OBJECTIVES:

Provision of access to the following infrastructure(s):
SoFSI/EQUALS (UBRI) and STRULAB (UPAT) (joint, synchronous access for Hybrid Simulation)

Name of the infrastructure and its installations:
UKCRIC National Facility for Soil Structure Interaction (SoFSI) and EQUALS (hereafter: SoFSI/EQUALS RI) – STRULAB RI

Location (town, country) of the infrastructure:
Bristol, UK and University of Patras, Greece

Web site address:
https://sofsi.bristol.ac.uk and www.strulab.civil.upatras.gr

Reference contact for potential TA user groups:

Anastasios Sextos – a.sextos@bristol.ac.uk

George Mylonakis – G.Mylonakis@bristol.ac.uk

DESCRIPTION OF THE INFRASTRUCTURE:
This WP refers to a joint access to two RIs (UBRI-UPAT) for conducting geographically distributed Hybrid Simulation (HS), to enable collaborative research across geographical boundaries and support blue sky, curiosity-driven research irrespective of location. Hybrid Simulation (HS) is a novel multi-site, on-line, computer-controlled integrated testing-analysis scheme, where part of the structural system of interest can be simulated numerically, while other sub-components (i.e., typically the ones with the most critical or nonlinear behavior), are tested physically. Hybrid Simulation combines the most attractive features of both testing and analysis, to provide test results of enhanced reliability even for very complex structures and infrastructure. The numerical to physical coupling is achieved via a transfer system comprising of a test frame (e.g., UPAT), a soil pit (e.g., UBRI) or other entities, actuators, sensors and an interface analysis coordination program which links the physical part to the numerical one. The main advantage of this coupled experimental and computational approach is that different equipment and experimental infrastructures, but also different analysis platforms can be combined to realistically study the response of complex systems to environmental loads that would be impossible to be explored within a single facility.
STRULAB is among the few European laboratories employing the hybrid simulation method with distributed hybrid simulation, comprising international participation. SoFSI/EQUALS on the other hand, is a node of the UK Network for Earthquake Engineering Simulation (UK-NEES), which forms part of the world wide NEES. NEES promoted for years participation of remote users in experiments via high performance video conferencing and, where appropriate, direct interactivity and control of test and data acquisition equipment, enabling senior researchers to interact remotely with their junior staff at the lab. Examples of successful UBRI and UPAT RIs involve local Hybrid Simulation within a single site (case of structure-pipe-structure interaction in a natural gas pressurizing station studied in the framework of the H2020 project EXCHANE-Risk) and distributed HS across multiple sites (case of a seismically excited bridge-soil system tested in the framework of the FP7 project EXCHANGE-SSI).
From the side of UBRI, a proposal may choose to utilize any of the four installations provided, that is: (a) the 6m x 4m biaxial shaking table with a 50t capacity, capable of meeting BELLCORE test standards with a peak acceleration at 2g and maximum frequency of 50Hz, (b) the 6m x 5m x 4m soil pit, (c) the Hexapod or (d) the 3m by 3m, 6DOF shaking table. The corresponding installation in the STRULAB of the UPAT installation includes a 18x16m strong floor and two, 5.5m-tall orthogonally placed, strong walls for uniaxial or biaxial testing. For a detailed description of the two collaborating Laboratories reference can be made to the individual presentation provided in WP9 and WP5 for UBRI and UPAT, respectively.

Services currently offered by the infrastructures:
Given that the experiments to be conducted in the framework of this WP will take place in (at least) two sites, the users will take advantage of the combined services of the involved RIs. For more details one can refer to the individual WP9 and WP5 for UBRI and UPAT, respectively.
The tests can conceptualize a wide range of structures and infrastructures, typically of large dimensions, for which sub-structuring and geographically distributed HS can be highly beneficial due to their size (and scale) limitations or because the required equipment is not available in a single facility. Such potential proposals for joint TA access may involve cutting edge, multi-disciplinary, multi-hazard research on long bridges, special, irregular and base isolated buildings, offshore wind turbines, nuclear industry applications as well as lifelines (water, wastewater and natural gas pipelines) among others. The envisaged Hybrid Simulation between UPAT and UBRI will also enable consideration of soil and its dynamic interaction with the foundation and the superstructure which is impossible to be combined with testing of a large structure within the same laboratory. To demonstrate the feasibility of the proposed TA scheme, indicative examples are shown in the figure below for researching the response of a bridge under earthquake and wind loading, while testing experimentally the contribution of the pile group foundation of the pier or that of abutment-embankment interaction.
Because of latency limitations (such as internet network delays) that hinder the execution of geographically distributed Real-Time Hybrid Simulation (RTHS), the tests to be performed shall involve rate-independent phenomena (e.g., a sand damper) or materials, for which (non-continuous, non-real time) pseudo-dynamic testing at an extended time scale among remote sites is a challenging, yet feasible approach.

Overview of a potential HS involving the seismic (left) and wind response (right) of a soil-bridge system.

Depending on the context of the research proposals and provided that the experimental programme envisaged is technically feasible, other partners with experience on hybrid experimentation or multiple hazard assessment, may potentially participate as a third – numerical – analysis node, either by computationally analysing the response of a dedicated subsystem or for producing the forcing function at various points of the excited specimen, respectively. In such a case, given that they will not be offering explicit TA as part of this WP, their contribution shall be considered as provided in kind. The scenario of sequential (i.e., non-concurrent) multi-hazard loading on critical infrastructure (e.g., severe wind after a major earthquake, as has been for instance the recent case of Haiti) may also form a possible collaboration framework that will establish synergy between two TA projects executed in the framework of two linked WPs (e.g. WP9 and WP11). Overall, the two RIs leading this HS WP (UBRI-UPAT) will explore means of collaboration with other consortium RIs and their research groups, as this will not only provide users with ways of performing advanced research combining the most appropriate tools and competences of SoA facilities and cultivate transdisciplinary collaboration, but will also pave the way in conducting multi-site RTHS in the near future when technological developments (e.g., 5G networks) permit it.

DESCRIPTION OF WORK:
Modality of access under this proposal:
The stages for offering user access to the joint SoFSI/EQUALS – STRULAB Research Infrastructure and its installations involve: (a) the opening of the call, (b) feedback to the potential users while preparing their proposals, (c) proposal review (see final section) and (d) continuous support to ensure high quality delivery of the foreseen curiosity-driven research (see next section).
A typical project employing hybrid simulation lasts approximately 16 calendar months, including 6 months for the definition of the HS programme and the design of the specimens to be tested across the two partner RIs, 3 months for construction, 2 months for instrumentation, 2 months for validation and preliminary testing, specimen actual testing, and 3 months for post-processing the results. Users are expected to attend in person at any site unless there is a force majeure imposed by pandemic or other unforeseen situations. Projects may involve users from several institutions and countries from across Europe and beyond. An important part of the user experience, especially for the training of younger researchers, is their direct participation in the design, construction and execution of the tests including training on HS.
Users will be given access to the SoFSI/EQUALS – STRULAB Research Infrastructure on an access day basis as described in the WP9 and WP5 for UBRI and UPAT, respectively.

Support offered under this proposal:
Given the multi-site nature of this WP, the users will take advantage of the combined support of the involved RIs. For more details one can refer to the individual WP9 and WP5 for UBRI and UPAT, respectively. Tailored to the needs of HS the users of this WP will additionally receive support using a standalone, small scale (table-top) setup for hybrid testing (two twins exist at the universities of Patras and Bristol). The mini tables operate on the same method and software used for actual HS testing and will be made available to users/trainees to delve into the hybrid simulation method, either performed locally or via distributed, networked, multi-site substructured testing. Training videos and material will be made available through the project web portal.

Outreach to new users:
This integrated WP will promote cross-discipline fertilisation, synergy building among different RIs and knowledge/technology transfer across different scientific fields, particularly within the structural, geotechnical and wind engineering community for mitigating the effects of natural and man-made disasters. Outreach activities are already described in the individual WP9 and WP5 for UBRI and UPAT, respectively.

Review procedure under this proposal:
Efficient and transparent review is key for the success of the particular WP. The evaluation panel will ensure that the proposals to be selected prescribe an innovative, yet technically feasible geographically distributed HS, focusing on rate-independent, multi-disciplinary phenomena and maximizing the synergies between the RIs of this consortium.
For details on the TA evaluation process, please refer to Task 1.2 of WP1 and the process followed by the TA-SEP in particular.