TY - JOUR A1 - Chaves Spoglianti de Souza, Roberto A1 - Andreini, M. A1 - La Mendola, S. A1 - Zehfuß, J. A1 - Knaust, Christian T1 - Probabilistic thermo-mechanical finite element analysis for the fire resistance of reinforced concrete structures N2 - 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. KW - Thermo-mechanical PY - 2019 U6 - https://doi.org/10.1016/j.firesaf.2018.12.005 SN - 0379-7112 SN - 1873-7226 VL - 104 SP - 22 EP - 33 PB - Elsevier AN - OPUS4-48583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chaves Spoglianti de Souza, Roberto A1 - Andreini, M. A1 - La Mendola, S. A1 - Zehfuß, J. A1 - Knaust, Christian T1 - Probabilistic thermo-mechanical finite element analysis for the fire resistance of reinforced concrete structures N2 - 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. KW - Fire Safety KW - Concrete KW - Probabilistic KW - Finite Elements PY - 2018 U6 - https://doi.org/10.1016/j.firesaf.2018.12.005 SN - 0379-7112 VL - 104 SP - 22 EP - 33 PB - Elsevier AN - OPUS4-47422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Knaust, Christian T1 - Modellierung von Tunnelbränden T1 - Modeling tunnel fires – Coupling of fluid and structure N2 - 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. N2 - The current technology allows the coupling of the temperaturedependent heat transfer mechanisms in case of fire within the structural components and at their surface by means of computational fluid dynamics (CFD). In this paper the thermal coupling of a fluid and a solid region in case of a 100 MW tunnel fire caused by a truck was carried out with CFD. The transient fire simulations were performed with the CFD program ANSYS Fluent. The fire was modeled by the combustion of n-heptane (C7H16) using the eddy dissipation model. The fluid and the solid region were coupled by an interface. The unsteady heat conduction for the 0.4 m thick concrete structure is modeled by using the Fourier heat transfer equation. The transient thermal behavior of quartz containing concrete component was analyzed. Temperature-dependent material properties were considered. KW - Wärmeleitung KW - Berechnungen analytische und empirische KW - ANSYS Fluent KW - Radiation KW - Computational fluid dynamics KW - Temperature dependent properties KW - Analytical and empirical calculations KW - Wärmeübertragung KW - Strahlung KW - Temperaturabhängige KW - Heat transfer KW - Conduction PY - 2016 U6 - https://doi.org/10.1002/bate.201600045 SN - 0932-8351 SN - 1437-0999 VL - 93 IS - 8 SP - 543 EP - 554 PB - Ernst & Sohn Verlag für Architektur und technische Wissenschaften CY - Berlin AN - OPUS4-37211 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Knaust, Christian A1 - Hofmann-Böllinghaus, Anja T1 - Full scale investigations of fast spreading room fires N2 - 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. PY - 2014 UR - http://www.hanser-elibrary.com/doi/pdf/10.3139/120.110518 SN - 0025-5300 VL - 56 IS - 1 SP - 7 EP - 15 PB - Hanser CY - München AN - OPUS4-30232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Palis, Stephan A1 - Sträubig, Felix A1 - Voigt, Sascha A1 - Knaust, Christian T1 - Experimental investigation of the impact of water mist on high-speed non-premixed horizontal methane jet fires N2 - In this paper, the influence of a fixed water mist firefighting system on a high-speed non-premixed horizontal methane jet fire is investigated with focus on its effect on temperatures and heat load of the jet fire and on ist surroundings. Six tests are performed in which gas is released out of an orifice with a diameter of 1 mm and a release pressure of up to 186 bar. In addition to temperature and radiation measurements, the release pressure, gas mass flow rate and exhaust gas concentrations are detected to determine the heat release. Video and IRanalysis are used to evaluate the interactions between jet fire and water mist. The experiments show, that water mist reduces the temperatures inside the jet fire flow field and its radiative heat flux. It can lower the Risk of ignition of adjacent surfaces and materials, as temperatures fall below autoignition temperatures of common materials like plastics. Although water mist does not extinguish the fire, it has an impact on the energy release by reducing combustion efficiency due to heat exchange with the water mist and oxygen displacement. KW - Fixed firefighting system KW - Jet fire KW - Water mist KW - Fire test KW - Methane KW - Supersonic flow PY - 2020 U6 - https://doi.org/10.1016/j.firesaf.2020.103005 VL - 114 SP - 103005 PB - Elsevier Ltd. AN - OPUS4-50963 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Voigt, Sascha A1 - Sträubig, Felix A1 - Palis, Stephan A1 - Kwade, A. A1 - Knaust, Christian T1 - Experimental comparison of Oxygen Consumption Calorimetry and Sensible Enthalpy Rise Approach for determining the heat release rate of large-scale lithium-ion battery fires N2 - From a fire safety point of view, the burning behavior of lithium-ion batteries is of high interest. The heat release rate (HRR) is the most important fire parameter to analyze the fire hazards of burning objects, so that an accurate determination of it is crucial. In this paper, two different measurement techniques, the Oxygen Consumption Calorimetry (OCC) and the Sensible Enthalpy Rise Approach (SERA) are simultaneously performed in the same calorimeter to measure the HRR of two different types of lithium-ion batteries. HRR values as well as total energies determined by SERA are higher than measured with OCC: The total energy released is about 10–12 times (SERA) and 6–9.5 times (OCC) the electrical stored energy for both battery types, whereas the timescales of the release differ strongly between the types, resulting in maximum HRRs of 3.4 MW (SERA) and 1.5 MW (OCC) for one module of type A and 0.8 MW (SERA) and 0.6 (OCC) of type B respectively. Furthermore, a sensitive dependency of the HRR measurement with SERA on the position of the wall temperature measurement is observed. KW - Fire tests KW - Lithium-ion-batteries KW - Heat release rate KW - Calorimetry KW - Sensible enthalpy rise approach KW - Oxygen consumption calorimetry PY - 2021 U6 - https://doi.org/10.1016/j.firesaf.2021.103447 SN - 0379-7112 IS - 126 PB - Elsevier Ltd. AN - OPUS4-53441 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hahn, S.-K. A1 - Rost, M. A1 - Kusche, Christian A1 - Knaust, Christian A1 - Krause, U. T1 - Dokumentation der Entwicklung des m-Faktors und neuer Aspekt der Verbrennungseffizienz T1 - Structural fire protection in industrial buildings - development of the m-factor and new aspect of the combustion efficiency N2 - 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. KW - Abbrandfaktor KW - DIN 18230 KW - Indrustriebau KW - Brandschutz im Brandlast KW - Verbrennungseffizienz PY - 2017 U6 - https://doi.org/10.1002/bate.201700020 SN - 0932-8351 SN - 1437-0999 VL - 94 IS - 6 SP - 337 EP - 343 PB - Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG CY - Berlin AN - OPUS4-40962 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Eberwein, Robert A1 - Rogge, Andreas A1 - Behrendt, F. A1 - Knaust, Christian T1 - Dispersion Modeling of LNG-Vapor on Land – A CFD-Model Evaluation Study N2 - Based on methane from renewable resources, LNG is an alternative fuel for heavy and long-distance traffic in land transport. Contrary to its positive properties, the fuel contains risks from an explosion and extremely low temperatures for personal and infrastructure safety. CFD-models are suitable for doing risk analyses for arbitrary scenarios. For examining how to model for risk research the dispersion of LNG-vapor, this paper contains a model variant study, with an evaluation by experiments. This paper describes the use of the CFD-code ANSYS Fluent for simulating experiments of the ‘LNG Safety Program Phase II‘. The content of the well-documented experiments was the research of the vaporization rate of LNG on land and the dispersion of LNG-vapor in the air. Based on the comparison to two experiments, overall 12 CFD-model variants with varying thermal and turbulence parameters were examined how they affect the transient LNG-vapor dispersion in air. The definition of turbulence-boundary-condition at the domain borders had the biggest impact on modeling, followed by the turbulence model. The most accurate model variant had been applied for observing the spreading behavior of LNG-vapor in the air after evaporation on land and analyzing the influence of the LNG-composition to the dispersion. The results show that the mixture of LNG-vapor and the air in the free field is cooler than the ambient air and spreads like a heavy gas on the ground. KW - LNG KW - CFD KW - Heavy gas KW - Model evaluation PY - 2020 U6 - https://doi.org/10.1016/j.jlp.2020.104116 VL - 65 SP - 104116 PB - Elsevier Ltd. AN - OPUS4-50697 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hofmann-Böllinghaus, Anja A1 - Knaust, Christian A1 - Krüger, Simone A1 - Raspe, Tina A1 - Deubel, Jan T1 - Detailed analysis of a smouldering fire scenario at the murder scene - experimental and numerical investigations N2 - 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. KW - Fire investigation KW - Smouldering fire KW - Fire development KW - Crime KW - Numerical modelling PY - 2014 U6 - https://doi.org/10.1002/fam.2222 SN - 0308-0501 SN - 1099-1018 VL - 38 IS - 8 SP - 806 EP - 816 PB - Heyden CY - London AN - OPUS4-32016 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Voigt, Sascha A1 - Sträubig, Felix A1 - Palis, Stephan A1 - Kwade, A. A1 - Knaust, Christian T1 - CFD-analysis of Sensible Enthalpy Rise Approach to determine the heat release rate of electric-vehicle-scale lithium-ion batteries N2 - This paper analyses the suitability of the Sensible Enthalpy Rise Approach for measuring the heat release rate of electric-vehicle-scale lithium-ion batteries. An apparatus is designed that meets the conditions of an electric-vehicle-scale lithium-ion battery fire by using cement board as wall material. Modifications of the Sensible Enthalpy Rise Methodology are presented due to the high emissivity and inhomogeneous temperature distribution of the apparatus wall material: a power 4 approach for the heat flow from the walls to the ambient air and an alternative determination methodology for the wall temperature. A one factor at a time parameter study is performed with Computational Fluid Dynamics simulations, investigating a new calibration method based on a fit approach compared to common methods, the wall temperature determination, the approach for the ambient heat flow, the calibration power and the volume flow at the outlet. The simulations show, that suitable estimations of the heat release rate are obtained by using the modifications for wall temperature determination and the power 4 approach for the ambient heat flow. The three calibration methods provide suitable constants, if the calibration power in the same order of magnitude as the mean of the heat release rate profile of the test object. KW - Lithium-ion batteries KW - Heat Release Rate KW - Calorimetry KW - Sensible Enthalpy Rise Approach KW - Computational Fluid Dynamics PY - 2020 U6 - https://doi.org/10.1016/j.firesaf.2020.102989 VL - 114 SP - 1 EP - 14 PB - Elsevier Ltd. AN - OPUS4-50964 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -