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.

Regarding Design of Plinth Beam
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
Yogesh101
SEFI Member
SEFI Member


Joined: 04 Dec 2020
Posts: 4

PostPosted: Wed Feb 17, 2021 6:23 am    Post subject: Regarding Design of Plinth Beam Reply with quote

Do we need to design plinth beam to its span? While designing a building in etabs, the r/f of plinth beam of 7m is very less even with minimum section size. So, i'm confused whether it should be designed according to its span or not.
Back to top
View user's profile Send private message
hishamajmalpc
Progressive Member
Progressive Member


Joined: 09 Nov 2015
Posts: 49

PostPosted: Wed Feb 17, 2021 10:28 am    Post subject: Reply with quote

what you meant by 'design by its span'?
Back to top
View user's profile Send private message
Yogesh101
SEFI Member
SEFI Member


Joined: 04 Dec 2020
Posts: 4

PostPosted: Wed Feb 17, 2021 10:36 am    Post subject: Reply with quote

What I meant was, we design the depth as span/(12-15). Do i need to do that for plinth beam?
Back to top
View user's profile Send private message
hishamajmalpc
Progressive Member
Progressive Member


Joined: 09 Nov 2015
Posts: 49

PostPosted: Wed Feb 17, 2021 10:51 am    Post subject: Reply with quote

span/12 is for prliminary sizing of beam. You should check this depth for flexure,shear and deflection.
Back to top
View user's profile Send private message
Dr. N. Subramanian
General Sponsor
General Sponsor


Joined: 21 Feb 2008
Posts: 5457
Location: Gaithersburg, MD, U.S.A.

PostPosted: Wed Feb 17, 2021 11:20 pm    Post subject: Re: Regarding Design of Plinth Beam Reply with quote

Dear Er Yogesh

Plinth beams are normally supporting considerable height of brickwork and hence act as composite beams. Hence they need not be designed for the normal BM. In such cases, for normal spans of 3-4 m, we assume a depth of 150 mm to 200 mm only and design for a BM of Wl^2/30. See also the IS code on piles(I think it is IS 2911). Usually 2 nos 12 mm bars are provided at top and bottom

Best wishes
Subramanian
Yogesh101 wrote:
Do we need to design plinth beam to its span? While designing a building in etabs, the r/f of plinth beam of 7m is very less even with minimum section size. So, i'm confused whether it should be designed according to its span or not.
Back to top
View user's profile Send private message
hishamajmalpc
Progressive Member
Progressive Member


Joined: 09 Nov 2015
Posts: 49

PostPosted: Fri Feb 19, 2021 5:57 am    Post subject: Reply with quote

Sir,
Most of the cases there will be openings in wall (Doors/windows). Can we assume composite action in those cases?
Back to top
View user's profile Send private message
Yogesh101
SEFI Member
SEFI Member


Joined: 04 Dec 2020
Posts: 4

PostPosted: Fri Feb 19, 2021 11:34 am    Post subject: Re: Regarding Design of Plinth Beam Reply with quote

Thank You Sir, for your clarification. I got it.
Back to top
View user's profile Send private message
Ujjwal
SEFI Member
SEFI Member


Joined: 07 Apr 2009
Posts: 12

PostPosted: Fri Feb 19, 2021 1:53 pm    Post subject: Re: Regarding Design of Plinth Beam Reply with quote

Dr. N. Subramanian wrote:
Dear Er Yogesh

Plinth beams are normally supporting considerable height of brickwork and hence act as composite beams. Hence they need not be designed for the normal BM. In such cases, for normal spans of 3-4 m, we assume a depth of 150 mm to 200 mm only and design for a BM of Wl^2/30. See also the IS code on piles(I think it is IS 2911). Usually 2 nos 12 mm bars are provided at top and bottom

Best wishes
Subramanian
Yogesh101 wrote:
Do we need to design plinth beam to its span? While designing a building in etabs, the r/f of plinth beam of 7m is very less even with minimum section size. So, i'm confused whether it should be designed according to its span or not.


The experience with 150 or 200 mm depth was not satisfactory as hundreds of buildings in expansive soil developed cracks in masonry. We ,therefore, provide depth and reinforcement considering the entire dead weight to be supported by the beam.
Back to top
View user's profile Send private message
someshwar ganti
General Sponsor
General Sponsor


Joined: 06 Feb 2010
Posts: 74

PostPosted: Sat Feb 20, 2021 2:15 am    Post subject: Reply with quote

I feel that a Plinth beam cannot be designed as a Normal Continuous beam like that in a Roof beam.

1. the Plinth beam is Normally casted on a CRS masonry, which gives it support through out the length of the BEAM hence our normal BM equations will not really apply,  

   Please note for a roof beam the wall is constructed much later hence normal equations apply.


Besides the Wall load on the plinth beam, most of the sites (especially factory sheds etc) will have tractors, tippers running on the some of the bays of the plinth beams, These beams survive only because there is a CRS wall supporting the beam through out.

hence in my opinion , design it as a normal beam because the construction loads on plinth beams (atleast in some bays ) is much higher than the wall load on the beams, in such a case the CRS support below the beam will prevent the deflection etc hence the failure.
Back to top
View user's profile Send private message
Ujjwal
SEFI Member
SEFI Member


Joined: 07 Apr 2009
Posts: 12

PostPosted: Sat Feb 20, 2021 12:14 pm    Post subject: Reply with quote

someshwar ganti wrote:
I feel that a Plinth beam cannot be designed as a Normal Continuous beam like that in a Roof beam.

1. the Plinth beam is Normally casted on a CRS masonry, which gives it support through out the length of the BEAM hence our normal BM equations will not really apply,  

   Please note for a roof beam the wall is constructed much later hence normal equations apply.


Besides the Wall load on the plinth beam, most of the sites (especially factory sheds etc) will have tractors, tippers running on the some of the bays of the plinth beams, These beams survive only because there is a CRS wall supporting the beam through out.

hence in my opinion , design it as a normal beam because the construction loads on plinth beams (atleast in some bays ) is much higher than the wall load on the beams, in such a case the CRS support below the beam will prevent the deflection etc hence the failure.
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