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At least 20% of existing railway bridges in Sweden are reinforced concrete (RC) trough bridge that consist in a slab carried by two longitudinal main beams. As these bridges are getting old, there is an urging need to assess their remaining capacity with the aim of prolonging their service lives. The limited literature on the topic has pointed out that there is a significant difference between the capacity predicted by available codes and that obtained experimentally. In this paper, a review of the Bridge and Tunnel Management database (BaTMan) of railway infrastructure in Sweden, is carried out to gain an overview of the current state of the Swedish railway bridge, with focus on trough bridges. Then, a non-linear finite element model is calibrated using the experimental results of the previous testing of a decommissioned trough bridge. The model is used in a parametric study where the effect of key mechanical parameters on the capacity of trough bridges is studied. ISBN for host publication: 978-385748183-3

As emission regulations in the EU are becoming stricter, the reduction of greenhouse gas emissions from the construction industry has become a pressing need. As part of the efforts related to this issue, it has been found that Environmental Life Cycle Analysis (LCA) approaches are required to optimize the design, construction, operation, and maintenance of buildings and infrastructure assets. In this paper, The Institution of Structural Engineers guidance on how to calculate the embodied carbon in structures is used as LCA model and evaluated in a case study. The guidance divides the structure´s life cycle into five stages (A1-A3: Product, A4-A5: Construction process, B1-B7: Use, C1-C4: End of live and D: Benefits and loads beyond the system boundary) and the environmental impact is measured in terms of carbon dioxide equivalent emissions (kgCo2e) or global warming potential (GWP). The model was applied to an existing reinforced concrete trough bridge, which is a structure type commonly used in Swedish railways. Results show that that the model was effective and simple for investigating the environmental impact of the studied structure.

In Sweden, a substantial amount of railway bridges is approaching their intended lifespans and are planned to be replaced. However, it is not sustainable neither from a financial nor an environmental perspective to replace these bridges if they are still sound and safe. Thus, an evaluation of their actual capacity is required with the aim of extending their lifespans. A way to obtain a more accurate capacity is to determine the loads that are acting on them. Available literature points out the lack of experimental investigations on sleeper-ballast contact pressure, as well as on the stress distribution along and across the ballast. Consequently, railway bridge design has been based on traditional rather than rational assumptions, which can be quite conservative. In this paper, a review of models is carried out for evaluating stress patterns on the surface of the slab on ballasted concrete bridges. Then, a simplified finite element model of a concrete trough bridge, a common type of structure in Sweden, is used in a parametric analysis aimed to understand how the identified pressure distribution patterns affect the performance of this type of structure. Finally, with the purpose of studying how some parameters influence the bridge safety, a probabilistic reliability analysis is used. The reliability index beta (b) is obtained using the polynomial response surface method and its value is compared for different boundary condition scenarios. Also, the sensitivity factors for the considered random variables are compared and analyzed. Results show that the assumption of support condition and pressure pattern has a significant impact on the capacity, failure mode and probability of failure of this type of structure. ISBN för värdpublikation: 978-981-18-2016-8

The bond failure is studied of a reinforced concrete trough bridge strengthened with near surface mounted reinforcement of carbon fibre reinforced polymer (CFRP) bars. The bars were embedded in epoxy resin in pre-sawed groves in the soffit of the bridge edge beams. The failure was modelled with 3D nonlinear finite elements, and it was possible to study the process from initiation to final collapse. A local bond failure in the interface between the concrete and the epoxy resin initiated a redistribution of forces in the bridge leading to yielding in the longitudinal and vertical steel reinforcement, rupture of stirrups and finally a full failure of the bridge. The bridge was a 50-year-old typical concrete railway trough bridge in Örnsköldsvik, in northern Sweden. It was going to be dismantled due to a relocation of the railway line. The aim of the loading test was to get detailed information of the bridge behaviour all the way up to the final failure. The test was a part of the European Research Project “Sustainable Bridges” regarding assessment and strengthening of existing bridges. The bridge was strengthened in bending before the loading test to avoid an uninteresting flexural failure. Failure was reached for an applied load of 11,7 MN by pulling downwards a steel beam placed in the middle of one of the two spans. The FE calculations presented here show the effect of the strengthening with CFRP, the effect of the epoxy when using the Near Surface Mounted Reinforcement (NSMR) strengthening method and the high load-carrying capacity of this bridge type Forskningsfinansiär: European Union 6th Framewok Program; The Federal Institute for Materials Research and Testing (BAM); Botniabanan; Cervenka Consulting; Nordisk Spännarmering; Savonia University of Applied Sciences; University of Oulu; Skanska Sverige AB; STO Skandinavia AB; Örnsköldsviks kommun; University of Minho (UMINHO) Sustainable Bridges

The aim of the current project is to digitalize inspections and monitoring of structures’ health using drones in order to identify and allow for easier inspection of damages in transport infrastructure. The objectives set are to perform aerial photogrammetry to recreate the as-is condition to enable off-site inspection of difficult to reach areas in structures and identify damages – e.g. cracks, spalling, corrosion. The drone is controlled either autonomously or with the use of a remote control by a pilot from the ground. The drone can carry a wide range of imaging technologies including still, video and infrared sensors. The high flexibility and accessibility of drones in hard-to-reach or risk exposed areas makes the airborne photogrammetry a better alternative to the ground-based method. Given the potential of UAVs to help bridge inspectors performing inspections off-site, the Swedish Transport Administration developed a demonstration project to evaluate the effectiveness and future opportunities within inspection field. Five bridges of varying sizes and types were selected as demonstrators. Data collection including the 3D model creation has been performed by three different contractors while the model-based inspection for all bridges was performed by the same team. It has been shown that the 3D models could serve as a tool for bridge inspectors from which measurements could be extracted and certain damages identified. A full off-site inspection is currently not feasible as some areas of the bridges were difficult to capture. The models are only providing near-surface information, and therefore, in-depth inspection should not be overlooked. The difficulty to capture local defects such as delaminations and narrow cracks also reduces versatility. The main conclusion from the study is that drones cannot be used independently to conduct inspections. Currently, they can only be used as a complement to traditional inspections. The added value of a 3D model derives from the possibility of using it as tool to better plan large inspections in the field and/or future maintenance work.