Temperaturberäkningar i utvändig brandutsatt stålkonstruktion: FDS kombinerat med TASEF i jämförelse med Eurokod
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Access balconies are commonly used at residential buildings. This provides access to apartments as well as an escape route in the event of fire. Since the access balcony is an escape route the structure also assigns certain requirements of the fire resistance. Part of the aims of this study was to evaluate temperatures arising in an external steel column of a typical access balcony. The calculations of temperatures were made by combining the calculation programs FDS and TASEF. The adiabatic surface temperature was calculated with output from FDS and was then further used as input in TASEF. Another part of the aims was also to assess the combination of the programs to see if it is suitable to use in design situations. The object of the study was to investigate how constant heat release rates of different values influence the steel temperature of the columns. The columns were assumed to lose a significant level of its strength when exceeding a critical temperature of 550 °C. The geometry of the case study consisted of a fire compartment with one opening, where an access balcony was located above the opening. A method where it was possible to change the dimensions and material of the columns subsequently was used and therefore the columns were not given any dimensions in FDS. The proposed positions of the columns were along the edge of the balcony, at the same distance from the façade. One column was located in the centreline of the opening and one at the side of the opening. The temperature of the steel was calculated in two dimensions at three different heights. In FDS three different simulations were performed and the heat release rate was the only parameter changed. Constant heat release rates of 6, 8 and 10 MW were used but only the simulation of 6 MW was later able to be used for an analysis of the steel temperature. Results obtained from FDS and TASEF showed then a maximum steel temperature of 820 °C after one hour at the top of the column located at the centreline of the opening. At a corresponding time and height of the column, placed at the side of the opening, the maximum temperature reached 750 °C. The maximum temperatures always occurred at the sides turned towards the opening. At all sides towards the opening the steel temperature exceeded the critical temperature. The critical temperature was not reached at the two lowest heights at sides turned away from the opening. At the sides turned away from the opening it is obvious that heat transfer within the column has occurred since the adiabatic surface temperature was lower than the corresponding calculated steel temperature. The results from the column in the centreline of the opening from the calculation programs were used in a comparison with corresponding results from the Eurocodes EN 1991-1-2 and EN 1993-1-2. The steel temperature of the column and gas temperatures in the fire compartment and along the balcony was compared. Results according to the Eurocode generally showed lower temperatures. A reason could be the chain of assumptions made in the calculation procedure and these may lead to an unrealistic result. The numerical model with the use of FDS to obtain parameters for adiabatic surface temperature and then use this as input in TASEF turned out to work well. Validation against full-scale tests was wanted and performed to the extent it was possible. A lot of parameters in the tests were different from the case study, which made the comparison problematic. Differences in the tests were for example the heat release rate, the location of the columns or that the balcony was missing in the geometry.
Place, publisher, year, edition, pages
2013. , 96 p.
Teknik, FDS, TASEF, Eurokod, brand, temperatur, beräkning, utvändig, konstruktion, simulering, stål, pelare, loftgång
IdentifiersURN: urn:nbn:se:ltu:diva-51979Local ID: 92352828-d0a7-4928-aeb8-25c508ffe27dOAI: oai:DiVA.org:ltu-51979DiVA: diva2:1025345
Subject / course
Student thesis, at least 30 credits
Fire Engineering, master's level
Validerat; 20130615 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved