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Hydrogen fuel cell vehicles (HFCVs) may cause fires in the event of an accident. When the high-pressure hydrogen storage cylinders are exposed to fire for a long time, there will be a risk of catastrophic consequences such as leakage, jet fire and explosion. Fire test is the main method to study the safety performance of hydrogen storage cylinders. During the firing process, the wall and internal temperature of the hydrogen storage cylinder rise gradually, and the thermally activated pressure relief device (TPRD) of the cylinder reaches a certain temperature and then releases high-pressure hydrogen to prevent the cylinder from bursting. As the hydrogen storage cylinder is in the fire environment, the release of high-pressure hydrogen will be ignited to form a jet fire and cause damage to personnel and equipment. In this paper, CFD software Fluent was used to numerically simulate the local fire test of the hydrogen storage cylinder with high-temperature air as the fire source. The variation law of cylinder wall temperature, gas temperature and pressure inside the cylinder, and the activation of TPRD were analyzed. At the same time, on the basis of the fire test simulation, a high-pressure hydrogen jet fire simulation numerical model caused by the TPRD action was established. The velocity field, temperature field and hydrogen concentration distribution of the jet fire were obtained, and the overpressure generated by the jet fire and the flame length size were analyzed. The results show that the high-pressure hydrogen released by TPRD was ignited under the fire condition to produce a jet flame and generated an overpressure in the jet direction, and the influence range of the overpressure was smaller than the influence range of the jet flame. • The internal temperature, pressure and wall temperature variation laws of cylinders were analyzed. • Hydrogen jet fire flow field changes after TPRD activation were simulated. • The influence range of overpressure in the direction of the jet is smaller than that of the jet flame. • The length of the jet flame is affected by the initial injection pressure and the TPRD discharge diameter. [ABSTRACT FROM AUTHOR]

The role of steel connections is essential in structural fire design and analysis for steel-framed composite structures. The current structural design provisions provide strength reduction factors of load-carrying members and their end-connection elements at elevated temperatures, based on small-scale experiments under uniform heating conditions. The realistic thermal and structural evolution in member connections, especially as part of full-scale floor assemblies exposed to a large compartment fire, has not been well characterized. A large compartment fire experiment was recently conducted on a 9.1 m by 6.1 m composite floor assembly as part of a two-story steel-framed building. The test assembly had a total of ten shear-tab (fin-plate) connections subjected to combined fire and mechanical loading. This paper presents the measured thermal response of these connections to fire and comparison with the corresponding Eurocode 3 predictions with two methods (1) incorporating the beam bottom flange temperature at midspan and (2) the section factor method. The results show that the Eurocode 3 methods conservatively predict the maximum temperature during heating and the cooling rate but overestimate the high-temperature strength of connections when estimated using the section factor method, showing that the Eurocode 3 simplified approaches are not meant to provide the details of the failure mode for connections. This study suggests that estimating the strength of connections using strength reduction factors may not guarantee a safe structural fire design. In addition, this paper estimated the total axial force (from slab and beam) at the composite connection via using the strain gauge measurements close to the column bases which were not exposed to fire. It suggests realistic axial load and rotational demand on the shear connection due to restraints to thermal elongation or contraction of supported members should be considered in future design guidance as should designing and detailing the connections for ductility to withstand the inelastic deformation demands during the heating and the cooling phases. [ABSTRACT FROM AUTHOR]

To obtain a precise finite-element model (FEM) for analyzing the dynamic response of corroded beams at high temperatures, a stepwise FEM modification strategy is proposed based on the improved extreme learning machine. Three concrete beams were designed and cast, and the dynamic response characteristics of corroded concrete beams at room temperature and high temperature are discussed. Firstly, electrical accelerated corrosion tests and vibration tests were conducted on simply supported beams at room temperature. The fundamental frequencies of concrete beams under different corrosion ratios were measured. The attenuation law of fundamental frequency with corrosion ratio also was studied. Subsequently, the FEM under different corrosion ratios was modified. The bond-slip between steel bars and concrete under different degrees of corrosion was considered during the correction process. Finally, a vibration test at high temperature was performed. The modal attenuation law of corroded beams at high temperatures was analyzed. Based on the modified FEM, numerical analysis at high temperature was performed. The proposed FEM modification strategy and the study of the attenuation regularities of modal information under fire exposure provide a foundation for further research on the damage development of corroded reinforced concrete (RC) beams under fire exposure. [ABSTRACT FROM AUTHOR]

The design of Type B radioactive transport package should be able to withstand the fire accident scenario in transportation accident conditions. For the simulation of the fire scenario, there are mainly three methods: pool fire test, furnace test and thermal radiation test. This paper tried to carry out the fire test with the furnace method that the conditions in the furnace can be more carefully controlled. The paper described the requirements of fire test, test conditions and measurement test methods and analysed the temperature change of fire site and the heat flux data of the surface of the package during the fire test. The test results seemed that the fire test method could provide satisfactory thermal environment for fire test of Type B radioactive transport package. [ABSTRACT FROM AUTHOR]

Fire is generally recognized as a major threat to the protection of historic timber architecture. Thus, there is an urgent need to study the fire properties of historic timber structures so as to better protect them in the future. Two types of commonly used wood species (pine and poplar) were selected as test specimens and three types of surface treatments (Chinese traditional coating, modern flame retardant, and a combination of the two methods) were applied. The specimens were subjected to a semi-full-scale fire test. The charring rate and the surface heating curve were calculated during the fire test to assess the flammability of various woods under different treatments. Results showed that the fire properties of traditional-coated wood were better than the modern type, but large amounts of smoke were released during combustion. The combination of traditional and modern methods did not significantly improve the overall fire properties and was even worse than the traditional treatment alone. At the same time, the fire properties of the modern method are highly correlated with the type of wood species used. The above results can provide informative advice on the selection of suitable surface treatments for the subsequent restoration of ancient buildings. [ABSTRACT FROM AUTHOR]

To evaluate the influence of fire-retardant coating on the fire resistance of assembled frame tunnel, the temperature field distribution law of tunnel joint components coated with intumescent fire-retardant coating was analyzed by fire test, and the influence of fire-retardant coating on the temperature, deformation and damage of assembled frame tunnel under fire was studied by finite element numerical simulation. The results showed that the fire-retardant coating hindered the heat transfer to the tunnel lining, greatly reduced the temperature peak of the tunnel lining, and delayed the time of the temperature peak. The thickness of fire-retardant coating affected the heating rate and temperature peak of tunnel lining under fire, but when the thickness of the intumescent fire-retardant coating was greater than 10 mm, changing the thickness of fire-retardant coating couldn't effectively reduce the deformation of tunnel under fire. The maxi- mum deformation of the prefabricated frame tunnel under fire was the mid-span position of the roof, and the most serious damage was the position of the tunnel joint, which could indirectly improve the fire resistance of the prefabricated frame tunnel by optimizing the mechanical performance of the joint structure. [ABSTRACT FROM AUTHOR]

To address the difficulty in conducting fire tests to verify the fire-resistance limit of large one-way slabs with heavy loads in a metro, a scale fire test method is proposed based on the bearing capacity calculation of the one-way slab under fire. The scale fire test method adapted the hypothesis that the deflection of the one-way slab under fire is close to a half-sine function and the plane section hypothesis. The validity of this hypothesis is verified through fire tests and finite element simulations. The scale fire test method achieves a similar temperature field and mechanical behavior between the scaled model and full-scale model of the one-way slab. The results of the fire tests showed that the temperature field and mechanical behavior of the scaled model were consistent with those of the full-scale model, with an error in fire resistance of 4.7%. The calculation results and fire test results are essentially consistent, with an error of 6.5%, and according to the calculation of the one-way slab fire-resistance limit, the key factor affecting the fire resistance of the one-way slab under fire is the temperature of the bottom rebars. Using the scale fire test method, the size effect of the one-way slab under fire still exists, and larger slabs have a greater deformation capacity. [ABSTRACT FROM AUTHOR]

Fire suppression and rapid cooling methods are required to reduce the risk of battery fires. However, the liquid and solid residues generated during fire extinguishing pose a risk to the environment and human health. With the aim of correlating the extinguishing efficiency and environmental impact of the residues, fire tests were carried out on NMC lithium-ion pouch cells using different agents, namely water mist, F-500 water additive 2 % (v/v) and CO2. The combination of cell temperature measurements and videos allowed the efficiency of the extinguishing agents to be assessed. It was found that the efficiency of the water-based agents was higher than that of the gaseous agents (cooling rate of 30.5 ± 4.9 °C/s for water mist, 36.5 ± 6.4 °C/s for F-500 and 20.0 ± 1.4 °C/s for CO2). Analysis of solid and liquid residues using gas chromatography and induced coupled plasma showed that the use of F-500 resulted in a higher (one order of magnitude) concentration of VOCs in solid residues compared to the other extinguishing agents. The comparison of these concentrations of VOCs with the limits established for waste (EU Regulation N. 1357/2014) showed that the solid residues did not exceed the concentration limit for classification as hazardous waste. Regarding the concentration of metals, the highest values in the solid and liquid residues are due to Li, Ni and Cu. Based on these values, all solid samples can be classified as carcinogenic and toxic for reproduction. While the concentration of metals in the liquid residues was higher than the limit value that poses a risk to aquatic organisms. The overall results showed the need for site remediation and waste management procedures in the event of a major accident.

This paper provides an experimental investigation of a kerosene/air burner (the NexGen burner designed on the FAA's proposed ISO 2685 standard), which is used to generate flame/burnt gases impinging on material samples in the field of fire safety. The purpose of this study is to characterize this burner, and experimental means are implemented to better understand the effects of the equivalence ratio on the spatial distribution of the gas temperature (thermocouples), the heat flux (heat flux gauge), and gas emission species. Hence, the measured flame temperature, heat flux, and heat release rate increase up to a critical value of equivalence ratio equal to 1.03. Furthermore, a pyrolysis test was carried out on composite materials and the results of the comparative analysis of carbon‐phenolic, carbon‐BMI, and carbon‐PEKK materials show that carbon‐PEKK had the lowest mass loss, highest back‐face temperature without significant material delamination, and the lowest concentration of gas emission species. [ABSTRACT FROM AUTHOR]

The construction industry's growing demand for earthen materials faces a hurdle due to limited knowledge regarding their fire performance. The present work aims to assess the fire behavior of compressed earthen bricks, particularly focusing on spalling. Two influencing parameters were studied: the influence of cement stabilization and water content. To ensure equivalent compressive strength, compaction levels and cement content were thoughtfully chosen, as mechanical properties greatly influence fire behavior. In the material selection phase, unstabilized earthen bricks were compacted across a range of loading levels from 40 to 60 MPa. Subsequently, a loading level of 50 MPa was chosen for fire testing. Cement-stabilized earthen bricks were compacted at a Proctor level pressure with cement content varying from 2.5 to 10%. Additionally, Polypropylene fibers were incorporated into both types of bricks to assess their impact on fire behavior. Various water contents were tested, with samples maintained at hydric equilibrium through different curing conditions. Fire tests with a rapid heating rate (ISO 834-1 standard fire) were performed. Preliminary evaluation of the samples' fire behavior was based on their stability/instability during heating. Unstabilized samples exhibited thermal instability at intermediate water contents (50 and 75% RH), resulting in the detachment of their heated faces accompanied by a sound. However, they remained stable when dried or fully saturated. The inclusion of polypropylene fibers reduced the risk of instability. On the other hand, cement-stabilized bricks exhibited thermal stability, with no surface peeling observed, regardless of water content. The presence of cracks contributed to this stability. [ABSTRACT FROM AUTHOR]

Understanding the susceptibility to spalling of concrete members in case of fire is important to evaluate the residual load-bearing capacity. The investigations of the spalling phenomenon of a concrete mixture using real scale members are necessary but expensive to carry out. Reducing the specimen size leads to an increase of boundary effects that can result in a reduced spalling or absence of spalling. In this study, fire tests were carried out on unrestrained, single-sided exposed, cuboid shaped specimens (0.6 m × 0.6 m × 0.29 m) as well as unrestrained and steel ring restrained cylindrical specimens (Ø = 0.47 m, h = 0.29 m), which induce different boundary conditions. These fire tests were carried out on two ordinary concrete mixtures. The two mixtures differ only in the type of aggregates (quartz gravel and basalt grit) and were used to investigate the influence of the thermal expansion of the aggregate on the spalling behaviour of the concrete. The results show a significant increase of the spalling depth due to the restrained thermal expansion achieved by the applied steel rings. Additionally, the type of aggregate has a direct influence on the spalling behaviour of a concrete mixture. The reduction of the boundary effects by the steel rings recreate the test conditions in the centre of a large concrete member. Thus, this type of specimen is suitable to determine the susceptibility to spalling of a material (screening-tests) as preliminary investigations to full scale fire tests. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Four U-shaped steel-concrete composite beams (USCB) were designed and tested under the ISO-834 standard fire curve and distributed vertical load. The research parameters were the load ratio and shear connector form. The temperature distribution, fire resistance, and failure modes of the USCB specimen were investigated. The fire tests showed that the failure mode of the specimen is flexural damage and the connection interface between the flange and web of the composite beam remains intact. The temperature of the fire-resistance reinforcements is below 500°C when the specimens reached the fire resistance, which is in the early stage of material degradation and has high residual strength. The fire resistance increased (improve by 51%) with the decrease of load ratio (0.7 to 0.4) and was not affected by the shear connector form. Then a numerical simulation was applied to establish the temperature field model and fire resistance model of USCB, and the simulation results of the temperature field and fire resistance were in good agreement with the test results. The parameter analysis indicated that the load ratio, the diameter of fire-resistance reinforcement and fire protection layer have an obvious impact on the fire performance. Based on the heat transfer mechanism analysis, the temperature calculation methods for U-shaped steel, fire-resistant reinforcement and concrete were proposed. Moreover, a flexural bearing capacity calculation method for the USCB under the standard temperature rise curve is proposed, which can be applied to calculate fire resistance. [ABSTRACT FROM AUTHOR]

So far too long, people have been working hard to develop fire prevention measures to deal with lithium ion battery (LIB) fires. LIB fires have a high calorific value, a rapid burning and spread speed and a high risk of re-ignition and explosion. Under thermal runaway, LIB fires develop from the inside out, preventing fire extinguishing agents from entering the interior of LIB, thus resulting in low extinguishing efficiency or even failure of the extinguishing agents. Based on the principle of 'isolation and stifling', fire-blocking blanket can effectively inhibit the spread of fire, suppress the combustion intensity and reduce the smoke emission. This paper digs into the detailed performance requirements of fire blanket to block LIB fires. By conducting laboratory tests to mimic LIB fires, the candidate materials including fiber materials, woven textile and woven fabrics with organic coatings are systematically investigated. Performance of the materials are evaluated, including fire resistance, thermal insulation, tensile strength at break and blast resistance, respectively. The testing results help to screen out the best material for LIB fire blanket, and high-silica glass fiber coated by polyurethane has the best thermal and mechanical properties among all materials tested. This paper also presents a three-layer structured design of blanket, which can pass all the tests proposed. [ABSTRACT FROM AUTHOR]

Fire is generally recognized as a major threat to the protection of historic timber architecture. Thus, there is an urgent need to study the fire properties of historic timber structures so as to better protect them in the future. Two types of commonly used wood species (pine and poplar) were selected as test specimens and three types of surface treatments (Chinese traditional coating, modern flame retardant, and a combination of the two methods) were applied. The specimens were subjected to a semi-full-scale fire test. The charring rate and the surface heating curve were calculated during the fire test to assess the flammability of various woods under different treatments. Results showed that the fire properties of traditional-coated wood were better than the modern type, but large amounts of smoke were released during combustion. The combination of traditional and modern methods did not significantly improve the overall fire properties and was even worse than the traditional treatment alone. At the same time, the fire properties of the modern method are highly correlated with the type of wood species used. The above results can provide informative advice on the selection of suitable surface treatments for the subsequent restoration of ancient buildings.

High-pressure hydrogen jet fire from a storage tank impinging another tank located nearby is a worst-case incident scenario. This could result in storage vessel rupture with catastrophic consequences implying life and property loss. The concept of microleaks-no-burst (μLNB) performance of hydrogen storage tanks of Type IV is explained. In this study, the breakthrough safety technology of explosion free in fire self-venting (TPRD-less) tank with nominal working pressure (NWP) of 70 MPa is validated again st the most extreme fire conditions of an impinging hydrogen jet from 70 MPa tank. The results of the successful performance of self-venting tank in momentum-dominated hydrogen impinging jet fire are analysed. This work expands further the experimental validation domain of the explosion free in fire self-venting tanks to scenario of impinging fire of the highest applied intensity of HRR/A = 19.5 MW/m2. • The concept of explosion free in fire self-venting (TPRD-less) tank is discussed. • Self-venting operation of 70 MPa tank is demonstrated in extreme jet fire conditions. • Tank did not rupture but leaked under realistic impinging hydrogen jet fire (70 MPa). • Jet fire of largest known specific heat release rate of HRR/A = 19.5 MW/m2 was applied. • The technology has the potential to exclude tank rupture in fires onboard of trains, ships, etc. [ABSTRACT FROM AUTHOR]

The U-shaped steel-concrete composite beam (USCB) has the superiority of good stiffness, high load-bearing capacity, and good fire performance. In this paper, the numerical simulation and theoretical derivation were conducted for the thermal transfer and fire-resistant research of USCBs. Four fire tests on USCB specimens under the current standard temperature rising curve were used to validate the fire design method. The temperature field models and fire-resistance models were set up to research heat-transfer and structural mechanisms, and the analysis showed that the fire condition of different concrete sections was different in the USCBs, and the internal force redistribution happened in the composite beam. Then, the parametric analysis shows that the load ratio, the diameter of fire-resistance reinforcement, and the thickness of the fire protection layer have significant effects on the fire performance. The temperature calculation methods of U-shaped steel, different concrete sections, and fire-resistant reinforcement are proposed based on the conducted research. Moreover, a flexural bearing capacity calculation method for the USCB under the standard temperature rise curve is proposed allowing for the influence of material strength reduction under high temperatures, which can also be used to calculate the fire resistance. Finally, the calculation tables for the fire protection layer thickness and the corresponding design method are proposed based on the delaying temperature mechanism. [ABSTRACT FROM AUTHOR]

Two fire tests were carried out on planar steel sub-frames to study the catenary mechanism of steel frame beams exposed to fire. The temperature distribution of steel frame structure and catenary mechanism of steel frame beam under different fire protection conditions were studied by experiments. According to axial forces and deformations of frame beams in fire, the formation and development of catenary mechanism were illustrated. A analysis method, which could calculate the internal force and deflection of steel frame beams exposed to fire, was proposed based on the matrix analysis method and plastic hinge theory. This method could consider the degradation of mechanical properties of rotation constraints at high temperatures. The method was validated against fire test data, and the influence of different initial constraint conditions on the catenary mechanism of steel frame beams exposed to fire was analyzed using this proposed method. It is shown that the initial axial constraint stiffness has a significant effect on the axial force and deformation of the steel frame beam at elevated temperatures, while the initial flexural strength and rotational stiffness of the joint mainly affect the position and sequence of plastic hinge formations of steel frame beam at elevated temperature. [ABSTRACT FROM AUTHOR]

The paper describes the breakthrough microleaks-no-burst (μLNB) safety technology of explosion free in fire self-venting hydrogen tanks that do not require thermally-activate pressure relief devices (TPRD). The technology implies melting of the hydrogen-tight liner before hydrogen-leaky double-composite wall loses its load-bearing ability. Hydrogen then flows through the wall's microchannels and either burns in microflames on its own or together with resin. The experimental validation of the technology is presented for 7 prototypes with the nominal working pressure of 70 MPa made of carbon-carbon or carbon-glass composites. The prototypes are fire tested at the specific heat release rate HRR/A = 1 MW/m2 characteristic for gasoline/diesel spill fires. The μLNB technology eliminates catastrophic consequences of tank rupture in fire: blast waves, fireballs, and projectiles. The technology limits hydrogen accumulation in naturally ventilated enclosures. It reduces the risk of hydrogen-powered vehicles to an acceptable level below that for fossil fuel automobiles, including underground parking and tunnels. It provides an unprecedented level of life safety and property protection. • Breakthrough safety technology of explosion free in fire tank is introduced. • The tank made of 2 composites is self-venting in fire and does not require TPRD. • The microleaks-no-burst concept of tank performance in fire is explained. • 4 carbon-carbon and 3 carbon-glass tanks are successfully tested in 1 MW/m2 fire. [ABSTRACT FROM AUTHOR]

To address the difficulty in conducting fire tests to verify the fire-resistance limit of large one-way slabs with heavy loads in a metro, a scale fire test method is proposed based on the bearing capacity calculation of the one-way slab under fire. The scale fire test method adapted the hypothesis that the deflection of the one-way slab under fire is close to a half-sine function and the plane section hypothesis. The validity of this hypothesis is verified through fire tests and finite element simulations. The scale fire test method achieves a similar temperature field and mechanical behavior between the scaled model and full-scale model of the one-way slab. The results of the fire tests showed that the temperature field and mechanical behavior of the scaled model were consistent with those of the full-scale model, with an error in fire resistance of 4.7%. The calculation results and fire test results are essentially consistent, with an error of 6.5%, and according to the calculation of the one-way slab fire-resistance limit, the key factor affecting the fire resistance of the one-way slab under fire is the temperature of the bottom rebars. Using the scale fire test method, the size effect of the one-way slab under fire still exists, and larger slabs have a greater deformation capacity.

Composite slabs, consisting of a steel section, profiled sheet and concrete, have been used successfully in composite construction for many years. In order to increase the maximum span widths, trapezoidal sheets with deeper ribs are increasingly being used. The use of modern deep steel decking changes the load‐bearing behaviour of the shear studs towards greater flexibility and ductility, but also towards a lower load‐bearing capacity. In recent years, a significant amount of research has been carried out into the load bearing behaviour of shear studs in profiled sheets, resulting in the development of a new design approach in the draft prEN 1994‐1‐1. Compared to the Ultimate Limite State (ULS), scarce research has been conducted for elevated temperature. It is therefore difficult to evaluate the compatibility of the new design approach from the draft with the existing regulations from EN 1994‐1‐2. In order to fill this gap in knowledge, push‐out tests have been carried out on trapezoidal sheets under elevated temperature. The focus of this paper is to describe the experimental approach and the first results. [ABSTRACT FROM AUTHOR]

This paper presents the details and analysis of a fire test conducted on a reduced web section (RWS) connection for steel framed construction. The test was completed in the fire laboratory at Tampere University in order to assess how these connections, usually selected and designed for their seismic performance, behave under fire conditions. RWS connections were first devised for fixed joints in steel framed buildings, with a view to moving the plastic hinge away from the column face during an extreme event such as an earthquake, thus improving the ductility of the structure. Until now, there was very little known of their behaviour under fire conditions. Accordingly, the current paper provides a detailed description and analysis of the fire test on a RWS connection, during which the arrangement lasted for around 16 minutes of standard fire exposure. It also describes the development of a numerical model, which is validated against the test data. The purpose of the model is to enable a more thorough examination of the various parameters and variables that may exist in a real structure, subjected to a real fire. [ABSTRACT FROM AUTHOR]

The utilization of wind power has increased almost exponentially during the last decade, leading to the growth in both the number and size of wind turbines. Modern turbine blades are typically made of fiberglass sandwiched around a balsa wood (BW) core. With an increase in the use of wind energy a collateral issue of what to do with the large and voluminous wind turbine blades (WTB) that reached end-of-life has arisen. Through previous research, we developed a recycling process that will keep these turbine blades out of the landfill by considering recycled wind turbine blades as a feedstock for second generation composite panels. The objective of this research is to further the research by understanding the effect that different compositions of wood and fiberglass have on the properties of these panels. Through testing, it was found that the addition of balsa wood increases the modulus of rupture (MOR) and the modulus of elasticity (MOE). The internal bonding (IB) strength values are well above that of typical particle board. All panels tested were visibly more resistant to water sorption than typical particle board. The thermal conductivity for all samples was within the typical range for particleboard. Fire test result indicates that the addition of balsa wood increases the heat and visible smoke release rate of composites. [ABSTRACT FROM AUTHOR]

Copyright of Wood Industry / Drvna Industrija is the property of Drvna Industrija and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fire resistance of load-bearing wooden structures is evaluated by the charring of surface layers of wooden bearing elements. The degree of resistance is determined by the onset and course of charring; these basic parameters are affected by the cover structure as well as by cavity fillers between the individual bearing elements. This article focuses on analysing the structure of fire protection covers based on gypsum boards, namely gypsum plasterboards and gypsum fibreboards. The foundation for the current analysis, based on the ignition temperature of the load-bearing timber element under the fire cover, includes the results of experimental fire tests carried out on test specimens in a fire furnace with a standard time-temperature curve set to simulate a fire. In addition, a numerical analysis of the temperature behaviour in the structure was carried out in order to compare the experimental results with the values obtained by mathematical analysis. Finally, the influence of the cover layers on the resulting fire resistance of the analysed structures is evaluated.

Glued laminated timber beams exposed to fire of a variable duration were tested in three point bending. Three types of model geometries taking into account the effect of burning were created. Each model was examined for five material data sets. The maximum deflection obtained from FEM simulations was compared with the corresponding deflection wel derived from a three point bending test of burnt beams. The analysis was performed with the help of Ansys® software limiting attention to a liner elasticity with the maximum applied force Fel selected at the proportionality limit observed experimentally. Majority of FEM models provided smaller deflections compared to measurements except for the material set adopting Young’s moduli from the compression test. The best fit was observed for the material data set obtained from homogenization. No predominant preference among individual geometries was found promoting the computational model based on reduced cross-section as sufficiently accurate.

The reasons behind the occurrence of a second/end peak heat release rate (PHRR) during wood combustion under radiative heating were determined. Effects of the type of rear material, wood thickness, char progression, and its microstructure, as well as moisture content/transport in spruce wood, were studied. Rear materials used were insulating Kaowool, conducting steel, and the same wood but physically separated from test specimen by aluminium foil. The intensity of the second/end PHRR with Kaowool was almost 50% more than that of the sample with steel. Thus, the second/end peak is governed by the boundary condition defined by the rear material, which determines the heat losses at the rear side of the specimen and consequently the temperature of the specimen. Higher specimen temperature enhances the pyrolysis rate, thereby causing the second/end PHRR. The appearance times and values of the second/end PHRR for 30, 20, and 10 mm wood were 1740 s/78 kWm−2, 685 s/134 kWm−2, and 450 s/160 kWm−2, respectively. Char progressed to the rear of the samples even with a thin (8 mm) conductive steel substrate. Cracks in char grew almost three times wider during the second/end PHRR compared to the sample with no second/end peak. Char cracking had no significance on the time of occurrence of the second/end PHRR but affected the overall heat release. High moisture content reduced the charring rate and delayed the time of occurrence of the second/end PHRR as more water was needed to undergo a phase change, requiring a higher amount of energy. [ABSTRACT FROM AUTHOR]

This study investigates the impact of fire on the cracking behavior of immersed tunnels. A reduced-scale (1:5) model of an immersed tunnel was constructed to conduct fire tests in both traffic tubes using the HCinc curve as the applied fire. Temperature field changes were carefully monitored during the test by thermocouples and infrared thermography on the outer surface of the tunnel's ceiling. The continuous temperature field and temperature changes in the concrete cracks were recorded by infrared thermography. By integrating the temperature field distribution in concrete and the behavior of concrete cracking, an analysis of the depth of concrete cracking in the immersed tunnel under fire was conducted. The concrete cracks exceeded 150 mm at 95 min of the fire test. The results indicate that the inner concrete exposed to fire undergoes thermal expansion, leading to tensile cracking of the outer concrete. Additionally, the fire-exposed surface of the tunnel is vulnerable to cracking due to a temperature decrease. Thus, the design of fire resistance of immersed tunnels should take into consideration the potential for concrete cracking caused by thermal strain. [ABSTRACT FROM AUTHOR]

To study the fire resistance of monolithic composite beams and separated composite beams with composite slabs under hinge constraints, constant-load temperature rise tests were conducted on a full-scale two-span continuous beam. The test phenomena, temperature distribution, displacement changes, and failure modes of the composite beam were studied during the entire process of the fire. The results showed that the cracking of the seams between the precast slabs of the separated composite slabs led to an increase in the burned area of the composite slabs and an increase in the temperature of the composite beams. No obvious cracking was observed at the postpouring seams of the monolithic composite slabs, the integrity and fire resistance of which were better. After the temperature stopped increasing, the steel beam cooled faster than the concrete composite slabs. The deformation recovery of the steel beam was restricted by the composite slabs, which were subject to the joint action of the constraining force generated by the deformation recovery of the steel beam and the external load, resulting in longitudinal cracks along the medial axis of the top of the slabs. The deformation recovery ratios of the two types of composite beams with composite slabs under hinged conditions after the temperature stopped increasing were similar. The calculation method of the axial force and horizontal displacement of the composite beam with composite slabs under the hinge constraint at the beam end in the fire was established, and the calculation results were in good agreement with the test results, with good calculation accuracy. [ABSTRACT FROM AUTHOR]

Compared with traditional timber boards, timber–concrete composite (TCC) boards demonstrate a higher rigidity and bearing capacity, improved vibration, and better behavior under seismic conditions. However, they become charred when exposed to fire due the combustibility of timber, and the fire safety of this material is considered essential. In this research, 60 min fire exposure tests and residual load-carrying capacity tests following fire exposure were carried out on three full-scale composite boards, two of which were covered with an innovative form of gypsum board protection. The effect of the innovative protection on the temperature field and fire resistance of the TCC boards was studied in detail. The test results indicate that the fire resistance of the TCC boards was effectively improved by using the innovative protection. If the coverage ratio is identical, a wider single gypsum board can demonstrate a slight increase in residual carrying capacity. Finite element models of TCC boards were established to investigate the temperature field during fire exposure and the residual load-carrying capacity of the TCC boards after fire exposure, demonstrating high applicability and accuracy. The conclusions in this paper can provide reference for fire design in engineering. [ABSTRACT FROM AUTHOR]

The collapse and deterioration of infrastructures due to fire events are documented annually. These fire incidents result in multiple deaths and property loss. In this paper, a reliable and practical numerical methodology was introduced to facilitate the whole process of fire simulations and increase the practicality of performing comprehensive parametric studies in the future. These parametric studies are crucial for understanding the factors that affect thermal–structural responses and avoiding the high cost of destructive tests. The proposed algorithm comprises a fully nonlinear coupled thermal-stress analysis involving thermal and structural material nonlinearity and the thermal–structural response during a fire. A detailed numerical modeling analysis was performed with ABAQUS to achieve the proposed algorithm. The results of the proposed numerical methodology were validated against published experimental work. The experimental work includes a full-scale RC beam loaded with working loads and standard heating conditions to simulate real-life scenarios. The tested beam failed during the fire, and its fire resistance was recorded. The results demonstrated a good correlation with the experimental results in thermal and structural responses. Moreover, this paper presents the direct coupling technique (DCT) and the advantages of using DCT over the traditional sequential coupling technique (SCT). [ABSTRACT FROM AUTHOR]

Guided by the technical requirements for tunnel fire safety, an overview of tunnel piston wind, combustion models, and full-size and small tunnel fire tests is presented. Firstly, the theoretical model and numerical calculation methods for piston wind tunnel fires are presented from the perspective of numerical simulation. Then, full-scale and small-scale test models for tunnel fires are presented, and the advantages and disadvantages of single-row, multi-row, single-fire source, and multi-fire source test methods are described. Finally, key breakthrough directions for future numerical and experimental research on piston winds and tunnel fires are proposed, specifically the mastery of underground tunnel fire development prediction methods. This involves mastering the full-scene elemental fire testing technology for underground tunnel operation systems; developing multi-channel data acquisition technology for fire tests under the effect of multiple disturbances such as high temperature and high humidity; and mastering the smoke flow law during fires in complex tunnel projects. [ABSTRACT FROM AUTHOR]

Glued laminated timber beams exposed to fire of a variable duration were tested in three point bending. Three types of model geometries taking into account the effect of burning were created. Each model was examined for five material data sets. The maximum deflection obtained from FEM simulations was compared with the corresponding deflection wel derived from a three point bending test of burnt beams. The analysis was performed with the help of Ansys® software limiting attention to a liner elasticity with the maximum applied force Fel selected at the proportionality limit observed experimentally. Majority of FEM models provided smaller deflections compared to measurements except for the material set adopting Young's moduli from the compression test. The best fit was observed for the material data set obtained from homogenization. No predominant preference among individual geometries was found promoting the computational model based on reduced cross-section as sufficiently accurate. [ABSTRACT FROM AUTHOR]

During fire incidents, optical fibers located within a fire-resistant cable are usually exposed to temperatures of 800°C to 1000°C. Hot fibers generate narrowband thermal (incandescent) radiation and collect broadband thermal radiation originating from the heated surroundings. The power of the second component, initially negligible, increases with time due to the rising number of fiber cracks and other defects acting as couplers for external radiation. Thermal radiation may interfere with fiber attenuation measurements performed during a fire test, but is rather unlikely to prevent data transmission with typical GbE and 10GbE transceivers during a fire. This problem may be remedied by combining the following methods: using single mode fibers instead of multimode fibers, using bandpass filters to block thermal radiation, and selecting proper transmitter power, wavelength and photodetector. [ABSTRACT FROM AUTHOR]

To provide references for the fire prevention design of steel–concrete–steel immersed tube tunnels, four types of test conditions—no fire protection, fireproof coating insulation, single-layer seam fireproof boards, and double-layer seam fireproof boards—were carried out using partial full-size structural test members. Additionally, the thermal insulation effects of various fireproofing technology solutions were contrasted and analyzed. Combined with the numerical simulation analysis, the temperature distribution law inside the tube structure under various fireproofing measures and the temperature rise law of measuring points at different depths were studied, and the protective effect of the fireproof layers on the tube structure under high fire temperature was demonstrated. The results of the numerical simulation and the experimental data agree well. The results show that adding fireproof layers can significantly lower both the steel shell's surface temperature and the depth of fire impact. Without fire protection, the surface temperature of the bottom steel shell exceeds 300 °C at 69 s, and the member bursts. The fireproof coatings are cracked and flaking and cannot meet the fire resistance limits. Both single-seam and double-seam schemes of calcium silicate boards can meet the fire resistance limit requirements and the latter has a better heat insulation effect. [ABSTRACT FROM AUTHOR]

During fire incidents, optical fibers located with-in a fire-resistant cable are usually exposed to temperatures of 800◦C to 1000◦C. Hot fibers generate narrowband thermal (incandescent) radiation and collect broadband thermal radiation originating from the heated surroundings. The power of the second component, initially negligible, increases with time due to the rising number of fiber cracks and other defects acting as couplers for external radiation. Thermal radiation may interfere with fiber attenuation measurements performed during a fire test, but is rather unlikely to prevent data transmission with typical GbE and 10 GbE transceivers during a fire. This problem may be remedied by combining the following methods: using single mode fibers instead of multimode fibers, using bandpass filters to block thermal radiation, and selecting proper transmitter power, wavelength and photodetector.

Cross-laminated timber has been used in buildings since the 1990s. In the last years, there has been a growing interest in the use of this technology, especially with the adoption of the product in increasingly taller buildings. Considering that the product is manufactured from a combustible material, wood, authorities that regulate the fire safety in buildings and the scientific community have carried out numerous research and fire tests, aiming to elaborate codes which contemplate the use of cross-laminated timber in tall buildings. This paper discusses the main results obtained from the fire resistance test of a cross-laminated timber slab carried out in the horizontal gas furnace (3.0 m × 4.0 m x 1.5 m) from the University of Sao Paulo. A vertical load of 3 kN/m2 was applied over the slab and the specimens were exposed to the standard fire curve for 30 min. In addition to the 30-min test, the research also evaluated the thermal behavior of the samples during the 24 h after the burners were turned off. Throughout the test, the slab maintained the integrity and the thermal insulation, and no falling-off of the charred layer was observed. However, the 24-h test indicated that it is mandatory to consider the loss of stiffness and strength of timber caused by the thermal wave observed during the decay phase.

In this study, fire tests of four single-section scaled-down utility tunnels were conducted. By analyzing temperature and structural responses of the utility tunnel throughout the fire exposure, the effects on the fire behavior of two different construction methods, cast-in-situ and prefabricated, and of two different materials, ordinary concrete and full lightweight concrete, were explored. The results of the study showed that the shear failure of the cast-in-situ utility tunnel occurred at the end of the top or bottom plate, and the failure of the prefabricated utility tunnel occurred at the junction of the prefabricated member and post-cast concrete. As the temperature increased, the temperature gradient along the thickness direction of the tunnel became apparent. The maximum temperature difference between the inner and outer wall surfaces was 531.7 °C. The highest temperature occurred in the cooling stage after stopping the heating, which provided a reference for the fire protection design and rescue of the utility tunnel. The displacement of the top plate of the prefabricated utility tunnel was 16.8 mm, which was 41.8% larger than that of the cast-in-situ utility tunnel. The bearing capacities of the ordinary concrete utility tunnel and full lightweight concrete utility tunnel after the fire loss were 27% and 16.8%, respectively. The full lightweight concrete utility tunnel exhibited good ductility and fire resistance and high collapse resistance. [ABSTRACT FROM AUTHOR]

Burning of hydrogen produces high-grade heat, which can be used for zero-carbon power generation and/or heating and in heat-intensive industries. In combination with water electrolysis, hydrogen combustion provides efficient energy storage method for variable renewables. Hydrogen combustion systems are compact, powerful and highly maneuverable in comparison with fuel cells. We present experimental results of fire tests of a water-cooled hydrogen-oxygen steam generator (HOSG). This fast-response device has start-up time less than 15 s to thermal capacity of 147 kW. Temperature of generated steam is within 1173–1273 K, parameters of steam and energy conversion efficiency can be adjusted the water-to-hydrogen ratio. The maximum efficiency of conversion of chemical energy of hydrogen into enthalpy of steam is 98.7%. [Display omitted] • Experimental results on hydrogen-oxygen steam generator (HOSG). • High temperature steam (900–1000 °C). • Start-up time to capacity of 147 kW is less than 15 s. • Water cooling absorbs combustion heat and protects the device. • 98.7% efficiency of hydrogen HHV conversion to steam enthalpy. [ABSTRACT FROM AUTHOR]

The size effect has its origin in fracture mechanics and describes the formation as well as propagation of cracks in brittle and solid materials in dependence of the specimen size. However, the size effect in concrete spalling describes the damage behaviour on a macroscopic scale for different sized specimens in case of fire. Concrete spalling is a very complex and yet not fully understood phenomenon. To reduce the effort of fire tests to analyse the spalling behaviour of concrete mixtures, this study investigates the susceptibility to spalling for six different concrete mixtures and three specimen sizes. The sizes were divided in full scale slabs (1.8 m × 1.2 m × 0.3 m), intermediate scale cuboids (0.6 m × 0.6 m × 0.3 m) and small scale cylinders (Ø0.15 m × 0.3 m). For this purpose, a novel test set-up was built to test six intermediate scale or twelve small scale specimens simultaneously to ensure a similar heating regime for every specimen. All specimens were fire exposed on one side and remained unrestrained. A size effect occurred for four of the six concrete mixtures. Compared to the full scale specimens the spalling was reduced significantly for all smaller specimen sizes. Additionally, spalling did not occur for the small scale specimens. The results show that the specimen size is an essential parameter to investigate the susceptibility to spalling of a concrete mixture. For future investigations the testing conditions must be adjusted for the intermediate scale specimens to recreate the conditions of the slabs. [ABSTRACT FROM AUTHOR]

The conventional approach to satisfying the fire resistance requirements in designing reinforced concrete (RC) structures is to ensure enough concrete cover depth for the steel reinforcements. The objective is to prevent the temperature of steel reinforcements from rising too quickly. However, excessive concrete cover depth may increase the risk of concrete spalling during a fire and lead to a larger crack width. Fire is a natural heat source that can activate the shape memory effect of iron-based shape memory alloys (Fe-SMA) to generate recovery stress. This study proposes a new active approach for improving the fire performance of RC structures based on the Fe-SMA. The main objective is to investigate the feasibility of improving the fire performance of RC structures through the recovery stress generated by Fe-SMA under fire. The fire test of nine Fe-SMA RC beams was conducted. The temperature profile in the furnace was similar to ISO834, and the maximum temperature exceeded 800 °C. The flexural behavior of the concrete beams reinforced with Fe-SMA during and after the fire was tested. The experimental results demonstrate that the Fe-SMA has great potential in improving the fire performance of RC structures. The mid-span deflection of the Fe-SMA RC beams under fire is significantly lower than the conventional RC beams. The fire resistance of Fe-SMA RC beams increases from 97 min to 133 min at load level 0.3 and from 69 min to 103 min at load level 0.5. The residual deformation of Fe-SMA RC beams reduces from 46.3 mm to 27.6 mm at load level 0.3 and from 34.7 mm to 19.8 mm at load level 0.5. In addition, after 1 h of fire exposure, the Fe-SMA can develop permanent prestress after the beam cools to room temperature, improving the mechanical properties after fire. The residual bearing capacity and residual stiffness of the Fe-SMA RC beams are 21% and 86%–121% higher than the conventional RC beams, respectively. The prestress generated by Fe-SMA after 1 h of fire exposure was estimated using the equivalent section method. • A fire test of Fe-SMA RC beam was conducted for the first time. • The fire resistance of Fe-SMA RC beam is increased. • The deflection of Fe-SMA RC beam under fire is substantially decreased. • The residual deformation of Fe-SMA RC beam is reduced. • The residual mechanical properties of Fe-SMA RC beam are significantly improved. [ABSTRACT FROM AUTHOR]