Stockholm, Sweden
Stockholm, Sweden

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Norrstrom A.C.,KTH Royal Institute of Technology | Lov A.,KTH Royal Institute of Technology | Lov A.,Sweco AB
Applied Geochemistry | Year: 2014

Elevated concentrations of uranium (U) from natural sources have been measured in drinking water from private drilled wells in Sweden and many other countries world-wide. Although U is a radioactive element, radioactivity is not the main concern, but rather chemical toxicity, e.g. kidney damage. Uranium chemistry is complex and U in water has a very high tendency to form complexes with other compounds. Since speciation is crucial for the properties of U, and therefore the removal efficiency, this study determined theoretical U species in drinking water from private drilled wells using the geochemical model Visual MINTEQ. The drinking water samples used in modelling were from two datasets: (1) 76 water samples selected from a previous survey of 722 wells; and (2) samples of drinking water from 21 private wells sampled in May 2013. The results showed that neutrally charged U complexes dominated in the pH range 6.7-7.8, which is common in private drilled wells. This has important implications for removal method, since charge is an important factor for U removal efficiency. In the alkaline pH range, one of two calcium-UO2 carbonate complexes dominated and calcium (Ca) concentration proved to be a key factor determining the Ca-UO2 carbonate complex formed: the neutral Ca2UO2(CO3)3 0(aq) or the negative CaUO2(CO3)3 2 -. Complexes with organic carbon (C) varied greatly in the acidic range, indicating that it is crucial to measure organic C content in the water since it is critical for the dissolved organic matter (DOM)-UO2 complex formation. Therefore before U removal method is selected, some crucial parameters for complex formation should be measured. Based on our results, such measurements should include pH, Ca, alkalinity and organic C concentration, as these determine the type of complexes formed and their charge. © 2014.

Setreus J.,KTH Royal Institute of Technology | Wallnerstrom C.J.,KTH Royal Institute of Technology | Hilber P.,KTH Royal Institute of Technology | Boos C.,Vattenfall | Goransson R.,Sweco AB
2010 IEEE 11th International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2010 | Year: 2010

One major objective of maintenance management activities in electrical distribution systems is to find the right level of investments. Within an MSc thesis project at KTH, the probabilistic reliability software RACalc has been developed to support the decision making in the distribution system maintenance planning and risk analysis. This paper describes the algorithms in RACalc and shows on present status on RADPOW, an additional reliability tool developed within the research group. Calculations with RACalc is in this paper exemplified with a case study on an existing Swedish distribution system, were the program is used to determine the components' importance to the system reliability indices. The result show that if the failure rate can be decreased by 10% on the 21% most important components, the overall system reliability improvement is more than 7%. ©2010 IEEE.

Schindhelm R.,Bundesanstalt For Strassenwesen Bast Federal Highway Research Institute | Calderaro J.F.G.,University of Valencia | Udin C.,Sweco AB | Larsson P.,Sweco AB | And 3 more authors.
19th Intelligent Transport Systems World Congress, ITS 2012 | Year: 2012

This paper presents results of a stakeholder analysis which was performed by the EasyWay Cooperative Systems Task Force. The study focuses on the road operator which is one of the stakeholder groups relevant for the deployment and operation of cooperative systems. The road operator will not only be affected by the impacts of cooperative systems but may also play an active part in the operation of cooperative services. Optional function schemes of selected cooperative services are described and related potential roles of the road operator in the operation process of these services are identified. Results of a deepened analysis of the developed function schemes and role profiles are shown which give insight in expectations and aspirations towards cooperative services from a road operator's view.

Fragiacomo M.,University of Sassari | Lukaszewska E.,SWECO AB
Journal of Structural Engineering (United States) | Year: 2015

Timber-concrete composite beams (TCCs) are made from a concrete topping fastened to a timber beam. Different methods can be used to construct the TCCs. The concrete topping can be either poured on the timber beam with preinstalled connectors or prefabricated off-site and then connected to the timber beam. The timber beam can be shored during assembling with the concrete topping or left unshored. The use of the shored construction is usually recommended as a way to reduce long-term deflection; however, it is costly. This paper investigates the influence of the construction method on the long-term behavior. A previously developed rigorous uniaxial finite element (FE) software has been first validated on some long-term tests performed in Sweden on TCCs with prefabricated concrete slabs and different connection systems. The FE model has then been used to carry out some analyses where the deflection in the long term has been compared with the same TCC constructed in different ways. Parameters investigated include the mode of construction of the concrete slab (prefabricated off-site or cast in situ), the assembly of the composite beam (with shored or unshored timber beam), the storage time of the concrete slab, and the time between the end of construction and the application of the live load. The outcomes of this numerical study indicate that by prefabricating the concrete slab it is possible to reduce the long-term deflection, particularly when the slab is stored for at least 28-56 days before it is connected to the timber beam and when the timber beam is shored for at least 1 day. In these cases, the effect of concrete shrinkage is reduced, as well as the instantaneous and delayed deflection due to the self-weight of the beam. Conversely, systems with concrete poured on the timber beam should be shored for a longer time (at least 7 days). Shoring the timber beam does not markedly change the increase in long-term deflection due to concrete shrinkage; however, it does raise the tensile stresses in the concrete slab during the period the shores are left in place, leading to the potential for cracking when stiff shear connectors are used and for long shoring times. © 2015 American Society of Civil Engineers.

Fragiacomo M.,University of Sassari | Lukaszewska E.,SWECO AB
Proceedings of the Institution of Civil Engineers: Structures and Buildings | Year: 2011

The timber-concrete composite structure consists of timber joists or beams effectively interconnected to a concrete slab cast on top of the timber members. This type of structure is finding new applications in multi-storey buildings and short-span bridges. Most of the research performed to date has focused on systems where 'wet' concrete is cast on top of timber beams with mounted connectors. This paper presents a novel composite system where the concrete slab is prefabricated off-site with connectors already embedded and then connected to the timber joists on site. The advantages of this method include reduced cost and better quality control of the materials, absence of 'wet' components on site during building erection and reduced concrete shrinkage effects on the composite beam. The paper reports an overview of a pilot research project conducted at Luleå University of Technology, Sweden, which includes direct shear tests to failure of different connection systems, bending tests to failure, dynamic (vibration) tests and long-term tests under sustained load of full-scale composite beams. The paper also reports the mechanical properties of the connection, which can be used within a simple design method given in Eurocode 5. The economic advantages of prefabrication and the possibility of demounting the structure make the proposed floor system very promising.

Fragiacomo M.,University of Sassari | Lukaszewska E.,SWECO AB
Engineering Structures | Year: 2013

This paper presents the results of long-term experimental tests performed on prefabricated timber-concrete composite beams intended for use in a proposed floor system, in which the concrete slab is prefabricated off-site and connected to the timber beam using one of two novel connection systems (either steel tubes inserted into the concrete slab and coach screws, or metal plates embedded in the concrete slab and nailed to the timber beams). In the experimental programme two beam specimens representing strips of composite floor were subjected to sustained (quasi-permanent service) loading for almost a year in an indoor, unheated and unconditioned environment. Throughout the test, mid-span deflection, relative slips at various connector locations, strains in the concrete slab and timber beam, and the ambient relative humidity and temperature, were continuously monitored. Both specimens showed only minor increases in deflection, slips and strains over time, demonstrating excellent overall long-term behaviour. The findings are consistent with a major advantage of prefabrication in this context; the concrete cures and can thus freely shrink before the slab is connected to the timber beam, thereby minimising stresses and deflection in the composite beam. Results of accompanying numerical analyses are also presented. A rigorous uniaxial finite element model was first validated against experimental results, and then used to predict the total deflection at the end of the 50-year service life of the specimens tested and of other specimens with different connection system not tested. The total deflection was found to be in the range of 3.5-4 times the elastic deflection due to the quasi-permanent load condition (excluding the self-weight of the beam). This value was always lower than the acceptable limit of span length over 200, with better predicted performance from stiffer connection systems such as notches cut in timber and glued-in dowels. © 2013 Elsevier Ltd.

Glamheden R.,Golder Associates | Olofsson I.,Svensk Karnbranslehantering AB | Fredriksson A.,Sweco AB
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

The Swedish Nuclear Fuel and Waste Management Co (SKB) has conducted site investigations for a final repository in Sweden. The site investigations establish site descriptive models for two candidate sites. These models were the result of an interaction of several geoscientific disciplines, including rock mechanics. As a part of the planning work for the site investigations, a rock mechanics site descriptive modelling strategy was developed. The modelling strategy included two approaches for estimation of rock mass properties, an empirical approach based on classification systems and a theoretical approach using numerical models. The theoretical approach was originally developed only for evaluation of properties of bedrock and minor deformations zones. However, the geological conditions at the candidate sites required a modified approach applicable for large deformation zones. Presented in this paper is a project that was carried out for verification of the theoretical approach for determination of mechanical properties of such zones. © 2012 Taylor & Francis Group, London.

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