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logeshcivil SEFI Member
Joined: 07 Aug 2017 Posts: 14 Location: Coimbatore

Posted: Fri Aug 10, 2018 11:10 am Post subject: Design of bi axially loaded isolated footing 


Hello sefians
i have a huge problem while deigning an isolate footing.I received the horizontal and vertical reactions for a PEB structure which is resting on a RCC column. I have a formed a 2D frame of the structure for calculating the reactions and moments at the bottom node.
The reactions are
x = 0
y = 484 kN
z = 501 kN
The moment are
x= 0
y = 3257 kNm
z = 26.59 kNm
Here in this the moment is predominant and so the minimum bearing pressure is negative. So please help me in solving the problem
Thank You in advance
_________________ Yours
Logesh 

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sakumar79 ...
Joined: 18 Apr 2008 Posts: 668

Posted: Fri Aug 10, 2018 1:17 pm Post subject: 


Dear Sir,
When you have large horizontal force at base of PEB structure, you can consider a plinth beam along the force direction and two stub columns at either end with a pedestal for the PEB stanchion at the centre. This will make it into a Portal structure. The moment will cause an uplift to one column and downward force in the other but the force will reduce as you increase the distance between the two columns.
Yours sincerely
S Arunkumar


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logeshcivil SEFI Member
Joined: 07 Aug 2017 Posts: 14 Location: Coimbatore

Posted: Sat Aug 11, 2018 4:09 am Post subject: Design of bi axially loaded isolated footing 


Dear Arun Kumar,
Thank you for your suggestion.
If i were to do as your suggestion I have to provide plinth beam along the direction of horizontal force which is 50 m, which i think is not economical.Is there any other solution.
I hove also few more doubts.
 How do i calculate loss of contact area if minimum bearing pressure is negative and also eccentricity is outside the footing.
 Can i omit negative bearing pressure and proceed the calculation with positive bearing pressure only.If not , then please suggest me a solution.
I have attached a picture for you reference.
Thanks in advance
sakumar79 wrote:  Dear Sir,
When you have large horizontal force at base of PEB structure, you can consider a plinth beam along the force direction and two stub columns at either end with a pedestal for the PEB stanchion at the centre. This will make it into a Portal structure. The moment will cause an uplift to one column and downward force in the other but the force will reduce as you increase the distance between the two columns.
Yours sincerely
S Arunkumar 
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Logesh 

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sakumar79 ...
Joined: 18 Apr 2008 Posts: 668

Posted: Sat Aug 11, 2018 7:27 am Post subject: 


Dear Er Logesh,
I think you misunderstand me. I am not talking about a 50 m long Plinth Beam. I am talking about a Plinth Beam may be 3 to 5 m long depending on your forces (half inside and half outside the building). This will be somewhat similar to a Two Pile Pilecap system.
Hope that helps,
Arunkumar


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Jayant Lakhlani General Sponsor
Joined: 26 Jan 2003 Posts: 191 Location: Rajkot, Gujarat, India

Posted: Sat Aug 11, 2018 7:30 am Post subject: Top and bottom reinforcement in isolated footing 


Dear Logesh
There seems to be something wrong with magnitude of Y moment, i.e. 3257 kNm. Suggest to review the analysis.
Regards.
Jayant Lakhlani
For
Lakhlani Associates
From: logeshcivil [mailto:forum@sefindia.org]
Sent: 10 August 2018 16:41
To: general@sefindia.org
Subject: [SEFI] Re: Top and bottom reinforcement in isolated footing
Hello sefians
i have a huge problem while deigning an isolate footing.I received the horizontal and vertical reactions for a PEB structure which is resting on a RCC column. I have a formed a 2D frame of the structure for calculating the reactions and moments at the bottom node.
The reactions are
x = 0
y = 484 kN
z = 501 kN
The moment are
x= 0
y = 3257 kNm
z = 26.59 kNm
Here in this the moment is predominant and so the minimum bearing pressure is negative. So please help me in solving the problem
Thank You in advance
Yours
Logesh
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snsdec SEFI Member
Joined: 07 Aug 2010 Posts: 1

Posted: Sat Aug 11, 2018 8:30 am Post subject: Top and bottom reinforcement in isolated footing 


Dear logesh,
Pl check moment y I think something wrong in analysis
Thanks
On Sat 11 Aug, 2018, 1:14 PM Jayant Lakhlani, <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:  Dear Logesh
There seems to be something wrong with magnitude of Y moment, i.e. 3257 kNm. Suggest to review the analysis.
Regards.
Jayant Lakhlani
For
Lakhlani Associates
From: logeshcivil [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: 10 August 2018 16:41
To: general@sefindia.org (general@sefindia.org)
Subject: [SEFI] Re: Top and bottom reinforcement in isolated footing
Hello sefians
i have a huge problem while deigning an isolate footing.I received the horizontal and vertical reactions for a PEB structure which is resting on a RCC column. I have a formed a 2D frame of the structure for calculating the reactions and moments at the bottom node.
The reactions are
x = 0
y = 484 kN
z = 501 kN
The moment are
x= 0
y = 3257 kNm
z = 26.59 kNm
Here in this the moment is predominant and so the minimum bearing pressure is negative. So please help me in solving the problem
Thank You in advance
Yours
Logesh
Download Attachments:
~WRD000.jpg

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perumal12379 SEFI Member
Joined: 05 Mar 2017 Posts: 2

Posted: Sat Aug 11, 2018 8:30 am Post subject: Top and bottom reinforcement in isolated footing 


While designing the single frame, if you are using staad then analysis in plane not in space.
On Sat, Aug 11, 2018 at 10:43 AM, Jayant Lakhlani <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:  Dear Logesh
There seems to be something wrong with magnitude of Y moment, i.e. 3257 kNm. Suggest to review the analysis.
Regards.
Jayant Lakhlani
For
Lakhlani Associates
From: logeshcivil [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: 10 August 2018 16:41
To: general@sefindia.org (general@sefindia.org)
Subject: [SEFI] Re: Top and bottom reinforcement in isolated footing
Hello sefians
i have a huge problem while deigning an isolate footing.I received the horizontal and vertical reactions for a PEB structure which is resting on a RCC column. I have a formed a 2D frame of the structure for calculating the reactions and moments at the bottom node.
The reactions are
x = 0
y = 484 kN
z = 501 kN
The moment are
x= 0
y = 3257 kNm
z = 26.59 kNm
Here in this the moment is predominant and so the minimum bearing pressure is negative. So please help me in solving the problem
Thank You in advance
Yours
Logesh
Download Attachments:
~WRD000.jpg

Posted via Email


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nimal ranasinghe SEFI Member
Joined: 27 May 2009 Posts: 3

Posted: Sat Aug 11, 2018 8:30 am Post subject: Top and bottom reinforcement in isolated footing 


Unless the column is fully cantilevered and having a eccentric crane girder fixed with a heavy pay load this moment is unrealistic. Kindly check your 2D model and assumptions for the connectivity and cross check with a manual calculation with simple distribution coefficients
Nimal
Sent from my iPhone
On Aug 11, 2018, at 1:13 PM, Jayant Lakhlani <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:  Dear Logesh
There seems to be something wrong with magnitude of Y moment, i.e. 3257 kNm. Suggest to review the analysis.
Regards.
Jayant Lakhlani
For
Lakhlani Associates
From: logeshcivil [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: 10 August 2018 16:41
To: general@sefindia.org (general@sefindia.org)
Subject: [SEFI] Re: Top and bottom reinforcement in isolated footing
Hello sefians
i have a huge problem while deigning an isolate footing.I received the horizontal and vertical reactions for a PEB structure which is resting on a RCC column. I have a formed a 2D frame of the structure for calculating the reactions and moments at the bottom node.
The reactions are
x = 0
y = 484 kN
z = 501 kN
The moment are
x= 0
y = 3257 kNm
z = 26.59 kNm
Here in this the moment is predominant and so the minimum bearing pressure is negative. So please help me in solving the problem
Thank You in advance
Yours
Logesh
Download Attachments:
~WRD000.jpg

Posted via Email


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Solanki Dimpesh SEFI Member
Joined: 10 Apr 2018 Posts: 1

Posted: Sat Aug 11, 2018 8:30 am Post subject: Top and bottom reinforcement in isolated footing 


Hello sir, As PEB are long free span frame structure. The moment at bottom of the column will be very much because of lateral load and high eave height. This is the reason why designer use pin connection instead of fixed connection, which reduce the foundation size. My suggestion would be to use pin support.
Then design the base plate and column pedestal using reactions. The isolated foundation will then have moment because of Fx & Fz and different in level.
Regards 
Dimpesh Solanki
+91 9987443194
Techniqes, Mumbai.
On Sat 11 Aug, 2018, 1:16 PM Jayant Lakhlani, <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:  Dear Logesh
There seems to be something wrong with magnitude of Y moment, i.e. 3257 kNm. Suggest to review the analysis.
Regards.
Jayant Lakhlani
For
Lakhlani Associates
From: logeshcivil [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: 10 August 2018 16:41
To: general@sefindia.org (general@sefindia.org)
Subject: [SEFI] Re: Top and bottom reinforcement in isolated footing
Hello sefians
i have a huge problem while deigning an isolate footing.I received the horizontal and vertical reactions for a PEB structure which is resting on a RCC column. I have a formed a 2D frame of the structure for calculating the reactions and moments at the bottom node.
The reactions are
x = 0
y = 484 kN
z = 501 kN
The moment are
x= 0
y = 3257 kNm
z = 26.59 kNm
Here in this the moment is predominant and so the minimum bearing pressure is negative. So please help me in solving the problem
Thank You in advance
Yours
Logesh
Download Attachments:
~WRD000.jpg

Posted via Email


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devendrarathi SEFI Member
Joined: 12 Sep 2012 Posts: 3

Posted: Sat Aug 11, 2018 8:30 am Post subject: Top and bottom reinforcement in isolated footing 


Please share the staad file so that we can identify if there is any mistake n staad
On Sat 11 Aug, 2018, 13:15 Jayant Lakhlani, <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:  Dear Logesh
There seems to be something wrong with magnitude of Y moment, i.e. 3257 kNm. Suggest to review the analysis.
Regards.
Jayant Lakhlani
For
Lakhlani Associates
From: logeshcivil [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: 10 August 2018 16:41
To: general@sefindia.org (general@sefindia.org)
Subject: [SEFI] Re: Top and bottom reinforcement in isolated footing
Hello sefians
i have a huge problem while deigning an isolate footing.I received the horizontal and vertical reactions for a PEB structure which is resting on a RCC column. I have a formed a 2D frame of the structure for calculating the reactions and moments at the bottom node.
The reactions are
x = 0
y = 484 kN
z = 501 kN
The moment are
x= 0
y = 3257 kNm
z = 26.59 kNm
Here in this the moment is predominant and so the minimum bearing pressure is negative. So please help me in solving the problem
Thank You in advance
Yours
Logesh
Download Attachments:
~WRD000.jpg

Posted via Email


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