Travelling Fires for Structural Design

Traditional methods for specifying thermal inputs for the structural fire analysis of buildings assume uniform burning and homogeneous temperature conditions throughout a compartment, regardless of its size. This is in contrast to the observation that accidental fires in large, open-plan compartments tend to travel across floor plates, burning over a limited area at any one time. This thesis reviews the assumptions inherent in the traditional methods and addresses their limitations by proposing a methodology that considers travelling fires for structural design. Central to this work is the need for strong collaboration between fire safety engineers to define the fire environment and structural fire engineers to assess the subsequent structural behaviour. The traditional hypothesis of homogeneous temperature conditions in postflashover fires is reviewed by analysis of existing experimental data from wellinstrumented fire tests. It is found that this assumption does not hold well and that a rational statistical approach to fire behaviour could be used instead. The methodology developed in this thesis utilises travelling fires to produce more realistic fire scenarios in large, open-plan compartments than the conventional methods that assume uniform burning and homogeneous gas phase temperatures which are only applicable to small compartments. The methodology considers a family of travelling fires that includes the full range of physically possible fire sizes iv within a given compartment. The thermal environment is split into two regions: the near field (flames) and the far field (smoke away from the flames). Smaller fires travel across a floor plate for long periods of time with relatively cool far field temperatures, while larger fires have hotter far field temperatures but burn for shorter durations. The methodology is applied to case studies showing the impact of travelling fires on generic concrete and steel structures. It is found that travelling fires have a considerable impact on the performance of these structures and that conventional design approaches cannot automatically be assumed to be conservative. The results indicate that medium sized fires between 10% and 25% of the floor area are the most onerous for a structure. Detailed sensitivity analyses are presented, showing that the structural design and fuel load have a larger impact on structural behaviour than any numerical or physical parameter required for the methodology. This thesis represents a foundation for using travelling fires for structural analysis and design. The impact of travelling fires is critical for understanding true structural response to fire in modern, open-plan buildings. It is recommended that travelling fires be considered more widely for structural design and the structural mechanics associated with them be studied in more detail. The methodology presented in this thesis provides a key framework for collaboration between fire safety engineers and structural fire engineers to achieve these aims

Decoherence, einselection, and the quantum origins of the classical

Decoherence is caused by the interaction with the environment. Environment monitors certain observables of the system, destroying interference between the pointer states corresponding to their eigenvalues. This leads to environment-induced superselection or einselection, a quantum process associated with selective loss of information. Einselected pointer states are stable. They can retain correlations with the rest of the Universe in spite of the environment. Einselection enforces classicality by imposing an effective ban on the vast majority of the Hilbert space, eliminating especially the flagrantly non-local "Schr\"odinger cat" states. Classical structure of phase space emerges from the quantum Hilbert space in the appropriate macroscopic limit: Combination of einselection with dynamics leads to the idealizations of a point and of a classical trajectory. In measurements, einselection replaces quantum entanglement between the apparatus and the measured system with the classical correlation.Comment: Final version of the review, with brutally compressed figures. Apart from the changes introduced in the editorial process the text is identical with that in the Rev. Mod. Phys. July issue. Also available from http://www.vjquantuminfo.or

The Influence of Travelling Fires on a Concrete Frame

Peer-reviewed paper published in the journal Engineering Structures. Work conducted at the University of Edinburgh in collaboration with Arup and funding from the BRE Trust and Arup.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

Experimental Review of the Homogeneous Temperature Assumption in Post-Flashover Compartment Fires

Peer reviewed paper published in Fire Safety JournalTraditional 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

Towards a fragility assessment of a concrete column exposed to a real fire – Tisova Fire Test

Fires can cause substantial damage to structures, both non-structural and structural, with economic losses of almost 1% GDP in developed countries. Whilst design codes allow engineers to design for the primary design driver, property protection is rarely, if ever, designed for. Quantification and design around property protection has been used for some time in the seismic community, particularly the PEER framework and fragility analyses. Fragility concepts have now started to be researched predominantly for steel-composite structures, however, there has been little to no research into the quantification of property protection for concrete structures, whether in design or in post-fire assessments of fire damaged structures. This paper presents selected results from the thermal environment around, and the thermal response of, a concrete column from a large scale structural fire test conducted in Tisova, Czech Republic, inside a four-storey concrete frame building, with concrete and composite deck floors. From the results of the fire test, assessments of the fire intensity are made and used to model the potential thermal profiles within the concrete column and the implications that high temperature might have on the post-fire response of the concrete column. These thermal profiles are then used to assess the reduction of the columns cross-sectional area and are compared to a quantified damage scale for concrete columns exposed to fire. This analyses presented herein will also show that common methods of defining fire intensity through equivalent fire durations do not appropriately account for the complexities of the thermal and structural response of concrete columns exposed to a travelling fire

Behaviour of continuous reinforced concrete floor slabs subjected to different compartment fires

Fundamental Research Funds for the Central Universities, China University of Mining and Technolog

Flavor Asymmetry of Antiquark Distributions in the Nucleon

1. Introduction 2. Possible violation of the Gottfried sum rule 2.1 Gottfried sum rule 2.2 Early experimental results 2.3 NMC finding and recent progress 2.4 Small $x$ contribution 2.5 Nuclear correction: shadowing in the deuteron 2.6 Parametrization of antiquark distributions 3 Expectations in perturbative QCD 3.1 Operator product expansion 3.2 Perturbative correction to the Gottfried sum 4 Theoretical ideas for the sum-rule violation 4.1 Lattice QCD 4.2 Pauli exclusion principle 4.3 Mesonic models 4.3.1 Meson-cloud contribution 4.3.2 Chiral models 4.3.3 Anomalous $Q^2$ evolution 4.4 Diquark model 4.5 Isospin symmetry violation 4.6 Flavor asymmetry ubar-dbar in nuclei 4.7 Relation to nucleon spin 4.8 Comment on effects of quark mass and transverse motion 5 Finding the flavor asymmetry ubar-dbar in various processes 5.1 Drell-Yan process 5.1.1 Fermilab-E866 results 5.2 W and Z production 5.3 Quarkonium production at large $x_{_F}$ 5.4 Charged hadron production 5.5 Neutrino scattering 5.6 Experiments to find isospin symmetry violation 6 Related topics on antiquark distributions 7 Summary and outlookComment: 3+79 pages, LATEX2e, 29 eps figures. Physics Reports in press. Complete postscript file is available at http://www.cc.saga-u.ac.jp/saga-u/riko/physics/quantum1/structure.html Email: [email protected]

A Priori Modelling of Fire Test One

Chapter 10 in the book: The Dalmarnock Fire Tests: Experiments and Modelling, Edited by G. Rein, C. Abecassis Empis and R. Carvel, Published by the School of Engineering and Electronics, University of Edinburgh, 2007. ISBN 978-0-9557497-0-4An international round-robin study of fire modelling was conducted prior to the Dalmarnock Fire Tests in order to assess the state-of-the-art of fire modelling in real scenarios. The philosophy behind the Dalmarnock Fire Tests was to provide instrumentation density suitable for comparison to field models and designed the scenario for maximum test reproducibility. Each participating team independently simulated a priori the test using a common detailed description of the compartment geometry, fuel packages, ignition source and ventilation conditions. The aim of the exercise was to forecast the test results as accurately as possible, and not to provide an engineering analysis with adequate conservative assumptions or safety factors. The modelling results and experimental measurements are compared among themselves, allowing for conclusions on the robustness, reliability and accuracy of current modelling practices. The results indicate large scatter and considerable disparity among predicted fires and also differing from the experimental data. The Dalmarnock Fire Test One was benchmarked against a second test to establish the potential experimental variability. The scatter of the simulations is much larger than the experimental error and the experimental variability. The study emphasises on the inherent difficulty of predicting fire dynamics and demonstrates that the main source of scatter is originated in the many degrees of freedom and the uncertainty in the input parameters. The conclusions from the study are made public to encourage debate and exchange of views on the topic of fire modelling

Round-robin study of a priori modelling predictions of the Dalmarnock Fire Test One

Peer-reviewed journal paper published in 2009 about the international modelling exercise conducted in 2006.An international study of fire modelling was conducted prior to the Dalmarnock Fire Test One in order to assess the state-of-the-art of fire simulations using a round-robin approach. This test forms part of the Dalmarnock Fire Tests, a series of experiments conducted in 2006 in a high-rise building. The philosophy behind the tests was to provide measurements in a realistic fire scenario involving multiple fuel packages and non-trivial fire growth, and with an instrumentation density suitable for comparison with computational fluid dynamics models. Each of the seven round-robin teams independently simulated the test scenario a priori using a common detailed description of the compartment geometry, fuel packages, ignition source and ventilation conditions. The aim of the exercise was to forecast the fire development as accurately as possible and compare the results. The aim was not to provide an engineering analysis with conservative assumptions or safety factors. Comparison of the modelling results shows a large scatter and considerable disparity among the predictions, and between predictions and experimental measurements. The scatter of the simulations is much larger than the error and variability expected in the experiments. The study emphasises on the inherent difficulty of modelling fire dynamics in complex fire scenarios like Dalmarnock, and shows that the accuracy to predict fire growth (i.e. evolution of the heat released rate) is, in general, poor