International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 08 Issue: 03 | Mar 2021
p-ISSN: 2395-0072
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EFFECT OF SOIL STRUCTUE INTERACTION ON SEISMIC RESPONSE OF FRAMED STRUCTURE JAJULA NARESH 1, BEERAIAH 2 1M.Tech
(Structural Engineering), 2Assistant Professor (Civil Engineering Department) Priyadarshini Institute Of Technology & Management Guntur A.P. ----------------------------------------------------------------------------***-------------------------------------------------------------------------ABSTRACT :- Seismic response of structures is quite
response during an earthquake is arrived at based on
complex because of the randomness in loading and
national classification of soil. Such a study is relevant in the
complexity in modelling. Framed structures are usually
context of designers moving from ductility based design to
analysed assuming a fixed-base structure while ignoring
performance based design.
the flexibility of soil and foundation. Seismic codes permit
Keywords: soil structure interaction (SSI) static analysis,
to compute seismic forces depending upon the nature of
response spectrum analysis (RSA), fixed base, modal
soil classified into three categories viz, soft, medium and
analysis, soil spring, elastic continuum, fixed base, seismic
rock. The interaction between the super-structure and
response.
sub-structure (SSI) is investigated by modeling the soil as
INTRODUCTION
elastic continuum. Soil property in terms of G (Shear
During an earthquake the dynamic response of a structure
modulus) and ν (Poisson’s ratio) is taken to find the soil
depends on the characteristics of ground motion,
stiffness in all six directions. The value of G and ν are taken
surrounding soil medium, its properties and the structure
based on the classification given by IS 1893 and other
itself. The process by which the response of the soil
international references. These values are then used to
influences the motion of the structure and the response of
compute the stiffness in all the six degrees of freedom. The
soil is termed as soil structure interaction (SSI). The
broad classification as given by international codes and
seismic soil structure interaction of multi-story buildings
their influence in estimating the seismic forces are
becomes very important after the destruction structures in
investigated. The effects of soil- structure interaction on
major earthquakes.
the seismic response of framed structures with 6 storeys
Usually in the seismic design of framed buildings,
have been considered with base supported as fixed base
soil structure interaction is neglected and the dynamic
and ignoring the flexibility of soil. The same was repeated
response of the structure is evaluated under the
for different soil conditions. As per IS1893 and other
assumption of a fixed or a hinged base response. The
international codes the structure is analysed in both static
period of vibration of the structure is calculated based on
and Response Spectrum Analysis (RSA). The static and
this assumption and the seismic loads are evaluated.
dynamic response results are compared. The modal
However, during actual seismic loading the soil undergoes
analysis has been done to get deformation and natural
deformations or settlements, which are imposed to the
mode of vibration with its own modal damping ratio. The
foundation, and also due to the actual soil parameters, the
effect of such soil structure interaction on the overall
period of vibration of the structure increases. The increase
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