scholarly journals Development of an Analytical Model to Determine the Heat Fluxes to a Structural Element Due to a Travelling Fire

2021 ◽  
Vol 11 (19) ◽  
pp. 9263
Author(s):  
Marion Charlier ◽  
Jean-Marc Franssen ◽  
Fabien Dumont ◽  
Ali Nadjai ◽  
Olivier Vassart

The term “travelling fire” is used to label fires which burn locally and move across the floor over a period of time in large compartments. Through experimental and numerical campaigns and while observing the tragic travelling fire events, it became clear that such fires imply a transient heating of the surrounding structure. The necessity to better characterize the thermal impact generated on the structure by a travelling fire motivated the development of an analytical model allowing to capture, in a simple manner, the multidimensional transient heating of a structure considering the effect of the ventilation. This paper first presents the basic assumptions of a new analytical model which is based on the virtual solid flame concept; a comparison of the steel temperatures measured during a travelling fire test in a steel-framed building with the ones obtained analytically is then presented. The limitations inherent to the analyticity of the model are also discussed. This paper suggests that the developed analytical model can allow for both an acceptable representation of the travelling fire in terms of fire spread and steel temperatures while not being computationally demanding, making it potentially desirable for pre-design.

2022 ◽  
Vol 237 ◽  
pp. 111866
Author(s):  
Roberto Parot ◽  
José Ignacio Rivera ◽  
Pedro Reszka ◽  
José Luis Torero ◽  
Andrés Fuentes

2021 ◽  
Author(s):  
Matt Harrison ◽  
Joshua Gess

Abstract Using Particle Image Velocimetry (PIV), the amount of fluid required to sustain nucleate boiling was quantified to a microstructured copper circular disk. Having prepared the disk with preferential nucleation sites, an analytical model of the net coolant flow rate requirements to a single site has been produced and validated against experimental data. The model assumes that there are three primary phenomena contributing to the coolant flow rate requirements at the boiling surface; radial growth of vapor throughout incipience to departure, bubble rise, and natural convection around the periphery. The total mass flowrate is the sum of these contributing portions. The model accurately predicts the quenching fluid flow rate at low and high heat fluxes with 4% and 30% error of the measured value respectively. For the microstructured surface examined in this study, coolant flow rate requirements ranged from 0.1 to 0.16 kg/sec for a range of heat fluxes from 5.5 to 11.0 W/cm2. Under subcooled conditions, the coolant flow rate requirements plummeted to a nearly negligible value due to domination of transient conduction as the primary heat transfer mechanism at the liquid/vapor/surface interface. PIV and the validated analytical model could be used as a test standard where the amount of coolant the surface needs in relation to its heat transfer coefficient or thermal resistance is a benchmark for the efficacy of a standard surface or boiling enhancement coating/surface structure.


Author(s):  
T Schioler ◽  
S Pellegrino

This article presents a novel bistable structural element that has high stiffness in stable configurations, but requires only a small amount of energy to be switched from one configuration to the other. The element is based on a planar linkage of four bars connected by revolute joints, braced by tape-spring diagonals. A description of the concept is presented, along with a detailed theoretical analysis of its mechanical behaviour. Experimental measurements obtained from a prototype structure are found to be in very good agreement with the predictions from this analytical model.


Author(s):  
Marina Erenberg ◽  
Claus Bletzer ◽  
Martin Feldkamp ◽  
André Musolff ◽  
Marko Nehrig ◽  
...  

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.


2021 ◽  
Vol 59 (1) ◽  
pp. 77-107

Political risk concerns the profits and investment plans of international business (MNCs, FDI). The Social Dimensions of Political Risk – SDPR is an unchartered territory of political risk. Consequently, on the basis of the analysis of theories of risk, political risk, systems, values and globalization the concept for SDPR is generated. This concept is based on basic assumptions: 1) society is a system whose elements are subsystems; 2) the societal subsystem is at the core of society; 3) the relation between societal subsystem and society is such as the relation element – system; 4) political risk is systemic; 5) values are axial to the system, and their carrier is the societal subsystem; 6) laws are an artificial construct that has only a value function, but is not a value; 7) the incommensurability between values and the above mentioned artificial construct generates SDPRs that are relevant to the risk for society. A formal theoretical and analytical model of SDPR and a value triangle and conceptual index of SDPR based on it are introduced. Key conclusions pertain to the following: the need for reconsider the paradigm of democracy; greater participation of the societal subsystem; need for subsystems’ mutual restraint based on the principle of authorities’ restraint.


2019 ◽  
Vol 11 (12) ◽  
pp. 3389
Author(s):  
Heong-Won Suh ◽  
Su-Min Im ◽  
Tae-Hoon Park ◽  
Hyung-Jun Kim ◽  
Hong-Sik Kim ◽  
...  

Large-scale fires mainly due to the ignition of thermal insulation materials in the ceiling of piloti-type structures are becoming frequent. However, the fire spread in these cases is not well understood. Herein we performed small-scale and real-scale model tests, and numerical simulations using a fire dynamics simulator (FDS). The experimental and FDS results were compared to elucidate fire spread and effects of thermal insulation materials on it. Comparison of real-scale fire test and FDS results revealed that extruded polystyrene (XPS) thermal insulation material generated additional ignition sources above the ceiling materials upon melting and propagated and sustained the fire. Deformation of these materials during fire test generated gaps, and combustible gases leaked out to cause fire spread. When the ceiling materials collapsed, air flew in through the gaps, leading to flashover that rapidly increased fire intensity and degree of spread. Although the variations of temperatures in real-scale fire test and FDS analysis were approximately similar, melting of XPS and generation of ignition sources could not be reproduced using FDS. Thus, artificial settings that increase the size and intensity of ignition sources at the appropriate moment in FDS were needed to achieve results comparable to those recorded by heat detectors in real-scale fire tests.


2018 ◽  
Vol 9 (4) ◽  
pp. 319-341 ◽  
Author(s):  
Ana Sauca ◽  
Thomas Gernay ◽  
Fabienne Robert ◽  
Nicola Tondini ◽  
Jean-Marc Franssen

Purpose The purpose of this paper is to propose a method for hybrid fire testing (HFT) which is unconditionally stable, ensures equilibrium and compatibility at the interface and captures the global behavior of the analyzed structure. HFT is a technique that allows assessing experimentally the fire performance of a structural element under real boundary conditions that capture the effect of the surrounding structure. Design/methodology/approach The paper starts with the analysis of the method used in the few previous HFT. Based on the analytical study of a simple one degree-of-freedom elastic system, it is shown that this previous method is fundamentally unstable in certain configurations that cannot be easily predicted in advance. Therefore, a new method is introduced to overcome the stability problem. The method is applied in a virtual hybrid test on a 2D reinforced concrete beam part of a moment-resisting frame. Findings It is shown through analytical developments and applicative examples that the stability of the method used in previous HFT depends on the stiffness ratio between the two substructures. The method is unstable when implemented in force control on a physical substructure that is less stiff than the surrounding structure. Conversely, the method is unstable when implemented in displacement control on a physical substructure stiffer than the remainder. In multi-degrees-of-freedom tests where the temperature will affect the stiffness of the elements, it is generally not possible to ensure continuous stability throughout the test using this former method. Therefore, a new method is proposed where the stability is not dependent on the stiffness ratio between the two substructures. Application of the new method in a virtual HFT proved to be stable, to ensure compatibility and equilibrium at the interface and to reproduce accurately the global structural behavior. Originality/value The paper provides a method to perform hybrid fire tests which overcomes the stability problem lying in the former method. The efficiency of the new method is demonstrated in a virtual HFT with three degrees-of-freedom at the interface, the next step being its implementation in a real (laboratory) hybrid test.


2018 ◽  
Vol 8 (1) ◽  
pp. 147-155 ◽  
Author(s):  
Bartłomiej Sędłak ◽  
Jacek Kinowski ◽  
Paweł Sulik ◽  
Grzegorz Kimbar

Abstract Arguably, one of the most important requirement a building have to meet in case of fire is to ensure the safe evacuation of its users and the work of rescue teams. Consequently, issues related to the risks associated with falling parts of facades are fairly well known around Europe. Even though not equally well defined as other fire safety requirements concerning glazed facades, there is plenty of test methods for assessment of facades regarding falling parts, mostly based on an approach related to fire spread. In this paper selection of test method for assessment of facades regarding falling parts is briefly presented. However, focus of this work is on fire test of typical glazed segment of façade performed in ITB Laboratory. Results of the test positively verifies conjecture that solutions with glass units configured with thin, tempered glass panes on the outer side should pose no threat. However, the question has been raised whether the behaviour of other glass unit solutions (with additional coatings or laminated) would be similar.


2017 ◽  
Vol 21 ◽  
pp. 33-36
Author(s):  
Ruxandra Dârmon ◽  
Mircea Suciu

The fire safety regulations in Romania require that in case of a fire occurring into a building, it should be prevented to spread to any adjacent structure or neighbouring façade. Apart from the minimum prescribed distances between the buildings, there is no other benchmark or guidance for an approved calculation method to prove compliance with this provision. The British regulations have specified that the heat fluxes on the surfaces exposed to radiation from a fire within the adjacent buildings should not exceed a heat flux of 12.6 kW/m2. The purpose of this article is to review some of the empirical calculation methods for the incident radion flux given in the international literature and to compare their results for a practical aplication.


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