Traditional visual inspections of existing infrastructure have limitations such as safety risks, limited accuracy for subsurface defects, and subjective assessments. Modern inspection techniques like terrestrial laser scanning, closerange photogrammetry (CRP), and infrared scanning offer faster and more accurate data collection, allowing for more informative and precise descriptions of objects, while minimizing traffic disturbances often associated with visual inspections. In this paper, CPR, a non-destructive survey technique for reconstructing 3D shapes from 2D images, is used for the inspection of five bridges in Northern Sweden. The surveys were performed under different weather conditions, using different data acquisition equipment and personnel with different levels of experience. The acquired images were used to create 3D models of the bridges and to evaluate the evolution of damages over time. Results showed that although better models were created when using equipment with higher specifications, cheap gear such as GoPro or cellphones can also be used for the cases in which a lower level of detail is required. Furthermore, initial experience of the personnel does not seem to have high influence on the results.

As worldwide infrastructure is ageing, significant efforts have been paid to the development of strengthening techniques that will restore or increase the initial capacity of existing structures. Considering that it is expected that shear failure happens in a less ductile mode than that observed under bending actions, special attention has been devoted to shear strengthening methods. These methods included externally bonded fiber reinforced polymers (EB-FRP), near-surface mounted (NSM-FRP) method, and the embedded trough-section (ETS) technique, among others. In this paper, ETS method is used for the strengthening in shear of a reinforced concrete railway bridge located in Finland. The ETS method consists in the embedment of FRP or steel bars through predrilled holes into the concrete core. The bars are bonded to the concrete using adhesives. The paper includes a brief review of recent advances in the use of ETS and comparison with other available techniques, the description of the case study, instrumentation of the bars using fiber optic sensors (FOS) for strain monitoring, the procedure used for the installation of the bars in the field, and a preliminary analysis of the data collected.

In this paper, experiences on the development of an assessment method for existing bridges are presented. The method is calibrated using the results of full-scale testing to failure of a prestressed bridge in Sweden. To evaluate the key parameters for the structural response, measured by deflections, strains in tendons and stirrups and crack openings, a sensitivity study based on the concept of fractional factorial design is incorporated to the assessment. Results showed that the most significant parameters are related to the tensile properties of the concrete (tensile strength and fracture energy) and the boundary conditions. A finite element (FE) model in which the results of the sensitivity analysis were applied, was able to predict accurately the load-carrying capacity of the bridge and its failure mode. Two additional existing prestressed concrete bridges, that will be used to improve further the method, are also described, and discussed.

Six railway bridges have been scanned using infrared scanning (IR), close range photogrammetry (CRP) and terrestrial laser scanning (TRS) to reconstruct point clouds and evaluate the potential of the technologies for building information modelling (BIM) and assessment purposes. The results may also help to improve bridge inspection routines. This is done by evaluating the accuracy and quality of the point clouds, time consumption, safety and traffic disturbance. Wireless Monitoring has been used in a demonstration project in Sweden. It consists of a base station and nodes. The base station receives signals from the node antennas and transmits the signals to the cloud. The nodes are equipped with strain gauges, crack opening devices, temperature sensors or other suitable sensors for the investigation purpose. Results from the methods and conclusions regarding further use will be presented.

Five bridges of different types have been tested to failure and the results have been compared to analyses of the load-carrying capacity using standard code models and advanced numerical methods. The results may help to make accurate assessments of similar existing bridges. There it is necessary to know the real behaviour, weak points, and to be able to model the load-carrying capacity in a correct way. The five bridges were: (1) a strengthened one span concrete road bridge - Stora Höga ; (2) a one span concrete rail trough bridge loaded in fatigue – Lautajokk; (3) a two span strengthened concrete trough railway bridge - Övik; (4) a one span railway steel truss bridge -Åby; and (5) a five span prestressed concrete road bridge - Kiruna. The unique results in the paper are the experiences of the real failure types, the robustness/weakness of the bridges, and the accuracy and shortcomings/potentials of different codes and models for safety assessment of existing structures.

Three Swedish concrete bridges have been tested to failure and the results have been compared to assessment using standard code models and advanced numerical methods.

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Four bridges of different types have been tested to failure and the results have been compared to the load-carrying capacity calculated using standard code models and advanced numerical methods. The results may help to make accurate assessments of similar existing bridges. Here it is necessary to know the real behaviour, weak points, and to be able to model the load-carrying capacity in a correct way. The four bridges were: (1) a one span steel truss railway bridge; (2) a two span strengthened concrete trough railway bridge; (3) a one span concrete trough bridge tested in fatigue; and (4) a five span prestressed concrete road bridge. The unique results in the paper are the experiences of the real failure types, the robustness/weakness of the bridges, and the accuracy of different codes and models.

Tests have been carried out at service- and ultimate load levels of a 55 year-old prestressed concrete girder bridge. The bridge, located in Kiruna, Sweden, was continuous in five spans with a tota ...

Starting in 2003 the European Union has funded three consecutive research projects dealing with maintenance, life length, capacity and repair/strengthening of railway bridges. The main results are that many bridges are capable of carrying increased loads and can have an increased service life if up to date technologies are used for assessment, monitoring, maintenance and strengthening. In order to obtain good value for the money spent in the projects, it is important to plan, coordinate and manage the projects in an efficient way. Long range projects of four years seem to be more effective than shorter projects of two and three years.

Innovative Intelligent Railways, In2Rail, is a European Horizon 2020 Project with the objective to enhance capacity, increase reliability and reduce Life Cycle Costs of European Railways. Bridges and Tunnels is the main focus in Work Package 4. The aim is to study, benchmark and further develop new Inspection Technologies in order to create more proactive maintenance procedures. In this paper some preliminary results are presented.

Methods for assessment and strengthening of existing bridges need to be tested and calibrated. To do this, a full-scale loading to failure was carried out in 2014 on a 55 year-old post-tensioned five span girder bridge in Kiruna, Sweden, with a total length of 121.5 m. The tests focussed on: (a) failure of the main girders, (b) failure of the slab, (c) condition of post-tensioned tendons, and (d) the performance of two carbon fibre reinforced polymer (CFRP) strengthening systems. The following are the results: 1. The main girders failed after extensive yielding of the reinforcement in a combined bending- shear failure. Preliminary comparisons with existing codes indicate a high safety. Preliminary comparisons with finite element assessment methods give good correspondence. 2. The slab failed suddenly due to punching shear. Preliminary comparisons with codes indicate a very high safety. 3. The post-tension tendons generally were in a good condition. 4. The first strengthening system consisting of prestressed laminates of CFRP was applied to one of the outer main girders. The system failed due to debonding of the CFRP at about ¾ of the ultimate load. The second system consisted of near surface mounted CFRP rods applied to the mid main girder. It showed no signs of slip in the anchorage zones and the CFRP sustained maximum strains of about 1.2 % without fibre rupture.

Conference paper written by Niklas Bagge, Gabriel Sas, Jonny Nilimaa, Thomas Blanksvärd, Lennart Elfgren, Yongming Tu and Anders Carolin presented at IABSE Workshop: Safety, Robustness and Condition Assessment of Structures, Helsinki, Finland, 11-12 February 2015.

This paper presents the results from three tests to failure of different types of bridges: a two span reinforced concrete railway trough bridge; a five-span prestessed concrete beam bridge; and a one span metal railway truss bridge. The results show that the capacity of the structures are underestimated by current standards, while numerical analysis combined with material testing can provide more accurate results. Some examples are also presented on how deficiencies in capacity can be mitigated using fiber reinforced polymer strengthening systems.

A finite element (FE) model was calibrated using the data obtained from a full-scale test to failure of a 50 year old reinforced concrete (RC) railway bridge. The model was then used to assess the effectiveness of various strengthening schemes to increase the load-carrying capacity of the bridge. The bridge was a two-span continuous single-track trough bridge with a total length of 30 m, situated in Ornskoldsvik in northern Sweden. It was tested in situ as the bridge had been closed following the construction of a new section of the railway line. The test was planned to evaluate and calibrate models to predict the load-carrying capacity of the bridge and assess the strengthening schemes originally developed by the European research project called Sustainable bridges. The objective of the test was to investigate shear failure, rather than bending failure for which good calibrated models are already available. To that end, the bridge was strengthened in flexure before the test using near-surface mounted square section carbon fiber reinforced polymer (CFRP) bars. The ultimate failure mechanism turned into an interesting combination of bending, shear, torsion, and bond failures at an applied load of 11.7 MN (2,630 kips). A computer model was developed using specialized software to represent the response of the bridge during the test. It was calibrated using data from the test and was then used to calculate the actual capacity of the bridge in terms of train loading using the current Swedish load model which specifies a 330 kN (74 kips) axle weight. These calculations show that the unstrengthened bridge could sustain a load 4.7 times greater than the current load requirements (which is over six times the original design loading), whilst the strengthened bridge could sustain a load 6.5 times greater than currently required. Comparisons are also made with calculations using codes from Canada, Europe, and the United States.

There is a need to extend the life and capacity of many existing bridges. One of the objects of the EU FP7 Project MAINLINE, 2011-2014, was to facilitate this. Guidelines for assessment and strengthening methods are presented as well as case studies in which existing bridges are studied in order to extend their life length. One example is the prestressing of the slab in a one-span concrete trough bridge in order to increase its load-carrying capacity. Horizontal holes were drilled trough the slab and in them steel bars were placed and post-tensioned. In this way a compressive stress was introduced into the concrete section so that it’s bending and shear capacity was increased. In another study a metal truss bridge was monitored in order to check strain and stress ranges in critical connections to enable an enhanced evaluation of the remaining fatigue resistance. The studied bridge was then replaced and loaded to failure to study its robustness and the reliability of applied assessment methods. The results could then be applied to prolong the life of an identical twin bridge located in the northern part of Sweden. A Life Cycle Assessment Tool (LCAT) has been developed to enable Infrastructure Managers to choose optimal maintenance strategies.

To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests are planned for a 50 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden. Both non-destructive and destructive full-scale tests will be performed. This paper summarises the test programme, which comprises evaluation of the structural behaviour of the bridge, the residual forces in the prestressed steel, methods for strengthening using carbon fibre reinforced polymers (CFRP) and the shear resistance of the bridge slab.

There is a need to extend the life and capacity of many existing railway bridges. One of the objects of the EC-FP7-Project MAINLINE, 2011-2014, is to facilitate this. Guidelines for assessment and strengthening methods are presented as well as case studies in which existing bridges are being studied in order to extend their life length. Case studies on bridges tested to failure in order to calibrate assessment methods are also presented. Fatigue is often a vital question. A Life Cycle Assessment Tool (LCAT) is being prepared to enable Infrastructure Managers to choose optimal maintenance strategies.

Carbon Fibre Reinforced Polymers (CFRP) has found an increased application in strengthening of concrete structures. Mostly the CFRP is used as externally bonded reinforcement. However, prestressing ...

The railway concrete arch bridge over Kalix river : dynamic properties and load carrying capacity