Fire Technology最新文献

The malfunction of electrical equipment exposed to fire smokes is a major issue in nuclear facilities safety assessments. For over 15 years, the ASNR has been carrying out studies to provide data on electrical malfunctions obtained from reference equipment. Thus, ASNR decided to perform an analytical study to explore the malfunction phenomenon, and to understand how far the soot contained in the smoke promotes electrical malfunctions. An analytical device (called DANAIDES) was specifically designed to expose supplied electrical equipment to a thermal stress and/or a mass concentration of soot (in steady state). First, the experimental protocol plans to study the effect of soot on electrical malfunctions caused by the heating of the components. In a second step, the equipment is confronted to another malfunction type caused by electrical leakage currents through carbon bridges due to the soot deposit. After showing that the presence of soot clearly shortens the thermal malfunctions time, since the thermal stress around the equipment is sufficient, the study was also able to highlight that soot caused leakage current malfunctions, from temperatures significantly below the heat stress threshold. This study highlighted the fundamental role of carbon aerosols in the occurrence of electrical malfunctions. This is a first step towards possibly taking the presence of soot into account in safety criteria, which to date are only based on a temperature threshold. However, to define a reliable malfunction criterion based on a critical soot threshold, a similar study should be conducted with real fire soot, so that the results can be considered generalizable and representative of real fire scenarios.

EXIT89 is a pioneering evacuation model developed for high-rise building emergencies, integrating network modeling to simulate occupant movement during crises. This short communication examines its development by Dr. Rita F. Fahy, its applications in critical case studies, and its influence on fire safety codes. The impact of EXIT89 on evacuation modeling and high-rise fire safety is considered, especially in terms of how it laid foundational groundwork for contemporary models.

This study introduces an improved three-phase evaluation approach to assess the residual strength and structural response of reinforced concrete (RC) beams subjected to fire exposure. Highlighting the potential for RC structures to be utilized again after fire incidents, this research emphasizes the need for comprehensive assessment and rectification to determine their remaining strength. The methodology employs a systematic approach, segmented into three essential phases: pre-fire testing (conducted at room temperature), fire testing including a cooling phase, and post-fire (residual) testing. These evaluations were carried out on two full-scale beam specimens, each 200 mm wide, 300 mm deep, and spanning 2000 mm in length. One RC beam was not exposed to fire, while the other one was subjected to fire on three sides. Each RC beam was then tested under the four-point bending setup until failure to determine the remaining strength. The furnace temperature curve was also compared with BS 476-20 and ASTM E119-00a standard fire curves for reference. The investigation revealed that factors such as thermal degradation of the concrete and pre-loading significantly affect the post-fire performance of the RC beam, leading to irrecoverable plastic deformation. This was evidenced by a 26% reduction in ultimate load and a 51% decrease in secant stiffness for the fire-exposed beam. Additionally, the beam exhibited a 5 mm residual deflection in the unloaded state and a significant 75.8% increase in deflection at ultimate load, rising from 22.3 to 39.2 mm. Further analysis demonstrated the limitations of the 500 °C Isotherm method, which underestimated residual capacity by 16.5%, compared with Finite Element Analysis simulations that closely matched experimental results with only a 1.2% difference. The proposed three-phase evaluation not only deepens the understanding of the structural behavior under fire exposure but also provides a systematic framework for assessing its continued usage throughout its service life.

Titanium-clad bimetallic steel (TCBS) is an ideal material for corrosive environments due to its excellent corrosion resistance. Fire poses a significant threat to TCBS plate girders, necessitating the evaluation of their residual capacity for repair and reinforcement after exposure to fire. However, research on the post-fire resistance of TCBS plate girders is lacking. A finite element modeling method was used to examine the residual capacity of TCBS plate girders after elevated temperature, whose accuracy was validated against experimental results. A parametric analysis involving 384 TCBS plate girder models was conducted, considering the effects of exposure temperature, cooling method, web geometry, and loading length. Based on numerical results, the design approach in EN 1993-1-5 was validated. Furthermore, a predictive formula for the buckling coefficient of the TCBS plate girder under patch loading was proposed, significantly enhancing the accuracy of buckling capacity calculation compared to EN 1993-1-5. Additionally, based on the resistance model in EN 1993-1-5 and the proposed formula for buckling coefficient, strength reduction functions for TCBS plate girders after various exposure temperatures and cooling methods were proposed. The research results provide an important basis for evaluating the residual bearing capacity of TCBS plate girders after fire.

Bench-scale fire testing has gained popularity as a highly controllable and cost-effective solution, overcoming many of the shortcomings of traditional large-scale fire resistance tests. Whereas gas-fired radiant panels have demonstrated significant success in this area, the present study introduces a novel High-Intensity Fast-Response Electric radiant Panel (HIFREP). Utilizing electrically operated radiation emitters, it provides more precise and quasi-instantaneous control over the thermal boundary conditions. HIFREP delivers high and stable heat fluxes up to 105 kW/m², and, due to the low thermal inertia of the emitters, can rapidly adjust its output to changes in the input. In this regard, the time constant of the emitters has been found to be less than 1 s, both during heating and cooling. It eliminates gas combustion and hence avoids the need for extraction hoods when testing the fire performance of non-combustible materials, making it suitable for traditional structural testing laboratories. The presented High-Intensity Fast-Response Electric radiant Panel also provides a reliable tool for the validation of FEM simulation results by accurately replicating the thermal boundary conditions in structural fire engineering analyses.

The rise of engineered timber in tall buildings highlights the need for research on timber structural behavior under fire conditions. Despite significant advancements in understanding timber cracking models under thermal radiation over the past decade, a critical gap persists in experimental data regarding the evolution and quantitative gauging of cracks during the burning of timber. In this communication, a novel methodology was developed that could clearly gauge the crack dimensions on timber surfaces under fire conditions using narrow-spectrum illumination and the ridge detection algorithm for image processing. Pinewood samples, with a thickness of 20 mm and a width of 100 mm, were exposed to a constant radiant heat flux of 30 kW/m², and the evolution of surface crack parameters was measured as an implementation and validation of the apparatus and method. Based on narrow-spectrum illumination, this work introduces a practical apparatus with image processing for surface crack dimension gauging of burning timber samples. This methodology is compatible with current reaction-to-fire tests (ISO 5660-1: 2015) and Fire Propagation Apparatus (FPA) tests (ISO 12136: 2011), improving combustibility testing through the incorporation of observations on solid material crack development.

In the summer of 2022, a series of heatwaves caused an unprecedented wave of wildfires across the UK. London, in particular, was badly affected. Its green spaces wilted, and the drying vegetation provided the fuel for wildfires. The London Fire Brigade (LFB), one of the largest firefighting organisations in the world, was overwhelmed. On 19th July 2022, it experienced its busiest day since World War II. Our work represents a first attempt to examine and quantify the link between heatwaves and wildfires in a city. We combine fire incident data from the LFB and meteorological data from the Met Office, from 2009 to 2022, identifying vapour pressure deficit (VPD) as a key driver of wildfires in the urban habitants of Greater London. Wildfire activity is characterised using the number of recorded wildfires, and the time spent at incidents by the LFB’s fire pumps. We find that VPD is able to explain up to 61% of the variation in number of London wildfires. Relative humidity, and maximum daily temperature are only able to explain 44% and 42% of the variation respectively. We find that the Met Office’s definition of a heatwave—defined for the purpose of public health—is unsuited to describe the process of vegetation drying, and propose a new definition using data from the Met Office, based on vapour pressure deficit. Further, using the time spent at incidents by the LFB’s pumps, we define and identify the concept of a firewave, in order to foresee the potential arrival of another wave of extreme wildfires in London and prepare accordingly. It is hoped that the results will be of operational value to the LFB, and lay the foundation for further work investigating the role of heatwaves and VPD in increasing wildfire hazards in cities and other urban environments worldwide.

In the combined smoke exhaust system for tunnel fires, the critical velocity for longitudinal mechanical auxiliary ventilation is usually a fixed value. However, the uncertain development speed and scale of the fire often result in an excessive critical velocity, hindering early-stage personnel evacuation and rescue. To address this challenge, this study introduces the proportional-integral–differential (PID) control algorithm for regulating longitudinal mechanical auxiliary ventilation velocity in combined smoke exhaust system. Initially, we conduct a theoretical analysis of the PID control algorithm's application in combined smoke exhaust system. Subsequently, through numerical simulations, we demonstrate the system's stability in varying fire scenarios characterized by different development speeds during development periods and heat release rates during stable periods. And then, an analysis is conducted on the impact of the control system on the smoke exhaust system performance. The results reveal that the control system can maintain good smoke stratification downstream of the fire source, especially during fire development period, facilitating early personnel evacuation and rescue. Moreover, the smoke exhaust efficiency of the combined system is significantly enhanced. Finally, a detailed implementation plan for deploying this control method in practical engineering applications is presented.

Frequent wildfires increasingly impact tourist populations, yet there is a shortage of evidence-based, human-centered tools for wildfire risk reduction tailored to these areas. Most current tools focus primarily on assessing and reducing physical vulnerabilities, overlooking human aspects. While some community wildfire management guidelines exist, actionable strategies for disaster managers to address tourist-specific vulnerabilities are absent. This study aligned with existing vulnerability assessment methodologies, utilizing qualitative interviews, site visits, and literature review to identify key characteristics of tourist vulnerabilities and develop effective mitigation strategies. As a result, we developed TOURSAFE—a freely accessible tool for disaster risk managers in tourist areas. Based on human behavior in fire scenarios, expected evacuation decisions, and key actors’ expertise, TOURSAFE assists in identifying tourism-related wildfire vulnerabilities and offers relevant, adaptable mitigation strategies. This tool is easy to use, accessible, and provides actionable advice for short-, medium-, and long-term planning.

This article presents findings specific to antidepressants and narcotics use in fire-related deaths. The findings in this article originate from a larger study on illicit drug, prescription drug, and over-the-counter (OTC) sleep aid use in fire related deaths and drug impact on human behavior in fire. The larger study considered drug impact on fire cause and human behavior factors, i.e., receipt of cue, perception of threat, response to threat, and movement time. Drug and alcohol use data was collected from the State of Maryland, Office of the Chief Medical Examiner (OCME) for fire deaths occurring between 2005 and 2019. Data on fire origin and cause and occupant actions was gathered from fire investigation reports issued by the State of Maryland, Office of the State Fire Marshal (OSFM), local county and city jurisdictions, and from the National Fire Incident Reporting System (NFIRS). Antidepressant and narcotic user cohorts were significantly overrepresented in the dataset when compared to individuals using other types of drugs. The most predominant fire cause in these cohorts was smoking, and there is a known interdependence between antidepressant and narcotic use and smoking. The combination of smoking while taking an antidepressant or narcotic (which may cause drowsiness) is likely an important factor. Research shows that smoke alarms provide little benefit to those intimate with (and often ignited by) fire, such as individuals that fall asleep while smoking. The results of this study indicate that risk reduction solely focused on technology-driven fire protection approaches, such as smoke alarms, is insufficient in addressing the occurrence of fire deaths in all drug user populations. Fire prevention approaches must also include community risk reduction programs focused on improving safety culture through a reduction in high-risk behaviors.