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Daily Digest Tue Sep 28 23:00:03 2004

 
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ibarua
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PostPosted: Thu Sep 30, 2004 2:26 am    Post subject: Daily Digest Tue Sep 28 23:00:03 2004 Reply with quote

29 September, 2004

Re.: Masonry infill walls
--------------------

The pointraised by Amit Dutt deserves attention. When and how do we account for the added stiffness from infill walls, and when do we ignore it?

Do we take into account the stiffness of 5" (half brick thick) walls with say 25-30% window openings, but with a lintel band at say 2.1 m height from FFL? Will the story stiffness be the same if the walls were 10" or full brick thick?

Indrajit Barua
Guwahati, Assam.

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sdec.in
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PostPosted: Thu Sep 30, 2004 5:48 am    Post subject: Daily Digest Tue Sep 28 23:00:03 2004 Reply with quote

Well obviously, the siffness of thicker walls will be higher, but the
imp question as rightly pointed out by you is whether or when to
consider brick infills in storey stiffness for the purpose of
determination of soft storey.
I would like to narrate a conv that I shared with an EQ expert frm
Roorkee:
He told me that the infill panels are to be considered after
approximately comparing the length of masonry walls, as a thumb rule so
that the diff in stiffness can be determined and a soft storey
confirmed. However, this will hold good only if frame stiffness is
similar on the floors; if not then the 2.5 times EQ moments rule needs
to be applied.
Can Dr S K Jain throw more light on this pl.?
Sangeeta

-----Original Message-----
Message From  ibarua@deguild.com [mailto:ibarua@deguild.com]
Sent: Thursday, September 30, 2004 8:26 AM
To: sdec@bol.net.in
Subject: Daily Digest Tue Sep 28 23:00:03 2004



29 September, 2004

Re.: Masonry infill walls
--------------------

The pointraised by Amit Dutt deserves attention. When and how do we
account for the added stiffness from infill walls, and when do we ignore
it?

Do we take into account the stiffness of 5" (half brick thick) walls
with say 25-30% window openings, but with a lintel band at say 2.1 m
height from FFL? Will the story stiffness be the same if the walls were
10" or full brick thick?

Indrajit Barua
Guwahati, Assam.

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skjain.iitk
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PostPosted: Fri Oct 01, 2004 6:52 pm    Post subject: Daily Digest Tue Sep 28 23:00:03 2004 Reply with quote

Very interesting issue from Mr. Barua.

The stiffness contribution will depend on the thickness of the wall.
More the thickness, more the stiffness.

For openings, you will have to reduce the stiffness. An empirical value
based on a parametric study by a student at IITK gave that the
lateral stiffness of infill can be ignored if the opening area is
40% or more of the wall area in elevation.

Mr. Barua mentions of a lintel band: I have seen in the north-eastern
part of the country, lintel bands being provided in RC Frame building.
Do we really need those? I do not think those are needed for ordinary
apartment type buildings with small spans and small storey height.
Moreover, the lintel bands means interruption of casting of column
concrete and if not done well, it could weaken the columns. Any
suggestions?

Best regards,

Sudhir K Jain

On Thu, 30 Sep 2004 ibarua@deguild.com wrote:

Quote:


29 September, 2004

Re.: Masonry infill walls
--------------------

The pointraised by Amit Dutt deserves attention. When and how do we account for the added stiffness from infill walls, and when do we ignore it?

Do we take into account the stiffness of 5" (half brick thick) walls with say 25-30% window openings, but with a lintel band at say 2.1 m height from FFL? Will the story stiffness be the same if the walls were 10" or full brick thick?

Indrajit Barua
Guwahati, Assam.









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