| 1. |
- Bagge, Niklas, et al.
(author)
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Loading to failure of a 55 year old prestressed concrete bridge
- 2015
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In: IABSE Workshop Helsinki 2015. - Zurich : International Association for Bridge and Structural Engineering. - 9783857481376 ; , s. 130-137
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Conference paper (peer-reviewed)abstract
- In order to provide relevant data for calibration and development of methods for assessment ofexisting bridges, a 55 year old posttensioned concrete bridge has been subjected to non-destructiveand destructive tests. The bridge, located in Kiruna, Sweden, was a 121 m long girder bridgecontinuous in five spans. The test programme included failure loading of the girders and slab,respectively, condition assessment of the post-tensioned cables and material tests. Moreover, twostrengthening systems, using carbon fibre reinforcing polymer (CFRP), were evaluated. In this paperthe experimental programme and some preliminary results are presented to give an insight to researchproject.
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| 2. |
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| 3. |
- Bagge, Niklas, et al.
(author)
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Protecting a five span prestressed bridge against ground deformations
- 2015
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In: IABSE Conference Geneva 2015. - Geneva : International Association for Bridge and Structural Engineering. - 9783857481406 ; , s. 255-262
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Conference paper (other academic/artistic)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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| 4. |
- Blanksvärd, Thomas, et al.
(författare)
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Test to failure of a steel truss bridge – Calibration of assessment methods
- 2014
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Ingår i: Bridge Maintenance, Safety, Management and Life Extension. - London : CRC Press, Taylor & Francis Group. - 9781138001039 - 9781315760698 ; , s. 1076-1081
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Konferensbidrag (refereegranskat)abstract
- The steel truss railway bridge at Åby River was built in 1957 with a span of 32 m (105 feet). In 2012 it was replaced by a new steel beam bridge and the old bridge was placed beside the river. It was tested to failure to study its remaining load-carrying capacity in September 2013. The test was carried out by Luleå University of Technology by commission from Trafikverket as a part of the European Research Project MAINLINE (www.mainline-project.eu). In this paper some preliminary results are given. Two hydraulic jacks, anchored by cables to the bedrock, pulled the bridge downwards. The bridge remained elastic up to about three times the original design load and the load could then be almost doubled with substantial yielding deformations before a buckling failure appeared in the top girders for a load of ca. 11 MN (1000 short tons) for a midpoint deflection of ca. 0, 2 m (8 inches). No brittle or fatigue failure in any of the joints appeared and the bridge proved to behave in a ductile way with a substantial hidden capacity.
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| 5. |
- Cai, Jianguo, et al.
(författare)
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Bistable behavior of the cylindrical origami structure with Kresling pattern
- 2015
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Ingår i: Journal of mechanical design (1990). - : ASME International. - 1050-0472 .- 1528-9001. ; 137:6
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Tidskriftsartikel (refereegranskat)abstract
- The deployment of a cylinder based on origami with Kresling pattern, whose basic mechanisms are formed by the buckling of a thin cylindrical shell under torsional loading, is studied in this paper. The model consists of identical triangular panels with cyclic symmetry and has a small displacement internal inextensional mechanism. First, geometric formulation of the design problem is presented. Then, assuming that the deployment and folding process is uniform, the bistable behavior of the cylinder is discussed. It can be found that, during the deployment, the dimensionless strain energy increases first and then reduces to zero but followed by another sharp increase. Moreover, the limit condition of geometry parameters for the bistable phenomenon is also discussed. Finally, the bistable behavior is also studied by using numerical simulations for simple and more complex case of the cylinder with multistory. The numerical results agree well with the analytical predictions. Therefore, comparisons with finite element predictions have shown that the analytical solutions given in this paper are accurate and have validated the assumptions made in the derivations.
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| 6. |
- Cao, Dafu, et al.
(författare)
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Study on the flexural behaviors of rc beams after Freeze-Thaw cycles
- 2015
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Ingår i: International Journal of Civil Engineering. - 1735-0522. ; 13:1, s. 92-101
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Tidskriftsartikel (refereegranskat)abstract
- order to investigate the flexural behaviors of RC beams after freeze-thaw cycles, compressive strength test of concrete cubes after 0, 50, 100, 125 freeze-thaw cycles were made, and static flexural experiment of 48 RC beams after 0, 50, 100, 125 freeze-thaw cycles were made. The relationships of relative compressive strength, mass loss rate, relative dynamic elastic modulus and numbers of freeze-thaw cycles were analyzed. The influences of different numbers of freeze-thaw cycles on the flexural behaviors of RC beams with different concrete grades were studied. The results show that concrete cubes’ mass, relative dynamic elastic modulus and compressive strength decrease with the increasing of freeze-thaw cycles, and high-strength grade concrete could slow down the damage caused by freeze-thaw cycles. Experimental values of test beams stiffness under short-term load were smaller than theory value. Some under-reinforced RC beams occurs over-reinforced failure mode after freeze-thaw cycles. Boundary reinforcement ratio of RC beams after certain numbers of freeze-thaw cycles was derived and its correctness was verified by experiment. Current code for design of concrete structures about crack load and ultimate load are still suitable for RC beams after freeze-thaw cycles
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| 7. |
- Cao, Jie, et al.
(författare)
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Effects of Temperature and NaCl Concentration on the Adsorption of C-S-H Gel in Cement Paste : A Multi-fidelity Molecular Dynamics Simulation
- 2023
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Ingår i: Building for the Future: Durable, Sustainable, Resilient - Proceedings of the fib Symposium 2023 - Volume 2. - : Springer. - 9783031325106 - 9783031325113 ; , s. 499-508
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Konferensbidrag (refereegranskat)abstract
- The durability and compressive strength of concrete will vary with the material components, ambient temperature, external intrusion. Using molecular dynamics (MD) methods to study the dynamic behavior of particles in cement-based materials can help us understand the underlying mechanism of property changes in concrete caused by above factors at the atomic level. So far, MD methods have been widely used to analyze the physical and chemical properties of concrete materials and the interaction mechanism between different interfaces at the nanoscale. However, too much complexity in the models will reduce the result accuracy and increase the computational cost. A suitable neural network structure can not only ensure the accuracy of analysis results, but also reduce the computational cost. In this work, MD methods are applied to build the models to explore the diffusivity of Na+ and Cl− in the calcium silicate hydrate (C-S-H) gel pores at different concentration and temperatures. In the process of running models, part of the MD models’ fidelity is reduced to save the computational cost, then the trained multi-fidelity physics informed neural network framework was used to obtain more accurate analysis results. The combination of MD simulations and deep learning methods expands the application range of MD in the field of concrete structure, has good development prospect and application value.
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| 8. |
- Cao, Jie, et al.
(författare)
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Molecular dynamics simulations of ion migration and adsorption on the surfaces of AFm hydrates
- 2023
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 615
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Tidskriftsartikel (refereegranskat)abstract
- Chloride salts can cause severe corrosion damage to reinforcing steel bars in cement-based materials whereas nitrite salts inhibit corrosion. The storage and release of these two anions in cement materials occurs mainly at the interface of monosulfoaluminate (AFm) hydrates. In this paper, molecular dynamics are used to analyze the interaction between anions and AFm phases and clarify the competitive relationships between the anions at adsorption sites on the AFm surface. It was found that the ordered structure of the [Ca2Al(OH)6]+ layers of the AFm plays a key role in anion adsorption and that the mobility of ions desorbed from AFm layers decreases linearly with increasing proximity to the AFm surfaces.
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| 9. |
- Casas, Joan Ramon, et al.
(författare)
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Assessment methods for elderly rail infrastructure : MAINLINE, Deliverable D1.2, EU FP7
- 2013
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Rapport (refereegranskat)abstract
- An accurate and advanced assessment will allow keeping in service many assets that otherwise will be condemned to repair, strengthening and/or replacement. Because interventions in many bridges at the same time is not economically feasible, their advanced assessment could help prioritize the repair/strengthening works in the coming years. The main objective of this deliverable is to present the existing possibilities for an accurate assessment of railway assets condition. The two specific objectives of this report are:1. - To describe a set of proposed advanced assessment methods that may be incorporated in the life-cycle management of railway infrastructures2. - To see how the costs and benefits of the proposed advanced assessment methods may be incorporated within a LCA framework.The scope of this report is limited to the assessment of relevant railway infrastructure assets. The assessment methods considered will be those applicable to the following asset types: Cuttings Metallic Bridges Lined Tunnels Track (including rails, sleepers, ballast, switches and crossings).The most appropriate assessment method for every specific infrastructure asset strongly depends on many variables. This deliverable seeks to help the assessing engineer, first showing the available alternatives and, after that, in the decision making for the best method and technique to be used within a Life-Cycle Assessment framework, where the optimization of cost in a wide sense (including environmental costs) is the final objective.
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| 10. |
- Du, Linpu, et al.
(författare)
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Shaking table test on a novel mega-frame suspended structural system
- 2022
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 52
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Tidskriftsartikel (refereegranskat)abstract
- This paper designed a 1/20 scaled two-segment 19-story mega-frame suspended structure. The seismic behaviors of the structure equipped with viscous dampers (named damping suspended structure, DSS) or rigid connecting rods (named normal suspended structure, NSS) were studied and evaluated by a series of shaking table tests, where three seismic ground motions with two intensities were selected as input motions. Both acceleration and displacement responses of the primary and suspended structures were recorded. The results revealed that the mega-frame suspended system showed good seismic behaviors and viscous dampers could effectively improve its energy dissipation capacities. For DSS, the maximal acceleration and displacement reduction of suspended structures were 75.4% and 39.8% while those of the primary structure were 29.4% and 35.3% respectively. White noise tests showed all models were at the elastic stage under all cases. Evident relative displacements between the primary and subordinate structures were observed for DSS, in this case, the suspended floors were considered as the additional mass of the primary structure and the energy could be dissipated by the swing of suspended floors. The energy dissipation mechanism of DSS was theoretically analyzed while the effect of connection forms on vibration reduction was discussed.
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