Research interest: vision
Besides
inside the structure, look around it.
Actions on civil structures have to
be carefully modelled, because generally they are not deterministic quantities.
Hence their design values come from statistic analysis, where the action is
viewed as a random variable or a stochastic process. In other terms, the
physical system that produce the action energy – the exciting system in the
following – is not studied from a mechanical point of view. The universe of
interest is than restricted to the civil structure and the action is treated as
one of its boundary conditions. This approach is often justified by the fact
that:
- the
energy source is far from the structure;
- the
characteristic length and/or time scales of the exciting system are very
different from the ones of the civil structure;
- the
parameters of the exciting system governing laws are too many, randomly varying
or simply unknown;
- the
knowledge of the mechanical behaviour of the exciting system is of scarce
interest in the design process;
- the
exciting and structural systems can be assumed with good accuracy as uncoupled.
For instance, the study of the
structural dynamic response to the earthquake or to the gusty wind generally
falls under these conditions, so that the ground acceleration or the wind
velocity can be described by their power spectral density, disregarding the
mechanical behaviour of the systems which produce them.
In some other cases, the conditions
stated above do not longer hold: the energy source is around the structure or
even very close to it, the exciting and structural systems share common
characteristic length and time scales, the knowledge of the exciting system can
inspire new design solutions to suppress its energy or to mitigate its effects
on structures, they are coupled in the sense that the response of the former is
the excitation of the latter and vice versa.
Fluid-structure interaction belongs
to this class of problems: for instance, most of the aerodynamic and
aeroelastic phenomena in civil engineering but also sloshing problems for
reservoirs or hydrodynamic problems for bridge piers. Other coupled system of
interest for structural engineering refers to soil-structure interaction or
crowd-structure interaction.
In these cases, it is recommended to
characterise the mechanical behaviour of the exciting system, even if its
modelling is far from an easy task and/or it cannot be ascribed to the solid
mechanics, so that a multi-physics modelling and specific competences in both
structural dynamics and other disciplines are required.
In situ measurements or laboratory tests,
although possible and required for validation purposes, are difficult to be
performed for such kind of coupled multiphysical phenomena. The computational
approach can represents an effective complementary tool because similitude
requirements are easy to be fulfilled and accurate parametrical studies can be
performed in both physical or unphysical conditions in order to point out the
role of a single design parameter on the overall mechanical response.