Alexandra Bystrom

Fire Safety Engineering, Structural Engineering, Safety Engineering

8.03

Publications

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    Alexandra Byström · Ulf Wickström
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    ABSTRACT: This paper shows and demonstrates how an analysis of the energy and mass balance of a fully developed (ventilation controlled) compartment fire can be used as a basis for simple and accurate predictions of fire temperatures. The model has been applied on compartments of light weight concrete structures. A finite element FE analysis has been used to solve the heat transfer equation. Effects of moisture were considered for material properties of the surrounding structure. The results were validated with experiments. The model then accurately predicted the fire temperatures and among other things it showed the influence of moisture in the surrounding structure on the fire temperature. Parametric temperature curves according to EN 1991-1-2, 2002 were shown to overestimate the fire temperature.
    Full-text · Article · Jan 2016
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    Dataset: DATA

    Full-text · Dataset · Jun 2014
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    ABSTRACT: A localized fire is a fire which in a compartment is unlikely to reach flash-over and uniform temperature distribution. Designing for localized fires is generally more difficult than for flash-over compartment fires because of the complexity of the problem. There is also a lack of experimental data. We report here on a full scale test series on a steel column exposed to localized fires. The setup is a 6 meters tall hollow circular column, ϕ = 200 mm with a steel thickness of 10 mm. The unloaded column was hanging centrally above different pool fires. Temperatures of gas and steel were measured by thermocouples, and adiabatic surface temperatures at the steel surface were measured by plate thermometers of various designs. The results are compared with estimates based on Eurocode 1991-1-2 which in all cases studied overestimate the thermal impact for this setup. The input from plate thermometers was used to compute the steel temperatures using finite element methods. Excellent agreement was found if the radiation exchange within the column due to asymmetry of the exposure was taken into account.
    Full-text · Article · Jun 2014 · Journal of Structural Fire Engineering
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    Alexandra Byström · Xudong Cheng · Ulf Wickström · Milan Veljkovic
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    ABSTRACT: Adiabatic surface temperature is an efficient way of expressing thermal exposure. It can be used for bridging the gap between fire models and temperature models, as well as between fire testing and temperature models. In this study, a full-scale compartment fire experiment with wood crib fuel was carried out in a concrete building. Temperatures were measured with plate thermometers and ordinary thermocouples. Five plate thermometers and five thermocouples with a diameter of 0.25 mm were installed at different positions. These two different temperature devices recorded different temperatures, especially near the floor surface. The adiabatic surface temperature was derived by a heat balance analysis from the plate thermometer measurements. The thermal inertia of the plate thermometer was taken into account to correct the measured results. In addition, the fire experiment scenario was also simulated with fire dynamics simulator. The fire source was specified as a given heat release rate, which was calculated from the measured mass loss rate of the wood fuel. The adiabatic surface temperatures at these measuring positions were simulated by the fire dynamics simulator model and compared with the experimental adiabatic surface temperatures. The comparative results showed that fire dynamics simulator predicted the adiabatic surface temperature accurately during the steady-state period.
    Full-text · Article · Jan 2013 · Journal of Fire Sciences
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    J Sjöström · A Byström · D Lange · U Wickström
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    ABSTRACT: This study investigates the thermal exposure to a full scale steel column exposed to localized fires. The steel column is a six meters long cylinder with a diameter of 200 mm. The fires are heptane and diesel fires from cylindrical pans of diameter 1.1 m and one diesel fire using a pan of 1.9 m in diameter. The main result is the experimental data on gas and steel temperatures. All experimental data can be found on the SP website http://www.sp.se/en/index/services/localized_fire/sidor/default.aspx and in the Appendix of this report. A comparison to calculations using the Eurocode recommendations for localized fires is also conducted. Even when using assumptions to keep the thermal exposure to the structure at a low level the Eurocode calculations greatly overestimate the thermal exposure. We also conduct finite element calculations using plate thermometer measurements as input and describe the temperature evolution in the column considering the heat exchange within the hollow column. The project is a collaboration between SP Fire Technology and Luleå Technical University. It is fully financed by Brandforsk, the Swedish Fire Research Board. Key words: Thermal exposure, localized fire, steel column, plate thermometers, Eurocode
    Full-text · Book · Jan 2013
  • Alexandra Byström · Xudong Cheng · Ulf Wickström · Milan Veljkovic
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    ABSTRACT: A fire experiment with wood crib was conducted in a concrete building under low ambient temperature of −10 °C to explore fire development and temperature distribution. The concrete building consists of a two-storey compartment with the size of 9.0 m by 5.0 m by 4.8 m high and a four-storey stairwell with the size of 5.0 m by 2.4 m by 10.0 m high. The fuel mass loss rate and temperatures at different positions were measured. Two fire cases, with different assumed ambient temperatures of −10 °C and 20 °C respectively, were then simulated by using FDS software to investigate the effect of ambient temperature and compare with the experimental results. The numerical results show that the calculated heat release rate is in reasonably good agreement with the measured full-scale result before water suppression. The calculated temperatures in the hot combustion gas layer at different positions agree also very well with the measured values. However, the measured fresh air temperature at the floor level near the fire source is higher than the calculated value. This discrepancy may partly depend on measuring errors as analyzed in the paper.
    No preview · Article · May 2012 · Building and Environment
  • Xudong Cheng · Alexandra Byström · Ulf Wickström · Milan Veljkovic
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    ABSTRACT: A pool fire test was conducted in an uninsulated steel container under low ambient temperature condition, at −20°C. The heat balance of the enclosure fire was analyzed. The size of the container was 12 m× 2.4 m and 2.4 m high, and it was made of 3-mm-thick steel. During the fire test, the fuel mass loss rate was recorded and the temperatures at different positions were measured with high-temperature thermocouples and plate thermometers. The fire scenario was simulated by using fire dynamics simulator software, and the simulated and measured results were compared. The coarse high-temperature thermocouple responded slower, and therefore, temperature measured by the high-temperature thermocouple was corrected to eliminate the effect of the thermal inertia. Furthermore, a simple two-zone model was proposed for estimating gas temperature in the enclosure of the highly conductive steel walls assuming a constant combustion rate. The convective and radiative heat transfer resistances at the inside and outside surfaces of the enclosure were analyzed.
    No preview · Article · Mar 2012 · Journal of Fire Sciences
  • Alexandra Byström · Johan Sjöström · Ulf Wickström · Milan Veljkovic

    No preview · Chapter · Jan 2012
  • Alexandra Byström · Johan Sjöström · Ulf Wickström · Milan Veljkovic

    No preview · Chapter · Jan 2012
  • Alexandra Byström · Ulf Wickström · Milan Veljkovic
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    ABSTRACT: The concept of Adiabatic Surface Temperature (AST) opens possibilities to calculate heat transfer to a solid surface based on one temperature instead of two as is needed when heat transfer by both radiation and convection must be considered. The Adiabatic Surface Temperature is defined as the temperature of a surface which cannot absorb or lose heat to the environment, i.e. a perfect insulator. Accordingly, the AST is a weighted mean temperature of the radiation temperature and the gas temperature depending on the heat transfer coefficients. A determining factor for introducing the concept of AST is that it can be measured with a cheap and robust method called the plate thermometer (PT), even under harsh fire conditions. Alternative methods for measuring thermal exposure under similar conditions involve water cooled heat flux meters that are in most realistic situations difficult to use and very costly and impractical. This paper presents examples concerning how the concept of AST can be used in practice both in reaction-to-fire tests and in large scale scenarios where structures are exposed to high and inhomogeneous temperature conditions.
    No preview · Article · Jul 2011

  • No preview · Chapter · Jan 2011

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