www.sefindia.org

[k.gangadharan]

SUB: econference on tall buildings
        foundation design of tall buildings
When designing high rise buildings is it necessary to model the
foundation also along with the model of the superstructure to get a
clear picture & understanding of  the behaviour of the structure and &
its mode shapes during earthquake.
Normally for tall buildings, piled raft foundations are adopted.What
are the parameters of the soil and the piled raft along with the
structural model required for such an analysis.
Is there any software to do a combined analysis for the structure.and
its foundation together.
Alternately can we model the structure with a fixed base resting on
the piled raft and do a 3-D analyse using our preferred software for earthquakeand wind analysis with  other combinations of dead  and imposed
loads.After analysing the structure , we can import the reactions.at
the bottom of the column  to the piled raft and do a second analysis
for the piled raft for all load combinations and design the piled
raft.
For analysis of the piled raft, there are softwares available like
SAFE or any other similar software.A FE analysis of the raft with
spring constants for pile support can be done.
The exact length of the piles may be difficult for the initial
analysis as this can be determined only after the completion of the
piling work.
What is the best option and the correct method, experts can offer
their remarks..

regards

K.gangadharan
Structural consutant
econferenceee