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Autor

  • Knaust, Christian (9)
  • Krause, U. (4)
  • Hofmann-Böllinghaus, Anja (3)
  • Andreini, M. (2)
  • Chaves Spoglianti de Souza, Roberto (2)
  • La Mendola, S. (2)
  • Zehfuß, J. (2)
  • Auerkari, Pertti (1)
  • Deubel, Jan (1)
  • Hahn, S.-K. (1)
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Erscheinungsjahr

  • 2019 (1)
  • 2018 (1)
  • 2017 (1)
  • 2016 (3)
  • 2014 (2)
  • 2013 (1)

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  • Englisch (6)
  • Deutsch (3)

Referierte Publikation

  • ja (9) (entfernen)

Schlagworte

  • ANSYS Fluent (1)
  • Abbrandfaktor (1)
  • Analytical and empirical calculations (1)
  • Berechnungen analytische und empirische (1)
  • Brandschutz im Brandlast (1)
  • Brandschutz im Industriebau (1)
  • Computational fluid dynamics (1)
  • Computational fluid dynamics (CFD) (1)
  • Concrete (1)
  • Conduction (1)
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Organisationseinheit der BAM

  • 7 Bauwerkssicherheit (9)
  • 7.0 Abteilungsleitung und andere (4)
  • 7.5 Technische Eigenschaften von Polymerwerkstoffen (4)
  • 7.3 Brandingenieurwesen (1)

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Dokumentation der Entwicklung des m-Faktors und neuer Aspekt der Verbrennungseffizienz (2017)
Hahn, S.-K. ; Rost, M. ; Kusche, Christian ; Knaust, Christian ; Krause, U.
Vor dem Hintergrund der Zurückziehung der DIN 18230 Teil 2 zur Bestimmung des m-Faktors von Materialien für die Brandlastbewertung im Industriebau müssen neue Wege gefunden werden, wie das Abbrandverhalten alternativ quantifiziert werden kann. Der Beitrag fasst die Entstehung und die Entwicklung der Bestimmungsweise von Abbrandfaktoren zusammen und gibt Ausblick auf eine neue Möglichkeit zur Bewertung von Brandlasten, die Verbrennungseffizienz.
Probabilistic thermo-mechanical finite element analysis for the fire resistance of reinforced concrete structures (2018)
Chaves Spoglianti de Souza, Roberto ; Andreini, M. ; La Mendola, S. ; Zehfuß, J. ; Knaust, Christian
This paper presents a probabilistic methodology based on the thermo-mechanical finite elements analysis to investigate the impact of the variability of the thermal properties of the concrete in the fire safety of structures. This is meant to evaluate if characteristic values or safety factors for the conductivity and specific heat are required during the semi-probabilistic structural fire safety assessment. To illustrate the use of the proposed methodology, this work includes a case-study with a tunnel lining which considers the uncertainties related to the thermal and mechanical properties of the concrete, the soil load, and the temperatures described by the standard temperature-time curve. Two failure criteria are considered: one was the maximum temperature of 300 °C at the reinforcement and the other based on the temperature-dependent strength as provided in the Eurocode EN 1992-1-2. Several finite element analyses are performed. The design of experiments is executed by a Correlation Latin Hypercube Sampling. The calculated probability of failure has different values depending on the adopted failure criteria. A sensitivity analysis using the Spearman's rank correlation coefficient was carried out and demonstrates that the uncertainty related to the specific heat has the greatest impact on the results.
Probabilistic thermo-mechanical finite element analysis for the fire resistance of reinforced concrete structures (2019)
Chaves Spoglianti de Souza, Roberto ; Andreini, M. ; La Mendola, S. ; Zehfuß, J. ; Knaust, Christian
This paper presents a probabilistic methodology based on the thermo-mechanical finite elements analysis to investigate the impact of the variability of the thermal properties of the concrete in the fire safety of structures. This is meant to evaluate if characteristic values or safety factors for the conductivity and specific heat are required during the semi-probabilistic structural fire safety assessment. To illustrate the use of the proposed methodology, this work includes a case-study with a tunnel lining which considers the uncertainties related to the thermal and mechanical properties of the concrete, the soil load, and the temperatures described by the standard temperature-time curve. Two failure criteria are considered: one was the maximum temperature of 300 °C at the reinforcement and the other based on the temperature-dependent strength as provided in the Eurocode EN 1992-1-2. Several finite element analyses are performed. The design of experiments is executed by a Correlation Latin Hypercube Sampling. The calculated probability of failure has different values depending on the adopted failure criteria. A sensitivity analysis using the Spearman's rank correlation coefficient was carried out and demonstrates that the uncertainty related to the specific heat has the greatest impact on the results.
Modellierung von Tunnelbränden (2016)
Knaust, Christian
Heute verfügbare Technik ermöglicht es, die Wärmetransportmechanismen im Brand, an der Bauteiloberfläche und im Bauteil mittels CFD zu koppeln. Die Kopplung von Fluid und Struktur wurde am Beispiel eines 100-MW-Tunnelbrands mit CFD (Computational Fluid Dynamics) untersucht. Die instationären Berechnungen wurden mit dem CFD-Programm ANSYS Fluent durchgeführt. Der infolge eines Lkw-Unfalls verursachte n-Heptan-(C7H16)-Brand wurde mit dem Eddy-Dissipation-Verbrennungsmodell modelliert. Das Fluid- und Solid-Gebiet wurden durch ein ‚Interface‘ gekoppelt. Die instationäre Wärmeleitung des Bauteils mit einer Höhe von 0,4 m wurde mit der dreidimensionalen Fourier´schen Wärmeleitungsgleichung modelliert und das instationäre thermische Verhalten des quarzhaltigen Betonbauteils analysiert. Temperaturabhängige Stoffkennwerte wurden berücksichtigt.
Detailed analysis of a smouldering fire scenario at the murder scene - experimental and numerical investigations (2014)
Hofmann-Böllinghaus, Anja ; Knaust, Christian ; Krüger, Simone ; Raspe, Tina ; Deubel, Jan
Based on forensic evidence, a smouldering fire was observed to have occurred at a murder scene. Identification of a reasonable timeline – specifically the fire dynamics of the ignition and fire growth that occurred coincident with the death that took place – became an important focus of the criminal investigation that followed. The fire service was called when a neighbour saw a grey smoke escaping through the ventilation system of the bathrooms on the roof of the house. One flat door with elevated temperatures was found. The fire fighter who entered the flat first reported later that the flat was completely filled with smoke and all windows were closed. When the fire fighter opened the balcony door, he saw flames on the sofa that he extinguished. Then he found a body on the floor. The autopsy showed later that the victim was dead before the fire started. The police suspected that the murderer probably had deliberately set the fire to destroy evidence. One suspect had been witnessed to be in the flat approximately 2 h before the fire was detected by the neighbour. The aim of this project was to investigate how the fire most likely started and developed.
Full scale investigations of fast spreading room fires (2014)
Knaust, Christian ; Hofmann-Böllinghaus, Anja
Brände in Wohnungen entwickeln sich heutzutage sehr schnell, weil der Anteil an brennbaren Materialien in Einrichtungsgegenständen und elektrischen Geräte in den letzten Jahren signifikant zugenommen hat. Insbesondere Brände in Kinderzimmern können sehr gefährlich sein, was mehrere Brände in Deutschland in den letzten Jahren belegen. Um die Brand- und Rauchentwicklung bei einem solchen Brand zu untersuchen, wurde ein Testraum wie ein typisches Kinderzimmer möbliert und mit 36 Thermoelementen sowie einem Druckmessgerät ausgestattet. Zusätzlich wurden Rauchmelder installiert. Der Brand wurde mittels eines Teelichts initiiert, das für ca. eine Sekunde mit einer Matratze in Kontakt gebracht wurde. Der Feuerüberschlag fand nach nur vier Minuten statt. Sowohl die Brandlast als auch die Brand- und Rauchentwicklung wurden untersucht. Vorschriften zur Brandsicherheit von Einrichtungsgegenständen, elektrischen Geräten und Spielzeugen wurden diskutiert. Ergänzend wurde der Temperaturanstieg im Brandraum unter Anwendung des Verfahrens von McCaffrey vorhergesagt.------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Fires in homes develop very fast nowadays, because the amount of combustible materials in furniture and electrical devices has increased significantly in recent years. Especially fires in children's rooms can be very hazardous as several recent fires in Germany showed. To investigate the fire and smoke development in such a fire the test room was furnished like a typical children’s room and equipped with 36 thermocouples and a pressure measurement device. Also smoke detectors were installed. The fire was ignited by a small candle which was in contact with a mattress only for one second. Flashover occurred only after 4 minutes. The fire load and the fire and smoke development were investigated. The fire safety regulations for the furnishings, electrical devices and toys were discussed. Additionally the temperature rise in the compartment was predicted according to the method of McCaffrey.
CFD modeling approach of smoke toxicity and opacity for flaming and non-flaming combustion processes (2016)
Löhnert, Andrea ; Monreal, Nils ; Knaust, Christian ; Hofmann-Böllinghaus, Anja ; Krause, U.
Current engineer’s methods of fire safety design include various approaches to calculate the fire Propagation and smoke spread in buildings by means of computational fluid dynamics (CFD). Because of the increased computational capacity, CFD is commonly used for prediction of time-dependent safety parameters such as critical temperature, smoke layer height, rescue times, distributions of chemical products, and smoke toxicity and visibility. The analysis of smoke components with CFD is particularly complex, because the composition of the fire gases and also the smoke quantities depends on material properties and also on ambient and burning conditions. Oxygen concentrations and the temperature distribution in the compartment affect smoke production and smoke gas toxicity qualitatively and quantitatively. For safety designs, it can be necessary to take these influences into account. Current smoke models in CFD often use a constant smoke yield that does not vary with different fire conditions. If smoke gas toxicity is considered, a simple approach with the focus on carbon monoxide is often used. On the basis of a large set of experimental data, a numerical smoke model has been developed. The developed numerical smoke model includes optical properties, production, and toxic potential of smoke under different conditions. For the setup of the numerical model, experimental data were used for calculation of chemical components and evaluation of smoke toxicity under different combustion conditions. Therefore, averaged reaction equations were developed from experimental measurements and implemented in ANSYS CFX 14.0.
Ansätze zur numerischen Berechnung von Brandeinwirkungen auf Bauteile (2016)
Kaudelka, Sven ; Knaust, Christian ; Krause, U.
Bei der Erstellung von brandschutztechnischen Nachweisen für Industriebauten werden häufig Ingenieurmethoden des Brandschutzes genutzt. Dazu zählen die Modellierung und Berechnung von Brandszenarien mittels numerischer Strömungsmechanik (computational fluid dynamics, CFD). In dieser Arbeit wurde ein auf numerischer Strömungs- und Strukturmechanik basierendes Verfahren zur brandschutztechnischen Bemessung von Bauteilen am Beispiel einer Industriehalle angewendet. Instationäre Temperaturverläufe aus der Heißgasschicht dienten dabei als Eingangswerte für die Bauteilberechnung. Aus den Ergebnissen wurde die äquivalente Branddauer berechnet, mit der die rechnerisch erforderlichen Feuerwiderstandsdauern der Bauteile bestimmt werden konnte.
Approaches towards a generic methodology for storage of hazardous energy carriers and waste products (2013)
Lerena, P. ; Auerkari, Pertti ; Knaust, Christian ; Vela-Wallenschus, Iris ; Krause, U.
Energy carriers – either conventional or 'new' ones – have to be provided in large amounts to meet the requirements of permanent availability and reliable supply of electricity. Depending on their state of aggregation, energy carriers are either stored in large masses (if solid or liquid) or at elevated pressures (if gaseous). Both impose the hazard of large-scale fire, in the latter case additionally the danger of explosion or unintended release. Very similar hazards occur for wastes. Solid wastes are present in large masses and only a small part is recycled. Most of the solid wastes are used in energy conversion. The main gaseous waste is CO2. During capturing also the hazard of unintended release exists. In this article, existing approaches for safe storage and fire prevention are discussed and a generic methodology is outlined. This methodology consists of the following steps: • gaining knowledge about the behaviour of the material stored (reactivity, thermal stability, etc.), • assessing the environmental conditions for the storage site (neighbourhood, safety distances, etc.), • assessment of prospective consequences of an incident and • development of individual loss prevention conceptions. All steps require both experimental testing and theoretical considerations about accident scenarios as integral parts of the methodology.
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