CROSS FLOW EFFECTS ON THE FLAME HEIGHT OF AN INTERMEDIATE SCALE DIFFUSION FLAME

Kolb,Gilles,Torero,Jose L,Most,Jean-Michel,Joulain,Pierre 한국화재소방학회 1997 한국화재소방학회 학술대회 논문집 Vol.1997 No.-

An experimental study has been conducted at an intermediate scale to study the effect of a cross flow on a purely buoyant fire. Video taping of the flame and post processing of the images by means of a novel technique provide a contour of a mean flame for all cases studied. This flame contour allows the determination of a mean flame length and a mean flame height. The mean flame length and height are recorded as functions of the forced flow velocity. Three dimensional flow patterns are formed in the flame trailing edge affecting both the mean flame length and height. The three dimensional patterns are studied systematically as functions of the cross flow velocity to quantify the effect of confinement on the flame geometry.

Overview of the Benefits of Structural Fire Engineering

Jowsey, Allan,Scott, Peter,Torero, Jose Council on Tall Building and Urban Habitat Korea 2013 International journal of high-rise buildings Vol.2 No.2

The field of structural fire engineering has evolved within the construction industry, driven largely by the acceptance of performance-based or goal-based design. This evolution has brought two disciplines very close together - that of structural engineering and fire engineering. This paper presents an overview of structural systems that are frequently adopted in tall building design; typical beams and columns, concrete filled steel tube columns and long span beams with web openings. It is shown that these structural members require a structural analysis in relation to their temperature evolution and failure modes to determine adequate thermal protection for a given fire resistance period. When this is accounted for, a more explicit understanding of the behaviour of the structure and significant cost savings can be achieved. This paper demonstrates the importance of structural fire assessments in the context of tall building design. It is shown that structural engineers are more than capable of assessing structural capacity in the event of fire using published methodologies. Rather than assumed performance, this approach can result in a safe and quantified design in the event of a fire.

Some Considerations for the Fire Safe Design of Tall Buildings

Cowlard, Adam,Bittern, Adam,Abecassis-Empis, Cecilia,Torero, Jose L. Council on Tall Building and Urban Habitat Korea 2013 International journal of high-rise buildings Vol.2 No.1

In any subject area related to the provision of safety, failure is typically the most effective mechanism for evoking rapid reform and an introspective assessment of the accepted operating methods and standards within a professional body. In the realm of tall buildings the most notable failures in history, those of the WTC towers, widely accepted as fire induced failures, have not to any significant extent affected the way they are designed with respect to fire safety. This is clearly reflected in the surge in numbers of Tall Buildings being constructed since 2001. The combination of the magnitude and time-scale of the WTC investigation coupled with the absence of meaningful guidance resulting from it strongly hints at the outdatedness of current fire engineering practice as a discipline in the context of such advanced infrastructure. This is further reflected in the continual shift from prescriptive to performance based design in many parts of the world demonstrating an ever growing acceptance that these buildings are beyond the realm of applicability of prescriptive guidance. In order for true performance based engineering to occur however, specific performance goals need to be established for these structures. This work seeks to highlight the critical elements of a fire safety strategy for tall buildings and thus attempt to highlight some specific global performance objectives. A survey of tall building fire investigations is conducted in order to assess the effectiveness of current designs in meeting these objectives, and the current state-of-the-art of fire safety design guidance for tall structures is also analysed on these terms. The correct definition of the design fire for open plan compartments is identified as the critical knowledge gap that must be addressed in order to achieve tall building performance objectives and to provide truly innovative, robust fire safety for these unique structures.

Graded Otx2 activities demonstrate dose-sensitive eye and retina phenotypes

Bernard, Clé,mence,Kim, Hyoung-Tai,Torero Ibad, Raoul,Lee, Eun Jung,Simonutti, Manuel,Picaud, Serge,Acampora, Dario,Simeone, Antonio,Di Nardo, Ariel A.,Prochiantz, Alain,Moya, Kenneth L.,Kim, Ji Oxford University Press 2014 Human Molecular Genetics Vol.23 No.7

<P>In the human, mutations of <I>OTX2</I> (<I>Orthodenticle homeobox 2</I> transcription factor) translate into eye malformations of variable expressivity (even between the two eyes of the same individual) and incomplete penetrance, suggesting the existence of subtle thresholds in OTX2 activity. We have addressed this issue by analyzing retinal structure and function in six mutant mice with graded Otx2 activity: <I>Otx2<SUP>+/+</SUP></I>, <I>Otx2<SUP>+/AA</SUP></I>, <I>Otx2<SUP>+/GFP</SUP></I>, <I>Otx2<SUP>AA/AA</SUP></I>, <I>Otx2<SUP>AA/GFP</SUP></I> and <I>Otx2<SUP>GFP/GFP</SUP></I>. Null mice (<I>Otx2<SUP>GFP/GFP</SUP></I>) fail to develop the head and are embryonic lethal, and compound heterozygous <I>Otx2<SUP>AA/GFP</SUP></I> mice show a truncated head and die at birth. All other genotypes develop until adulthood. We analyzed eye structure and visual physiology in the genotypes that develop until adulthood and report that phenotype severity parallels Otx2 activity. <I>Otx2<SUP>+/AA</SUP></I> are only mildly affected whereas <I>Otx2<SUP>+/GFP</SUP></I> are more affected than <I>Otx2<SUP>+/AA</SUP></I> but less than <I>Otx2<SUP>AA/AA</SUP></I> mice. <I>Otx2<SUP>AA/AA</SUP></I> mice later manifest the most severe defects, with variable expressivity. Electrophysiological and histological analyses of the mouse retina revealed progressive death of bipolar cells and cone photoreceptors that is both Otx2 activity- and age-dependent with the same ranking of phenotypic severity. This study demonstrates the importance of gene dosage in the development of age-dependent pathologies and underscores the fact that small gene dosage differences can cause significant pathological states.</P>

Upward Flame Spread for Fire Risk Classification of High-Rise Buildings

McLaggan, Martyn S.,Gupta, Vinny,Hidalgo, Juan P.,Torero, Jose L. Council on Tall Building and Urban Habitat Korea 2021 International journal of high-rise buildings Vol.10 No.4

External fire spread has the potential to breach vertical compartmentation and violate the fire safety strategy of a building. The traditional design solution to this has been the use of non-combustible materials and spandrel panels but recent audits show that combustible materials are widespread and included in highly complex systems. Furthermore, most jurisdictions no longer require detailing of spandrel panels under many different circumstances. These buildings require rapid investigation using rational scientific methods to be able to adequately classify the fire risk. In this work, we use an extensive experimental campaign of material-scale data to explore the critical parameters driving upward flame spread. Two criteria are outlined using two different approaches. The first evaluates the time to ignition and the time to burnout to assess the ability for a fire to spread, and can be easily determined using traditional means. The second evaluates the preheated flame length as the critical parameter driving flame spread. A wide range of cladding materials are ranked according to these criteria to show their potential propensity to flame spread. From this, designers can use conservative approaches to perform fire risk assessments for buildings with combustible materials or can be used to aid decision-making. Precise estimates of flame spread rates within complex façade systems are not achievable with the current level of knowledge and will require a substantial amount of work to make progress.

A Review and Analysis of the Thermal Exposure in Large Compartment Fire Experiments

Gupta, Vinny,Hidalgo, Juan P.,Lange, David,Cowlard, Adam,Abecassis-Empis, Cecilia,Torero, Jose L. Council on Tall Building and Urban Habitat Korea 2021 International journal of high-rise buildings Vol.10 No.4

Developments in the understanding of fire behaviour for large open-plan spaces typical of tall buildings have been greatly outpaced by the rate at which these buildings are being constructed and their characteristics changed. Numerous high-profile fire-induced failures have highlighted the inadequacy of existing tools and standards for fire engineering when applied to highly-optimised modern tall buildings. With the continued increase in height and complexity of tall buildings, the risk to the occupants from fire-induced structural collapse increases, thus understanding the performance of complex structural systems under fire exposure is imperative. Therefore, an accurate representation of the design fire for open-plan compartments is required for the purposes of design. This will allow for knowledge-driven, quantifiable factors of safety to be used in the design of highly optimised modern tall buildings. In this paper, we review the state-of-the-art experimental research on large open-plan compartment fires from the past three decades. We have assimilated results collected from 37 large-scale compartment fire experiments of the open-plan type conducted from 1993 to 2019, covering a range of compartment and fuel characteristics. Spatial and temporal distributions of the heat fluxes imposed on compartment ceilings are estimated from the data. The complexity of the compartment fire dynamics is highlighted by the large differences in the data collected, which currently complicates the development of engineering tools based on physical models. Despite the large variability, this analysis shows that the orders of magnitude of the thermal exposure are defined by the ratio of flame spread and burnout front velocities (V_S / V_BO), which enables the grouping of open-plan compartment fires into three distinct modes of fire spread. Each mode is found to exhibit a characteristic order of magnitude and temporal distribution of thermal exposure. The results show that the magnitude of the thermal exposure for each mode are not consistent with existing performance-based design models, nevertheless, our analysis offers a new pathway for defining thermal exposure from realistic fire scenarios in large open-plan compartments.