Fire Safety Journal最新文献

Experiments on reduced scale compartments with timber ceilings and floors were conducted to investigate the ignition of the ceiling and growth to flashover. Pool fires of various sizes were ignited and measurements were made of temperature in the plume and ceiling jet, and mass of the timber ceiling and floor. The compartment geometry was also systematically varied. The results showed that ignition of the ceiling occurred when the measured temperature at ceiling level was between 328 °C and 347 °C. This aligned with intermittent flame impingement on the ceiling from the initiating fire. Following ignition of the ceiling, in most cases the fire subsequently spread across the ceiling resulting, ultimately, in ignition of the floor. It was found that duration of preheating of the ceiling (by the ceiling jet) strongly influenced flame spread. In some cases, ignition occurred, but did not result in continuous flame spread across the ceiling – in these cases it was found that the ceiling jet was cooler due to wider geometry of the compartment. The data were compared against existing correlations from the literature, and it was found that existing methods may be used to predict whether ignition of the ceiling may occur and the conditions for flashover.

A meta-analysis was conducted on 100 structural mass timber compartment fire experiments. The analysis investigated temperature, heat release rate, auto-extinction and delamination. Dissimilarities in the compartment geometry, ventilation, and exposed timber surfaces of these experiments could be accounted for using two parameters, α and %A_O (applicable to near cubic, ventilation-controlled compartments) defined as the shape-modified ventilation factor and opening ratio. The correlation coefficient for the total heat release rate (HRR) with the area of timber for the large and medium scale data was 0.97 and 0.74, respectively. Similarly, the correlation of medium scale data for the contribution of timber to the heat release rate was 0.90. A statistical analysis revealed a higher probability for auto-extinction to occur for exposure levels below 20%. Above 20% exposure, the risk for sustained flaming and delamination increase substantially. Auto-extinction was shown to depend strongly on delamination, with a 93% probability of occurrence given no delamination. The use of PUR HBS adhesive was shown to cause delamination in 73% of the cases, with PUR HBX delaminating in 33% of cases.

This paper experimentally investigates the thermophysical properties of high–strength steel wires (HSSWs) that are widely used in infrastructures to fill this knowledge gap in design standards and studies on the performance of cables in fires. The mass densities, specific heat capacities, and thermal conductivities of HSSW specimens with strengths of 1670, 1860, 1960, and 2160 MPa were measured at temperatures from 20 to 800 °C. Results show that compared with general hot-rolled structural steels, the specific heat capacity of grade 1960 and 2160 HSSWs is observably lower between 400 and 700 °C, and its peaks occur at higher temperatures. The thermal conductivity of HSSW steels is appreciably below that of hot-rolled steels. These measured thermophysical properties of HSSWs at high temperatures lay a critical material-level foundation for future heat transfer studies and safety evaluation of structural cables in fires.

The fire resistance remains a challenging topic for engineered wood and bamboo structures due to the combustibility of wood and bamboo and the usage of organic adhesives, which are temperature-sensitive substance in fire. As an alternative solution, this paper investigated a novel bamboo-based composite prepared with magnesium oxysulfide inorganic adhesive (inorganic-bonded bamboo composite, InorgBam), and the fire tests were carried out to investigate the post-fire mechanical properties and charring behavior of InorgBam. The reduction effect of fire exposure on compressive or tensile strength parallel-to-grain was experimentally studied. The effects of fire exposure surface numbers, grain direction, geometric dimension and exposure time on charring rate were discussed. Results showed that the InorgBam can be maintained the post-fire strength under compressive or tensile loads parallel to grain without significant degradation when the exposure temperature below 250 °C. The temperature of the char front was determined to be approximate 350°C by using an interpolation method. The charring rate was mainly dominated by the exposure time and decreases nonlinearly with the increase of exposure time, and the charring rate with multi-sided fire exposure was approximately 1.1 times of that exposed to one-sided fire. Finally, a nonlinear model was proposed to predict the charring rate of InorgBam material, which provides a basic reference for understanding the fire resistance of InorgBam material exposed to fire.

To mitigate the risks linked to hydrogen and oxygen (H₂–O₂) combustion through CHF₃ additives, Reactive Force Field Molecular Dynamics (ReaxFF MD) simulations are performed in this study. The primary objective is to investigate the inhibition mechanism of CHF₃ on H₂–O₂ combustion from 2000 K to 2800 K. The simulation results demonstrate that the reaction pathways of hydrogen combustion are changed under the extended second explosion limit, and the main radicals involved in elementary reactions transform from H, OH, and O to H, OH, and HO₂. CHF₃ predominantly engages in reactions with H radicals to impede the continuation of chain reactions by forming stable HF molecules. OH radicals react with modest amounts of secondary fluorides such as CHF₂OH, CH₂F, and so on, while HO₂ radicals are combined with even fewer intermediates like CHF₂O and CHFOH to prevent chain propagations. Moreover, comprehensive and novel reaction pathways are proposed for the inhibition of H₂–O₂ combustion by CHF₃. The parameters of the reaction kinetics indicate that the ignition delay is advanced and the activation energy for the combustion process is increased under the influence of CHF₃. This study is expected to provide practical guidance on the inhibition of H₂–O₂ combustion by CHF₃.

With increasing population, the demand for high-rise residential buildings has been increasing. The challenges posed by firefighting and evacuation during fires in high-rise buildings have attracted considerable attention. This study explores the fire safety facilities and management in high-rise residential buildings in Vietnam and the knowledge and awareness of residents regarding fire safety. These aspects were assessed using a questionnaire answered by residents of 32 high-rise buildings in Vietnam. The answers reveal that most residents had basic knowledge of fire safety in high-rise buildings, but their preparedness of a fire event was inadequate. It is recommended that the implementation of safety regulations and measures for reducing the risk of fires in buildings be enforced. Besides analyzing descriptive statistics, a multiple regression analysis was conducted to explore the key factors influencing the level of awareness and knowledge of fire safety among the residents of high-rise buildings. The results indicate that education level, gender, living floor, and participation in fire drills are the key factors influencing residents' levels of knowledge and awareness. The survey results serve as supportive reference for the relevant stakeholders for reducing the risk of fires and the resulting losses. Furthermore, this study offers valuable insights for future studies on high-rise residential buildings in Vietnam at larger scales.

Due to their high aesthetic value, energy-efficient properties, and contribution to daylighting, the demand for using glass panels in modern buildings has considerably increased over the past decades. However, ordinary glass panels are highly susceptible to cracking during a fire because of the temperature difference between the part of the glass exposed to the fire and the part protected by the frame. Damage to the glass can allow additional oxygen intake, leading to the flashover phenomenon significantly increasing fire severity. Laminated glass is superior to ordinary glass in its impact resistance, sound insulation, and ability to maintain post-breakage integrity. This paper provides a simplified method to study the effect of temperature gradients on the cracking behaviour of laminated glass panels. The temperature of the unprotected portion of the glass panel is first estimated by evaluating the mid-thickness temperature using the general heat transfer equation. Then, equations developed based on a parametric study that utilized ABAQUS are proposed to estimate the exposed and unexposed surface temperatures. This step was followed by evaluating the temperature of the protected glass portion. Subsequently, a method based on strain-equilibrium principles was developed to predict the corresponding maximum thermal stress. Comparisons with experimental and numerical work by others validated the proposed method.

Tensile testing was performed on ASTM A416 cold-drawn 7-wire strands under varying combinations of applied loading and high temperature in three phases: “steady-state” tests, for which increasing load is applied to a specimen at steady-state temperature; “transient” tests, for which the ambient specimen is initially loaded to a constant target tension value and the temperature is then increased until the specimen fractures; and “creep” tests, for which the specimen is subjected to a constant target combination of temperature and tensile loading for a prolonged period of time, during which it accumulates creep strains until fracturing. Temperature-induced decreases in ultimate strength and proportional limit are relatively consistent compared to the existing literature for a wide range of cold-drawn strands fabricated under different governing standards. Steady-state tests produced slightly more thermally induced strength loss compared to transient tests, which suggests that design-basis predictions that are founded on steady-state test results can be used to conservatively predict the thermally induced strength loss in strands that are increasingly heated during fire exposure. Strands loaded to a stress utilization ratio beyond 70 % of their thermally dependent ultimate strength can experience a significant increase in creep strain under prolonged thermal exposure.

This paper presents a finite element model for a multi-story structure subjected to traveling fire. The structure selected has been previously investigated in experimental studies. The study investigates the effect of the number and positions of the panels exposed to fire on the fire behavior of the composite floor in the structure. Parameter analyses were conducted, including floor thickness, reinforcement arrangement, loads, position and number of panels exposed to fire, and traveling fire. The study shows that there are three different patterns of membrane action: ring type, diagonal U type, and opposite side U type. The moment and axial force of the steel beam near the fire panel increase gradually, while the internal force change of the steel beam at a distance from the panel exposed to fire is relatively small. The axial force of the edge and corner columns changed more significantly compared to the axial force of the middle column. Furthermore, the displacement, fire resistance, failure mode, and membrane action of the floors depend primarily on the position of the panels exposed to fire, the traveling fire, and the interaction among members.

Geopolymer has excellent mechanical properties at elevated temperatures, but geopolymer concrete may not be so because of the large difference in thermal properties between geopolymer and aggregate which could lead to substantial thermal stresses when they are in a high temperature environment. In this paper we present an experimental investigation on the mechanical properties of GGBS-FA-SF blended geopolymer concrete with and without steel fibres at elevated temperatures. The influences of exposure temperature, coarse aggregate and steel fibre on the failure mode, compressive strength, elastic modulus, peak strain, and ductility of the geopolymer mortar and geopolymer concrete are examined. Based on the experimentally obtained data, empirical temperature-dependent stress-strain constitutive equations are also proposed, which can be used for the fire safety analysis and design of geopolymer concrete with and without steel fibres.