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Temperature distribution and charring penetrations in timber assemblies exposed to parametric fire curves : Comparisons between tests and TASEF predictionsAndersson, Isac, Ek, Niklas January 2017 (has links)
Four furnace tests have been performed using two different parametric fire curves and the results are compared with computer simulations and Eurocode calculations. What differentiates the parametric fire curve from other fire curves is in particular the cooling phase, something that has proven to be hard to model for timber structures. A literature study and computer simulations were followed by experimental work performed at SP Wood Building Technology in Stockholm. The computer simulations were performed using the computer code TASEF. The predictions from TASEF were compared with measurements from the fire tests to evaluate how well the program can predict temperature distribution using a parametric fire curve. The four fire tests were executed at SP Wood Building Technology, glued laminated timber beams were used in all tests. When preparing the test specimens thermocouples were installed to measure temperature distribution, the thermocouples were installed in drilled holes. A deviation study regarding these drill-holes was performed as a part of the preparations. The temperature distributions measured during the tests were compared with the temperature distribution predicted by TASEF. Charring rate and charring depth were obtained from the fire tests, from the TASEF simulations but also by using equations given in the Eurocode. Since TASEF simulates temperature distribution and not charring depth, the 300 °C isotherm was assumed to represent the charring depth. The results from all three methods were compared and evaluated. The agreement between experiments and TASEF predictions regarding temperature distribution and charring depth were in general very good. Parametric fire curves with opening factors of 0.02 m1/2 and 0.04 m1/2 were used in four fire tests. TASEF performed more accurate predictions regarding the temperature distribution for the small opening factor but looking at the charring depth the predictions were better for the bigger opening factor. It is recommended to perform further studies and find out the reason for this behaviour. Comparing the charring depths measured at the tests with values calculated using Eurocode 5 there were some differences in charring depths. Charring depths for the horizontal direction of the beams were much alike, but when comparing the charring depths for the vertical direction there is a significant difference. The equations regarding charring depth for wood exposed to parametric fire curves in Eurocode 5 underestimate the charring depth. It is recommended to evaluate these equations further. For one of the timber beams delamination occurred, this has previously been assumed not to occur to glued laminated beams. More studies should be performed regarding delamination of glued laminated beams exposed to fire. / Fyra brandtester i en brandprovningsugn har genomförts med två olika parametriska brandkurvor och resultatet har jämförts med datorsimuleringar och Eurocode-beräkningar. Det som särskiljer parametriska brandkurvor från andra brandkurvor är nedkylningsfasen, något som har visat sig svårt att modellera för träkonstruktioner. Litteraturstudier och datorsimuleringar följdes av experimentellt arbete som utfördes vid SP Träbyggande och Boende i Stockholm. Datorsimuleringarna har utförts med datorkoden TASEF. Simuleringsresultat från TASEF jämfördes med mätningar från brandtesterna för att utvärdera hur bra TASEF kan förutse temperaturdistributionen då en parametrisk brandkurva används. De fyra brandtesterna förbereddes och utfördes på SP Träbyggande och Boende, limträbalkar användes i samtliga tester. När testbalkarna förbereddes inför brandtesterna installerades termoelement för att mäta temperaturdistributionen. Termoelementen installerades i borrhål. Som en del av förberedelserna gjordes en avvikelsestudie för dessa borrhål. Temperaturdistributionen som uppmättes under testerna jämfördes med temperaturdistributionen från TASEF-simuleringar. Från brandtester, TASEF-simuleringar och från ekvationer i Eurocode erhölls förkolningshastighet och förkolningsdjup. Eftersom TASEF simulerar temperaturer och inte förkolningsdjup användes 300 °C isotermen som då antogs representera förkolningsdjupet. Resultatet från alla tre metoder jämfördes och utvärderades. Generellt stämde temperaturdistributionen och förkolningsdjupen från TASEF-simuleringarna väldigt bra överens med de experimentella resultaten. Under testerna användes parametriska brandkurvor med öppningsfaktorer av 0.02 m1/2 och 0.04 m1/2. TASEF simulerade mer noggranna resultat gällande temperaturdistributionen för kurvan med den lägre öppningsfaktorn medan simuleringar för kurvan med den högre öppningsfaktorn gav bättre resultat för förkolningsdjupet. Det rekommenderas att göra fler studier för att ta reda på anledningen till detta beteende. Genom att jämföra förkolningsdjup som uppmättes efter brandtesterna med beräknade värden från Eurocode förekom vissa skillnader. Förkolningsdjup för bredden av balkarna var likartade, medan förkolningsdjupet för höjden av balkarna hade en signifikant skillnad. Ekvationerna i Eurocode underskattade förkolningsdjupet, det rekommenderas därför att utvärdera dessa ekvationer ytterligare. För en av limträbalkarna inträffade delaminering, detta har tidigare antagits vara osannolikt för limträbalkar. Fler studier borde utföras angående delaminering av limträbalkar exponerade för parametriska brandkurvor.
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Hållbara balkar : En jämförelse av bärförmåga och klimatpåverkan hos stål-, trä-, och stålförstärkta träbalkarIvansson, Viktor January 2023 (has links)
The contemporary imperative of sustainable development has established an unprecedented degree of urgency, in view of the intransigent challenges posed by the persistent and ever-increasing energy and climate crises. In 2019, the Swedish building industry accounted for 21% of the nation’s total greenhouse gas emissions, with the structural framework of a building contributing to 34% of its overall emissions. In response to climate change and the housing demand caused by a growing population, sustainable construction solutions are needed. By substituting steel beams with timber beams, the carbon emissions caused by the building industry can be reduced significantly. This study investigates whether timber based, or steel-reinforced timber beams can provide comparable load-bearing capacity to steel beams while reducing carbon. How this impacts the cross-sectional height of the beams is also taken into consideration. Different load-bearing properties were calculated according to Eurocode using Excel for all the surveyed beams. The carbon emissions were calculated based on the weight of each beam combined with climate data obtained from the Swedish National Board of Housing, Building and Planning. Findings suggest that timber-based beams made from glulam or laminated veneer lumber exhibit moment capacity and bending stiffness on par with those of steel beams while reducing the carbon emissions drastically, but at the cost of increased cross-section height. Steel beams were identified as the main source of carbon emissions. Consequently, also making steelreinforced timber beams only marginally successful in reducing carbon emissions if at all.
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