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- Bagge, Niklas, et al.
(författare)
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Protecting a five span prestressed bridge against ground deformations
- 2015
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Ingår i: IABSE Conference Geneva 2015. - Geneva : International Association for Bridge and Structural Engineering. - 9783857481406 ; , s. 255-262
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A 55 year-old, 121.5 m long, five span prestressed bridge was situated in the deformation zone close to a mine in Kiruna in northern Sweden. There was a risk for uneven ground deformations so the bridge was analyzed and monitored. Results and measures taken to ascertain the robustness of the bridge are presented.The analysis resulted in an estimate that the bridge could sustain 24 mm in uneven horizontal and 83 mm in uneven vertical displacement of the two supports of a span. To be able to sustain larger deformations, the columns of the bridge were provided with joints, where shims could be inserted to counteract the settlements. To accomplish this, each one of the 18 columns of the bridge was unloaded by help of provisional steel supports. The column was then cut and a new foot was mounted to it. This made it possible to lift each individual column with two jacks, when needed, and to adjust its height by inserting or taking away shim plates.The deformations of the bridge and the surrounding ground were monitored. The eigenmodes of the bridge were studied with accelerometers and by analysis with finite elements (FE) models. Comparison indicated good agreement between the model and the actual bridge, with calculated eigenfrequencies of 2.17, 4.15 and 4.67 Hz, for the first transversal, vertical and torsional modes, respectively. Measurements during winter resulted in higher values due to increased stiffness caused by frozen materials.
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- Carlswärd, Jonas, et al.
(författare)
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Avoiding undesirable end results of bonded steel fibre concrete overlays : observations from tests and theoretical calculations
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 49, s. 93-112
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Tidskriftsartikel (refereegranskat)abstract
- Due to a high degree of damages and undesirable final results of bonded overlays, research has been conducted to develop recommendations on design and execution. Laboratory and half scale tests as well as theoretical analyses have been carried out including e. g. base and end restraint tests on overlays with various reinforcement, concrete qualities, substrate preparing and curing. Also, analytical and numerical calculations have been performed. Results reveal that the bond between overlay and substrate is the most critical parameter for a successful final result. Other key parameters are shrinkage and curing, while fibre and bar reinforcement generally proved to be less significant. Theoretical models work well on this case and will be further developed
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- Carlswärd, Jonas, et al.
(författare)
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Prediction of stress development and cracking in steel fiber-reinforced self-compacting concrete overlays due to restrained shrinkage
- 2010
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Ingår i: Fiber-Reinforced Self-Consolidating Concrete. - : American Concrete Institute. - 9780870313981 ; , s. 31-49
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Konferensbidrag (refereegranskat)abstract
- Shrinkage cracking of self-compacting concrete (SCC) overlays with and without steel fibres has been assessed through laboratory testing and theoretical analysis. Test results verified that steel fibre reinforcement has a crack width limiting effect. However, the contribution in case of fibre contents up to 0.75 vol% was not found to be sufficient to distribute cracks in situations where bond to the substrate was nonexistent. Thus, even higher steel fibre contents (or other types of fibres) are required in order to control cracks. A distributed pattern of fine cracks was however obtained even for unreinforced SCC within bonded areas of the overlays. This implies that steel fibres, or other crack reinforcement, are not required if high bond strength is obtained. An analytical model, proposed to assess the risk of cracking and to predict crack widths in overlays, was found to give reasonable correlation with experimental results
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