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Load Transfer

 
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kvsscivil
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Joined: 26 Jan 2003
Posts: 15

PostPosted: Fri Oct 08, 2004 7:52 am    Post subject: Load Transfer Reply with quote

Dear Friends

In one of my projects, I have to support a column of size 250 x 900mm on a 400 x 800mm size column below. The transition is coming at 5th floor of a 30 storied building. The longer dimension of the above column is having an equal offsets on either side of the longer dimension of the column below. For the column design at 6th floor (above the transition), what size of column shall be taken? Should I have to take only the bearing area ( contact area) available for the column at below? or can I take the actual size of above column? I cannot provide any corbels, etc. for smooth transfer of load because of architectural reasons. But by sloping down the reinforcement bars from column above to below in 1 in 6, can we ensure the smooth load transfer? Please comment.

Thanks / Regards,

Sudhakar


          
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PostPosted: Fri Oct 08, 2004 9:11 am    Post subject: Load Transfer Reply with quote

Let's summarize ... the section of your column upto 5th lvl  (let's say 15
mts lvl. ) is 400x800 & you need to provide a column section above that with
a cross section of 250x900 .. right ? Okay now considering that it's
feasible , what I'll suggest you is something like this ... Design the
column above 5th lvl till 6th lvl , i.e: from 15 mts lvl to 18 mts lvl
assuming a cross section of 250x800 ( and not as 250x900) , for appropriate
design forces as obtained from Analysis. And at 5th lvl  (where the
transition is taking place ) , you don't bend/slope  the main column
reinforcements which are available from below i.e. which are coming from 4th
lvl say 12 mts lvl.
Column section above 6th lvl can be designed as 250x900 , and column
reinforcements can be suitably adjusted at 6th lvl.
But then you have do some good joint detailing exercise regarding such
situation. Your idea should be that the joint where the transition is taking
place musnot be a weak joint.

There can be other ways also . So better do some RnD on this before
implementing anything and also consult some much experienced people.



Regards
Malay

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PostPosted: Fri Oct 08, 2004 2:12 pm    Post subject: Load Transfer Reply with quote

1. For the column design at 6th floor (above the transition), what size of column shall be taken?:

You have to design for bottom moment of column at fifth floor for size of 250x900 and for top moment of fourth floor roof for 400x800.

2. Should I have to take only the bearing area ( contact area) available for the column at below?
Normally in such high storied buildings bearing will not be crucial for the column at higher level ( i.e, 250x900) and will not be a problem for 400x800 as the full load will not be present at fifth floor level.

3. I cannot provide any corbels, etc. for smooth transfer of load because of architectural reasons. But by sloping down the reinforcement bars from column above to below in 1 in 6, can we ensure the smooth load transfer?

By providing 1:6 slope bent, we can provide smooth flow.


Thanks/ Regards,

K. Surya Prakash


-----Original Message-----
Message From  kvsscivil@yahoo.com [mailto:kvsscivil@yahoo.com]
Sent: Friday, October 08, 2004 6:52 PM
To: Surya Prakash Karri
Subject: Load Transfer



Dear Friends

In one of my projects, I have to support a column of size 250 x 900mm on a 400 x 800mm size column below. The transition is coming at 5th floor of a 30 storied building. The longer dimension of the above column is having an equal offsets on either side of the longer dimension of the column below. For the column design at 6th floor (above the transition), what size of column shall be taken? Should I have to take only the bearing area ( contact area) available for the column at below? or can I take the actual size of above column? I cannot provide any corbels, etc. for smooth transfer of load because of architectural reasons. But by sloping down the reinforcement bars from column above to below in 1 in 6, can we ensure the smooth load transfer? Please comment.

Thanks / Regards,

Sudhakar


          
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kvsscivil
SEFI Member
SEFI Member


Joined: 26 Jan 2003
Posts: 15

PostPosted: Sat Oct 09, 2004 9:18 am    Post subject: Load Transfer Reply with quote

Dear All

As Mr. Surya Prakash mentioned, it is clear for what moments the columns
above and below the transition shall be designed ( at 5th and 6th
levels). And ofcoarse the corresponding vertical load shall be taken for
the design at respective levels and 1 in 6 slope will take care of the
load transfer.

But, in my problem I have column offset of 50mm on either side of column
below (at 5th level) over a slab thickness of 200mm. Just for academic
interest, what happens if the offset is quite large? say, 300mm of
more? Still bars in 1 in slope will transfer load to bottom? Is there
any limit beyond which we cannot transfer load from a larger dimensioned
column above to shorter dimensioned column below by sloping the bars?


Thanks / Regards,

Sudhakar



-----Original Message-----
Message From  ksp [mailto:ksp@lntecc.com]
Sent: Saturday, October 09, 2004 1:12 AM
To: sudhakar@trcintl.com
Subject: Load Transfer


1. For the column design at 6th floor (above the transition), what size
of column shall be taken?:

You have to design for bottom moment of column at fifth floor for size
of 250x900 and for top moment of fourth floor roof for 400x800.

2. Should I have to take only the bearing area ( contact area) available
for the column at below?
Normally in such high storied buildings bearing will not be crucial for
the column at higher level ( i.e, 250x900) and will not be a problem for
400x800 as the full load will not be present at fifth floor level.

3. I cannot provide any corbels, etc. for smooth transfer of load
because of architectural reasons. But by sloping down the reinforcement
bars from column above to below in 1 in 6, can we ensure the smooth load
transfer?

By providing 1:6 slope bent, we can provide smooth flow.


Thanks/ Regards,

K. Surya Prakash


-----Original Message-----
Quote:
Message From  kvsscivil@yahoo.com [mailto:kvsscivil@yahoo.com]
Sent: Friday, October 08, 2004 6:52 PM
To: Surya Prakash Karri
Subject: Load Transfer



Dear Friends

In one of my projects, I have to support a column of size 250 x 900mm on
a 400 x 800mm size column below. The transition is coming at 5th floor
of a 30 storied building. The longer dimension of the above column is
having an equal offsets on either side of the longer dimension of the
column below. For the column design at 6th floor (above the transition),
what size of column shall be taken? Should I have to take only the
bearing area ( contact area) available for the column at below? or can I
take the actual size of above column? I cannot provide any corbels, etc.
for smooth transfer of load because of architectural reasons. But by
sloping down the reinforcement bars from column above to below in 1 in
6, can we ensure the smooth load transfer? Please comment.

Thanks / Regards,

Sudhakar



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acpl_sefi
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Joined: 26 Jan 2003
Posts: 63

PostPosted: Sat Oct 09, 2004 1:35 pm    Post subject: Load Transfer Reply with quote

Dear All

If the column rebar have been sized such that columns are stronger than beams, then this will have to be rechecked where sizes of columns change--since effective depth & width will change just above & below floor due to the taper in the rebar as well as the size of column

Vipul  


On Sat, 09 Oct 2004 kvsscivil@yahoo.com wrote :
Dear All

As Mr. Surya Prakash mentioned, it is clear for what moments the columns
above and below the transition shall be designed ( at 5th and 6th
levels). And ofcoarse the corresponding vertical load shall be taken for
the design at respective levels and 1 in 6 slope will take care of the
load transfer.

But, in my problem I have column offset of 50mm on either side of column
below (at 5th level) over a slab thickness of 200mm. Just for academic
interest, what happens if the offset is quite large? say, 300mm of
more? Still bars in 1 in slope will transfer load to bottom? Is there
any limit beyond which we cannot transfer load from a larger dimensioned
column above to shorter dimensioned column below by sloping the bars?


Thanks / Regards,

Sudhakar



-----Original Message-----
Message From  ksp [mailto:ksp@lntecc.com]
Sent: Saturday, October 09, 2004 1:12 AM
To: sudhakar@trcintl.com
Subject: Load Transfer


1. For the column design at 6th floor (above the transition), what size
of column shall be taken?:

You have to design for bottom moment of column at fifth floor for size
of 250x900 and for top moment of fourth floor roof for 400x800.

2. Should I have to take only the bearing area ( contact area) available
for the column at below?
Normally in such high storied buildings bearing will not be crucial for
the column at higher level ( i.e, 250x900) and will not be a problem for
400x800 as the full load will not be present at fifth floor level.

3. I cannot provide any corbels, etc. for smooth transfer of load
because of architectural reasons. But by sloping down the reinforcement
bars from column above to below in 1 in 6, can we ensure the smooth load
transfer?

By providing 1:6 slope bent, we can provide smooth flow.


Thanks/ Regards,

K. Surya Prakash


-----Original Message-----
Message From  kvsscivil@yahoo.com [mailto:kvsscivil@yahoo.com]
Sent: Friday, October 08, 2004 6:52 PM
To: Surya Prakash Karri
Subject: Load Transfer



Dear Friends

In one of my projects, I have to support a column of size 250 x 900mm on
a 400 x 800mm size column below. The transition is coming at 5th floor
of a 30 storied building. The longer dimension of the above column is
having an equal offsets on either side of the longer dimension of the
column below. For the column design at 6th floor (above the transition),
what size of column shall be taken? Should I have to take only the
bearing area ( contact area) available for the column at below? or can I
take the actual size of above column? I cannot provide any corbels, etc.
for smooth transfer of load because of architectural reasons. But by
sloping down the reinforcement bars from column above to below in 1 in
6, can we ensure the smooth load transfer? Please comment.

Thanks / Regards,

Sudhakar



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