PSI - Issue 64

Chris Mundell et al. / Procedia Structural Integrity 64 (2024) 191–198 Chris Mundell / Structural Integrity Procedia 00 (2019) 000–000

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The Omnia proposal harnesses their teams’ expertise in acoustic monitoring, and utilizing the same apparatus, to induce guided waves that can assess condition in addition to detecting wire breaks. 2.2.1. Progress to date The Omnia-headed team have been commissioned to undertake two phases of development to date; a numerical study with small scale testing, and; larger scale testing to validate numerical concepts and theory. The initial phase of finite element modelling involved incremental increases in modelling complexity, moving from detecting responses in a 2D, single plain bar through to a 3D-modelled concrete-encased 7-wire wound strand. At each stage of testing, the team have been careful to test multiple frequencies and wave forms and ensure full understanding of the wave propagation and the associated response before moving onto subsequent stages, including identification of defect patterns such as breaks or section loss. The technology has shown promise that defects within grouted tendons can be identified up to a range of (currently) approximately 4m when utilising an excitation source connected directly to a strand. At the time of writing, Omnia are undertaking large scale testing to validate the numerical studies, having constructed a 9m beam with stressed tendons encased in concrete. A number of ‘windows’ have been cast into the beam to allow the connection of excitation devices, in addition to control defects to be detected by the system. Trials are ongoing, with positive results indicating that the hypotheses of the numerical studies are borne out in practical application. Next steps for these technologies have been mapped out, but each technology must next be evaluated on its own merits and assessed with respect to those criteria set out in the initial moonshot ‘call for ideas’. Likelihood of successful development through to a deployable technology will be key considerations, along with scalability and impact; to secure further investment the project team must be satisfied that a suitable return on investment will be achieved in the form of a high-impact technology that will lead to a step change in current asset management approaches. 3. Non destructive testing – technology appraisal Trials 3.1. Aims of the trial National Highways have secured a number of sections of the A14 Huntingdon Viaduct - including two sections with half joints – with the intention of undertaking blind trials of various forms of higher-TRL NDT technologies. The overall approach is to deploy these technologies across the three sections, followed by controlled hydrodemolition of the sections and extraction of key features (e.g. PT ducts and anchorages). By comparing the NDT results with as found condition, the project team will be able to determine the effectiveness of various technologies and identify particular strengths and limitations. These findings will be used to develop improved approaches and process maps for asset investigations, laying different technologies together to complement each other and respond to the specific challenges faced on a structure-by-structure basis. The trial does not just consider technology – gathering good data is a combination of people, process and technology; Having the appropriate equipment for a situation can be rendered ineffective if it is deployed in a sub optimal arrangement, or used by insufficiently trained teams. This study therefore captures what ‘best practice’ looks like, and also includes duplication of specific pieces of equipment to attempt to distinguish differences in quality

through different applications. 3.2. Sample Details & History

The A14 Huntingdon Railway Viaduct (HRV) was constructed in 1975, carrying four lanes of traffic over six spans and crossing both local distributor roads and the East Coast Main Line (rail link). In December 2019, new routes were opened which rendered the structure obsolete. The main span consists of a main drop-in span formed of simply-supported precast beams (with transverse post