Congratulations to our ME student, Mr Conor Flannery who successfully defended his final thesis yesterday. His research investigated the procedure of using ground-based radar interferometry to develop and validate a finite element model of the Loopline Bridge in Dublin, Ireland. This wrought iron lattice truss girder railway bridge provides a rail connection between the north and south of Dublin City. The 40-metre span of the bridge over the River Liffey was focused on for this study. This span consists of two main truss lattice girders and cross girders that support the bridge deck and two railway tracks.
Information on the bridge, provided by Iarnród Éireann, was used to create a 3D finite element model using RFEM, a commercial software package. The model was verified with theoretical calculations and experimental tests from the literature to ensure it was behaving as expected without any extreme localised deflections.
The dynamic deflection at midspan of the Loopline Bridge was measured for two train crossing events using ground-based radar interferometry by Murphy Geospatial in January 2018. A single train crossing event showed the deflection of the loaded side of the span with respect to the unloaded side. Additionally, a dual train crossing event demonstrated the twist in the deck from the train loads travelling in opposite directions on separate sides of the bridge. The same loading conditions were simulated in the finite element model and the resulting deflections were extracted. A comparison between both sets of deflection data was carried out, their correlation validating that the model accurately captured the behaviour of the real Loopline Bridge structure for both train loading scenarios.