www.sefindia.org

STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

 Forum SubscriptionsSubscriptions DigestDigest Preferences   FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups  RegisterRegister FAQSecurity Tips FAQDonate
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log in to websiteLog in to websiteLog in to websiteLog in to forum 
Warning: Make sure you scan the downloaded attachment with updated antivirus tools  before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.

Design Corner Eccentric Footing on Both Side
Goto page 1, 2  Next
 
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> SEFI General Discussion
View previous topic :: View next topic  
Author Message
kiranklk
SEFI Regulars
SEFI Regulars


Joined: 26 Dec 2010
Posts: 34
Location: Banglore

PostPosted: Tue Mar 01, 2011 6:27 am    Post subject: Design Corner Eccentric Footing on Both Side Reply with quote

Hi Please Anybody Tell Me How to Design Corner EccentricFooting on Both Side Without Starp Beam. And Please Suggest me Any Books ForReference and Excel Spread Sheets.


Regards Kiran.
Back to top
View user's profile Send private message Visit poster's website
B.V.Harsoda
General Sponsor
General Sponsor


Joined: 19 Jan 2009
Posts: 2297
Location: RAJKOT,GUJARAT, INDIA

PostPosted: Tue Mar 01, 2011 8:05 am    Post subject: Reply with quote

Refer Links:-

http://www.sefindia.org/forum/search.htm?cx=011309042287105965323%3A-rusg9dz88q&ie=UTF-8&q=shoe+footing&cof=FORID%3A11&siteurl=www.sefindia.org%2F#857


http://www.sefindia.org/forum/search.htm?cx=011309042287105965323%3A-rusg9dz88q&ie=UTF-8&q=l+footing&cof=FORID%3A11&siteurl=www.sefindia.org%2F#870
Back to top
View user's profile Send private message
B.V.Harsoda
General Sponsor
General Sponsor


Joined: 19 Jan 2009
Posts: 2297
Location: RAJKOT,GUJARAT, INDIA

PostPosted: Tue Mar 01, 2011 8:15 am    Post subject: Reply with quote

Useful Spreadsheets Link:-


http://www.engineering-international.com/
Back to top
View user's profile Send private message
Dr. N. Subramanian
General Sponsor
General Sponsor


Joined: 21 Feb 2008
Posts: 5383
Location: Gaithersburg, MD, U.S.A.

PostPosted: Tue Mar 01, 2011 2:42 pm    Post subject: Re: Design Corner Eccentric Footing on Both Side Reply with quote

Dear Er Kiran,

It is very difficult to provide ecc. footings with out connecting it to adjacent footing with strap beams, unless it is having very low AF. When it has ecc. on both axes, it is not advisable to attempt such a footing, because footing is very important to any structure, and the loss of footing due to loss of contact may be catastrophic to any building. That is the reason why it is not included in any book. For both side ecc. footing, I suggest you to combine other footings and provide a raft, as we do in lift wells.

Best wishes
NS

kiranklk wrote:
Hi Please Anybody Tell Me How to Design Corner EccentricFooting on Both Side Without Starp Beam. And Please Suggest me Any Books ForReference and Excel Spread Sheets.


Regards Kiran.
Back to top
View user's profile Send private message
B.V.Harsoda
General Sponsor
General Sponsor


Joined: 19 Jan 2009
Posts: 2297
Location: RAJKOT,GUJARAT, INDIA

PostPosted: Tue Mar 01, 2011 4:27 pm    Post subject: Reply with quote

In previous posting Er. Vikramjeet has been Explained nicety as Below:-


"L- Footings  is generally required to be provided at the edge of
property line. This footing, if not connected to internal column, is
subjected to very high  moment due to eccentricity  of load  w r t
footing centreline.
It is always preferable to connect this footing with some
internal column through a strap beam so that moment
due to eccentricity is taken care by this beam.For economy
in strap beam, it is necessary to take footing dimension
in direction of eccentricity,as less as possible,say, half the other.

"For edge footing without strap beam,it is difficult to satisfy
the no upliftment condition as redistribution is not permitted
for footings resting on soils.Even if some redistribution is
taken it may give very high value of upliftment of footing
and max pressure after redistribution is quite high(it has to be
less than SBC)
Some designers take advantage
of passive soil resistance(with some  FOS) offered by the edge wall
to relieve eccentric  moment but in that case edge wall shall
be strong enough to withstand this passive relief moment.

Long back I had seen a paper  written by structural expert and author
Sh UH Varyani on the analysis of edge footing w/o strap
beams. This might be available in some of his books
."



In Second Post said that

"in my opinion ,try to provide strap beam as  per situation
given below in view of L-footing already cast without
strap beam.

i)assuming that  columns are not cast above top of footing

In this situation you can provide the strap beam
connecting this column to internal column at
top of footing level .

ii)assuming that  columns are  cast above top of footing
upto GL/PL
In this situation you can provide the strap beam(tie beam)
connecting this column to internal column at
GL/PL but edge column reinf provided shall be adequate
enough to transfer the eccentric moment  upto
strap / tie beam level. You can take advantage of
passive relief from soil(with some FOS) on edge wall on
either side of column .Also the orthogonal cross wall (if it exists)
will help. ( by way of its triangular load component beyond
footing line  through dispersion which will provide counter
eccentricity)"






Back to top
View user's profile Send private message
vikram.jeet
General Sponsor
General Sponsor


Joined: 26 Jan 2003
Posts: 2212

PostPosted: Wed Mar 02, 2011 5:24 am    Post subject: Design Corner Eccentric Footing on Both Side Reply with quote

Corner Footing

As suggested by eminent members, the corner footing must have  
balancing strap beams in both directions to counter the eccentric
moments .These beams must be provided at footing level itself.

Avoidance of strap beam:(costly option)

A] If plinth beams are provided tie-ing the columns in
both directions

(i) The column section of corner column below plinth level shall be
increased appreciably to take care of additional bi-axial moment s
due to eccentricities in both directions. Column Reinf shall be  
worked out accordingly.

(ii) Plinth beam in each direction shall be designed for addtional
tensile force =M/Df
M = P*e
e = eccenricity= distance between CL footing and CL column
Df = fondation depth upto plinth level

This tensile force in plinth beam must have a counter force form other side
corner column, otherwise inner columns must share it.

(iii) Column above plinth beam level can have normal reinforcement

B] If plinth beams are NOT provided and roof beams are
available at roof level (i.e next floor level)

(i) The column section of corner column below roof level shall be
increased suitably to take care of additional bi-axial moment s
due to eccentricities in both directions.Column Reinf shall be  
worked out accordingly.

(ii) Roof beam in each direction shall be designed for addtional
tensile force =M/(Df +H)
M = P*e
e = eccenricity= distance between CL footing and CL column
Df = fondation depth upto plinth level
H= roof height above Plinth level
This tensile force in roof beam must have a counter force form other side
corner column, otherwise inner columns must share it.

(iii) Column reinf above plinth beam level can can be slightly reduced
since addtional moment (due to eccentric) varies upto roof level.

Other reductions in eccentric moments

(i) Passive less active relief from soil on side faces


Best wishes and regds

vikramjeet




-- ญญ

Posted via Email
Back to top
View user's profile Send private message
B.V.Harsoda
General Sponsor
General Sponsor


Joined: 19 Jan 2009
Posts: 2297
Location: RAJKOT,GUJARAT, INDIA

PostPosted: Wed Mar 02, 2011 8:01 am    Post subject: Reply with quote

Thank you Very much Er. Vikramjeet ji, Your Knowledge ia appreciable. As rightly said by  Dr. NS Sir,due to certain reasons such footings not included in any book ,but considering cost of land & requirement of client, it is not avoidable at all times. In such situations we have to do some thing. It wiil be great work if we can be helpfull in this subject to needful structural Engineers. In past we have discussed several times.Now I request to Er. Vikramjeet ji to submit, Article Regarding L-footing & Corner Eccentric footings in Forum.

Thanks
&
Best Wishes,

B. V. Harsoda    
Back to top
View user's profile Send private message
vikram.jeet
General Sponsor
General Sponsor


Joined: 26 Jan 2003
Posts: 2212

PostPosted: Wed Mar 02, 2011 9:40 am    Post subject: Design Corner Eccentric Footing on Both Side Reply with quote

Thank you, respected Harsoda sahab.

As informed by you , lot of discussion in this regard has been taken place on sefi.
These footings are not very un -common . IS codes do not provide any guidelines
in this regard .
Books on design/analysis do talk about provision of strap beams and their analysis.
However provision of these footings without strap beams is dealt seldom.The
analysis of L- footings is ,I think,dealt by our respected UH Varyani sahab in his book  
on MS buildings which is part of his Paper in ICJ.

I have posted my recent views on L -footings without strap beams purely based  
on basics.The basic idea is that eccentricity moment on footing need to be  
resisted through either a strap beam (if present) /or through column itself being
tied at certain level above.

As suggested , I would be glad to write on sefi at some future date after noting
the comments of members.

with kind regards

vikramjeet


Thank you Very much Er. Vikramjeet ji, Your Knowledge ia appreciable. As rightly said by Dr. NS Sir,due to certain reasons such footings not included in any book ,but considering cost of land & requirement of client, it is not avoidable at all times. In such situations we have to do some thing. It wiil be great work if we can be helpfull in this subject to needful structural Engineers. In past we have discussed several times.Now I request to Er. Vikramjeet ji to submit, Article Regarding L-footing & Corner Eccentric footings in Forum.

Thanks
&
Best Wishes,

-- ญญ

Posted via Email
Back to top
View user's profile Send private message
binaya shahi
SEFI Member
SEFI Member


Joined: 03 Jun 2015
Posts: 19

PostPosted: Wed Mar 30, 2016 1:22 pm    Post subject: width of strap beam. Reply with quote

One of my friends told me that the width of strap footing must be greater than the column without referring to any code or book or reasoning. I want to ask if its true coz I don't think it must be true. I have designed a strap beam of 9 inch width and 22 inch depth to connect two columns of dimensions 12"x12". Isn't my 9 inch wide strap beam allowed for 12 inch wide column?
Back to top
View user's profile Send private message
es_jayakumar
General Sponsor
General Sponsor


Joined: 24 Nov 2011
Posts: 1339
Location: Cochin

PostPosted: Fri Dec 13, 2019 3:32 am    Post subject: Reply with quote

Dear SEFIans,

Please comment on the rationality of the design of a corner column isolated-footing attached here, that had appeared in this forum at sometime. I was not convinced with the principle / logic of this design.

E S Jayakumar



Warning: Make sure you scan the downloaded attachment with updated antivirus tools  before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.
DESIGN OF FOOTING FOR CORNER COLUMN.doc
 Description:

Download
 Filename:  DESIGN OF FOOTING FOR CORNER COLUMN.doc
 Filesize:  111 KB
 Downloaded:  535 Time(s)

Back to top
View user's profile Send private message
Display posts from previous:   
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> SEFI General Discussion All times are GMT
Goto page 1, 2  Next
Page 1 of 2

 

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


© 2003, 2008 SEFINDIA, Indian Domain Registration
Publishing or acceptance of an advertisement is neither a guarantee nor endorsement of the advertiser's product or service. advertisement policy