In-Depth Temperature Profiles in Pyrolyzing Wood

The move towards performance-based design of the fire resistance of structures requires more accurate design methods. An important variable in the fire performance of timber structures is the in-depth temperature distribution, as wood is weakened by an increase of temperature, caused by exposure to high heat fluxes. A proper prediction of temperature profiles in wood structural elements has become an essential part of timber structural design. Current design methods use empirically determined equations for the temperature distribution but these assume constant charring rates, do not account for changes in the heating conditions, and were obtained under poorly defined boundary conditions in fire resistance furnaces. As part of this research project, a series of experimental in-depth temperature measurements were done in wood samples exposed to various intensities of radiant heat fluxes, with clearly defined boundary conditions that allow a proper input for pyrolysis models. The imposed heat fluxes range from 10 kW/cm^2, which generates an almost inert behaviour, to 60 kW/cm^2, where spontaneous flaming is almost immediately observed. Mass loss measurements for all the imposed heat fluxes were also performed. The second part of this project dealt with the modelling of the pyrolysis process, with an emphasis placed on temperature prediction. The main objective was to identify the simplest model that can accurately predict temperature distributions in wood elements exposed to fires. For this, an analysis of the different terms which have been included by several models in the energy equation has been done, by quantifying its magnitude. Five models with different degrees of simplification have been developed. Comparison with the experimental data has shown that a simple and accurate model of temperature profiles must include the rise in the solid sensible heat, the heat transferred by conduction, the heat of moisture evaporation, the heat of pyrolysis reaction and the effect of char oxidation

In-Depth Temperature Measurements of Timber in Fires

Modern construction relies more and more on metallic connectors. Their failure during fires is related to the glass transition of the lignin matrix at around 100°C. Based on this information, a series of tests were carried out exposing a wood specimen to various heat fluxes in a Cone Calorimeter. The aim of this research is to develop a sound temperature measurement methodology in wood samples exposed to high heat fluxes and to build a data-base in order to evaluate different wood pyrolysis models. The experiments yielded highly repeatable results that are seldom achieved with wood

Machine learning assisted remote forestry health assessment: a comprehensive state of the art review

Forests are suffering water stress due to climate change; in some parts of the globe, forests are being exposed to the highest temperatures historically recorded. Machine learning techniques combined with robotic platforms and artificial vision systems have been used to provide remote monitoring of the health of the forest, including moisture content, chlorophyll, and nitrogen estimation, forest canopy, and forest degradation, among others. However, artificial intelligence techniques evolve fast associated with the computational resources; data acquisition, and processing change accordingly. This article is aimed at gathering the latest developments in remote monitoring of the health of the forests, with special emphasis on the most important vegetation parameters (structural and morphological), using machine learning techniques. The analysis presented here gathered 108 articles from the last 5 years, and we conclude by showing the newest developments in AI tools that might be used in the near future

Summary of workshop large outdoor fires and the built environment

Large outdoorfires present a risk to the built environment. Wildfires that spread into communities, referred to as Wildland-Urban Interface (WUI)fires, havedestroyed communities throughout the world, and are an emerging problem infire safety science. Other examples are large urbanfires including those that haveoccurred after earthquakes. Research into large outdoorfires, and how to potentially mitigate the loss of structures in suchfires, lags other areas offire safety scienceresearch. At the same time, common characteristics betweenfire spread in WUIfires and urbanfires have not been fully exploited. In this paper, an overview of thelarge outdoorfire risk to the built environment from each region is presented. Critical research needs for this problem in the context offire safety scienceare provided.The present paper seeks to develop the foundation for an international research needs roadmap to reduce the risk of large outdoorfires to the built environment.Peer ReviewedPreprin

A Study of Fire Durability for a Road Tunnel: Comparing CFD and Simple Analytical Models

The durability of various typical tunnel sections in the event of a prescribed 100 MW fire has been assessed. Cast-iron sections, pre-cast concrete sections and in-situ concrete cut and cover sections are all considered to be part of a 1 km long road tunnel. An analysis of the tunnel constructions and surrounding geology (based on a real tunnel) has led to the estimation of failure temperatures for the structural elements, internal cladding systems, jet fans and their fixings. A commercial computational fluid dynamics (CFD) code was used to simulate various fire scenarios and calculate the times to failure of tunnel elements. Simulations were carried out for fires in different locations for the three section types. In parallel to the CFD study, an analytical model was devised to predict gas temperatures in the tunnel. Both models used the same input variables and general assumptions and great attention was given to establish the highest possible accuracy for all input variables and general assumptions. Comparing the predicted gas phase temperatures shows that there is less than a 20% difference between the complex CFD and the simple analytical model; this is well within the bounds of uncertainty inherent in either model and to the input parameters. Using both sets of gas phase temperatures, a detailed heat transfer study was carried out to calculate the temperature evolution of each of the tunnel elements. The differences in gas temperatures between the two modelling methods did not alter the conclusions regarding the time to failure of any tunnel elements. It is found that fire durability can be better analyzed by separating the fire environment into two zones, a near field close to the flames, where accuracy is defined by the assumptions, and a far field where the precision of the results is linked to the modelling method. This approach allows establishing that, for this particular case, failure of structural elements can only occur in the near field. This study shows that the detail of the calculations needs to be consistent with the accuracy of the input parameters and assumptions. Although CFD models can give highly detailed results, the implied accuracy of the results is defined by the assumptions inherent in the model setup, thus, there is the potential of a very costly and refined computation that leads to results of comparable accuracy to simple, less costly, models

Experimental Layout and Description of the Building

Chapter 2 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 978-0-9557497-0-4This chapter describes the experimental set-up of Dalmarnock Fire Tests One and Two. While Test One was planned to allow a fire to develop freely to post-flashover conditions, Test Two was designed to allow for ventilation management. A detailed account of the building layout, the set-up of the different experiments and measurements carried out during the full-scale tests is given, together with the specifics of the instrumentation installed in the building. A description of the fuel load and the ventilation conditions during both tests is also presented. Due to the large amount of data presented, the chapter is organised so that the most relevant information is shown in the main body of the text, and additional detail, such as the instrument coordinates, is appended in an annex at the end of the chapter

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

Carta, 1904 noviembre 12, París, de Pedro A. Reszka, Commissaire Général de L'Amérique Latine: journal quotidien a Rubén Darío

Sumario: Nota mecanografiada del Comisario General, Pedro A. Rezska, de la revista "L'Amérique Latine: journal quotidien" invitando a Rubén Darío a la inauguración de la primera Exposición Latino-Americana de Bellas Artes que tendrá lugar el 14 de noviembreFuente de ingreso: Adquisición por compra a Luis Díez de Pinedo con intervención y asesoramiento de Dionisio Gamallo Fierros (1965)Archivo personal de Rubén Darío custodiado por Francisca Sánchez del Pozo, en Navalsauz (Ávila

Retrieval of Vegetation Indices Related to Leaf Water Content from a Single Index: A Case Study of Eucalyptus globulus (Labill.) and Pinus radiata (D. Don.).

The vegetation indices derived from spectral reflectance have served as an indicator of vegetations biophysical and biochemical parameters. Some of these indices are capable of characterizing more than one parameter at a time. This study examines the feasibility of retrieving several spectral vegetation indices from a single index under the assumption that all these indices are correlated with water content. The models used are based on a linear regression adjusted with least squares. The spectral signatures of Eucalyptus globulus and Pinus radiata, which constitute 97.5% of the forest plantation in Valparaiso region in Chile, have been used to test and validate the proposed approach. The linear models were fitted with an independent data set from which their performance was assessed. The results suggest that from the Leaf Water Index, other spectral indices can be recovered with a root mean square error up to 0.02, a bias of 1.12%, and a coefficient of determination of 0.77. The latter encourages using a sensor with discrete wavelengths instead of a continuum spectrum to estimate the forestrys essential parameters