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| 2. |
- Sjöström, Johan, 1978-, et al.
(författare)
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En ny modell för gräsbrandsfara i Sverige
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Risken för antändning och snabb spridning av vegetationsbränder i skogsmark och i gräsmarkerskiljer sig markant. Gräsbränder sprider sig i dött fjolårsgräs, tidigt på våren, innan årets färskagräs hunnit växa till och dessa bränder kan spridas snabbt efter bara några timmars torrt väder.Risken klingar snabbt av med inväxten av färskt gräs för att i stort sett upphöra till sommaren.Skogsbränder har inte samma säsongsberoende av bränslet utan styrs mer av vädret. Därför skerde typiskt under sommaren och kräver oftast flera dagars torrt väder. Dessa skillnader gör attolika riskbedömningssystem måste användas för dessa två karakteristiska typer avvegetationsbränder.Här presenteras en ny modell för gräsbrandsfara som använder potentiell spridningshastighet iobetat, oklippt gräs som indikator på risk. Algoritmen tar väderhistoriken (snötäcke, relativluftfuktighet, vindhastighet, temperatur och solinstrålning) samt progressionen av årsgräsetsinväxt i beaktning. Modellen bygger på en modell för beräkning av fuktkvot i gräs utvecklad iNordamerika samt en modell för hur fuktkvoten och vindhastigheten inverkar påspridningshastigheten. Effekten av årsgräsets inväxt under svenska förhållanden beräknasgenom 25 års insats- och väder-data i tio regioner och en anpassning till tidigare utfördatestbränningar från snösmältning till gräsbrandssäsongens slut. Modellen kan uppdateras varjetimme, i linje med det uppdaterade brandrisksystemet i Sverige.Förslag till hur indelning i risknivåer ska utformas med avseende på riskindikatorn presenterasoch modellen sätts i bruk till våren 2021.
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| 3. |
- Wendt, Fabian, et al.
(författare)
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Ocean energy systemswave energy modelling task: Modelling, verification and validation ofwave energy converters
- 2019
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Ingår i: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 7:11
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Tidskriftsartikel (refereegranskat)abstract
- The International Energy Agency Technology Collaboration Programme for Ocean Energy Systems (OES) initiated the OES Wave Energy Conversion Modelling Task, which focused on the verification and validation of numerical models for simulating wave energy converters (WECs). The long-term goal is to assess the accuracy of and establish confidence in the use of numerical models used in design as well as power performance assessment of WECs. To establish this confidence, the authors used different existing computational modelling tools to simulate given tasks to identify uncertainties related to simulation methodologies: (i) linear potential flow methods; (ii) weakly nonlinear Froude-Krylov methods; and (iii) fully nonlinear methods (fully nonlinear potential flow and Navier-Stokes models). This article summarizes the code-to-code task and code-to-experiment task that have been performed so far in this project, with a focus on investigating the impact of different levels of nonlinearities in the numerical models. Two different WECs were studied and simulated. The first was a heaving semi-submerged sphere, where free-decay tests and both regular and irregular wave cases were investigated in a code-to-code comparison. The second case was a heaving float corresponding to a physical model tested in a wave tank. We considered radiation, diffraction, and regular wave cases and compared quantities, such as the WEC motion, power output and hydrodynamic loading.
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| 4. |
- Albrektsson, Joakim, et al.
(författare)
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Assessment of fire exposed concrete structures
- 2012
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Ingår i: fib Symposium 2012: Concrete Structures for Sustainable Community. - 9789198009811 ; , s. 619-622, s. 619-622
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Konferensbidrag (refereegranskat)abstract
- Annually, several concrete structures, such as buildings, bridges, parking garages and tunnels are exposed to fires. An assessment is then necessary to decide whether the structure can be repaired or needs to be replaced. In a recent research project, recommendations for assessments of fire exposed concrete structures have been developed. The recommendations are based on a literature survey, results from an experimental study, where ultrasonic measurements, microscopy, Digital Image Correlation (DIC) measurement on loaded core samples were used and practical experience of real post-fire structural assessments. A refined assessment of the fire damage is obtained by combining these test methods.
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| 5. |
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| 6. |
- Anderson, Johan, et al.
(författare)
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Experimental comparisons in façade fire testing considering SP Fire 105 and the BS 8414‐1
- 2018
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Ingår i: Fire and Materials. - : Wiley. - 0308-0501 .- 1099-1018. ; 42:5
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Tidskriftsartikel (refereegranskat)abstract
- A comparison between full‐scale façade fire tests where SP Fire 105 and BS 8414‐1 were used regarding repeatability and the use of modeling to discern changes in the setups is presented. Two test series according to BS 8414‐1 were repeated outside using the same façade systems on 2 different days, whereas for the SP Fire 105 a set of common façade systems in Sweden were tested indoors. In particular, the results show that the wind around the test setup may have a significant impact on the tests and that the heat exposure to the façade surface will depend on the thickness of the test specimen where an increased temperature in front of the façade, and a decreased temperature on the façade 2.1 m above the fire room, is observed experimentally. The heat exposure to the test specimen varies to a more limited extent when an uncontrollable free burning fire source is used (in this study heptane and wood, respectively) and that this variation increases when wind is present.
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| 7. |
- Anderson, Johan, et al.
(författare)
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Façade fire tests : Measurements and modeling
- 2013
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Ingår i: 1st International Seminar for Fire Safety of Facades, FSF 2013. - : EDP Sciences. - 9782759811007
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Konferensbidrag (refereegranskat)abstract
- In two recent papers [1, 2] the fire dynamics in a test rig for façade constructions according to the test method SP Brand 105 [3, 4] was investigated both experimentally and numerically. The experimental setup simulates a three-story apartment building (height 6.7m, width 4m and depth 1.6m), with external wall-cladding and a "room fire" at the base. The numerical model was developed in the CFD program Fire Dynamics Simulator (FDS) [5] with analogous geometry and instrumentation. The general features of the fire test were well reproduced in the numerical model however temperatures close to the fire source could not be properly accounted for in the model. In this paper the bi-directional probe measurements are elaborated on and the test used in Ref. [1] is revisited using different heat release rates in the numerical model. The velocity of the hot gases along the façade was well reproduced by the simulations although some deviations were found.
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| 8. |
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| 9. |
- Anderson, Johan, et al.
(författare)
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Fire dynamics in Façade fire tests : Measurement, modeling and repeatability
- 2015
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Ingår i: Applications of Structural Fire Engineering. - : Czech Technical University in Prague. - 2336-7318. - 9788001061947
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Konferensbidrag (refereegranskat)abstract
- Presented is a comparison between full-scale façade tests where SP Fire 105 and BS 8414-1 were used regarding repeatability and the use of modelling to discern changes in the set-ups. Results show that the air movements around the test set-up (the wind) may have a significant impact on the tests and that the heat exposure to the façade surface will among other depend on the thickness of the test specimen. Also demonstrated was that good results could be obtained by modelling of the façade fire tests giving us the opportunity to use these methods to determine the effect of a change in the experimental setup.
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| 10. |
- Anderson, Johan, 1973-, et al.
(författare)
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Fire Safety of Façades
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Façade fires do not occur often (in comparison to other major structure fires) but in recent years there have been a number of spectacular façade fires in high rise building such as the recent fire in Grenfell Tower, London.Under-ventilated compartment fires may cause flames to spill out of window openings impinging the façade, thus devastating façade fires may start on one floor leap-frogging to adjacent floors. It is therefore necessary to limit or delay fire spread to higher floors. Requirements built on large scale fire testing may decrease the risk of these types of fires provided that the building is constructed according to the specifications provided by the manufacturer. Different countries have different regulations and tests for façades. New materials and façade systems are continuously introduced which might call for an update of these tests and regulations.This report summarizes experimental and modelling efforts in characterizing the fire safety of façades using the Swedish SP Fire 105 and the British BS 8414 methods. Recent experimental results and modelling is presented exploring the variations in the fire exposure, fire load and the fuel used. The fire source and the heat exposure to the façade are characterized by additional temperatures measured by plate thermometers while some other aspects are only treated in the numerical study such as a change in fuel. It is found that the results from the BS 8414 are largely affected by wind and climate since the experimental test was performed outdoors, moreover fire spread on wooden façades is also briefly discussed.In order to obtain a deeper understanding of the test methods and the results CFD (Computational Fluid Dynamics) Modelling in FDS was used. The models were based on measured input parameters including uncertainties and an assessment of the impact of said uncertainties. The models could often reproduce the experimentally found temperatures qualitatively and quantitatively. A detailed discussion on the regulations and the tests that lead to the SP Fire 105 test method is also presented. Summaries of the façade testing methods and conditions in other European countries are presented in the appendices.Finally possible ways forward in updating the façade testing and regulations are discussed.
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