Two topics of practical significance are discussed : (a) The widely-held perception, reflected in a]4h5kJ';
most seismic codes, that soil-structure interaction (SSI) plays invariably a beneficial role ( and thus LAjre C<W
can be ignored in design to be on the safe side) is shown to be the result of a misconception J]4pPDm
stemming from the shape of current design response acceleration spectra for soft/deep soil + rN&@}Jt.
conditions. Properly normalising the structural period by a dominant period of motion before :JD*uu
statistically processing recorded response spectral values, produces completely different shape and ~Kiu "
g
size of spectral ordinates ; thus an increased period due to SSI may lead to higher response. _|f_%S8a_=
(b) Analytical, experimental and field evidence in recent years has started revealing that seismic <4%cKW0
design of shallow foundations could overcome the strict limitations of the so-called “capacity {$ P')> /
design”, by allowing significant sliding, uplifting, and even mobilisation of bearing–capacity ;,7/> Vt
failure mechanisms to occur. It is shown that under seismic conditions such dynamic inelastic– <!G%P4)
nonlinear response may merely lead to acceptable permanent horizontal and rotational al@Hr*'
deformations.
