Fire and Materials最新文献

Electrical fires perennially rank first in fire occurrence types, with conductor overcurrent being one of the main inducements. This topic draws significant attention from scientific researchers and fire investigators. To understand the overcurrent fault and combustion characteristics of copper-clad aluminum conductors, this paper examines 2.5 mm² copper-clad aluminum conductors that meet national standards, investigating morphological changes, temperature variations in the core and insulation layer, and flame propagation patterns under overcurrent conditions. Experiments using an electrical fault simulation device were conducted to study overcurrent failures of copper-clad aluminum conductors under 52.5–105 A conditions. The results indicate that when the current exceeds 67.5 A, the conductor undergoes a series of changes during energization, including smoking, expanding, carbonizing, burning, and breaking; at 52.5 A, the insulation layer reaches thermal equilibrium at 150 s without combustion; for currents between 60–67.5 A, wire core temperature variations can be divided into three stages; at 75 A, the insulation layer reaches thermal equilibrium 10s before breaking; currents above 82.5 A see a sharp increase in temperature in both the core and insulation layer before the conductor breaks; above 97.5 A, the conductor first breaks and then burns. The research results have significant theoretical value in improving the scientific rigor of fire accident investigations and forensic evidence examinations.

The outermost layer of a fire proximity suit needs to conform to a strict requirement of radiant protection performance (RPP) ≥ 20s, which is indicative of its ability of offering a protection for at least 20s duration from second degree burn upon radiant heat exposure (84 kW/m²). Typically, this layer is fabricated by laminating a single-side metallized PET (SMPET) layer with glass fabric. However, upon erosion of the deposited metal, this laminate is rendered unsuitable due to loss of reflectivity. Here, we explore the possibility of replacing the SMPET with its dual-metallized analogue (DMPET) and determine the effect of increasing the optical density (OD) on the adherence and protection level. Metallized films with OD varying from 2.2 to 4.8 were laminated with glass fabrics of twill, satin and plain weave pattern using a silicone adhesive. The peel adhesion strength of laminates prepared using DMPET was found to be higher (1.01 ± 0.03 N/mm), as compared to SMPET (0.63 ± 0.03 N/mm) and the resulting films did not undergo delamination during flexing. Laminates prepared from satin woven glass fabric exhibited lowest flexural rigidity followed by twill and plain woven glass fabric. Protection offered by the laminate from convective heat was quantified in terms of the thermal protective performance (TPP), and the abraded laminate prepared using DMPET (OD-4.8) was found to meet all the mandatory requirements of proximity clothing, offering an RPP of 27 s and a TPP of 62 cal/cm² s. In comparison, SMPET laminates exhibited lower level of adhesion and offered an RPP of only 7.5 s.

Combustible and noncombustible notions have evolved with time, along with the associated fire tests by which legislation classifies building materials. New Zealand, Japan, and Europe are just some of the many legislations that have followed this evolution, except for North American regulations, which remain attached to methods dating back to 1944. To better understand this stagnation in North American practices, this document first traces the evolution of Canadian regulations on fire classification of materials. Then, a parallel is drawn with the evolution of reaction to fire tests mandated in the National Building Code of Canada. Finally, this paper will review the current fire classification of materials concerning the combustibility concept based on the Steiner tunnel test and the flame spread rating criteria. The analysis reveals that the relevance of the test and its results are questionable, and the reciprocity between test measurement and its classification does not always coincide. Despite the revisions made through time, the classification of materials based on their fire properties remains distinctly binary.

A cross-laminated timber rib panel is a floor system comprising cross-laminated timber plates rigidly bonded to glued-laminated timber ‘rib’ beams. A design method was developed to estimate the fire resistance of cross-laminated timber rib panels, based on a bending load-carrying model. The bending load-carrying model calculates the bending load-carrying capacity of cross-laminated timber rib panels based on simulated temperature distributions of numerical models. The numerical models were validated against the experimental results of full-scale fire resistance tests. The proposed design method is based on the overall approach of the current revised draft of EN 1995-1-2:2004, that is, prEN 1995-1-2:2023, and provides conservative estimates of the bending load-carrying capacity. The effective width is one of the most important design parameters and its influence was studied in detail. A limit value of 60% of the effective width according to prEN 1995-1-1:2023 is proposed as effective width in fire.

In this article, we examine a chaos theory view of accidental dwelling fire injuries using data from a UK fire and rescue service over a 10-year period. Although chaos theory could not predict if or when a fire injury will occur for a given individual, chaos theory provided further information above and beyond the typical statistical analyses undertaken by fire and rescue services in terms of identifying pattern repetitions, interconnectedness of circumstances and sensitivity to initial conditions relating to the circumstances of accidental dwelling fire injuries. Householder behaviours such as attempting to tackle the fire or being under the influence of alcohol or drugs were the most prevalent circumstances relating to fire injury over the period studied. Proportions of smoke/toxic fumes inhalation injuries and injuries sustained attempting to fight the fire compared to the overall numbers of fire injuries per year showed pattern repetition over the period studied. In terms of interconnectedness, although there were roughly equal numbers of male and female fire injuries overall, the likelihood of an alcohol-/drug-related fire injury or a fire injury resulting from attempting to put out a fire was strongly connected with the gender of the householder involved.

In this paper, the influence of tunnel cross-sectional aspect ratio on the ceiling temperature profile and mass flow rate (MFR) of ceiling jet is studied theoretically and numerically, and 13 tunnel cross sections with different aspect ratios ($��\xi �$) are considered. A total of 26 full-scale numerical simulation cases are conducted using Fire Dynamics Simulator, and small-scale experiments are used to verify the accuracy of the simulations. Results show that the maximum ceiling temperature is more sensitive to the tunnel height and decreases with increasing aspect ratio, which can be divided into two regions, $��\xi �$ <1 and $��\xi �$ ≥1. When $��\xi �$ ≥1, the maximum ceiling temperature varies more linearly. The initial locations of the one-dimensional spread for the tunnel with different tunnel cross-sectional aspect ratios are similar, which are concentrated at 15–20 m from the fire source when taking the MFR increase rate of 0.001 as the criterion. By introducing the sectional coefficient, the MFR model and temperature attenuation model of ceiling jet are developed for the tunnels with $��\xi �$ <1 and $��\xi �$ ≥1, respectively. The results of this paper could provide definite reference value for the smoke control in tunnel fires.

There is great interest in developing methods to predict full-scale fire performance of mattresses and upholstered furniture for design and regulatory purposes using cone calorimeter and other small-scale test results. One method used in the past is a model developed during the European Combustion Behavior of Upholstered Furniture (CBUF) project. To support the further development of this model, cone calorimeter tests of polyurethane (PU) foam specimens 5–10 cm thick were conducted using incident heat fluxes between 5 and 35 kW/m². Temperatures were measured using thermocouples located on the surface and at four depths within 10 cm thick foam specimens to determine the effects of heat flux on heat transfer and foam degradation. Peak and average heat release rate (HRR) values for a particular thickness of foam increased with an increase in heat flux. An increase in heat flux decreased the times to reach the two peaks in the HRR curve, which represent the collapse of foam and burning of liquid products, as well as burning duration. Heat flux had a larger effect on the second HRR peak than the first peak. Significant temperature gradients were initially confined to the top portion of the foam. A surface temperature of 150–200°C was shown to be indicative of the onset of ignition, while a temperature of 150°C at a particular location was indicative of when temperatures began to more rapidly increase at deeper locations within the foam. Infrared video records were also used to examine three-dimensional burning behavior of the foam.

To investigate the problems of overload and excessive thermal insulation associated with building electrical fires caused by wires, a theoretical model of wire heat transfer is established, and the pyrolysis and combustion phenomena of the insulation layer are analyzed. The results showed that the temperature evolution of the wire underwent three stages: constant temperature, insulation heating, and high-temperature pyrolysis. The insulation layer experiences bulging, exhausting, carbonization, dripping, and burning in sequence, and insulation layer dripping requires at least 160 A of current. As the current increases, the temperature increase rate of the wire increases gradually, and the fusing time of the wire gradually decreases. Under the same current, 160°C is the turning point at which the temperature increases. The temperature increase rate of the copper wire is greater than that of the aluminum alloy wire, and the temperature increase rate of the bare wire is greater than that of the insulated wire. The fusing time of an aluminum alloy wire is less than that of a copper wire, and the fusing time of a bare wire is less than that of an insulated wire. The research results provide theoretical guidance for the prevention and investigation of building electrical fires.

Cavities form an integral part of many external wall systems (EWSs). Numerous external wall fires worldwide have been primarily due to combustible exterior cladding. However, the Grenfell Tower and Knowsley Heights fire incidents (in the UK) are examples where wall cavity materials have impacted fire spread. Wall cavity materials are typically regulated by small-scale fire test methods which do not necessarily represent the actual fire conditions that can exist within wall cavities. This experimental study proposes an intermediate-scale test (IST) protocol to examine cavity wall fire behaviour. This protocol is a modified version of the FM Global Cavity Fire Test method (within the FM 4411-2020 series). The study examines a broad range of cavity materials including sarking, polyester insulation, phenolic foam, PIR, and EPS. A low-intensity (6–8 kW) and high-intensity (~80 kW) ignition sources were used to represent two types of cavity fire scenarios. These two fire sizes were shown to differentiate reaction to fire behaviour between these materials and explore the “tipping point” in resulting fire behaviour (which may lie between these two intensities). This proposed cavity fire test protocol provides a suitable “elevated fire risk assessment tool” for combustible cavity materials.

The cover image is based on the Research Article Large eddy simulations fire modeling of JIS A 1310 façade calibration test with respect to sidewall by Xukun Sun et al., https://doi.org/10.1002/fam.3192.