart provides the factor to calculate modified pressure based on the eccentricity of the loading point for rectangular footings. Teng's charts are divided in 4 zones and for each zone the factor and formulae to calculate modified pressure is given. It shall be noted that these charts are only for calculation of bearing pressure for rectangular footing. The stability checks needs to be applied as usual.

Regards,

Jignesh Chokshi





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lele_raj
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PostPosted: Sun Jun 21, 2009 4:58 am    Post subject: Teng's curve Reply with quote

Thanks, Abhisekh and Vikram.jeet


Best regards,

Rajendra (Raj) Lele


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From: trustmeasfrnd <forum@sefindia.org>
To: general@sefindia.org
Sent: Saturday, 20 June, 2009 5:15:33 PM
Subject: [SEFI] Re: Teng's curve

     i guess enclosed extarct will help u from foundation design by Wyane C Teng .

with regards,
Abhisekh
     



     
Download Attachments:
Extracts from foundation design by Wyane C Teng





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patole
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PostPosted: Sun Jun 21, 2009 8:59 am    Post subject: Teng's curve Reply with quote

Dear Subramanian sir,

Yes you are correct, these are especially used for footings with AF & biaxial BM, which is everyday case now in 3D analysis softwares. I have verified these charts with multiple finite element analysis & found them OK.


Fintel charts are more common than Tengs curve, but doesn't provide "contact area" in case of uplift. Hence I had started using Teng's curves. Results in either cases are verified are found reasonable for calculating bearing pressure.


Most of the the Indian government publications other than codes are not updated frequently or out of print. EIL standards for civil structural are quite useful in industry but not available in proper archive.


On separate note, I have seen you always active on this forum and answering most of the queries very patiently. I appreciate your efforts. Keep it up. 


Also your addressing everyone an Er. is certainly great move (we used do it when I was in VJTI, but left after that)


Thanks for your contribution,


regards,


Vivek Patole

On Fri, Jun 19, 2009 at 7:59 PM, drnsmani <forum@sefindia.org (forum@sefindia.org)> wrote:
[quote]            Dear Er Vivek,

Thanks for attaching Teng's chart. I think it will be useful in the case of footings subjected to ecc. loading or footings with AF and BM.

But it will not be useful for tower foundations. Hence Er. Gurnam should follow the references as listed out by me or the Manual on Transmission line Towers published by Central Board of Irrigation and Power, New Delhi-It is very old and I am not sure whether out of print.

As Er Rajendra Lele has said, I am also hearing about these Teng's curves for the first time and never used it.

Best wishes
Subramanian
[quote="patole"]Friends,

Pl. see attached Teng's charts. These charts are use to calculate the contact area of foundation under vertical load + biaxial bending conditions. There is one chart with four graphs for four different conditions. Also this will provide you different formulas for calculating Maximum pressure under different conditions.


Pl. let me know if you need any further information on this


Vivek Patole


DCE
Chemtex India

On Fri, Jun 19, 2009 at 9:02 AM, drnsmani forum@sefindia.org (forum@sefindia.org))> wrote:

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JVCSNL
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PostPosted: Mon Jun 22, 2009 5:47 am    Post subject: Teng's curve Reply with quote

Dear Mr. Subramanian,

In most of the tall structures where the BM is very high due to lateral loads, it is very difficult to optimize the foundation sizes if we desire positive pressure below footing. To obtain good economy in design, we have to allow portion of footing to be in uplift (technically it is called unstressed).

In most of the engineering courses, the foundation design is limited to positive pressure below foundation. Hence, many of us would not be knowing about allowing negative pressures below footing and since, there is no medium between soil and footing pad to take this uplift forces, the equilibrium check become complex.


As informed in my earlier posts, the Teng's charts are quite popular in foundation engineering to obtain bearing pressure (called modified bearing pressure) below footings subjected to large eccentricities satisfying the equilibrium conditions.

Teng's Charts give graphical solution. One has to locate the Case of eccentricity and then use appropriate equation. This procedure is conditional and not general. Using charts in computer programs for foundation design is quite difficult and user interface is also required.

To overcome this conditional case based solution, I have attempted to formulate a generalized numerical method and presented a paper in ICCMS-2004 at IITK. You may refer to this paper, which gives basics of footings subjected to large biaxial moments and the generalized programming approach.

Regards,

Jignesh Chokshi

Quote:
Quote:
Quote:
forum@sefindia.org 19-06-2009 >>>

Dear Er Vivek,

Thanks for attaching Teng's chart. I think it will be useful in the case of footings subjected to ecc. loading or footings with AF and BM.

But it will not be useful for tower foundations. Hence Er. Gurnam should follow the references as listed out by me or the Manual on Transmission line Towers published by Central Board of Irrigation and Power, New Delhi-It is very old and I am not sure whether out of print.

As Er Rajendra Lele has said, I am also hearing about these Teng's curves for the first time and never used it.

Best wishes
Subramanian
[quote="patole"]Friends,

Pl. see attached Teng's charts. These charts are use to calculate the contact area of foundation under vertical load + biaxial bending conditions. There is one chart with four graphs for four different conditions. Also this will provide you different formulas for calculating Maximum pressure under different conditions.


Pl. let me know if you need any further information on this


Vivek Patole


DCE
Chemtex India

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scpatel_74
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PostPosted: Mon Jun 22, 2009 8:40 am    Post subject: Teng's curve Reply with quote

Dear Mr. Jignesh,

We are trying to develop generalised formulation same as you for rectangular/square footing with biaxial moments.

Is it possible to get the paper, as it is difficult to get proceedings (?)

Thanks and regards,
-Sanjay Patel


________________________________

From: JVCSNL [mailto:forum@sefindia.org]
Sent: Mon 6/22/2009 12:00 PM
To: general@sefindia.org
Subject: [SEFI] Re: Teng's curve


Dear Mr. Subramanian,

In most of the tall structures where the BM is very high due to lateral loads, it is very difficult to optimize the foundation sizes if we desire positive pressure below footing. To obtain good economy in design, we have to allow portion of footing to be in uplift (technically it is called unstressed).

In most of the engineering courses, the foundation design is limited to positive pressure below foundation. Hence, many of us would not be knowing about allowing negative pressures below footing and since, there is no medium between soil and footing pad to take this uplift forces, the equilibrium check become complex.


As informed in my earlier posts, the Teng's charts are quite popular in foundation engineering to obtain bearing pressure (called modified bearing pressure) below footings subjected to large eccentricities satisfying the equilibrium conditions.

Teng's Charts give graphical solution. One has to locate the Case of eccentricity and then use appropriate equation. This procedure is conditional and not general. Using charts in computer programs for foundation design is quite difficult and user interface is also required.

To overcome this conditional case based solution, I have attempted to formulate a generalized numerical method and presented a paper in ICCMS-2004 at IITK. You may refer to this paper, which gives basics of footings subjected to large biaxial moments and the generalized programming approach.

Regards,

Jignesh Chokshi


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vikram.jeet
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PostPosted: Mon Jun 22, 2009 9:20 am    Post subject: Teng's curve Reply with quote

Teng's Curves are not new to engineers and all engineers engaged in
Bridge design work are using these curves since 60's/even prior to that.

The upliftment of footing on rocky strata is being computed
using these curves and shall be within permissible limits as per IRC-78.

regards

vikramjeet

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thirumalaichettiar
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PostPosted: Mon Jun 22, 2009 11:16 am    Post subject: Reply with quote

Er.Jignesh Chokshi ,
Is it possible to upload your paper that was presented in ICCMS-2004 at IITK by you since many of us like me do not know how  to get the paper? This is for the benefit of all Sefians.

T.Rangarajan
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Dr. N. Subramanian
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PostPosted: Tue Jun 23, 2009 2:06 pm    Post subject: Re: Teng's curve Reply with quote

Dear Er Jignesh Chokshi,

Thanks for the info. As I am not an expert on bridge foundations, I was not aware of Teng's charts.  But when we are dealing with industrial buildings, we do encounter design of footings with Heavy BM but subjected to low AF, which will result in neg. pressure under soils, which is not allowed. It is really a challenge to design such a footing, as pile foundations are not normally adopted in such structures. Arya and Ajmani has dealt with this case, considering only the triangular  positive pressure under footing.

But do you recommend such footings with neg. soil pressure in seismic zones?

Glad to note that you presented a paper in ICCMS-2004 at IITK. Please upload it for the benefit of other Sefians, as requested by Er Rangarajan.

Best wishes
Subramanian

[quote="JVCSNL"]Dear Mr. Subramanian,

In most of the tall structures where the BM is very high due to lateral loads, it is very difficult to optimize the foundation sizes if we desire positive pressure below footing. To obtain good economy in design, we have to allow portion of footing to be in uplift (technically it is called unstressed).

In most of the engineering courses, the foundation design is limited to positive pressure below foundation. Hence, many of us would not be knowing about allowing negative pressures below footing and since, there is no medium between soil and footing pad to take this uplift forces, the equilibrium check become complex.


As informed in my earlier posts, the Teng's charts are quite popular in foundation engineering to obtain bearing pressure (called modified bearing pressure) below footings subjected to large eccentricities satisfying the equilibrium conditions.

Teng's Charts give graphical solution. One has to locate the Case of eccentricity and then use appropriate equation. This procedure is conditional and not general. Using charts in computer programs for foundation design is quite difficult and user interface is also required.

To overcome this conditional case based solution, I have attempted to formulate a generalized numerical method and presented a paper in ICCMS-2004 at IITK. You may refer to this paper, which gives basics of footings subjected to large biaxial moments and the generalized programming approach.

Regards,

Jignesh Chokshi

Quote:
Quote:
Quote:
forum@sefindia.org 19-06-2009 >>>

Dear Er Vivek,

Thanks for attaching Teng's chart. I think it will be useful in the case of footings subjected to ecc. loading or footings with AF and BM.

But it will not be useful for tower foundations. Hence Er. Gurnam should follow the references as listed out by me or the Manual on Transmission line Towers published by Central Board of Irrigation and Power, New Delhi-It is very old and I am not sure whether out of print.

As Er Rajendra Lele has said, I am also hearing about these Teng's curves for the first time and never used it.

Best wishes
Subramanian
patole wrote:
Friends,

Pl. see attached Teng's charts. These charts are use to calculate the contact area of foundation under vertical load + biaxial bending conditions. There is one chart with four graphs for four different conditions. Also this will provide you different formulas for calculating Maximum pressure under different conditions.


Pl. let me know if you need any further information on this


Vivek Patole


DCE
Chemtex India

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ibarua
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PostPosted: Sun Jun 28, 2009 11:49 am    Post subject: Teng's curve Reply with quote

28th June 2009

I confess that I'm also unaware of Teng's curve.

In 1974-75, we had to design a sugar mill building - built up rigid portal frame, span 28.5 m., eaves height 15 m., with a 15 t. EOT crane. The foundations had a high eccentricity (M/P). We took recourse to the triangular positive pressure under the footing (considering the reduced base area) as proposed in 'Steel Designer's Manual' The building has performed satisfactorily over the years.

Indrajit Barua.


On Tue, 23 Jun 2009 drnsmani wrote :
Quote:
Dear Er Jignesh Chokshi,

Thanks for the info. As I am not an expert on bridge
foundations, I was not aware of Teng's charts.  But
when we are dealing with industrial buildings, we do
encounter design of footings with Heavy BM but
subjected to low AF, which will result in neg. pressure
under soils, which is not allowed. It is really a
challenge to design such a footing, as pile foundations
are not normally adopted in such structures. Arya and
Ajmani has dealt with this case, considering only the
triangular  positive pressure under footing.

But do you recommend such footings with neg. soil
pressure in seismic zones?

Glad to note that you presented a paper in ICCMS-2004
at IITK. Please upload it for the benefit of other
Sefians, as requested by Er Rangarajan.

Best wishes
Subramanian

[quote="JVCSNL"]Dear Mr. Subramanian,

In most of the tall structures where the BM is very
high due to lateral loads, it is very difficult to
optimize the foundation sizes if we desire positive
pressure below footing. To obtain good economy in
design, we have to allow portion of footing to be in
uplift (technically it is called unstressed).

In most of the engineering courses, the foundation
design is limited to positive pressure below
foundation. Hence, many of us would not be knowing
about allowing negative pressures below footing and
since, there is no medium between soil and footing pad
to take this uplift forces, the equilibrium check
become complex.


As informed in my earlier posts, the Teng's charts are
quite popular in foundation engineering to obtain
bearing pressure (called modified bearing pressure)
below footings subjected to large eccentricities
satisfying the equilibrium conditions.

Teng's Charts give graphical solution. One has to
locate the Case of eccentricity and then use
appropriate equation. This procedure is conditional and
not general. Using charts in computer programs for
foundation design is quite difficult and user interface
is also required.

To overcome this conditional case based solution, I
have attempted to formulate a generalized numerical
method and presented a paper in ICCMS-2004 at IITK. You
may refer to this paper, which gives basics of footings
subjected to large biaxial moments and the generalized
programming approach.

Regards,

Jignesh Chokshi


Quote:

Quote:

Quote:
forum@sefindia.org 19-06-2009 >>>




Dear Er Vivek,

Thanks for attaching Teng's chart. I think it will be
useful in the case of footings subjected to ecc.
loading or footings with AF and BM.

But it will not be useful for tower foundations. Hence
Er. Gurnam should follow the references as listed out
by me or the Manual on Transmission line Towers
published by Central Board of Irrigation and Power, New
Delhi-It is very old and I am not sure whether out of
print.

As Er Rajendra Lele has said, I am also hearing about
these Teng's curves for the first time and never used
it.

Best wishes
Subramanian

patole wrote:
Quote:
Friends,

Pl. see attached Teng's charts. These charts are use
to calculate the contact area of foundation under
vertical load + biaxial bending conditions. There is
one chart with four graphs for four different
conditions. Also this will provide you different
formulas for calculating Maximum pressure under
different conditions.
Quote:


Pl. let me know if you need any further information
on this
Quote:


Vivek Patole


DCE
Chemtex India










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