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[abhyankar]

To, Mr. Rajedra,

In STAAD analysis the results vary as per the support condition i.e. fixed
or pinned. But to specify the type of support for any base of the column one
must know the following data:
1) Type of soil at the site - sandy / clayee or rock
2) Type of foundation system - Raft / Isolated footing / Pile foundations

Usually for very tall buildings, structural engineers require pile
foundation (subject to type of strata). Even the piles are classified as -
flexible / rigid. Based on this data one may define the support condition.
But in practice hardly one get the above data. Hence he may proceed with
'FIXED' support condition in case of pile foundations.

In case of Isolated footing if it is to be designed for axial load in
addition to the bi-axial moments then the size required may be higher. Hence
there is a tendency to reduce down the design moment on the isolated
footing. The lower design moments are obtained by specifying the support as
“松”。你的问题,我们设计footing as unsafe. The
answer is 'NO' because when we define the isolated footing as 'PINNED' the
same time the design moments in the column increase than the 'FIXED'
condition. Thus the overall safety is unaffected.

Note that this whole process is a matter of 'PROPER JUDGEMENT AND
EXPERINCE'. While seating in office we may not be able to do this task
correctly. Hence in case of important projects we must consult
GEOTECH-EXPERTS and other experts in STRUCTURAL ENGINEERING.

In case of flexible strata & flexible footings one may have to go for
'SPRING' type of footing. The results are very sensitive to the type of
support.

Regards
V. G. Abhyankar
(Design Engineer-HCC)

From: Rajendar
To:admin@www.buonovino.com
Sent: 24 November, 2003 10:17 AM

Hello,

How can have to give support conditions for multistoried buildings(Fixed or
hinged) at footing and column joint,using STAAD Analysis.please give reply
any one knows, because I am new for STAAD.

-Regards



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Hindustan Construction Company, Mumbai, India

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