| 1. |
- Shu, Jiangpeng, 1987, et al.
(författare)
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Field Destructive Testing of a Reinforced Concrete Bridge Deck Slab
- 2020
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Ingår i: Journal of Bridge Engineering. - : American Society of Civil Engineers (ASCE). - 1084-0702 .- 1943-5592. ; 25:9
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Tidskriftsartikel (refereegranskat)abstract
- Many bridge deck slabs in Europe are rated insufficient load-carrying capacity in shear and punching according to the Eurocodes. In the past, assessment models have mainly been developed from laboratory studies that simplified real-world conditions. Large-scale or full-scale field experiments are needed to validate more recent improved models. The goal of this study is to calibrate improved models using data obtained from a full-scale bridge deck slab shear test; the objective is to exploit and share our findings and to make recommendations for the planning, design, and implementation of such a complex experiment. Full-scale destructive tests of a 55-year-old reinforced concrete bridge deck slab on prestressed concrete girders were conducted to calibrate a model used to assess existing bridges. Concrete properties were also tested to evaluate the condition of the bridge. Results show that both the load-carrying capacity of the bridge deck slab and the strength of the concrete were much greater than were assumed in design. Finite-element analysis of the parameters governing loading positions and prestress in the girders showed that arch action and boundary condition simplification had important effects on shear distribution.
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| 2. |
- Nilimaa, Jonny, et al.
(författare)
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A Direct Tensile Strength Testing Method for Concrete from Existing Structures
- 2023
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Ingår i: CivilEng. - : MDPI. - 2673-4109. ; 4:1, s. 333-344
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Tidskriftsartikel (refereegranskat)abstract
- Tensile strength is a crucial property for the function, safety and durability of all concrete structures. The general procedure to assess the tensile properties of concrete from existing structures is to perform indirect tests and predict the tensile strength based on established empirical relationships. In this study, the direct tensile strength of concrete was investigated using cylindrical specimens. The aim of the study was to propose, test and evaluate a general method for direct tensile tests of concrete from existing structures. A total of 16 specimens were tested under deformation-controlled tensile-loading until failure. The concrete samples were prepared with 10 or 15 mm grooves at mid-height to obtain cracking in the groove region, where the crack-opening sensors were installed. The load and corresponding deformation were recorded continuously during the test to obtain the load–crack-width relationship of the concrete. The tests showed that the method can be used to assess the tensile properties of concrete from existing structures. The study provides important insights regarding the assessment of direct tensile strength of concrete and the results can be used to improve the structural health monitoring of existing structures and thereby ensure their safety and durability.
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| 3. |
- Nilimaa, Jonny
(författare)
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Smart materials and technologies for sustainable concrete construction
- 2023
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Ingår i: Developments in the Built Environment. - : Elsevier. - 2666-1659. ; 15
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Forskningsöversikt (refereegranskat)abstract
- This paper presents a comprehensive review of current trends and opportunities for sustainable concrete construction, emphasizing the importance of adopting eco-friendly practices to mitigate the industry's environmental impact. Green concrete, supplementary cementitious materials, permeable concrete, cool concrete, and the use of local materials are explored as sustainable materials and technologies. Innovations like self-healing concrete, 3D-printed concrete, photocatalytic concrete, electrified machineries, and carbon capture, utilization, and storage principles are also discussed, highlighting their potential to improve the sustainability of construction practices. Challenges faced in implementing sustainable concrete construction practices, such as technical, economic, and social barriers, are also addressed. The roles of governments, industry, and academia in promoting sustainable concrete construction are examined, stressing the need for interdisciplinary collaboration and research. Lastly, emerging trends and technologies, including digitalization, data-driven approaches, and circular economy principles, are identified as critical factors in driving the transition towards sustainable concrete construction.
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| 4. |
- Nilimaa, Jonny, 1986-, et al.
(författare)
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Validation of the Swedish Crack Risk Estimation Models
- 2017
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Ingår i: Proceedings of the 23rd Nordic Concrete Research Symposium. - Oslo : Nordic Concrete Federation. - 9788282080569 ; , s. 321-324
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Konferensbidrag (refereegranskat)abstract
- Thermal cracking may occur during the early hardening process of concrete as a result of the exothermic reactions between water and cement. An approach for thermal crack risk estimation and prevention was introduced in the Swedish design guidelines BRO 94. This paper studies and validates the current safety levels existing concrete structures. Three slab-frame structures were analysed and the preliminary crack risk estimations were compared to the actual cracking and post-estimations were carried out, using actual parameters. This paper shows that all the studied walls with a strain ratio over 70% were affected by thermal cracks.
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| 5. |
- Zhaka, Vasiola, et al.
(författare)
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Observations of Snow–Slush–Snow Ice Transformation and Properties of Brash Ice in Ship Channels
- 2023
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Ingår i: Water. - : MDPI. - 2073-4441. ; 15:13
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Tidskriftsartikel (refereegranskat)abstract
- The thickness and properties of brash ice are usually compared with the properties of the surrounding level ice. The differences between these ice types are important to understand since the consolidated brash ice layer is typically assumed to have the same properties as level ice. Therefore, significant effort in the measurement campaign during the winters of 2020–2021, 2021–2022, and 2023 was made to develop a better understanding of the full-scale brash ice channel development. The channels were located near the shore in the Bay of Bothnia, Luleå, Sweden. The main parameters investigated were the snow, slush, and total ice thicknesses, including ice formed from freezing water and from freezing slush as well as the ice microstructure and strength. To our knowledge, this is the first paper to report the influence of snow in brash ice channels. It was observed that a significant amount of snow covered the brash ice channels between the ship passages. After each ship passage, the snow was submerged and formed slush-filled voids, which thereafter transformed into snow ice (SI) clusters frozen together with columnar ice. The SI content in the brash ice and side ridges was estimated from image analyses. The analyses showed that the snow ice content was 73% in level ice in the vicinity of the ship channel, 58% in the side ridges of the channel, and 21% in the middle of the test channel, whereas in the main channel, the SI contents were 54%, 43%, and 41% in each location, respectively.
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| 6. |
- Zhaka, Vasiola, 1992-, et al.
(författare)
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Snow effects on brash ice and level ice growth
- 2024
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Ingår i: Journal of Glaciology. - : Cambridge University Press. - 0022-1430 .- 1727-5652.
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Tidskriftsartikel (refereegranskat)abstract
- Brash ice formation and accumulation occur at a faster rate in ship channels, harbours and turning areas compared to the surrounding level ice. Accurate prediction of brash ice thickness plays an important role in addressing operational challenges and optimisation of ice management strategies. This study enhances existing brash ice growth models by considering the effects of snow and accounting for brash ice expulsion towards the sides of ship channels at each passage. To validate the influence of these critical factors on brash ice thickness, three distinct ship channels located in the Bay of Bothnia, Luleå, Sweden, were investigated. For two test channels formed for study purposes, the slower growth rate of brash ice caused by snow insulation was more prominent than the brash ice growth acceleration caused by the snow–slush–snow ice transformation. In the third channel characterised by frequent navigation, the transformation of slush into snow ice played a more substantial role than snow insulation. In both test channels, the brash ice growth model performed optimally, assuming a 10% expulsion of brash ice sideways at each vessel passage. In the third, wider and more frequently navigated channel, a 1.2% brash ice expelling coefficient predicted well the measured brash ice thicknesses.
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| 7. |
- Elfgren, Lennart, 1942-, et al.
(författare)
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Load-testing used for quality control of bridges
- 2018
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Ingår i: Quality Specifications for Roadway Bridges. ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Load testing is a way to control the capacity and function of a bridge. Methods and recommendations for load testing are described and examples are given form tests carried out. In order not to damage the bridge being tested, the load must be limited, often to be within the serviceability limit state (SLS). Numerical models can be calibrated by load tests and then be used to check the carrying capacity for higher loads than what has been tested. Need for further work and recommendations are discussed. By effective planning costs can be saved and a more sustainable use of bridges can be obtained.
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| 8. |
- Häggström, Jens, et al.
(författare)
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Testing Bridges to Failure : Experiences
- 2017
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Ingår i: IABSE Symposium, Vancouver, 2017. - Zürich, Switzerland : IABSE - International Association for Bridges and Structural Engineering. - 9783857481536 ; , s. 2832-2839
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 9. |
- Bagge, Niklas, 1987-, et al.
(författare)
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Assessment and failure test of a prestressed concrete bridge
- 2017
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Ingår i: Life-Cycle of Engineering Systems. - Leiden : CRC Press/Balkema. - 9781138028470 ; , s. 1058-1063
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Konferensbidrag (refereegranskat)abstract
- 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 total length of 121.5 m. The overall aim of the study was to determinate the accuracy of assessment methods for existing structures and to provide procedures for optimized assessment. Before the tests a 2D finite element (FE) analysis was performed to predict the behavior and load-carrying capacity of the bridge. In order to more accurately assess the bridge response a 3D FE model has now been developed. The actual loading history and material properties has been considered in the model. A Life Cycle Cost Assessment of the bridge has also been performed
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| 10. |
- Bagge, Niklas, 1987-, et al.
(författare)
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Assessment of concrete bridges - Prestress forces : Experiences from full-scale testing to failure of a bridge in Kiruna
- 2017
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Ingår i: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation. - Oslo : Nordic Concrete Federation. ; , s. 267-270
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Konferensbidrag (refereegranskat)abstract
- To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests were carried out on a 55 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden. Both non-destructive and destructive full-scale tests were performed. This paper presents results regarding the residual forces in the prestressed reinforcement.
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