Fire Safety Journal最新文献

Many countries have implemented regulations or guidance concerning the use of elevators solely for people with mobility limitations for evacuation during fires. However, there is uncertainty regarding whether people without disabilities may want to use the elevators during an emergency, which could lead to inoperability of the elevators or crowd accidents. This research conceptualized a nudge solution that can reduce the undesirable motivation of people without disabilities to try to use elevators solely for people with mobility limitations. The solution is based on an ordinary phased-evacuation strategy and was assessed experimentally. Twenty-five participants who were fire safety professionals were gathered in a 47th-floor meeting room of a 50-story building. They were instructed to evacuate to the nearest staircase/elevator lobby where a wheelchair user was waiting for rescue by elevator. The participants were immersed in four virtual cases that replicated the evacuation behavior of other people without disabilities in the actual lobby. The results showed that reducing the queuing and wait time in the lobby by phased evacuation can reduce the motivation of people without disabilities to use the elevator. An ordinary phased-evacuation for crowd management can also contribute to safe elevator use by people with mobility limitations.

Backdraft is a special phenomenon in fire research because of its explosive consequence and the occurrence of uncertainty. The delay time of occurrence has been of interest in recent years as this influences the safety and efficiency of firefighting. This paper investigated the location of the opening and whether it affects the delay time of the backdraft. Results show that the location of the opening dramatically dominates the delay time. The hot/cold air mixing path and instantaneous localized fire ignitions determine the delay time. A ‘curtain-like’ effect for the backdraft time delay was observed. The lower opening demonstrates about 50–70 % delay time compared to the upper and middle locations. In the presence of identical fire conditions and door closure control, the extended flammable gas dilution resulting from the upper opening does not significantly impact the onset of backdraft. Hence, the effective volume above the ignition location determines the delay time of the backdraft. Furthermore, the choice of chamber material is a crucial factor influencing the likelihood of backdraft occurrence. Utilizing a material with enhanced cooling capacity reduces the probability of backdraft. This provides insight into the firefighting and intervention tactics when ventilation-restricted compartment fire occurs.

Buildings with different wall/ceilings present different burning characteristics, significantly increasing the difficulty in predicting enclosure fire development and spread. In this work, to investigate the mechanism of the influence of boundary conditions on compartment fire dynamics, a total of 54 bench-scale experiments with one quarter dimension of ISO 9705 were conducted with three boundary materials, namely, calcium silicate board, corrugated steel sheet and rock wool sandwich plate; for each boundary material, six different square pans of 80 mm, 100 mm, 150 mm, 200 mm, 250 mm and 300 mm were used to provide different energy release rates of fuel to determine the critical conditions for flashover occurrence and energy distribution in the compartment. Parameters such as the mass loss rate of fuel, temperatures of gas and wall/ceilings surfaces, start time of ejected flame and length of flame ejected from the opening were measured and analysed. It was found that with the identical pan size, flashover is most likely to occur in the compartment of the sandwich panel, and it is most difficult for flashover to occur in the compartment of the calcium silicate board. Among the three boundary conditions, compartments consisting of high thermal conductivity material on the inner surface of wall/ceilings (corrugated steel sheet and rock wool sandwich plate) show higher HRR, compartment gas temperature and inner wall/ceilings surface temperature. Through the experimental data at the pre-flashover stage, the relationships between the HRR, upper gas temperature, fuel pan size, compartment opening, and parameters of the boundary materials were quantitatively established by energy conservation to predict the occurrence of flashover, which is suitable for thermally thin, thermally thick and composite boundaries. Moreover, an energy distribution theory for the transient state was developed to predict the HRR of compartment fires very well under different boundary conditions and fuel loads.

This research presents an in-depth examination of the combustion characteristics of flame-retardant electrical wires, contrasting behavior with non-flame-retardant counterparts under jet flame heating. The study systematically investigates the pyrolysis process, ignition patterns, charring behavior, and the development of secondary flames in wires with different core diameters and insulation materials. Findings indicate the heightened susceptibility of thinner wires to rapid heating, pyrolysis and charring, leading to faster ignition and more intense secondary flame development. This insight is crucial for tailoring flame-retardant formulations to specific wire dimensions. The research also delves into the thermal dynamics within the wires, highlighting how the core diameter influences axial heat conduction and, consequently, the overall flame spread behavior and pyrolysis rate. A critical discovery is the relationship between heating duration and flame sustainability, establishing a specific range of heating times for sustaining secondary flames in flame-retardant wires. Theoretical models used in the study explained the critical heat flux heating time for wire ignition, offering insights into improved fire prevention strategies, particularly in prolonged heat exposure scenarios. These findings not only advance our understanding of flame-retardant wire behavior under fire conditions but also provide guidance for selecting and using electrical wires, thereby optimizing fire safety in diverse applications.

The structural performance of the bridges under fire accidents has gradually become one of the hot issues in bridge safety. The fire resistance of the cables is a critical factor in the structural performance of cable-stayed bridges. The mechanical properties of 1960 high-strength steel wires at elevated temperatures were investigated in this paper. Tensile tests on steel wires were performed at various high temperatures and after cooling. The failure modes and mechanical properties of steel wires after heating and cooling were investigated in detail. The results show that mechanical properties such as yield strength and ultimate strength are continuously degraded as temperature rises at both high-temperature and after-cooling test, while elastic modulus and elongation are not changed significantly after heating–cooling process. A constitutive model was proposed based on two-segment Ramberg–Osgood model for both high temperature and cooling processes. It is shown that the proposed model well reflects the material behavior for both processes.

Recent experiments conducted at the NIST examined steel-concrete composite floor systems designed per U.S. practice under standard fire. The first experiment designed per prescriptive provisions for a 2-hour fire rating with 60 mm²/m of reinforcement, developed a central breach integrity failure after approximately one hour of exposure. The second and third experiments, designed with 230 mm²/m of reinforcement, with the third one omitting the fire protection on the central steel beam, showed no failure within 2 hours. This paper describes a numerical investigation to gain further insights into the fire behavior of the composite systems tested in these experiments. Nonlinear finite element models were validated against the tests. Simulation of the first test shows concrete damage and rebar fracture in the hogging moment area corresponding with the cracks observed experimentally. Simulation of the third test captures the development of tensile membrane action, confirming the redistribution from the unprotected secondary steel member to the floor reinforcing steel. A sensitivity analysis allows identifying the minimum reinforcement steel for protected and unprotected central beams configurations. The results can support improvements of the fire requirements in the U.S. codes as well as application of performance-based structural fire design for composite structures.

The aim of the project is to investigate the possibility of using people's mobile phones to locate people in a tunnel environment using the mobile phone's Wi-Fi connection. In total, 39 different trials were carried out under different conditions in a road tunnel in Stockholm, Sweden. In the trials, the Wi-Fi-based predicted location has been compared with the actual location of the recruited 16 participants in the tunnel. The conditions include the number of people in a group, the number of available access points in the tunnel, whether the mobile phone has an active or passive connection, whether a person is moving or standing still and whether the mobile phone is held in the hand or is stored in the person's pocket. The results indicate that the mean value for the distance between actual and predicted locations is in the order of 20 m or less, which is higher than reported in other studies. Despite this, there is a good potential to locate individuals in a tunnel emergency as the distance between emergency exits is often much longer than the uncertainties in the predicted locations of people. Improving the location algorithms will possibly reduce the uncertainty of the predicted location.

One in five fire incidents in Australia is residential fire. There is a paucity of data on the economic costs of responding to residential fires. The limited research has centred on fire services without due recognition of the involvement of other agencies. This study aims to determine the economic costs of all first responders for responding to New South Wales (NSW) residential fires. This was conducted using Fire and Rescue NSW administrative data from 44,623 residential fire incidents between January 2005 and March 2015, together with other publicly available information. Costs were expressed in terms of constant 2022 Australian dollars. Fire and Rescue NSW personnel spent an average of 130 min per residential fire, involving eight personnel. The total economic costs to all responders, including personnel and resources, for responding to residential fires, averaged AU$ 9.5 million per annum and AU$ 2200 per incident. Both the total economic costs and costs per incident increased significantly by 1.4 % and 2.8 %, respectively, over a decade. This pioneering study sheds light on the costs of first responders for residential fires, providing valuable insights for policymakers to enhance preparedness for residential fires and associated consequences, recognising the broader economic impact extending beyond the primary agency.

Through a series of full-scale fire tests conducted in three different tunnels, the common characteristics of combustion and smoke temperature of double pool fires in actual operation tunnel environments are investigated. The evolution process of the coupling effects of shielding entrainment and thermal feedback enhancement is revealed. It is found that the ventilation state and the fire source spacing can alter the dominant relationship between the shielding entrainment effect and the thermal feedback enhancement effect, resulting in different evolution patterns of combustion characteristics and smoke flow patterns of double pool fires in tunnels. The heat release rate increases by 4 times when the double pool fire flames merge under the longitudinal ventilation compared with the double pool fire flames without fusion under the natural ventilation. The flame tilt angles of double pool fires were determined through the image processing method, and the prediction model of the flame inclination angle of downstream fire sources was established, considering fire source spacing. At the same time, the characteristic of temperature measured by Fiber Bragg Grating in double-source fire scenarios was investigated, developing a model to predict the longitudinal temperature rise distribution. It is found that the maximum temperature rise prediction model based on steady-state fire has poor applicability in the weak-plume fire scenario of full-scale tunnels. The analysis of the smoke flow patterns shows that the two-stage ventilation is more suitable for smoke control compared to full longitudinal ventilation in tunnel double-source fire accidents, especially for ensuring the safety of individuals trapped in the area between the two fire sources.