| 1. |
- Bröchner, Jan, 1948, et al.
(författare)
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Performance of performance specifications in design-build highway projects
- 2019
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Ingår i: Australasian Journal of Construction Economics and Building. - : UNIV TECHNOLOGY, SYDNEY-UTS EPRESS. - 1835-6354 .- 1837-9133. ; 19:2, s. 111-125
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Tidskriftsartikel (refereegranskat)abstract
- Design-build contracts with performance-based specifications are believed to raise productivity and the innovation rate. Such specifications for highway and bridge contracts may create risks, be too detailed or difficult to verify. The purpose has been to analyse how performance-based requirements are used in Swedish design-build contracts for highway projects. How contractors are encouraged to provide innovative technologies is emphasized. Generic documents from the Swedish Transport Administration for design-build contracts have been studied, and case studies of six design-build contracts with performance-based requirements have been made. Technical specifications for these contracts have been analysed and interviews held with both client and contractor project managers. Results include that it is along the time axis that major obstacles to innovation arise. Before the contractor is able to develop innovative solutions, the initial design plan restricts the highway geometry. During construction, a mix of performance and prescriptive requirement formulations is more of a challenge than clashes between performance requirements. The client may avoid performance language, more so for bridges than road surfaces, because of concerns with efficient maintenance in the future. It is recommended that performance-based specifications should be less detailed and that a life cycle view of highway projects should support innovative technologies.
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| 2. |
- de Frias Lopez, Ricardo
(författare)
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Granular Materials for Transport Infrastructures : Mechanical performance of coarse–fine mixtures for unbound layers through DEM analysis
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Granular materials are widely used as unbound layers within the infrastructure system playing a significant role on performance and maintenance. However, fields like pavement and railway engineering still heavily rely on empirically-based models owing to the complex behaviour of these materials, which partly stems from their discrete nature. In this sense, the discrete element method (DEM) presents a numerical alternative to study the behaviour of discrete systems with explicit consideration of the processes at particulate level governing the macroscopic response. This thesis aims at providing micromechanical insight into the effect of different particle sizes on the load-bearing structure of granular materials and its influence on the resilient modulus and permanent deformation response, both of which are greatly influenced by the stress level. In order to accomplish this, binary mixtures of elastic spheres under axisymmetric stress are studied using DEM as the simplest expression for gap-graded materials, which in turn also can be seen as a simplification of more complex mixtures.First, the effect of the fines content on the force transmission at contact level was studied. Results were used to define a soil fabric classification system where the roles of the coarse and fine fractions were defined and quantified in terms of force transmission.A behavioural correspondence between numerical mixtures and granular materials was established, where the mixtures were able to reproduce some of the most significant features regarding the resilient modulus and permanent strain dependency on stress level for granular materials.A good correlation between soil fabric and performance was also found. Generally, higher resilient modulus and lower deformation values were observed for interactive fabrics, whereas the opposite held for instable fabrics.Mixtures of elastic spheres are far from granular materials, where numerous additional factors should be considered. Nevertheless, it is the author’s belief that this work provides insight into the soil fabric structure and its effect on the macroscopic response of granular materials.
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| 3. |
- Mohammadi Mohaghegh, Ali, et al.
(författare)
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An Initial Investigation of the Possibility to Use Basalt Fibres for More Durable Concrete Structures in Norwegian Fish Farming
- 2014
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Konferensbidrag (refereegranskat)abstract
- Reinforcement corrosion in concrete structures in the harsh environment of the humid and cold climate of the Norwegian west coast is one of the most challenging problems pertaining to the design and construction of marine concrete structures. Using new materials with a higher strength and durability than steel reinforcement can be a good solution in such circumstances. In our study we investigate the use of new forms of macro fibres termed MiniBars made from basalt fibres. The paper presents our preliminary findings indicating that basalt fibres might provide more sustainable reinforcement in concrete barges.
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| 4. |
- Mohammadi Mohaghegh, Ali, et al.
(författare)
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Properties of Fresh Macro Basalt Fibre (MiniBar) Self-Compacting Concrete (SCC) and Coventional Slump Concrete (CSC) Aimed for Marine Applications
- 2015
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Ingår i: Nordic Concrete Research. - Ålesund : NORSK BETONGFORENING. - 0800-6377. ; 52:1, s. 43-61
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Tidskriftsartikel (refereegranskat)abstract
- Macro basalt fibres (MiniBar) with high corrosion resistance could be a suitable material in fibre concrete for marine applications. Due to the lack of knowledge about macro basalt fibre concretes (BFCs), the main objective of this paper is to assess the fresh state properties of macro basalt fibre conventional slump concrete and self-compacting concrete as the first step of developing BFC for concrete barges for fish farming on the west coast of Norway. To satisfy the requirements for marine applications, DNV and NS-EN standard rules are employed as the basis for the durability performance design. The concrete mix is designed to achieve densely compacted matrix by using the modified Andreasen & Andersen model as the particle size distribution target. In this paper, slump, flow-ability, passing-ability, fibre dynamic segregation and also flow rate as an indication for viscosity of different BFCs are measured and analysed. The result shows that there is a possibility to produce BF-SCCs with a fibre content of 1.15%. The fibres have an aspect ratio of 65.15. In addition, the mixture composed of a maximum gravel size of 16 mm shows a higher flowability in comparison with the maximum gravel size of 12 mm.
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| 5. |
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| 6. |
- Ahmed, Lamis, et al.
(författare)
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Dynamic Measurements for Determining Poisson’s Ratio of Young Concrete
- 2018
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Ingår i: Nordic Concrete Research. - 0800-6377. ; :58, s. 95-105
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of the elastic properties of concrete at early age is often a pre-requisite for numerical calculations. This paper discusses the use of a laboratory technique for determining Poisson’s ratio at early concrete age. A non-destructive test set-up using the impact resonance method has been tested and evaluated. With the method, it has been possible to obtain results already at 7 hours of concrete age. Poisson's ratio is found to decrease sharply during the first 24 hours to reach a value of 0.08 and then increase to approximately 0.15 after seven days.
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| 7. |
- Andersson, Louise, et al.
(författare)
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Continuous preventive bridge maintenance in Sweden - Field experiment on the effect of washing on concrete bridges
- 2019
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Ingår i: Proceedings of the fib Symposium 2019. - : International Federation for Structural Concrete. - 9782940643004 ; , s. 1135-1141, s. 1135-1141
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Konferensbidrag (refereegranskat)abstract
- Bridges are an important part of the infrastructure. For the bridges to have the longest possible service life with minimum repairs, the maintenance is of great importance. One type of bridge maintenance that is rarely researched is the continuous preventive maintenance. The continuous preventive maintenance consists of removal of vegetation, cleaning of bridge joints and drainage systems as well as high-pressure washing of the structure. The effects of washing is heavily discussed but not properly researched. A study on the effectiveness of washing concrete is therefore being conducted. A field experiment has been initiated where concrete specimens are installed on an edge beam of a road bridge. The specimens are of two recipes where one represents an old bridge with rather high water-cement ratio and the other one represents a new bridge with a low water-cement ratio. 50% of the specimens are washed annually, while the others are not. Each year samples are collected and tested for a chloride profile. The results for the first year of exposure have been determined. They are promising but are still only very preliminary. The effect of washing, if any, will be visible after a longer exposure.
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| 8. |
- Andersson, Louise, et al.
(författare)
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Continuous Preventive Bridge Maintenance of Swedish Municipalities : A Survey on Common Practice
- 2018
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Ingår i: Nordic Concrete Research. - Oslo : Walter de Gruyter GmbH. - 2545-2819 .- 0800-6377. ; 58
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Tidskriftsartikel (refereegranskat)abstract
- As part of a report [1] on continuous preventive bridge maintenance, a survey was conducted with Swedish municipalities. The survey’s focus was on bridges and preventive maintenance, as well as the demands and performance control stated by the municipalities. The preventive maintenance the survey focused on was the annual maintenance concerning washing, cleaning of drainage system and removal of vegetation. The survey showed both similarities and differences within the municipalities but also in comparison with Swedish Transport Agency (STA).
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| 9. |
- Andersson, Louise, et al.
(författare)
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Effect of High Pressure Washing on Chloride Ingress in Concrete : Development of an accelerated test method
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Bridges constitute an important part of the infrastructure. For the bridges to have the longest possible service life with minimum repairs, the maintenance is of great importance. One type of bridge maintenance that is rarely researched is the continuous preventive maintenance. The continuous preventive maintenance consists of removal of vegetation, cleaning of bridge joints and drainage systems as well as high-pressure washing of the structure. The effects of washing is discussed but not properly researched. A study on the effectiveness of washing concrete is therefore being conducted. An accelerated method is being developed to mimic field testing. The method has been developed through tests on small concrete specimens subjected to fluctuating temperature, fluctuating moisture, and repeatable exposure to de-icing salt in cycles. The specimens are of two recipes where one represents an old bridge with rather high water-cement ratio (0.6) and the other one represents a new bridge with a low water-cement ratio (0.4). The first two versions of the method are described. The second version shows promising results, but the method needs further development to incorporate additional factors.
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| 10. |
- Andersson, Louise, et al.
(författare)
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Effect of High-Pressure Washing on Chloride Ingress in Concrete : Development of an Accelerated Test Method
- 2022
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Ingår i: Nordic Concrete Research. - : Walter de Gruyter GmbH. - 0800-6377 .- 2545-2819. ; 67:2, s. 35-50
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Tidskriftsartikel (refereegranskat)abstract
- Bridges constitute an important part of the infrastructure. For bridges to have the longest possible service life with minimum repairs, the maintenance is of great importance. One type of bridge maintenance that is rarely researched is the continuous preventive maintenance. The continuous preventive maintenance consists of removal of vegetation, cleaning of bridge joints and drainage systems as well as high-pressure washing of the structure. The effect of washing is discussed but not properly researched. A study on the effectiveness of high-pressure washing on concrete is therefore being conducted. An accelerated test method is being developed to mimic field testing. The method has been developed through tests on small concrete specimens subjected to fluctuating temperature, fluctuating moisture, and repeatable exposure to de-icing salt during several cycles. The specimens are of two recipes where one represents an old concrete bridge with rather high water-cement ratio (0.6) and the other one represents a new concrete bridge with a low water-cement ratio (0.4). The first two versions of the method are described. The second version shows promising results, but the method needs further development to incorporate additional factors.
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