Development of smart integral bridges

The use of integral bridges with a combined bridge deck and abutment walls has been in use for many decades. However their current design is largely based on PD6694 guidelines, which involves a significant amount of empiricism and uncertainty. This is largely due to the unknown stress state and the stress-strain behaviour of the backfill soil behind the abutment walls. The designs can get more conservative with an increase in the span of the bridges. It is also worth noting that older bridges that have bearings can cease up and act like an integral bridge during later years of their service, applying similar loads on the abutment walls and the soil backfill behind these. There is a well-recognised need to reduce the carbon footprint of bridges while delivering a sustainable and resilient highway infrastructure that is robust under climate change. This proposal is aimed at investigating the integral bridge and abutment design with the ultimate aim of improving the design, reduce maintenance and increase the inspection intervals with suitable deployment of smart instrumentation during the construction of these bridges. With this view, the research proposal is divided into three interdependent phases.
Phase I: Deployment of smart instrumentation during bridge construction: In this phase the stakeholders such as the bridge owners, designers, contractors, Highways England, the academics and the research staff are brought together to design the deployment of smart instrumentation that can help with monitoring of thermal expansion of decks, bending moments and shear forces on the deck-abutment wall joints, earth pressures behind the abutment wall, strains mobilised in the backfill soil etc. The selected bridges with this smart instrumentation will be monitored over a long period of 5 to 10 years and will involve many thermal cycles.
Phase II: Development of physical and numerical modelling: Simplified physical models of the integral bridges and the backfill that are highly instrumented will be developed and tested in the large 10m diameter beam centrifuge at Cambridge. Soil strains in the backfill will be recorded directly using high
resolution imaging and use of the geo-PIV software. It is planned that about 5 to 6 centrifuge models will be tested varying the backfill soils, use of geo-foam blocks behind the abutment wall etc. The cost of the centrifuge testing is estimated at about £6k per test. The centrifuge data will be compared to field data, flowing from Phase I of the project at appropriate intervals. In addition, numerical modelling using the finite element method will be carried out and these models will be calibrated against the centrifuge test data. Also the results from the calibrated FE analyses will be compared to field monitoring data flowing from Phase I.
Phase III: Development of design guidelines: In this phase the validity of the current design guidelines is verified. With the view of minimising the carbon footprint and producing a resilient bridge structure that can cope with climate change concerns, the guidelines will be updated for use in future integral bridge design. It is also anticipated that use of more carefully chosen backfill materials with use of geofoams or geo-grids, the designs can be further optimised to minimise the abutment wall movement inducing large strains in the backfill. The possibility of using an optimal thickness of these geo-synthetic material sections to reduce soil strains and any subsequent soil deformation will be investigated.

The primary impact of the FIBE2 CDT will be the benefit to society that will accrue from the transformative effect that FIBE2 graduates will have upon current and future infrastructure. The current FIBE CDT has already demonstrated significant impact and FIBE2 will extend this substantially and with particular focus on infrastructure resilience. There will be further impacts across academic research, postgraduate teaching, industry-academia partnering and wider society. Our CDT students are excellent ambassadors and their skills and career trajectories are inspirational. Their outputs so far include >40 journal and conference papers, contributions to a CIRIA report, a book chapter and >15 prizes (e.g. Cambridge Carbon Challenge, EPSRC Doctoral Prizes, best presentation awards). Our students' outreach activities have had far reaching impacts including: Science Festival activities and engineering workshops for school girls. Our innovative CDT training approaches have shifted the culture and priorities in academia and industry towards co-creation for innovation. Our FIBE CDT features in the EPSRC document 'Building Skills for a Prosperous Nation'. Our attention to E&D has resulted in 50% female students with the inspirational ethos attracting students from wide ranging educational backgrounds.

FIBE2 CDT will build on this momentum and expand the scope and reach of our impact. We will capitalise on our major research and training initiatives and strategic collaborations within academia, industry and government to train future infrastructure leaders to address UK and global challenges and this will have direct and significant technical, economic and social impacts for UK infrastructure, its associated stakeholders and civil society at large.

As well as the creation of cohorts of highly skilled research cohorts with cross-disciplinary technical skills, further specific impacts include:

-a transformational cross-disciplinary graduate training and research approach in infrastructure with depth and breadth.

-new forms of Industry-University partnerships. Co-creation with industry of our training and research initiatives has already led to new forms of partnerships such as the I+ scheme, and FIBE2 will further extend this with the 'employer model' variant and others.

-skilled research-minded challenge-focused graduates for UK employers who will derive significant benefit from employing them as catalysts for enterprise, knowledge exchange and innovation, and thus to business growth opportunities.

-enhanced global competitiveness for industrial partners. With our extensive network of 27 industry partners from across all infrastructure sectors who will actively shape the centre with us, we will deliver significant impact and will embrace the cross-disciplinary research emergeing from the CDT to gain competitive advantage.

-support for policy makers at the highest levels of national and local government. The research outcomes and graduates will contribute to an evidence-based foundation for improved decision-making for the efficient management, maintenance and design of infrastructure.

-world-class research outcomes that address national needs, via the direct engagement of our key industrial partners. Other academic institutions will benefit from working with the Centre to collectively advance knowledge.

-wider professional engagement via the creation of powerful informal professional networks between researchers, practitioners, CDT alumni and CDT students, working nationally and internationally, including some hosted by FIBE2 CDT industry partners.

-future generations of infrastructure professional inspired by the FIBE2 CDT's outreach activities whereby pupils, teachers and parents gain insight into the importance of infrastructure engineering.

-the generation of public awareness of the importance of a resilient infrastructure to address inevitable and often unexpected challenges.