Project Spotlight: PLEXUS PLUS - first pseudo-static experimental test on integral abutments at the UKCRIC Soil-Foundation-Structure-Interaction Laboratory (SoFSI) of the University of Bristol

The UKCRIC project PLEXUS PLUS has been the first experimental campaign in the UKCRIC Soil-Foundation-Structure-Interaction Laboratory (SoFSI) lab. It was led by the University of Bristol and co-led by the University of Birmingham and the University of Southampton.

PLEXUS PLUS emerged from the successful experience of collaboration pioneered within the framework of the EPSRC project “UKCRIC - PLEXUS - Priming Laboratory experiments on infrastructure and Urban Systems”; a pump-priming project designed to establish the collaboration and practice frameworks needed for long-term, successful, collaborative UKCRIC laboratory environments.

The PLEXUS PLUS project had two objectives: (1) understanding soil-structure-interaction phenomena on abutment-backfill ensemble of integral bridges due to deck thermal expansion, and (2) employing several monitoring systems necessary to map settlements, strain and pressure characteristics behind the abutment and within the Soil Pit.

The setup of the Plexus Plus test consisted of a, hinged at the base, reinforced concrete flap, contained between two towers of concrete Lego blocks, and connected to a 1MN static actuator. The backfill is realised with approximately 50 tonnes of silica sand. The wall was monitored by means of strain gauges, optical fibre, pressure cells, and a digital image correlation. The sand was also instrumented with non-contact LVDT to measure settlements, a Ground Penetrating Radar to monitor density throughout the different phases of the test and arrays of accelerometers to measure site conditions based on ambient noise induced by the nearby 6x5m shaking table. A pseudo-static experiment of 100 constant cycles was performed mimicking the life-cycle thermal variation of integral bridges.

The first results obtained offered a quality benchmark case, within a well-controlled soil-structure interaction environment, that enhances our understanding of the long-term performance of integral bridge abutments. It also paves the way to even larger scale soil-structure interaction tests to reduce the epistemic uncertainty associated with the behaviour of such bridges and ultimately reduce unnecessary conservatism in design codes and guidelines.

PLEXUS PLUS Team:

• University of Bristol: Dr Flavia De Luca, Dr Raffaele De Risi, Prof Anastasios Sextos (PI), Prof George Mylonakis, Mr David Williams, Dr Tony Horsman. 
• University of Birmingham: Dr Sha Luo, Dr Daniel Boddice, Prof David Chapman, Prof Nicole Metje, Prof Christopher D. F. Rogers.
• University of Southampton: Dr David Milne, Dr John Harkness, Dr Louis Le Pen.

Read a publication related to this project.