Wireless monitoring for assessment of concrete railway bridges - Experiences from field tests

This paper focus on assessment on a prestressed three span concrete box bridge by the use of a wireless monitoring system in combination with visual inspection. The bridge is located in the very north of Sweden, in Abisko. A visual inspection of the bridge carried out the 18th of August in 2016 several crack patterns were mapped on the inside of the box girder bridge located near supports in the spans on both sides of the bridge. The cause of the cracks are not completely clear. To reveal the reason for cracking a long term project has been initiated by Trafikverket. Here a new developed wireless system has been used. Investigating change in crack widths by the use of LVDTs and strain gauges. Also accelerations are monitored together with the temperatures. In addition also fibre optic systems and non-destructive tests were carried out (not reported here). The results/conclusions presented in the paper are preliminary and final results will be presented 2021.Wireless monitoring for assessment of concrete railway bridges - Experiences from field testspublishedVersio

Non-destructive testing of prestressed concrete bridges - Experiments from field test

Most of the structures in the transport infrastructure are built of reinforced concrete, and many of our large bridges are built of prestressed concrete. A large part of these were built before 1980, and could theoretically have problems with both corrosion in tension cables, chlorides in injection mills and thin lightly damaged feed pipes. After 1980, the standards were tightened. Whether these theoretical problems are real is not fully mapped as basic investigations of these bridges have not been conducted in Sweden. International attempts have been made with methods of non-destructive testing (NDT) to identify problems in the form of cavities, corrosion or breakage in cables. These investigations have had limited success since no individual measurement technique has been shown to be able to be used to map the condition. However, it has also been shown that a combination of different NDT techniques can overcome some of the challenges and detect defects in ducts in prestressing systems installed in large concrete structures. The methodology described in this paper shows that it is possible to detect damages, but also that the results is very much dependent on the skills of the persons that use the equipment and evaluate the data.Non-destructive testing of prestressed concrete bridges - Experiments from field testpublishedVersio

FRP strengthening of RC walls with openings

Strengthening reinforced concrete (RC) walls with openings using fibre reinforced polymers (FRP) has been proved experimentally to be a viable rehabilitation method. However, very few theoretical investigations are reported. In this paper two methods of analysis are presented. Since openings vary in size, the analysis of a strengthened wall can be divided into frame idealization method for large openings, and combined disk and frame analysis for smaller openings. The first method provides an easy to use tool in practical engineering, where the latter describes the principles of a ductile strengthening method, relying on dislocation of yield lines and creation of a new yield mechanism. The frame idealization method can be considered as a safe guideline for real strengthening projects based on commonly used principles. The principles in the latter are new and promising, and need experimental verification before use in strengthening projects.Strengthening reinforced concrete (RC) walls with openings using fibre reinforced polymers (FRP) has been experimentally proven to be a viable rehabilitation method. However, very few theoretical investigations are reported. In this paper two methods of analysis are presented. Since openings vary in size, the analysis of a strengthened wall can be divided into frame idealization method for large openings, and combined disk and frame analysis for smaller openings. The first method provides an easy to use tool in practical engineering, where the latter describes the principles of a ductile strengthening method, relying on dislocation of yield lines and creation of a new yield mechanism. The frame idealization method can be considered as a safe guideline for real strengthening projects based on commonly used principles. The principles in the latter are new and promising, but need experimental verification before use in strengthening projects.Godkänd; 2009; 20091214 (gabsas

Asset Management of Existing Concrete Bridges Using Digital Twins and BIM: a State-of-the-Art Literature Review

The need to optimize investments in bridge maintenance has created a demand for improved bridge management systems (BMS). Outdated practices in bridge inspection and constant advances in information technology have also contributed to this demand. The use of Digital Twins (DT), although well established in other industries, is still incipient for asset management and structural analysis of bridges. There is a great deal of research on Building Information Modelling (BIM) for bridge inspection, but its post-construction potential is still under-explored. This study presents a state-of-the-art review of the literature on asset management for bridges using digital models such as BIM and digital twins. The review was conducting using a systematic approach. Despite the rapid increase in research on DT and the amount of existing research on BIM, several gaps remain to be addressed, such as the lack of consensus about the definition of digital twins, which has led to wrongful categorisation of digital models as DT. The complex data flow and software compatibility required to develop a functional DT have hindered the exploitation of their full potential so far. The integration of BIM post-construction to BMS and existing automation technologies can also significantly improve current practices of bridge management.Asset Management of Existing Concrete Bridges Using Digital Twins and BIM: a State-of-the-Art Literature ReviewpublishedVersio

Remote bridge inspection using optical methods

Routine bridge inspections usually consist of visual observations. These inspections are time-consuming and subjective. There is a need to identify new inspection techniques for infrastructure that reduce traffic disturbance, and improve the efficiency and reliability of the acquired data. This study compared the performance of three different imaging technologies for the three-dimensional (3D) geometric modelling of existing structures: terrestrial laser scanning, close-range photogrammetry, and infrared scanning. Each technology was used to assess six existing concrete railway bridges. The results suggest that all methods investigated can be used to create 3D models, however, with different level of completeness.Remote bridge inspection using optical methodspublishedVersio

Are available models reliable for predicting the FRP contribution to the shear resistance of RC beams

In this paper the trustworthiness of the existing theory for predicting the FRP contribution to the shear resistance of reinforced concrete beams is discussed. The most well-known shear models for EBR (External Bonded Reinforcement) are presented, commented on and compared with an extensive experimental database. The database contains the results from more than 200 tests performed in different research institutions across the world. The results of the comparison are not very promising and the use of the additional principle in the actual shear design equations should be questioned. The large scatter between the predicted values of different models and experimental results is of real concern bearing in mind that some of the models are used in present design codes

Plate bonding : strengthening of existing concrete structures with epoxy bonded plates of steel or fibre reinforced plastics

This thesis deals with several aspects of the plate bonding problem, i.e. when steel or fibre reinforced plastics (FRP) plates are bonded to a concrete structure with the use of an epoxy adhesive. Both theoretical work and laboratory tests are presented as well as a full scale test on a strengthened concrete bridge. Earlier work in the area of plate bonding as well as the use of epoxy adhesives in civil engineering are discussed. This report presents several original and new features, both in theory and practice. A linear elastic model is introduced for calculation of shear and peeling stresses at the end of an epoxy bonded plate situated underneath a concrete beam subjected to bending. For the non linear behaviour, when the concrete starts to fracture, a non linear fracture mechanics (NLFM) model is introduced. The report is divided into two main parts, the main text and the appendices. The appendices are mainly used to give detailed derivations and test results. One exception is an illustrative example of how to strengthen a T-beam. is given in Appendix H. The main text begins with an introduction and is followed by a presentation of earlier work in the area of plate bonding. The theory for plate bonding is presented, beginning with the simple truss model which is useful for design of plated structures for both bending and shear. The theory of elasticity applied to bars loaded in pure shear is investigated. Moreover, linear elastic formulas are derived for calculation of the shear and peeling stresses in the adhesive layer. The original differential formulas are quite easy to put together but very complicated to solve; therefore, a simplification is needed It has thus been ass~ that the steel plate has negligible stiffness in comparison to the concrete beam being strengthened. This is a fully acceptable simplification and leads to solutions that give good results compared with FE-analysis. When the concrete starts to fracture, linear elastic theory can not be used. Here a new concept for NLFM is introduced. This concept is based on criteria from Hillerborg, 1977, and also ideas from Gustavsson, 1987. For stiff adhesives is it easy to calculate the failure load by means of the fracture energy, Gf. However for softer bond zones numerical calculations are needed. The laboratory tests performed show that the derived truss model is acceptable for design purposes and that good agreement with test results are attained for both bending and shear. Also the theory of Volkersen, 1938, corresponds very well with the test results. When using FRP plates, however, strain levels must be taken into considerations in the design stage. The tests shows that CFRP (Carbon Fibre Reinforced Plastics) material is preferable to (GFRP) Glass Fibre Reinforced Plastics) material. Finally a full scale test on a strengthened bridge is presented. The results from this test show that the strengthening method, being both useful and practical, is acceptable for strengthening of existing concrete structures.Godkänd; 1994; 20070426 (ysko