The site-specific hazard was defined both by selection of natural ground motions and by defining an up-to-date method for the generation of simulated ground motions. The method allows to generate a number N of simulated ground motions starting from a few input parameters (Magnitude, Distance, soil type and fault type). A novel software tool was developed allowing to generate spectrum-compatible ground motions.
A numerical model was developed using the OpenSees platform. First, the numerical model of the shaking table test of EU/H2020 SERA/SERENA project was defined. The numerical model, including the model of the bridge and foundations with the piles and the soil domain, takes into account the soil-structure interaction by appropriate interfaces between structural and soil elements. Static and Dynamic analyses were performed, allowing to obtain results in terms of acceleration, frequencies, displacements, bending strains and earth pressures.
The numerical results were compared with the experimental ones. The comparison allowed to validate the numerical strategy, and the earth pressures obtained were compared with the new provisions contained in the new version of Eurocode 8 Part 2 on Bridges, allowing to draw suggestions and guidelines for the application of Eurocodes. The influence of different parameters was investigated, such as the increasing mass of the bridge deck, and the study of the areas of the backfill soil which are more likely to be damaged and therefore need mitigation strategies.
After the definition the earthquake ground motion and the numerical model of real integral bridges, a number of sets of earthquake-bridge samples was defined. A non-linear time history analysis is performed for each of the cases, allowing to obtain a certain damage state for each of the component of the bridge. While generally the damage of a conventional bridge is described by the damage of piers, in the case of integral bridges different damage indicators have to be defined, involving damage to the abutments-backfill system. This allowed to evaluate the vulnerability of such bridges.
The life-cycle performance of integral bridges was investigated by taking part to the experimental campaign of project PLEXUS PLUS funded by UKCRIC and composed by two tests:
- A small-scale pseudo-static test was conducted to simulate the effects of repeated thermal variations on the bridge throughout its lifespan, replicating the soil-structure interaction resulting from seasonal expansion and contraction of the bridge deck, and to assess the effectiveness of various monitoring techniques. By combining data from different instruments, a preliminary evaluation of the soil-structure interaction behaviour of the system was conducted.
- A large-scale pseudo-static experimental campaign (100 cycles) to reproduce the life-cycle thermal variations of integral bridges. It was the first experimental campaign to be carried out in the new National Facility for Soil-Foundation-Structure-Interaction Laboratory (SoFSI) at the University of Bristol.
The 6m x 5m x 4m Soil Pit was used, and settlements, strains and earth pressures were measured on the abutment and in the backfill soil. The large-scale test of Plexus Plus, besides being among the first comprehensive tests of Integral bridges at large scale, featured a number of innovative monitoring techniques including optical fibres, digital image correlation (DIC) and Ground Penetration Radar (GPR).
The results were disseminated through peer-reviewed journal papers (published and submitted). In addition, the results are published in five conference papers which are either published or submitted in major conferences in the field of earthquake engineering.
