摘要 :
In the frame of the European RFCS (Research Fund for Coal and Steel) TRAFIR (Characterization of TRAvelling FIRes in large compartments) project, three natural fire tests in a large compartment were conducted at Ulster University....
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In the frame of the European RFCS (Research Fund for Coal and Steel) TRAFIR (Characterization of TRAvelling FIRes in large compartments) project, three natural fire tests in a large compartment were conducted at Ulster University. The aim of this investigation was to understand the conditions in which the travelling fires develop and to study the impact of such fires on the surrounding steel structure. This paper provides details of the second fire test where the size of the openings was reduced to induce different ventilation conditions in comparison to the first fire test. During the test, behaviour of the travelling fire was observed and the gas temperatures at different levels and locations were recorded. The influence of travelling fires on the surrounding structure is studied in terms of the temperatures recorded in the selected steel columns and beams. The influence of change in the ventilation conditions is presented and highlighted through the comparison of results of the second fire test with those recorded earlier during the first fire test. It was found that the travelling fires produce non-uniform temperatures in the compartment irrespective of the ventilation conditions although the magnitude of this nonuniformity is related with the opening sizes. This non-uniformity exists along the length as well as along the height of the test compartment. It was found that for reduced opening sizes, more heat is retained within the compartment which induces higher temperatures in the surrounding steel structure. The transient heating of the surrounding structure caused by travelling fires should be considered while performing the structural fire design of large compartments. The results obtained during the test are state-of-the-art and will help in understating the behaviour of travelling fires and their influence on the surrounding structure which will help to devise fire design methods for future use.
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Purpose - The study investigates the performance of a three-story unprotected steel moment-resisting frame (SMRF) designed for high seismic demand in the fire-only (FO) and post-earthquake uniform and traveling fires (PEF). The pr...
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Purpose - The study investigates the performance of a three-story unprotected steel moment-resisting frame (SMRF) designed for high seismic demand in the fire-only (FO) and post-earthquake uniform and traveling fires (PEF). The primary objective is to investigate the effects of seismic residual deformation on the structure's performance in horizontally traveling fires. The traveling fire methodology, unlike conventional fire models, considers a spatially varying temperature environment. Design/methodology/approach - Multi-step finite element simulations were carried out on undamaged and damaged frames to provide insight into the effects of the earthquake-initiated fires on the local and global behavior of SMRF. The earthquake simulations were conducted using nonlinear time history analysis, whereas the structure in the fire was investigated by sequential thermal-structural analysis procedure in ABAQUS. The frame was subjected to a suite of seven ground motions. In total, four horizontal traveling fire sizes were considered along with the Eurocode (EC) parametric fire for a comparison. The deformation history, axial force and moment variation in the critical beams and columns of affected compartments in the fire heating and cooling regimes were examined. The global structural performance in terms of inter-story drifts in FO and PEF scenarios was investigated. Findings - It was observed that the larger traveling fires (25 and 48%) are more detrimental to the case study frame than the uniform EC parametric fire. Besides, no appreciable difference was observed in time and modes of failure of the structure in FO and PEF scenarios within the study's parameters. Originality/value - The present study considers improved traveling fire methodology as an alternate design fire for the first time for the PEF performance of SMRF. The analysis results add to the much needed database on structures' performance in a wide range of fire scenarios.
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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. Nume...
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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.
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Purpose - In the frame of the European RFCS TRAFIR project, three large compartment fire tests involving steel structure were conducted by Ulster University, aiming at understanding in which conditions a travelling fire develops, ...
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Purpose - In the frame of the European RFCS TRAFIR project, three large compartment fire tests involving steel structure were conducted by Ulster University, aiming at understanding in which conditions a travelling fire develops, as well as how it behaves and impacts the surrounding structure. Design/methodology/approach - During the experimental programme, the path and geometry of the travelling fire was studied and temperatures, heat fluxes and spread rates were measured. Influence of the travelling fire on the structural elements was also monitored during the travelling fire tests. Findings - This paper provides details related to the influence of travelling fires on a central structural steel column. Originality/value - The experimental data are presented in terms of the gas temperatures recorded in the test compartment near the column, as well as the temperatures recorded in the steel column at different levels. Because of the large data, only fire test one results are discussed in this paper.
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Close inspection of accidental fires in large, open-plan compartments reveals that they do not burn simultaneously throughout the whole enclosure. Instead, these fires tend to move across floor plates as flames spread, burning ove...
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Close inspection of accidental fires in large, open-plan compartments reveals that they do not burn simultaneously throughout the whole enclosure. Instead, these fires tend to move across floor plates as flames spread, burning over a limited area at any one time. These fires have been labelled travelling fires. Current structural fire design methods do not account for these types of fires. Despite these observations, fire scenarios most commonly used for the structural design of modern buildings are based on traditional methods that assume uniform burning and homogenous temperature conditions throughout a compartment, regardless of its size. This paper is Part II of a two part article and gives details of a new design methodology using travelling fires to produce more realistic fire scenarios in large, open-plan compartments than the conventional methods that assume uniform burning. The methodology considers a range of possible fire sizes and is aimed at producing results consistent with the requirements of structural fire analysis. The methodology is applied to a case study of a generic concrete frame by means of heat transfer calculations to infer structural performance. It is found that fires that are around 10% of the floor area are the most onerous for the structure, producing rebar temperatures equivalent to those reached from exposure to 106 min of the standard fire and approximately 200 ℃ hotter than that calculated using the Eurocode 1 parametric temperature-time curve. A detailed sensitivity analysis is presented, concluding that the most sensitive input parameters are related to the building design and its use and not the physical assumptions or numerical implementation of the method.
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摘要 :
Close inspection of accidental fires in large, open-plan compartments reveals that they do not burn simultaneously throughout the whole enclosure. Instead, these fires tend to move across floor plates as flames spread, burning ove...
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Close inspection of accidental fires in large, open-plan compartments reveals that they do not burn simultaneously throughout the whole enclosure. Instead, these fires tend to move across floor plates as flames spread, burning over a limited area at any one time. These fires have been labelled travelling fires. Current structural fire design methods do not account for these types of fires. Despite these observations, fire scenarios most commonly used for the structural design of modern buildings are based on traditional methods that assume uniform burning and homogenous temperature conditions throughout a compartment, regardless of its size. This paper is Part I of a two part article and is a literature review of the research on the new topic of travelling fires. A brief background to the traditional methods that assume uniform fires is given along with critiques of that assumption, such as the observation of heterogeneity among compartment temperatures and the travelling nature of fires in both accidental events and controlled tests. The research in travelling fires is reviewed, highlighting the pioneering work in the field to date, and compared to the state of the art. The main challenge in developing tools for incorporating travelling fires into design is the lack of large scale test data. Nonetheless, significant progress in the field has been made and two methodologies using travelling fires to characterise the thermal environment for structural analysis have recently been developed. The research in quantifying the structural response to travelling fires is also reviewed, demonstrating the benefit of collaboration between fire engineers and structural fire engineers.
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Timber is an innovative and sustainable construction material, but its uptake has been hindered by concerns about its performance in a fire. Current building regulations measure the fire performance of timber using the metric of f...
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Timber is an innovative and sustainable construction material, but its uptake has been hindered by concerns about its performance in a fire. Current building regulations measure the fire performance of timber using the metric of fire resistance tests. In these tests, the charring rate is measured under a series of heat exposures (design fires) and from this the structural stability is deduced. Charring rates are currently only well known for one heat exposure regime (standard fire), which restricts the use of performance-based design. This study aims to study charring rates under a range of design fires. We used a novel multiscale charring model validated at the microscale (mg-samples), mesoscale (g-samples), and macroscale (kg-samples) across different wood species exposed to different heating regimes and boundary conditions. At the macroscale, the model blindly predicts measured in-depth temperatures and char depths during standard and parametric fires with an error between 5% and 22%. Comparing simulations of charring under travelling fires, parametric fires, and the standard fire revealed two findings. Firstly, their charring behaviour differs with maximum char depths of 42 mm (travelling), 46 mm (parametric), and 59 mm (standard fire) at the end of the fire and one (standard fire) to four (travelling fire) charring stages (no charring, slow growth, fast growth, steady-state). Secondly, we observed zero-strength layers (depth between the 200 degrees C and 300 degrees C isotherm) of 7 to 12 mm from the exposed surface in travelling fires compared to 5 to 11 mm in parametric fires and 7 mm in the standard fire. Both, therefore, need to be considered in structural calculations. These results help engineers to move towards performance-based design by allowing the calculation of charring rates for a wide range of design fires. In turn, this will help engineers to build more sustainable, economical, and complex structures with timber.
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This paper presents the extended travelling fire method (ETFM) framework, which considers both energy and mass conservation for the fire design of large compartments. To identify its capabilities and limitations, the framework is ...
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This paper presents the extended travelling fire method (ETFM) framework, which considers both energy and mass conservation for the fire design of large compartments. To identify its capabilities and limitations, the framework is demonstrated in representing the travelling fire scenario in the Veseli Travelling Fire Test. The comparison between the framework and the test is achieved through performing a numerical investigation of the thermal response of the structural elements. The framework provides good characterization of maximum steel temperatures and the relative timing of thermal response curves along the travelling fire trajectory, though it does not currently address a non-uniform fire spread rate. The test conditions are then generalized for parametric studies, which are used to quantify the impact of other design parameters, including member emissivity, convective heat transfer coefficient, total/radiative heat loss fractions, fire spread rate, fire load density, and various compartment opening dimension parameters. Within the constraints of this study, the inverse opening factor and total heat loss prove to be the most critical parameters for structural fire design.
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The present paper investigates a travelling fire scenario in an elongated structure (Length 18 m x width 6 m x height 3 m) with a controlled fire source of six trays filled with diesel (width 4 m x length 0.5 m). The fire spread i...
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The present paper investigates a travelling fire scenario in an elongated structure (Length 18 m x width 6 m x height 3 m) with a controlled fire source of six trays filled with diesel (width 4 m x length 0.5 m). The fire spread is controlled manually by initiating fires consecutively in the pools. Fire dynamics simulator (FDS) is used to a-priori investigate variations in geometry, material data and fire load, whereas simulations using the final design and measured heat release rates (HRR) were performed after the test. The input to the model beside fire source and geometry are thermal material data. The FDS simulations were used to determine the appropriate size of the downstands (2 m from the ceiling in the final design) on the side to create a sufficiently one-dimensional fire spread. The post-test simulations indicate that although there are a lot of variations not included in the model similar results were obtained as in the test.
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With the rapid development of modern cities such as Hong Kong, increasingly more underground facilities and high-rise buildings are being built. Stairs provide important emergency access in these types of structures, especially fo...
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With the rapid development of modern cities such as Hong Kong, increasingly more underground facilities and high-rise buildings are being built. Stairs provide important emergency access in these types of structures, especially for upward travel. This study was a controlled experiment on ascending stairs in a typical public housing estate in Hong Kong. The participants were of different age, gender and occupation. Various movement characteristics, including ascent speed, maximum ascending level and changes in blood pressure and heart beat rate before and after the experiment were extracted and analysed. Ascending speed was related to the age of the participants and 95% of participants could ascend to four levels or more. The older participants had relatively greater differences in blood pressure and heart rate before and after the experiment. The study also showed the typical and unique movement characteristics of Hong Kong people. Taken together, the results of this study will be useful for the further development of evacuation models and for enhancing building design in Hong Kong and other Asian cities with similar pedestrian characteristics.
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