Two topics of practical significance are discussed : (a) The widely-held perception, reflected in 7 `c!
most seismic codes, that soil-structure interaction (SSI) plays invariably a beneficial role ( and thus Pt-O 1$C[
can be ignored in design to be on the safe side) is shown to be the result of a misconception :C,}DyZy
stemming from the shape of current design response acceleration spectra for soft/deep soil R|Uu
conditions. Properly normalising the structural period by a dominant period of motion before -pQ?ybQ
statistically processing recorded response spectral values, produces completely different shape and r)Ml-r =
size of spectral ordinates ; thus an increased period due to SSI may lead to higher response. -C!m#"PDW
(b) Analytical, experimental and field evidence in recent years has started revealing that seismic _u6MSRX[6$
design of shallow foundations could overcome the strict limitations of the so-called “capacity 4%JJ} {Ff
design”, by allowing significant sliding, uplifting, and even mobilisation of bearing–capacity P4|A\|t
failure mechanisms to occur. It is shown that under seismic conditions such dynamic inelastic– UQ@szE
nonlinear response may merely lead to acceptable permanent horizontal and rotational 141 xi; o
deformations.
