RESEARCH
Several infrasound wave conditioning concepts have been examined demonstrating the wave screening properties of meta-materials:
A) Pile arrays and foundation blocks: Work is being undertaken in developing systems able to trap low frequency waves and have wide band-gaps (0.5Hz-5.0Hz) required to mitigate the effects of seismic waves Such performance cannot be met by the currently proposed designs of seismic meta-material unit cell concepts.
B) Trapped rainbows: Work has been focused on developing efficient near- and on-surface meta-material concepts against Rayleigh surface waves.
C) Meta-material on a city scale: Work has focused on developing city-scale inelastic time-domain analysis tools and models to evaluate the effectiveness of the proposed meta-soils , as part of the design of a conceptual “Meta-City”.
A common characteristic of the concepts examined - and a major objective of the project indeed - is to prove simple, reliable and resilient meta-soil designs, leading to easy and low-cost implementation and maintenance to make use of meta-soils possible in both developed and developing countries with high seismic risks
Furthermore, a class of novel absorption and isolation concepts have been investigated:
A) Negative Stiffness Dampers (NSD): Work produced already has confirmed that the concept features not only enhanced wave damping, but also extended band-gaps, especially for seismic and low-frequency acoustic applications.
B) Micro-structured materials under frictional forces and self-oscillatory behaviour: Bifurcation phenomena - such as buckling and in flutter instability - guide the development of new technological concepts and tools for novel isolators in classical foundations. Inspired by elastic meta-materials with inertial locally resonant structures, nonlinear structures are designed with non-propagation frequencies in the infrasound range.
C) Meta-Columns: Vertically supported slender bodies. The concepts have already been implemented in designing systems that can protect structures from seismic shaking by promoting rocking behavior.
D) Meta-Panels: Mitigation measures at the receiver (building): Research on this topic has been focused on developing sound absorption panels incorporating negative stiffness inclusions and disordered phononic approaches.
The following meta-structures are currently under examination:
A) Meta Pipes: A class of meta-material-based solutions are currently under investigation, to protect underground pipes from seismic events.
B) Meta-Gravel: Research is focused on metamaterial concepts that can lead to superior behavior in blast/shock impacts.
C) Meta-Bridges”, traffic-ways and transportation: Research emphasis has been on bridge pier foundations, focused on the concepts of rocking and negative-stiffness dampers..
D) Meta-Rail/A novel paradigm for rail tracks: Meta-materials and novel absorbers are currently being considered in order to control dynamic excitations from high loaded trains.
TRAINING
At an individual level, each ESR has established a Personal Career Development Plan in coordination with their supervisor, tailored to their career goals. At the network level, each ESR has completed the following actions:
• All ESRs have completed at least one secondment in another academic INSPIRE team and one in a non-academic partner.
• 2 ESRs have spent 6 months at leading academic institutions in the United States, namely the California Institute of Technology and the University of California, Davis.
• Several Network meetings have been organized for ESRs to present their results, exchange ideas and experiences and discuss secondments between members. Most notable among them has been the organization of a Special Session titled “Innovative ground interventions and metamaterial concepts for structure protection” during the International Conference on Natural Hazards and Infrastructure (ICONHIC 2022).
• Three Training schools and three multi-disciplinary development and innovation workshops have been delivered, with more than 150 participants from 12 countries and featuring a diverse selection of lectures and seminars from worl renowned academics and industry leaders.
