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.

Floating Column
Goto page Previous  1, 2, 3, 4, 5
 
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> SEFI General Discussion
View previous topic :: View next topic  
Author Message
chidub
SEFI Member
SEFI Member


Joined: 03 Jan 2018
Posts: 2

PostPosted: Thu Aug 09, 2018 5:30 pm    Post subject: Floating Column Reply with quote

Thank you

On Thu 9 Aug, 2018, 10:23 PM sangeeta_wij, <forum@sefindia.org (forum@sefindia.org)> wrote:

Quote:
           First of all, a floating column is really not a column and secondly, never ever use it in a seismic zone III IV or V structure as even the gravity columns have to be checked for deflection compatibility as   Stated in the relevant clause of 1893. However, my sincere suggestion is to delete the terms like hidden beams and floating columns from your vocabulary as far as seismic design is concerned.

Regards
Sangeeta Wij
On Thu, 9 Aug 2018 at 9:14 PM, sharathkcu forum@sefindia.org (forum@sefindia.org))> wrote:

Quote:
           Dear Kumaresan,

According to IS 1893:2016 part 1 table 6, if floating column is part of primary lateral load resisting system, it is prohibited to use. Otherwise if it's only to resist gravity loads, you can design it as a conventional column using IS 456:2000.


On Thu, Aug 9, 2018, 12:51 PM r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co)) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co))) forum@sefindia.org (forum@sefindia.org) (forum@sefindia.org (forum@sefindia.org)))> wrote:

      --auto removed--
     



     




Posted via Email
Back to top
View user's profile Send private message
mohd_arastu
SEFI Regulars
SEFI Regulars


Joined: 21 Dec 2011
Posts: 24
Location: Delhi

PostPosted: Thu Aug 09, 2018 5:30 pm    Post subject: Floating Column Reply with quote

Dear Kumaresan


Read the clause 5.5 of IS 13920:2016


Buildings with floating columns and set back columns perform poorly, when any such irregularities are adopted, detailed nonlinear analyses shall be performed to demonstrate that there is no threat to lss of life and property.

On Thu, Aug 9, 2018, 9:13 PM sharathkcu <forum@sefindia.org (forum@sefindia.org)> wrote:

[quote]            Dear Kumaresan,

According to IS 1893:2016 part 1 table 6, if floating column is part of primary lateral load resisting system, it is prohibited to use. Otherwise if it's only to resist gravity loads, you can design it as a conventional column using IS 456:2000.


On Thu, Aug 9, 2018, 12:51 PM r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co)) forum@sefindia.org (forum@sefindia.org))> wrote:

      --auto removed--

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


Joined: 22 Jul 2015
Posts: 5

PostPosted: Thu Aug 09, 2018 7:30 pm    Post subject: Floating Column Reply with quote

Hi,Why to discourage someone from designing some adventurous designs? You may suggest that even if you design a floating column, the deflection check may make the structure uneconomical. 


On Thu 9 Aug, 2018, 10:22 PM sangeeta_wij, <forum@sefindia.org (forum@sefindia.org)> wrote:

Quote:
           First of all, a floating column is really not a column and secondly, never ever use it in a seismic zone III IV or V structure as even the gravity columns have to be checked for deflection compatibility as   Stated in the relevant clause of 1893. However, my sincere suggestion is to delete the terms like hidden beams and floating columns from your vocabulary as far as seismic design is concerned.

Regards
Sangeeta Wij
On Thu, 9 Aug 2018 at 9:14 PM, sharathkcu forum@sefindia.org (forum@sefindia.org))> wrote:

Quote:
           Dear Kumaresan,

According to IS 1893:2016 part 1 table 6, if floating column is part of primary lateral load resisting system, it is prohibited to use. Otherwise if it's only to resist gravity loads, you can design it as a conventional column using IS 456:2000.


On Thu, Aug 9, 2018, 12:51 PM r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co)) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co))) forum@sefindia.org (forum@sefindia.org) (forum@sefindia.org (forum@sefindia.org)))> wrote:

      --auto removed--
     



     




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


Joined: 08 Sep 2010
Posts: 2

PostPosted: Thu Aug 09, 2018 7:30 pm    Post subject: Floating Column Reply with quote

Dear Kumeran,

The new seismic code says the contribution of lateral force due to seismic force in floating column should not be considered but it insist to introduce outer core RCC wall and also it should be designed for greater than 90 percentage of seismic force of total force.I hope you will understand my reply.
Sent from Yahoo Mail on Android

[quote]  On Thu, 9 Aug 2018 at 21:12, sharathkcu
<forum@sefindia.org> wrote:

           Dear Kumaresan,

According to IS 1893:2016 part 1 table 6, if floating column is part of primary lateral load resisting system, it is prohibited to use. Otherwise if it's only to resist gravity loads, you can design it as a conventional column using IS 456:2000.


On Thu, Aug 9, 2018, 12:51 PM r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co)) forum@sefindia.org)> wrote:

      --auto removed--

Posted via Email
Back to top
View user's profile Send private message
Dr. N. Subramanian
General Sponsor
General Sponsor


Joined: 21 Feb 2008
Posts: 5538
Location: Gaithersburg, MD, U.S.A.

PostPosted: Thu Aug 09, 2018 8:38 pm    Post subject: Re: Floating Column Reply with quote

I wish to appreciate Er. Sangeeta Wij for giving the correct advice.

Columns should spring from the foundation concrete, which is well spread and transfers all the loads and moments to the earth below, through the well designed and detailed foundation system. But the so called "floating columns"(which were basically invented by the architects in order to fulfill their crazy ideas, without considering the structural implications) are springing from narrow, may be deep beams. When there is an earthquake or lateral load, enormous amounts of moments and shear are transferred at the joint of this floating column and supporting beam, which has to be resisted by the beam supporting it. The moments will cause heavy torsion on the beam. Hence in several past earthquakes the frames with floating columns have failed. The torsion may be reduced by cross-beam provided at this point of the same depth, but will complicate the joint reinforcement detailing.

The practice of floating columns in the upper storeys is very common in the cities in India. Close-up view shows shear cracks in the cantilever stub beam supporting a floating column in a 4-storey RC frame residential building in Ahmedabad                               (Source: http://www.iitk.ac.in/nicee/EQ_Reports/Bhuj/build_rc1.htm).

In the previous versions of IS 1893(Part 1) there was no mention of floating columns. To be honest, I heard of these terms, floating column and hidden beams only when I practiced with architects. But the committee of the present version (2016) of the code realized the danger of floating columns and hence mentioned it specifically in pp.16,Table 6, item (vi), and prohibits its use. The code considers it as a vertical irregularity. It has to be noted that the load path is disturbed when we have floating columns.

Of course in non-seismic zones, the floating column may not pose much danger, but the joint has to be properly designed and detailed.

The beams have flexural strength only when they have adequate depth. Hence the so called " hidden beams" or "concealed beams", which have a depth equal to the slab depth, which may in practical cases will vary from 100 mm to 150 mm, will not have enough flexural strength. Hence they  may be used only when the span is very small, say 6 to 6.5 feet. See also Section 5.11 of my RC Design book, OUP, 2013.

Best wishes
Subramanian

[quote="sangeeta_wij"]First of all, a floating column is really not a column and secondly, never ever use it in a seismic zone III IV or V structure as even the gravity columns have to be checked for deflection compatibility as   Stated in the relevant clause of 1893. However, my sincere suggestion is to delete the terms like hidden beams and floating columns from your vocabulary as far as seismic design is concerned.

Regards
Sangeeta Wij
On Thu, 9 Aug 2018 at 9:14 PM, sharathkcu <forum> wrote:

Quote:
            Dear Kumaresan,

According to IS 1893:2016 part 1 table 6, if floating column is part of primary lateral load resisting system, it is prohibited to use. Otherwise if it's only to resist gravity loads, you can design it as a conventional column using IS 456:2000.


On Thu, Aug 9, 2018, 12:51 PM r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co)) forum@sefindia.org (forum@sefindia.org))> wrote:

      --auto removed--

Posted via Email


Back to top
View user's profile Send private message
Dr. N. Subramanian
General Sponsor
General Sponsor


Joined: 21 Feb 2008
Posts: 5538
Location: Gaithersburg, MD, U.S.A.

PostPosted: Fri Aug 10, 2018 12:27 am    Post subject: Re: Floating Column Reply with quote

[quote="Dr. N. Subramanian"]I wish to appreciate Er. Sangeeta Wij for giving the correct advice.

Columns should spring from the foundation concrete, which is well spread and transfers all the loads and moments to the earth below, through the well designed and detailed foundation system. But the so called "floating columns"(which were basically invented by the architects in order to fulfill their crazy ideas, without considering the structural implications) are springing from narrow, may be deep beams. When there is an earthquake or lateral load, enormous amounts of moments and shear are transferred at the joint of this floating column and supporting beam, which has to be resisted by the beam supporting it. The moments will cause heavy torsion on the beam. Hence in several past earthquakes the frames with floating columns have failed. The torsion may be reduced by cross-beam provided at this point of the same depth, but will complicate the joint reinforcement detailing.In addition, note that EQ loads change directions and due to this the shear strength of joint concrete may be lost, leading to failure.

The practice of floating columns in the upper storeys is very common in the cities in India. Close-up view shows shear cracks in the cantilever stub beam supporting a floating column in a 4-storey RC frame residential building in Ahmedabad                               (Source: http://www.iitk.ac.in/nicee/EQ_Reports/Bhuj/build_rc1.htm).

In the previous versions of IS 1893(Part 1) there was no mention of floating columns. To be honest, I heard of these terms, floating column and hidden beams only when I practiced with architects. But the committee of the present version (2016) of the code realized the danger of floating columns and hence mentioned it specifically in pp.16,Table 6, item (vi), and prohibits its use. The code considers it as a vertical irregularity. It has to be noted that the load path is disturbed when we have floating columns.

Of course in non-seismic zones, the floating column may not pose much danger, but the joint has to be properly designed and detailed.

The beams have flexural strength only when they have adequate depth. Hence the so called " hidden beams" or "concealed beams", which have a depth equal to the slab depth, which may in practical cases will vary from 100 mm to 150 mm, will not have enough flexural strength. Hence they  may be used only when the span is very small, say 6 to 6.5 feet. See also Section 5.11 of my RC Design book, OUP, 2013.

Best wishes
Subramanian

sangeeta_wij wrote:
First of all, a floating column is really not a column and secondly, never ever use it in a seismic zone III IV or V structure as even the gravity columns have to be checked for deflection compatibility as   Stated in the relevant clause of 1893. However, my sincere suggestion is to delete the terms like hidden beams and floating columns from your vocabulary as far as seismic design is concerned.

Regards
Sangeeta Wij
On Thu, 9 Aug 2018 at 9:14 PM, sharathkcu <forum> wrote:

Quote:
            Dear Kumaresan,

According to IS 1893:2016 part 1 table 6, if floating column is part of primary lateral load resisting system, it is prohibited to use. Otherwise if it's only to resist gravity loads, you can design it as a conventional column using IS 456:2000.


On Thu, Aug 9, 2018, 12:51 PM r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co) (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co)) forum@sefindia.org (forum@sefindia.org))> wrote:

      --auto removed--

Posted via Email


Back to top
View user's profile Send private message
SATYAPAUL
General Sponsor
General Sponsor


Joined: 18 Sep 2008
Posts: 127

PostPosted: Fri Aug 10, 2018 3:30 am    Post subject: Floating Column Reply with quote

I AM NOT REFERRING TO ANY CODE OF PRACTICE.PROVIDE HINGE EITHER AT TOP OR BOTTOM TO JUST TRANSFER  GRAVITY LOAD ONLY.OTHERS CAN ALSO THINK ABOUT THIS. SATYA PAL On Thu, 09 Aug 2018 22:21:10 +0530 "sangeeta_wij"  wrote >                   First of all, a floating column is really not a column and secondly, never ever use it in a  seismic zone III IV or V structure as even the gravity columns have to be checked for deflection  compatibility as   Stated in the relevant clause of 1893. However, my sincere suggestion is to delete  the terms like hidden beams and floating columns from your vocabulary as far as seismic design is  concerned. >  > Regards > Sangeeta Wij > On Thu, 9 Aug 2018 at 9:14 PM, sharathkcu wrote: >  > [quote]            Dear Kumaresan, >  > According to IS 1893:2016 part 1 table 6, if floating column is part of primary lateral load resisting  system, it is prohibited to use. Otherwise if it's only to resist gravity loads, you can design it as a  conventional column using IS 456:2000. >  >  > On Thu, Aug 9, 2018, 12:51 PM r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co)  (r.kumaresancivil@gmail.co (r.kumaresancivil@gmail.co)) forum@sefindia.org (forum@sefindia.org))>  wrote: >  >       --auto removed-- >       > >  >  > --

Posted via Email
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 Previous  1, 2, 3, 4, 5
Page 5 of 5

 

 
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