[Show abstract][Hide abstract] ABSTRACT: The growing need for fire safety engineering (FSE) design around the world has led to higher education degrees, many of which lack strong foundations in fundamental knowledge and are somewhat deficient in developing skills (application of knowledge) and appropriate attitudes (reflective assessment and synthesis of knowledge). This paper discusses how such programmes are delivering professionals to an FSE industry that has not yet adequately defined competence. Motivated by the need to have a new generation of leaders in FSE that can drive the field through the ongoing and necessary transition to performance-based design that it is currently experiencing, a one-week, intensive global technical leadership seminar was held at Edinburgh University, supported by The Lloyd's Register Educational Trust (LRET). The Seminar was aimed at reflecting on the content and methodology required in comprehensive university programmes capable of educating in design for fire safety in the built environment. Performance-based design for fire, in which prescriptive codes are simply a tool within a performance-based mindset, offers many important benefits but also has many acknowledged problems and risks; this paper argues that paramount among the problems is the way that we, as a global engineering profession, educate and nurture FSE professionals. It is argued that fire safety is a relatively immature discipline, thus it should be supported by holistic, purpose-centred education that places an emphasis on learning environments broadly focused on design. Technical (fundamental) knowledge is clearly critically important, but it should not be the driving force, and it should not eclipse the development of the skills and attitudes essential for the future survival of fire safety engineering as a distinct, competency-based engineering discipline.
[Show abstract][Hide abstract] ABSTRACT: When building fires occur in large, open compartments they rarely burn uniformly across an entire floor plate of a structure. Instead, they tend to travel, igniting fuel in their path and burning it out as they move to the next fuel package. Current structural fire design methods do not account for these types of fires. This paper applies a novel methodology for defining a family of possible heating regimes to a framed concrete structure using the concept of travelling fires. A finite-element model of a generic concrete structure is used to study the impact of the family of fires; both relative to one another and in comparison to the conventional codified temperature–time curves. It is found that travelling fires have a significant impact on the performance of the structure and that the current design approaches cannot be assumed to be conservative. Further, it is found that a travelling fire of approximately 25% of the floor plate in size is the most severe in terms of structural response. It is concluded that the new approach is simple to implement, provides more realistic fire scenarios, and is more conservative than current design methods.
[Show abstract][Hide abstract] ABSTRACT: The fire-safe design of concrete structures, which incorporate post-tensioned prestressing tendons, has recently been the subject of debate within the structural engineering community, particularly when unbonded post-tensioned (UPT) prestressing tendons are used. Despite several studies aimed at furthering our understanding of the response of UPT concrete structures in fire, many aspects of their response in real fires remain poorly understood. An exhaustive summary of available test data, which have been used over the past five decades to generate fire design guidance for UPT concrete structures is given. Case studies showing the response of real UPT structures in severe building fires are also discussed. In both cases, the intent is to highlight inadequacies in the current state of knowledge for UPT buildings in fire and to prioritize areas for future research.
[Show abstract][Hide abstract] ABSTRACT: A new methodology to effectively forecast fire dynamics based on assimilation of sensor observations is presented and demonstrated. An inverse modelling approach with a two-zone model is used to forecast the growth of a compartment fire. Sensor observations are assimilated into the model in order to estimate invariant parameters and thus speed up simulations and recover information lost by modelling approximations. A series of cases of a compartment fire radially spreading at different growth rates (slow, medium and fast) are used to test the methodology. Spread rate, entrainment coefficient and smoke transport time are the invariant parameters estimated via a gradient-based optimization method with tangent linear differentiation. The parameters were estimated accurately within minutes after ignition and the heat release rate reproduced satisfactorily in all cases. Moreover, the temperature and the height of the hot layer are forecasted with a positive lead time between 50 and 80s, depending on the fire growth rate. The results show that the simple mass and energy conservation equations and plume correlation of the zone model are suitable to forecast the main features of a growing fire. Positive lead times are reported here for the first time in fire dynamics. The results also suggest the existence of an optimal width for the assimilation window. The proposed methodology is subject to ongoing research and the results are an important step towards the forecast of fire dynamics to lead the emergency response.
[Show abstract][Hide abstract] ABSTRACT: Standard flammability tests, like the Cone Calorimeter, were developed several decades ago and provided sufficient flammability data for the purposes of the time. However, recent pyrolysis models have revealed the limitations of the standard test in providing adequate data for current flammability analysis and modelling. This paper reviews the assumptions in the standard test and proposes a novel sample holder for the cone calorimeter which incorporates a large block of aluminium at the rear face of the sample under test. This allows the heat losses at the rear face of the sample to be measured precisely and enables more accurate calculation of the material flammability properties. Tests of PA6 and a nano-composite of PA6 & Cloisite 30B, carried out using the standard and new sample holders, are presented and discussed. The peak of high heat release rate observed in standard tests of PA6 is not observed using the novel sample holder, where the burning behaviour of PA6 and the nano-composite material are largely similar. The implications of these observations are discussed.
Polymer Degradation and Stability 03/2011; 96(3):314-319.
[Show abstract][Hide abstract] ABSTRACT: Small-scale experiments to investigate the self-sustaining decomposition (SSD) behaviour of NPK 16.16.16 fertilizer have been undertaken. These experiments show that this material will undergo self-sustaining decomposition and are used to give insight into the behaviour of the reaction. A three-step decomposition process is observed leading to a self-sustained reaction reaching temperatures of 200-350°C. The measured heat of reaction is 0.73-1.8 MJ/kg. Measurements are applied to the events that occurred aboard the ship Ostedijk in 2007 in which a SSD reaction occurred. The mass loss rate from the cargo was calculated to range from 0.5 kg/s on the first day to 12 kg/s on the last day. From this measurement, the maximum fire size was estimated to be in the range 5.8-29 MW.
Journal of hazardous materials 02/2011; 186(1):731-7.
[Show abstract][Hide abstract] ABSTRACT: The capabilities of the ventilation systems in the two road tunnels at Dartford (UK) are analysed using a multi-scale modelling approach. Both tunnels have complex semi-transverse ventilation systems with jet fans to control longitudinal flow. The construction and ventilation systems in the tunnels are described and the current emergency ventilation strategies are presented. The analysis includes a coupling of a 1D network model with 3D components, representing the operational jet fans, built using computational fluid dynamics. The jet fans were experimentally characterized on-site and the findings were compared to the model predictions. The predicted ventilation flows for each of the emergency ventilation strategies are presented and discussed. In cold-flow conditions, ventilation velocities significantly above 3 m/s can be generated throughout the tunnels. However, it is observed that 1/3 of the flow generated in the East tunnel is diverted from the tunnel up the extract shafts. The model was used to simulate various reduced fan combinations and thus the level of redundancy in each of the systems has been estimated. It is found that an acceptable level of ventilation may be produced in the West tunnel, even if several pairs of jet fans are disabled. In the East tunnel there is less redundancy, but an acceptable level of ventilation control can be maintained with one or two jet fans disabled.
Tunnelling and Underground Space Technology 07/2010;
[Show abstract][Hide abstract] ABSTRACT: Traditional methods for quantifying and modelling compartment fires for structural engineering analysis assume spatially homogeneous temperature conditions. The accuracy and range of validity of this assumption is examined here using the previously conducted fire tests of Cardington (1999) and Dalmarnock (2006). Statistical analyses of the test measurements provide insights into the temperature field in the compartments. The temperature distributions are statistically examined in terms of dispersion from the spatial compartment average. The results clearly show that uniform temperature conditions are not present and variation from the compartment average exists. Peak local temperatures range from 23% to 75% higher than the compartment average, with a mean peak increase of 38%. Local minimum temperatures range from 29% to 99% below the spatial average, with a mean local minimum temperature of 49%. The experimental data are then applied to typical structural elements as a case study to examine the potential impact of the gas temperature dispersion above the compartment average on the element heating. Compared to calculations using the compartment average, this analysis results in increased element temperature rises of up to 25% and reductions of the time to attain a pre-defined critical temperature of up to 31% for the 80th percentile temperature increase. The results show that the homogeneous temperature assumption does not hold well in post-flashover compartment fires. Instead, a rational statistical approach to fire behaviour could be used in fire safety and structural engineering applications.
[Show abstract][Hide abstract] ABSTRACT: Bending moment axial force interaction diagrams are a commonly used tool in any design office. When designing for fire conditions, the large axial forces which develop place an additional importance on the consideration of the interplay between axial forces and moments. This paper presents a new method for calculating the biaxial bending moment/axial force capacity for a general section through the use of the sectional tangent stiffness. A beam–column section subject to fire is assessed, and comparisons made with simplified design tools. It is concluded that derivation of the interaction surface from the tangent stiffness matrix is possible, and that current simplified methods for fire design cannot be assumed conservative.
Engineering Structures 06/2010; 32(6):1641-1649.
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