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Liquefied Hydrogen (LH2) or Liquefied Natural Gas (LNG) establish themselves as important energy carriers in the transport sector. Its storage requires tanks with Thermal Super Insulations (TSI) to keep the transported fluid cold. TSI has proven itself in various applications over a long time, but not in the land transport sector, where accidents involving collisions, fires, and their combination are to be expected. The focus of this study is to investigate the behavior of different types of TSI when exposed to a heat source that represents a fire. Therefore, a High-Temperature Thermal Vacuum Chamber (HTTVC) was used that allows the thermal loading of thermal insulation material in a vacuum and measuring the heat flow through the TSI in parallel. Within this study, 5 samples were tested regarding 3 different types of MLI, rock wool, and perlites. The thermal exposure caused different effects on the samples. In practice, this can be connected to the rapid release of flammable gases as well as a Boiling Liquid Expanding Vapour Explosion (BLEVE). These results are relevant for the evaluation of accident scenarios, the improvement of TSI, and the development of emergency measures.
Liquefied Hydrogen (LH2) or Liquefied Natural Gas (LNG)
establish themselves as important energy carriers in the transport
sector. Its storage requires tanks with Thermal Super Insulations
(TSI) to keep the transported fluid cold. TSI has proven itself in
various applications over a long time, but not in the land
transport sector, where accidents involving collisions, fires, and
their combination are to be expected. The focus of this study is
to investigate the behavior of different types of TSI when
exposed to a heat source that represents a fire. Therefore, a High-
Temperature Thermal Vacuum Chamber (HTTVC) was used that
allows the thermal loading of thermal insulation material in a
vacuum and measuring the heat flow through the TSI in parallel.
Within this study, 5 samples were tested regarding 3 different
types of MLI, rock wool, and perlites. The thermal exposure
caused different effects on the samples. In practice, this can be
connected to the rapid release of flammable gases as well as a
Boiling Liquid Expanding Vapour Explosion (BLEVE). These
results are relevant for the evaluation of accident scenarios, the
improvement of TSI, and the development of emergency
measures.
The importance of tanks for storing cryogenic fluids in the energy industry is increasing because of ongoing political conflicts and the implementation of more environmentally friendly energy sources. Key representatives for the application of cryogenic tanks are natural gas in the form of Liquefied Natural Gas (LNG) and hydrogen, e. g. in the form of Liquefied Hydrogen (LH2), for which significantly higher transport capacities can be achieved with the same transport volume using cryogenic storages than with storages based solely on overpressure.
What applies to all cryogenic transported fluids in common is their condition that must be maintained. Hence heat flows into the preserved fluid must be minimized. Thermal super Insulations (TSI) based on e. g. multilayer insulations (MLI), perlites, and vacuum are utilized for this purpose and have already proven themselves in similar applications. However, for the use of tanks for cryogenic fluids in the transport sector, there is insufficient knowledge regarding the course and consequences of incidents, which is due to the still short period of use and the few documented incidents, hence few investigations carried out in this field. Typical scenarios in the transport sector represent car accidents with collisions, fires, and their combination, which are associated with extraordinary loads on the tank.
The focus of this study is to investigate the behavior of TSI as a result of their thermal exposure to a heat source representing a fire. It is worth mentioning that this could lead to an increase of the heat flux into a tank by several orders of magnitude, and to permanent damage of the TSI, ultimately rapid release of flammable gas as well as a Boiling Liquide Expanding Vapour Explosion (BLEVE). For this purpose, a high temperature thermal vacuum chamber (HTTVC) has been developed that allows thermal loading of MLI or perlites in a vacuum and simultaneous measurement of heat flow through this TSI. The HTTVC is designed to represent realistic insulation conditions and to withstand thermal loads from typical design fires.
The HTTVC was applied to investigate TSI based on MLI and vacuum. It is shown that the thermal stress caused permanent damage to the TSI, with shrinkage, phase change, pyrolysis, and condensation being significant damage mechanisms. The results are relevant for the evaluation of accident scenarios and can thus contribute to the improvement of TSI and the development of emergency measures for the protection of persons and infrastructures.
The importance of tanks for storing cryogenic fluids in the energy industry is increasing because of ongoing political conflicts and the implementation of more environmentally friendly energy sources. Key representatives for the application of cryogenic tanks are natural gas in the form of Liquefied Natural Gas (LNG) and hydrogen, e. g. in the form of Liquefied Hydrogen (LH2), for which significantly higher transport capacities can be achieved with the same transport volume using cryogenic storages than with storages based solely on overpressure.
What applies to all cryogenic transported fluids in common is their condition that must be maintained. Hence heat flows into the preserved fluid must be minimized. Thermal super Insulations (TSI) based on e. g. multilayer insulations (MLI), perlites, and vacuum are utilized for this purpose and have already proven themselves in similar applications. However, for the use of tanks for cryogenic fluids in the transport sector, there is insufficient knowledge regarding the course and consequences of incidents, which is due to the still short period of use and the few documented incidents, hence few investigations carried out in this field. Typical scenarios in the transport sector represent car accidents with collisions, fires, and their combination, which are associated with extraordinary loads on the tank.
The focus of this study is to investigate the behavior of TSI as a result of their thermal exposure to a heat source representing a fire. It is worth mentioning that this could lead to an increase of the heat flux into a tank by several orders of magnitude, and to permanent damage of the TSI, ultimately rapid release of flammable gas as well as a Boiling Liquide Expanding Vapour Explosion (BLEVE). For this purpose, a high temperature thermal vacuum chamber (HTTVC) has been developed that allows thermal loading of MLI or perlites in a vacuum and simultaneous measurement of heat flow through this TSI. The HTTVC is designed to represent realistic insulation conditions and to withstand thermal loads from typical design fires.
The HTTVC was applied to investigate TSI based on MLI and vacuum. It is shown that the thermal stress caused permanent damage to the TSI, with shrinkage, phase change, pyrolysis, and condensation being significant damage mechanisms. The results are relevant for the evaluation of accident scenarios and can thus contribute to the improvement of TSI and the development of emergency measures for the protection of persons and infrastructures.
Packages for the transport of radioactive material shall meet the mechanical and thermal test requirements of the International Atomic Energy Agency (IAEA) regulations for package design approval. Besides mechanical testing, the Federal Institute for Materials Research and Testing (BAM) performs thermal tests in accordance with the IAEA regulations. The thermal test includes a 30-minute 800°C fully engulfing fire.
BAM continuously performs various thermal experiments for the investigation of the thermal response of packages with respect to the IAEA fire. The purpose of this paper is to give an overview of the already performed, ongoing and future physical tests and experiments of BAM in the field of thermal investigations. These research and development works shall support our competencies for the authority package design assessment.
BAM operates a propane gas fire test facility. To be able to carry out comparative investigations and validity between the propane fire and the in detail prescribed pool fire test in the regulations, BAM carries out various calorimetric tests and investigates the boundary conditions of the fire with the help of fire reference packages. At the same time, we are conducting various fire scenarios with wood-filled impact limiters. Large-scale fire tests of impact limiters are carried out on a full scale as well as on a small scale. Influencing variables are investigated in particular by means of geometric changes and the consideration of artificial damages, in particular holes. In addition to propane fire as a heat source, thermal scenarios are also investigated with hydrogen as heat source and an infrared radiator system to ignite test specimens. For these numerous test arrangements, the transferability to existing and newly developed transport package designs is essential and fruitful within the review of design approvals, especially for Dual Purpose casks with a long-lasting operation time.
The interest in hydrogen-based green energy is increasing worldwide, and the same is true for hydrogen-powered vehicles. Among the possible solutions to store hydrogen in such vehicles, cryogenic tanks equipped with multi-layer insulation (MLI) are the most promising to increase the amount of energy stored per unit volume. However, MLI is affected by severe deterioration when exposed to an external source of heat such as a fire following a car accident, leaving the tank unprotected and leading to failure in a relatively short time. In this work, a one-dimensional model to evaluate MLI thermal degradation when a liquid hydrogen tank is exposed to fire is presented. The relevance of taking MLI degradation into account when simulating the pressure increase due to external fire exposure is here demonstrated through the analysis of several case studies. The results show that MLI systems performance depletes within a few minutes of exposure to hydrocarbon poolfire.
This study provides an analysis on the fire safety of passengers and the fire protection of coaches and buses. A brief review of major bus fire incidents, an overview of current regulations in Europe, and their limitations are presented. The study finds that the current small-scale fire test methods described in UN ECE Reg No. 118 need to be replaced by test methods that can assess the reaction to fire of materials when exposed to ignition sources of varying sizes. To address these shortcomings, the study proposed an expert recommendation to update the material fire safety requirements and testing for buses. Additional measures are proposed, derived from objectives and strategies applied in other transport sectors, and can be tested through existing European and international standards, which are widely used by several industries. These measures aim to extend the time with tenable conditions for a safe evacuation in case of fire, reduce the degree of damage to buses, reduce the risk for fast and excessive thermal exposure on modern energy carriers needed for a more sustainable transport sector.
The interest in hydrogen-based green energy is increasing worldwide, and the same is true for hydrogen-powered vehicles. Among the possible solutions to store hydrogen in such vehicles, cryogenic tanks equipped with multi-layer insulation (MLI) are the most promising to increase the amount of energy stored per unit volume. However, MLI is affected by severe deterioration when exposed to an external source of heat such as a fire following a car accident, leaving the tank unprotected and leading to failure in a relatively short time. In this work, a one-dimensional model to evaluate MLI thermal degradation when a liquid hydrogen tank is exposed to fire is presented. The relevance of taking MLI degradation into account when simulating the pressure increase due to external fire exposure is here demonstrated through the analysis of several case studies. The results show that MLI systems performance depletes within a few minutes of exposure to hydrocarbon poolfire.
Liquefied Hydrogen (LH2) or Liquefied Natural Gas (LNG) establish themselves as important energy carriers in the transport sector. Its storage requires tanks with Thermal Super Insulations (TSI) to keep the transported fluid cold. The presentation includes 2 main topics of the department.
First TSI has proven itself in various applications over a long time, but not in the land transport sector, where accidents involving collisions, fires, and their combination are to be expected. To analyze fire scenarios a High-Temperature Thermal Vacuum Chamber (HTTVC) was developed that allows the thermal loading of thermal insulation material in a vacuum and measuring the heat flow through the TSI in parallel. Within this chamber, 5 samples were tested regarding 3 different types of MLI, rock wool, and perlites. In the presentation, the results are presented.
Second, the studying of accident scenarios enables the improvement of thermal superinsulation and to find novel insulation concepts. This is necessary for LH2 large-scale storages, for which state-of-the-art solutions are not suitable. Within the presentation, a novel insulation concept will be presented.
Acetylene pressure cylinders are widely used in the industrial sector for welding, flame cutting, or heating.
Sometimes during work, not only with acetylene cylinders, fires occur and in this case the risk of destruction increases and the behavior of such an exposed cylinder is unpredictable. The purpose of this study is to identify those critical conditions when acetylene cylinders burst and explode in fires. In the present study, acetylene cylinders were exposed to fire conditions. For this purpose, a woodpile as a source of fire was chosen, tested, and evaluated. In addition to the fire condition, this option guaranteed reproducibility and similar conditions for all tests. The individual cylinders were equipped with thermocouples measuring the shell temperature, and half of them were prepared in order to measure the temperatures inside the cylinder. An important factor was the measurement of the amount of pressure that was achieved during the destruction of the cylinder. For this purpose, a pressure transducer was attached to the outlet of the cylinder valve. Exposed to direct fire, they can explode in 10 min, which was confirmed. The critical pressure of 40 bar has been reached in 6 min, followed by destruction after 7 min in fire. Cylinders with internal thermocouples were destroyed when lower pressure was achieved. This confirms the fact that any change of the pressure cylinder affects the original properties. After the tests, the fragments of the selected cylinders were subjected to material tests. The results obtained in these tests are the main source of information for understanding the behavior of acetylene cylinders in fire and the possibility of increasing the safety of intervening rescue services in an emergency.
The risk analysis of road tunnels faces a growing complexity in fire scenarios, e.g. caused by new energy carriers. Essentially, such complex scenarios involve many interactions between the tunnel users, the fire source and the safety measures. One example is the alarm of tunnel users either initiated by the perception of smoke or by the fire alarm system. To consider these interactions for the quantification of consequences, e.g. fatalities, risk analysis requires a complex model. However, the complex model can compute in practice only few discrete scenarios due to its high computational cost, whereas risk analysis generally needs the consequences of a high number of random scenarios. Metamodels can solve this contradiction. They are able to approximate the consequences of many random scenarios with low computational cost based on the consequences of few discrete scenarios computed with the complex model. The efficiency of metamodels depends on the required number of these discrete scenarios. In this sense, this dissertation proposes an efficient metamodel within an innovative methodology for risk analysis of road tunnels to allow to consider an increased complexity of scenarios. This metamodel applies the following methods or models: the projection array-based design method specifies the experimental design for the discrete scenarios; the combination of the fire model FDS and the microscopic evacuation model FDS+Evac constitutes the complex model; and moving least squares produces the response surface model. The response surface model approximates the consequences of the random scenarios and therewith introduces an uncertainty, called metamodel uncertainty, which is quantified with the prediction interval method. Additionally, stochastic individual characteristics of tunnel users in discrete scenarios computed with FDS+Evac attribute evacuation uncertainties to the consequences. An original development in this dissertation, the ’direct approach’, directly transfers the evacuation uncertainties of the discrete scenarios to any random scenario. The evaluation of the metamodel in this dissertation shows following results. Firstly, the response surface model sufficiently represents the consequences of the complex model. Secondly, the metamodel uncertainty is also essential for this representation, but the prediction interval method reveals a drawback in the risk analysis. Potential approaches to deal with this drawback are discussed. Finally, the direct approach reproduces the evacuation uncertainty of the complex model which then clearly affects the consequences of random scenarios. Therefore, the consideration of the evacuation uncertainty plays an important role for the risk analysis. Furthermore, the projection array-based design method was adapted in this dissertation with two approaches, namely the combination of the experimental designs for FDS and FDS+Evac as well as their sequential refinement. Both approaches contribute to the efficiency of the metamodel. These results lead to following conclusions. Firstly, the metamodel efficiently integrates the consequences of discrete scenarios into risk analysis and thus allows to consider an increased complexity. Secondly, the metamodel is an advancement for risk analysis not only for road tunnelsbutalsomoregeneralinfiresafetyengineering. Forthesetworeasons,themetamodel might be interesting for other methodologies for risk analysis. In addition, the metamodel is generic and is therefore widely applicable on other issues beside from risk analysis, e.g. to assess the safety of structures related to time-consuming experiments depending on multiple variables.
Liquefied propane gas (LPG) tanks in a fully engulfing accidental fire experience a fast increase in internal pressure. The result is often a Boiling Liquid Expanding Vapor Explosion (BLEVE) that can result in a large fireball and flying debris over a radius of more than 100 meters.
In the last 30 years BAM has carried out more than 30 real scale fire tests on propane storage vessels across three test sites. The primary research goal was to identify systems that can delay or prevent a BLEVE. Early studies started with water deluge systems, and have since moved on to consider alternative protection systems.
It has been shown that an unprotected vessel fails within 10 minutes or less. Tests with different oil and propane fueled fires have given an overview on possible real accidents involving full-engulfing scenarios. LPG tanks of various sizes (2.7 m³, 3.6 m³, 4.8 m³, 6.7 m³) were used with different filling levels. Numerous protection systems, ranging from active systems like water systems to passive thick- and thin-film layers. Also, the degree of thickness of these layers was variated. Pressure relief valves (PRV) have also been investigated, both alone and in combination with protection systems.
This paper gives an overview of the work performed by BAM in the field of BLEVE prevention of protecting system since the last 30 years. It has been shown that e.g. with a full applied coating degree on the tank with and without PRV can be reached an exposition in a test fire scenario a duration of more than 60min. For partly coated tanks with and without PRV the duration time is like an unprotected vessel. Furthermore, it could be shown that the active water system also protects with technically correct design.
Accident safe packages for the transport of spent nuclear fuel and high-level waste shall fulfil international IAEA safety requirements. Compliance is shown by consecutive mechanical and thermal testing. Additional numerical analysis are usually part of the safety evaluation. For damage protection some package designs are equipped with wood filled impact limiters encapsulated by steel sheets. The safety of these packages is established in compliance with IAEA regulations. Cumulative mechanical and fire tests are conducted to achieve safety standards and to prevent loss of containment. Mechanical reliability is proven by drop tests. Drop testing might cause significant damage of the impact limiter steel sheets and might enable sufficient oxygen supply to the impact limiter during the fire test to ignite the wood filling. The boundary conditions of the fire test are precisely described in the IAEA regulatory. During the test the impact limiter will be subjected to a 30 minute enduring fire phase. Subsequent to the fire phase any burning of the specimen has to extinguish naturally and no artificial cooling is allowed. At BAM a large-scale fire test with a real size impact limiter and a wood volume of about 3m3 was conducted to investigate the burning behaviour of wood filled impact limiters in steel sheet encapsulation. The impact limiter was equipped with extensive temperature monitoring equipment. Until today burning of such impact limiters is not sufficiently considered in transport package design and more investigation is necessary to explore the consequences of the impacting fire. The objective of the large scale test was to find out whether a self-sustaining smouldering or even a flaming fire inside the impact limiter was initiated and what impact on the cask is resulting. The amount of energy, transferred from the impact limiter into the cask is of particular importance for the safety of heavy weight packages. With the intention of heat flux quantification a new approach was made and a test bench was designed.
Editorial façade fire safety
(2018)
This Special Issue of Fire and Materials brings together a collection of papers that were presented at the 2016 Interflam conference in the Fire & Facades session along with recent submissions to the Fire and Materials Journal that are very relevant to the Fire and Facades subject. Having attended the Interflam conference, all Fire and Materials Journal editors who attended realised the importance of this topic. We felt it important that this session content would both be reviewed and made available to a wider audience and that it was timely that we featured this increasing important topic in our journal. Accordingly, authors of selected papers were invited to update and extend their papers for journal submission, and other appropriate peer review papers subsequently submitted to the Journal were included in the collection.
As part of energy‐efficient renovations or for the construction of new buildings often external thermal insulation composite (ETIC) are used. In 2015, in Germany almost 37 million square meters were installed. But several fires involving ETIC systems with polystyrene foam (EPS) insulation in Germany led to an extensive discussion about fire safety of such systems. A collection initiated by the Frankfurt fire service of façade fires which include polystyrene insulation foam1 shows that more than two thirds of all reported fires started in front of buildings. In half of these fires burning waste containers were the first burning objects. Consequently, German building authorities called for tests of existing approved ETIC systems with EPS insulation in a fire Scenario representing a burning waste container. As these tests revealed weaknesses in the existing ETIC systems measures were introduced to enhance the systems. However, the recently introduced German test standard DIN 4102‐20 does not take These changes into account. The DIN test represents a fire where flames emerge an opening but is downscaled regarding the size of the fire load and therefore does not represent a fully developed fire in a room. In ETIC systems with EPS insulation, the render is an important factor for the fire performance of these systems as collapse of the render usually leads to very rapid fire development. Intermediate scale tests with ETICs specimens indicate that mechanical damages of the render weaken the System significantly. Challenges and possible measures to enhance fire safety of ETIC systems are discussed.
Unilateral thermal exposure of concrete building components induces moisture transport processes that have a significant influence on the spalling behaviour of dense high-strength concrete (HSC). These transport processes are based on evaporation and condensation mechanisms of liquid and gaseous water in the pores as well as the chemically bound water within the concrete. The low permeability of HSC and the formation of a saturated zone within building components (also known as a moisture clog) leads to high water-vapour pressures, which contributes to explosive spalling. The formation of these pressures has already been verified by means of pore-pressure measurement techniques. In addition, the redistribution of the moisture within concrete specimens subject to unilateral thermal exposure has been demonstrated on fractured surfaces. Investigations by means of the nuclear magnetic resonance (NMR) relaxometry technique and neutron radiography have shown one-dimensional changes in moisture distribution during thermal exposure.
However, none of these methods has been able to depict the moisture distribution in three dimensions (3D), so the link between pore size, concrete micro-structure and moisture content is missing. The research project presented in this paper aims to fill this gap by developing a new multi-level test methodology to characterise non-destructively the temporal course of spatial moisture distribution during unilateral thermal exposure. The procedure used during this programme included the collection of X-ray 3D-computed tomography (CT) measurements using a miniaturised specimen subjected to in-situ thermal exposure and the comparison of those CT results with the results of one-dimensional NMR-relaxometry before and after the heating process.
In the first step, a mobile heating device was developed, built and tested. To simulate a unilaterally-heated construction component, a cylindrical specimen made of HSC (Ø = 40 mm, L = 100 mm) was cast into an impermeable glass ceramic shell. The ceramic shell ensured a one-dimensional moisture flux and limited the thermal expansion of the concrete. An additional high-temperature wool (HTW) insulating shell ensured a one-dimensional heat flux. The heating device, which operated using infrared radiation (IR), allowed the unilateral heating of the specimens up to 300 °C using variable heating regimes.
In the second step, the mobile heating device was integrated into the CT-scanner, which enabled the collection of measurements before, during and after heating. By subtraction of successive 3D-CT images, X-ray attenuation differences could be resolved three-dimensionally in the specimen and interpreted as changes in the moisture content.
Initial results show that this test methodology can monitor the 3D changes of moisture content inside the specimen during thermal exposure. It enables the researcher to visualise areas with moisture accumulation as well as dehydrated areas inside the specimen. Comparative one-dimensional NMR-relaxometry measurements confirm the results of the CT image analysis.
Unilateral thermal exposure of concrete building components induces moisture transport processes that have a significant influence on the spalling behaviour of dense high-strength concrete (HSC). These transport processes are based on evaporation and condensation mechanisms of liquid and gaseous water in the pores as well as the chemically bound water within the concrete. The low permeability of HSC and the formation of a saturated zone within building components (also known as a moisture clog) leads to high water-vapour pressures, which contributes to explosive spalling. The formation of these pressures has already been verified by means of pore-pressure measurement techniques. In addition, the redistribution of the moisture within concrete specimens subject to unilateral thermal exposure has been demonstrated on fractured surfaces. Investigations by means of the nuclear magnetic resonance (NMR) relaxometry technique and neutron radiography have shown one-dimensional changes in moisture distribution during thermal exposure.
However, none of these methods has been able to depict the moisture distribution in three dimensions (3D), so the link between pore size, concrete micro-structure and moisture content is missing. The research project presented in this paper aims to fill this gap by developing a new multi-level test methodology to characterise non-destructively the temporal course of spatial moisture distribution during unilateral thermal exposure. The procedure used during this programme included the collection of X-ray 3D-computed tomography (CT) measurements using a miniaturised specimen subjected to in-situ thermal exposure and the comparison of those CT results with the results of one-dimensional NMR-relaxometry before and after the heating process.
In the first step, a mobile heating device was developed, built and tested. To simulate a unilaterally-heated construction component, a cylindrical specimen made of HSC (Ø = 40 mm, L = 100 mm) was cast into an impermeable glass ceramic shell. The ceramic shell ensured a one-dimensional moisture flux and limited the thermal expansion of the concrete. An additional high-temperature wool (HTW) insulating shell ensured a one-dimensional heat flux. The heating device, which operated using infrared radiation (IR), allowed the unilateral heating of the specimens up to 300 °C using variable heating regimes.
In the second step, the mobile heating device was integrated into the CT-scanner, which enabled the collection of measurements before, during and after heating. By subtraction of successive 3D-CT images, X-ray attenuation differences could be resolved three-dimensionally in the specimen and interpreted as changes in the moisture content.
Initial results show that this test methodology can monitor the 3D changes of moisture content inside the specimen during thermal exposure. It enables the researcher to visualise areas with moisture accumulation as well as dehydrated areas inside the specimen. Comparative one-dimensional NMR-relaxometry measurements confirm the results of the CT image analysis.
About 80 % of all fire fatalities in Germany occur in fires in homes1. UK statistics show that living and bed room fires are more often responsible for fatalities than kitchen fires although kitchen fires occur much more often2. It has been known for some time that modern materials tend to burn differently from older materials and it has been acknowledged that the amount of combustible plastics in homes has increased significantly over the last decades3-7. To investigate the influence of modern furniture and ventilation conditions of fires in homes a series of four large scale tests in two living rooms with adjacent rooms was performed by BAM and the Frankfurt fire service8. Two living rooms, one with older furniture and one with modern furniture were tested twice each. Each test started with the ignition of a paper cushion on an upholstered chair. The influence of modern materials on the fire development was investigated as well as the influence of the ventilation on the fire development. Two tests with closed windows and two tests with open windows were performed. Temperatures were measured in the living rooms and the adjacent rooms, gas compositions were measured in the adjacent rooms and videos were taken in all rooms. The ventilation as well as the different materials influenced the fire development regarding temperatures in the rooms and smoke production and composition significantly. The fire in the living room with modern furniture developed faster than the same setting with older furniture. More ventilation (open window) led to higher temperatures in the rooms and faster fire development as well. Smoke gas composition was measured in the adjacent rooms to assess the positive effect for a person being in the adjacent room and not in the room of fire origin. In all settings an upholstered chair was the first burning item. The modern upholstered chair was investigated in three pre-experiments under different conditions to enhance the understanding of the living room fires. The measured mass losses and derived mass loss rates have been used for numerical modelling of the pre-experiments.
A probabilistic approach for finite element analysis (FEA) for tunnel linings exposed to the nominal fire is presented. The probabilistic FEA accounted for the uncertainties distributions tied to the conductivity and specific heat as well as of the compressive strength, tensile strength, Young’s modulus, and ultimate strain in compression. To get an understanding on the influence of different probability density functions on the distribution of maximum displacements of the tunnel lining, a sensitivity analysis was performed. Four sets of FEAs were carried out with different probability distributions of the conductivity, the specific heat, and the compressive strength of the concrete, respectively. An experimental design based on a Latin Hypercube Sampling algorithm was performed to define the input parameters which describe each analysis case. A reliability analysis was executed considering a limit state function based on the temperature-dependent ultimate strain. The results show that, depending on the distribution adopted, the standard deviation of the maximum displacements can vary up to 47,4% of the minimum standard deviation. The large standard deviation is associated with the possibility of a greater displacement and, hence, to a structure more vulnerable to fire.
The joint research project AERIUS (BMBF), is working to determine the effectiveness and efficiency of CAF in comparison to pure water, water with foaming agents and nozzle-aspirated foams in an extensive series of firefighting experiments. The poster deals with a series of extinguishing tests with mixed-material burning cribs.
A novel deign of test equipment has been commissioned to investigate thermal stratification and boiling during fire exposure of pressure vessels. Extensive temperature measurements and video of the internal conditions during fire exposure are possible, and the equipment has been designed for future compatibility with laser-based velocity measurement techniques. It is expected to generate data large quantities of data that will be of use in validation of two- and three-dimensional CFD models for the prediction of pressure vessel behaviour in fire. Future work will seek to characterize the boundary layer conditions in detail for a range of test fluids, fill levels and fire-induced thermal boundary conditions.
Initial tests undertaken during commissioning may indicate that fire exposure of the vessel wall just above the liquid level can have a notable influence on the pressurization rate, by increasing the degree of superheat. Further experimental and modelling work is required to confirm and quantify this effect, or to rebut this conclusion.
A comparison between the results obtained from a Computational Fluid Dynamic (CFD) simulation and from the application of an empirical formula for determining the temperature distribution inside a tunnel in case of fire is presented. The temperature is measured and calculated at different distances from the location of the fire and at different time intervals. The fire considered varies with time following a time-heat release rate curve which has a parabolic growing phase, a constant period and a linear decay. The comparison reveals differences in the results. The temperatures calculated with the empirical formula resulted higher than the temperatures obtained by means of the CFD simulation. A list of possible reasons for this limited correspondence is also presented and commented. A proposal for further studies to better define the limitations of both the procedures and to define the influence of each parameter involved is finally presented.
A comparison between the results obtained from a Computational Fluid Dynamic (CFD) simulation and from the application of an empirical formula for determining the temperature distribution inside a tunnel in case of fire is presented. The temperature is measured and calculated at different distances from the location of the fire and at different time intervals. The fire considered varies with time following a time-heat release rate curve which has a parabolic growing phase, a constant period and a linear decay. The comparison reveals differences in the results. The temperatures calculated with the empirical formula resulted higher than the temperatures obtained by means of the CFD simulation. A list of possible reasons for this limited correspondence is also presented and commented. A proposal for further studies to better define the limitations of both the procedures and to define the influence of each parameter involved is finally presented.
Probabilistic thermo-Mechanical analysis of a concrete tunnel lining subject to fire The probability distributions of the parameters related to the thermal analysis was considered in order to study the variability of the results and to carry out a reliability analysis. This assessment considered as random variables the thermo-mechanical properties of the concrete, the maximum heat release rate (HRR), the duration of the period of maximum HRR, the convective coefficient, the emissivity at the surface exposed to the fire, the air velocity within the tunnel, and the initial fire radius. The temperature-time curve was described by a correlation. An experimental design based on a Latin Hypercube Sampling algorithm was performed to define the input parameters to each analysis case. The definition of a limit state function based on the punctual strain status has permitted to carry out a reliability analysis.
A probabilistic finite elements analysis (FEA) of a tunnel lining subject to fire is presented. The probability distributions of the parameters related to the thermal analysis was considered in order to study the variability of the results and to carry out a reliability analysis. This assessment considered as random variables the thermo-mechanical properties of the concrete, the maximum heat release rate (HRR), the duration of the period of maximum HRR, the convective coefficient, the emissivity at the surface exposed to the fire, the air velocity within the tunnel, and the initial fire radius. The temperature-time curve was described by a correlation. An experimental design based on a Latin Hypercube Sampling algorithm was performed to define the input parameters to each analysis case. The definition of a limit state function based on the punctual strain status has permitted to carry out a reliability analysis.
Methodologies on fire risk analysis in road tunnels consider numerous factors affecting risks (risk indicators) and express the results by risk measures. But only few comprehensive studies on effects of risk indicators on risk measures are available. For this reason, this study quantifies the effects and highlights the most important risk indicators with the aim to Support further developments in risk analysis. Therefore, a system model of a road tunnel was developed to determine the risk measures.
The system model can be divided into three parts: the fire part connected to the fire model Fire Dynamics Simulator (FDS); the evacuation part connected to the evacuation model FDS+Evac; and the frequency part connected to a model to calculate the frequency of fires. This study shows that the parts of the system model (and their most important risk indicators) affect the risk measures in the following order: first, fire part (maximum heat release rate); second, evacuation part (maximum preevacuation time); and, third, frequency part (specific frequency of fire). The plausibility of These results is discussed with view to experiences from experimental studies and past fire incidents.
Conclusively, further research can focus on these most important risk indicators with the aim to optimise risk analysis.
Although concrete itself is not a combustible material, concrete mixtures with high density, such has high-performance concretes (HPCs), are susceptible to significant damage during fires due to explosive spalling. Past research has shown that the inclusion of polymer fibers in high density concrete can significantly mitigate fire damage due to the contribution of the fibers to increased permeability levels at high temperature. This allows vapor pressures caused by the evaporation of internal water during fire to escape from the material without causing significant spalling. Recent microscopic investigations have also shown that the addition of polypropylene (PP) fibers to high-density HPC with a high amount of fine-aggregate has a considerable influence on the nature and character of crack formation due to autogenous shrinkage. Initial cracks, which originate from the fiber beds, undergo further expansion and propagation when concrete is subjected to thermal exposure in excess of 170 °C. It is thus of interest to determine whether the resulting cracks join the adjacent fiber beds and therefore contribute to a significant increase in the permeability of the concrete, which is directly correlated to lower pore pressures and reduced spalling during fire.
In this study, X-ray Computed Tomography (CT) was applied to provide a clear demonstration of the interaction between polymer fibers and cracking during thermal exposure. For this purpose, two concrete samples containing different polymer fiber types were subjected to incremental application of a defined thermal exposure. CT images were acquired before and after each thermal exposure and powerful image processing tools were used to segment the various material components, such as polymer fibers, cracks, aggregates and cement matrix, in each image. This enabled a detailed analysis of crack formation and propagation as well as the visualization and quantification of polymer fiber characteristics within the concrete. This paper will provide a description of the distribution and orientation characteristics of the polymer fibers within each sample obtained through the CT-based analysis. Using these results, the impact of fiber distribution and orientation characteristics on actual cracking geometries have been measured and visualized. This paper will also provide recommendations for further optimization of the selected materials and propose improved methods for future CT-based analysis techniques.
Forest fires start mostly in partial combustion. In this paper we present a hydrogen sensor to detect early stages of forest fires. First indoor experiments in a smoke density chamber with wood samples, proved that the sensor produce a strong signal change when the smouldering of wood starts, already before the CO concentration, measured in FTIR spectrometry, exceeds 10 ppm. Indoor experiments in a Smoke Density Chamber with wood samples show, that our sensor produces an earlier signal difference than a carbon monoxide detector. In outdoor experiments we were able to detect forest fire in a distance of 110 m.
Methodologies on fire risk analysis in road tunnels consider numerous factors affecting risks (risk indicators) and express the results by risk measures. But only few comprehensive studies on effects of risk indicators on risk measures are available. For this reason, this study quantifies the effects and highlights the most important risk indicators with the aim to Support further developments in risk analysis. Therefore, a system model of a road tunnel was developed to determine the risk measures.
The system model can be divided into three parts: the fire part connected to the fire model Fire Dynamics Simulator (FDS); the evacuation part connected to the evacuation model FDS+Evac; and the frequency part connected to a model to calculate the frequency of fires. This study shows that the parts of the system model (and their most important risk indicators) affect the risk measures in the following order: first, fire part (maximum heat release rate); second, evacuation part (maximum preevacuation time); and, third, frequency part (specific frequency of fire). The plausibility of These results is discussed with view to experiences from experimental studies and past fire incidents.
Conclusively, further research can focus on these most important risk indicators with the aim to optimise risk analysis.