Two topics of practical significance are discussed : (a) The widely-held perception, reflected in ]HK|x O(
most seismic codes, that soil-structure interaction (SSI) plays invariably a beneficial role ( and thus 2 R !1Vl
can be ignored in design to be on the safe side) is shown to be the result of a misconception i<*{Z ~B
stemming from the shape of current design response acceleration spectra for soft/deep soil [BpIzhy&}
conditions. Properly normalising the structural period by a dominant period of motion before *c+Kqz-
statistically processing recorded response spectral values, produces completely different shape and Qf|=xV,F
size of spectral ordinates ; thus an increased period due to SSI may lead to higher response. jz%%r Q(
(b) Analytical, experimental and field evidence in recent years has started revealing that seismic /{';\?w
design of shallow foundations could overcome the strict limitations of the so-called “capacity i0%S6vmaS
design”, by allowing significant sliding, uplifting, and even mobilisation of bearing–capacity Tc DkKa
failure mechanisms to occur. It is shown that under seismic conditions such dynamic inelastic– 7aJLC!
nonlinear response may merely lead to acceptable permanent horizontal and rotational 8_S<zE`Ha
deformations.
