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Query By Mr Mahadevan Iyer

 
This forum is locked: you cannot post, reply to, or edit topics.This topic is locked: you cannot edit posts or make replies.    www.sefindia.org Forum Index -> Past Discussions Year 2004
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jydesai1
SEFI Member
SEFI Member


Joined: 26 Jan 2003
Posts: 9

PostPosted: Mon Nov 01, 2004 6:12 am    Post subject: Query By Mr Mahadevan Iyer Reply with quote

Dear Mr Iyer

There are two cases of slabs with beams at ground level -



a) Slab supported by beams which transfer its load to the columns

b) Slab resting on the ground/compacted fill ("subgrade") below (Note:
If the subgrade due to some reason can't be compacted or its compaction
can't be reasonably controlled, it would be recommended to go for Case
a) above.



In the first case a) the slab with its load with masses as defined in
the Codes and elsewhere, will definitely transfer the inertial load of
these masses to the columns and should be treated as in case of other
upper floors for lumped mass-calculations and as an active diaphragm.
Essentially this becomes a part of the multi DOF lumped mass system.



In case b), the slab will be designed as "slab-on-grade". Since it does
not transfer its loads to the frame, it would not be correct to transfer
its inertia to the building frame. But, depending on the nature of its
connections to the columns, it may act as a horizontal passive diaphragm
and to that extent modify the horizontal response of the frame at this
level.



I would say one has to keep in mind the availability and limitations of
analytical modeling while detailing and selecting construction methods
to suit the design procedure.



J.Y.Desai



-----Original Message-----
Message From  general@sefindia.org [mailto:general@sefindia.org]
Sent: Monday, November 01, 2004 4:30 AM
To: J. Y Desai
Subject: Daily Digest Sun Oct 31 23:00:03 2004



----------------------------------------------------------

Message From  ibarua@deguild.com

Subject: Daily Digest Sat Oct 30 23:00:03 2004

Date: 31/10/04

Time: 08:16:23

----------------------------------------------------------



Re.: Query by Mahadevan Iyer

------------------------



If there is an RCC slab at the ground /parking floor level, then the
slab will be supported by the plinth beams, which will ib turn be
supported by the columns. The slab may transfer some or all the loads
imposed on it to the beams if the subgrade on which it rests settles, as
it is very much likely to, when loads are imposed upon it. Therefore,
such loads should be taken into account in the analysis.



I do not understand why a RCC slab has to be provided for the parking
area. Of course, plinth beams have to be provided; otherwise the ground
floor columns may behave as long columns, as it happened in some
buildings in Gujarat.



Indrajit Barua

Structural Engineer, Guwahati, Assam.



Dear sefians,



In a building if a slab alongwith plinth beams are

provided at the plinth level (for parking etc.)should

its seismic weight be lumped to the frame as is done

for higher floor levels?



Intuitively I feel that this should not be done, as the

said slab as well as beams transfer the load directly

to the soil.



The IS code (IS 1893-2002) does not address this issue.



I hope you will be kind enough to clarify.



MAHADEVAN IYER

M.Tech (Structural Engg.)(3rd Sem.)

V.N.I.T. Nagpur.

;nbsp;





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----------------------------------------------------------

Message From  anjandas1@sancharnet.in

Subject: solution to rectify the loose compaction of casting in rcc
retaining

wall of basement floor.

Date: 31/10/04

Time: 20:20:51

----------------------------------------------------------

Hi,

I am facing one retrofitting problem in newly constructed
basement floor.

Problem is something like this:

the r.c.c. retaining wall of small basement floor, which is recently
constructed, seems that water is leaking through out the retaining wall
upto 1200mm level . matter may be due to less compaction of casting.

now, question is how to rectify the same.

if anybody know the solution, it will be highly helpfull for me.



----------------------------------------------------------



----------------------------------------------------------

Message From  anjandas1@sancharnet.in

Subject:

Date: 31/10/04

Time: 20:22:47

----------------------------------------------------------

Hi,

I am facing one retrofitting problem in newly constructed
basement floor.

Problem is something like this:

the r.c.c. retaining wall of small basement floor, which is recently
constructed, seems that water is leaking through out the retaining wall
upto 1200mm level . matter may be due to less compaction of casting.

now, question is how to rectify the same.

if anybody know the solution, it will be highly helpfull for me.



----------------------------------------------------------

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