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INNOVATIVE GROUND INTERFACE CONCEPTS FOR STRUCTURE PROTECTION

Periodic Reporting for period 1 - INSPIRE (INNOVATIVE GROUND INTERFACE CONCEPTS FOR STRUCTURE PROTECTION)

Reporting period: 2019-03-01 to 2021-02-28

INSPIRE is an ambitious research programme which aims to foster a new generation of highly qualified researchers and engineers through an ensemble of research, training and dissemination actions. As a whole, the research produced during the projects aims to implement a holistic and novel soil-foundation-structure concept for the efficient protection of structures from all ground induced hazards, including earthquakes and all other sources of low-frequency noise and vibration excitations.
The key concept investigated in the project is that of meta-materials, natural or artificial materials or structures generated by periodically repeated unit blocks which exhibit extraordinary properties for inhibiting or conditioning wave propagation in all spatial directions over broad frequency bands.
The INSPIRE training programme will equip researchers with innovative and creative skills, implementing a joint multidisciplinary research training programme focused on the growth of scientific and technological knowledge and professional skills through research on individual, personalized projects. The project will be crucial for European innovation capacity as each one of the eleven participating companies will directly support a specific high-impact technological application, which can lead in directly exploitable new structure protection technological products or patented design concepts, tools and procedures in a market the global size of which is expected to reach USD 11.72 trillion by 2025. INSPIRE will create a legacy for the future generations of researchers, with training material and relationships with companies offering secondment opportunities for further cohorts of students outside of the project. Furthermore, apart from their research and development leadership in Europe, the Fellows will maintain their connection to the programme by developing parallel training for researchers in their organisations and even making this programme part of the graduate training scheme for industrial partners.
RESEARCH
To date, 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:
• 7 out of 15 ESRs have completed at least one secondment in another academic INSPIRE team and one in a non-academic partner. It is noted that due to the pandemic, the secondments plan has been updated to account for travel restrictions.
• 3 ESRs of the INSPIRE project have already spent at least 3 months at one of the industrial partners within secondment in industry-focused research skills, especially in research management, exploitation of research and Intellectual Property Rights.
• 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 have been the series of internal webinars organized as four half-day sessions each dedicated to research exchange among the consortium and a group of 3-4 ESRs.
• Two Training schools have already been held prior to annual meetings (where members of the network will exchange information and consolidate their collaboration). Both were open to external participants, especially those with an industrial background. Training schools have been very widely advertised within the relevant scientific community in order to attract a variety of young researchers, as well as to European enterprises, when appropriate, to enhance the knowledge transfer capability of the INSPIRE project.
INSPIRE will incorporate scientific and technological breakthroughs, mainly developed within the broad concept of meta-materials, to propose and implement holistic and novel soil-foundation-structure concepts for the efficient protection of structures from ground induced hazards. Expected results include:
• Interventions to the foundation soil intended to divert seismic waves or substantially attenuate the earthquake motion before exciting the structure.
• Broad-band isolation concepts incorporating negative stiffness inclusions and engineered microstructures of hyper-damping behavior aiming at high impact – infrastructure components.
• Urban scale soil-foundation-structure schemes integrating combinations of meta-concepts to provide seismic protection at a community level.
Schematic presentation of the INSPIRE concept