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trustmeasfrnd SEFI Member
Joined: 26 Jan 2003 Posts: 9
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Posted: Sat Jun 20, 2009 7:15 am Post subject: Tengs curve. |
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i guess enclosed extarct will help u from foundation design by Wyane C Teng .
with regards,
Abhisekh
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Extracts from foundation design by Wyane C Teng |
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lele_raj ...
Joined: 26 Jan 2003 Posts: 145
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Posted: Sat Jun 20, 2009 9:43 am Post subject: Teng's curve |
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Hi Mr Choksi,
I'll appreciate if you could send the charts as well....
Best regards,
Rajendra (Raj) Lele
P Please consider the environment before printing this e-mail or any attachment/s.
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 ...
Joined: 26 Jan 2003 Posts: 145
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Posted: Sun Jun 21, 2009 4:58 am Post subject: Teng's curve |
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Thanks, Abhisekh and Vikram.jeet
Best regards,
Rajendra (Raj) Lele
P Please consider the environment before printing this e-mail or any attachment/s.
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 SEFI Member
Joined: 11 Sep 2008 Posts: 10
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Posted: Sun Jun 21, 2009 8:59 am Post subject: Teng's curve |
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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 ...
Joined: 26 Jan 2003 Posts: 161
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Posted: Mon Jun 22, 2009 5:47 am Post subject: Teng's curve |
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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 >>>
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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 General Sponsor
Joined: 10 Apr 2008 Posts: 23
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Posted: Mon Jun 22, 2009 8:40 am Post subject: Teng's curve |
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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 General Sponsor
Joined: 26 Jan 2003 Posts: 3835
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Posted: Mon Jun 22, 2009 9:20 am Post subject: Teng's curve |
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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 Silver Sponsor
Joined: 26 Jan 2003 Posts: 3554
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Posted: Mon Jun 22, 2009 11:16 am Post subject: |
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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 General Sponsor
Joined: 21 Feb 2008 Posts: 5538 Location: Gaithersburg, MD, U.S.A.
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Posted: Tue Jun 23, 2009 2:06 pm Post subject: Re: Teng's curve |
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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 >>>
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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 General Sponsor
Joined: 26 Jan 2003 Posts: 1039
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Posted: Sun Jun 28, 2009 11:49 am Post subject: Teng's curve |
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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 >>>
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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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