The response of a structure and the characteristic of foundation medium confer
the interactive behavior of the system. During an earthquake, seismic waves are
transmitted through soil from the origin of disturbance to the structure, the wave motion of
the soil excites the structure, which in turn modifies the input-motion by its
movement relative to the ground. This interaction phenomenon is called
soil-foundation-superstructure interaction or simply soil-structure interaction (Wolf, 1985).
The interaction phenomenon is generally affected by the mechanism of
energy exchange between the soil and the structure, and the primary influence on the
building is to modify the natural period of vibration and hence the response in terms
of stress and strain (Chopra, 2003).
An analysis for estimating the dynamic response of a structure, including
soil-structure interaction, generally involves the application of such methods
as elastic wave propagation method, finite element method and the
mass-spring method. A perfect bond at the contact surface between the soil and structure
is assumed in all these methods. Depending on the material properties of the
soil medium, the source of dynamic excitation and the particular type of
foundation considered, the response of the structural system can be quite different.
Soil structure interaction represents an integrated system. However, this
complex problem is always analyzed in separate parts. This simplification is
generally necessary because of the intrinsic complexities of treating soil-structure
interaction as a whole, as each of the sub systems, by itself, represents a vast field of
possible mechanical idealization and a wide choice of physical and geometric
parameters (Wolf, 1985).
Two different approaches to the problem are commonly
found: (1) applying rigorous model to the super structure
where the soil is considered as a rigid base; and (2)
applying rigorous mechanical model to the soil without coupling it to
the superstructure just considering a raft on a simple
two-dimensional frame resting on the deformable soil (Chopra and Gutierrez,
1974). Dumanoglu and Severn (1976) worked on the influence of foundation media on
the response of the structure to earthquake, considering the spring
model. Wong and Luco (1978) studied the dynamic response of rectangular foundation to obliquely incident seismic
waves. Gupta and Penzien (1982) worked on developing
a hybrid model for the analysis of soil structure interaction under dynamic condition.
Further, studies on the effect of soil on the structure under wind and earthquake (Novak, 1974) as well
as on the soil-structure interaction due to damping
were also taken up (Novak and Hifnawy, 1983). Recently, Wang and Cheng
(2008) worked on the modal analysis for evaluating
the response of the structure. |
