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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 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]

Copyright of Hazard Control in Tunnelling & Underground Engineering is the property of Shandong University Scientific Journals Press 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.)

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]

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.)

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]

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]

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]

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]

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 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]

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]

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]

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]

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]

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]

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]

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]

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]

To improve the perceived equivalency of fire testing of combustible and non-combustible members we have proposed a simple modification in the fire resistance test procedure by introducing a lower limit of the heat release rate of the furnace. With this approach the combustion of the sample adds to the heat of the furnace, which is in contrary to current approach and does increase the severity of the test. To quantify the consequences, three wall assemblies were tested with pre-defined heat release curves and modified furnace conditions. The assemblies were timber walls built from two layers of Oriented Strain Boards (OSB, 25 mm thick) on a timber frame with an air cavity (100 mm). A reference experiment with a well-insulated wall was performed to determine the furnace's minimum heat release rate (HRR) required to maintain the standard (ISO 834) temperature/time curve. The first wall was tested with a standard fire resistance test, and in the 2nd and 3rd wall experiment, the furnace followed the minimum HRR value determined in a reference experiment. In experiment 2, the furnace ventilation matched the air requirements of the burners, and in experiment 3, the furnace was over ventilated. Peak temperatures measured in experiments 2 and 3 exceeded the standard temperature/time relation by 420°C and 600°C, respectively. The assembly's failure (integrity criterion) was observed after 27 min, 23 min and 14 min of experiments 1, 2 and 3, respectively. The limitations of the approach used related to reproducibility and validity are discussed. [ABSTRACT FROM AUTHOR]

The firefighting performance of eleven PFAS-free firefighting foams was evaluated using different fuels (Jet A1, commercial heptane and diesel) and types of water (freshwater and synthetic sea water). Moreover, different firefighting foam generation techniques and application methods were evaluated. The firefighting foams were generated as aspirated foams or as compressed air foams (CAFs). The results for CAF showed a higher performance, with respect to extinction time and burn-back resistance, compared to the foam generated using a UNI 86 nozzle. The CAF was not optimised, indicating a further potential of this foam generation technique. The results indicate that the time to fire knockdown decreases with decreasing foam viscosity. The heat flux was shown to be small, although the entire fuel surface was involved in the fire. The tests showed a dependence on fuel type; different products performed differently depending on the fuel. Tests using sea water showed that addition of salt to the foam solution generally prolonged the extinction time, although for one of the firefighting foams a shorter extinction time was observed. Out of the eleven evaluated PFAS-free products there was no product that outperformed the rest. None of the products in the study met the fire test performance requirements in all the referenced standards. Instead, the products seem to have different niches where they perform best e.g., with different types of fuel or water. [ABSTRACT FROM AUTHOR]

Precast concrete sandwich panels (PCSPs) are known for their good thermal, acoustic and structural properties. Severe environmental demands can be met by PCSPs due to their use of highly thermally insulating materials and non-metallic connectors. One of the main issues limiting the wider use of sandwich walls in construction is their unknown fire resistance. Furthermore, the actual behaviour of connectors and insulation in fire in terms of their mechanical performance and their impact on fire spread and the fire resistance of walls is not fully understood. This paper presents an experimental investigation on the structural and thermal behaviour of PCSPs with mineral-wool insulation and glass-fiber-reinforced polymeric bar connectors coupling two concrete wythes. Three full-size walls were tested following the REI certification test procedure for fire walls under fire and vertical eccentric and post-fire mechanical impact load. The three test configurations were adopted for the assessment of the connectors' fire behaviour and its impact on the general fire resistance of the walls. All the specimens met the REI 120-M criteria. The connectors did not contribute to the fire's spread and the integrity of the walls was maintained throughout the testing time. This was also confirmed in the most unfavourable test configuration, in which some of the connectors in the inner area of the wall were significantly damaged, and yet the structural connection of the concrete wythes was maintained. The walls experienced heavy heat-induced thermal bowing. The significant contribution of connectors to the stiffness of the wall during fire was observed and discussed. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental investigation on the fire response of steel beams and their bolted flange plate (BFP) connections. Using sub-frame assembly, full-scale steel beams with various BFP beam-to-column joints were examined under the ISO 834 standard fire condition. The failure modes, as well as the structural and thermal responses of the beam and the BFP connections were studied. The findings of the experimental studies indicate that the beam flexural failure occurs at the temperature range of 670–700°C when the mid-span deflection exceeds the limitation value specified in the BS-476. The BFP connections fail when the temperature exceeds 760°C, while the beam experiences deflections larger than span/20. The results also show that the bolt hole bearing and the bolt shear control the failure of the BFP connection in fire conditions. The BFP connection detail has a considerable effect on the fire response of the beam, e.g., increasing bolt shear strength in the BFP connection can improve the fire resistance and rating of the beam and its connections in steel moment-resisting frames. [ABSTRACT FROM AUTHOR]

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This paper presents the results of experimental research on the fire response of steel beams and their end-plate connections in column-tree moment-resisting frames (CMRFs). Using subframe assembly, full-scale steel beams with different stub-to-link end-plate connections were tested under a standard fire curve. The failure modes as well as the structural and thermal responses of the beam and the end-plate connections were studied. The influence of critical factors, including bolt grade and flange plate's size, were investigated. The findings of the experimental studies indicate that the beam flexural failure occurs at the temperature of 720°C when deflections surpass the limiting value specified in a relevant British Standard Institution standard. The end-plate connections fail when the temperature exceeds 760°C, while the beam experiences deflections larger than span/20. The results also show that the plate bending, the bolt tensile fracture, and thread stripping control the failure of the end-plate connection in fire conditions. The end-plate connection detail has a considerable effect on the fire performance of the beam, e.g., using Grade 8.8 bolts and thicker plates in the end-plate connection can enhance the fire resistance and rating of the beams and their connections in steel CMRFs. [ABSTRACT FROM AUTHOR]

Summary: To determine the degree of fire damage in reinforced concrete (RC) T‐beams, a damage identification method based on an improved support vector machine and firefly algorithm (FA‐SVM) is proposed herein. First, based on the fire test of 10 simply supported beams, a refined finite element model of simply supported T‐beams was established. A modal analysis of the simply supported beams was performed to obtain a sample library of the input and output parameters for the FA‐SVM identification network. Subsequently, the trained FA‐SVM identification network was used to predict the fire exposure duration of the samples. The sectional temperature during the fire exposure duration could be calculated by using the finite element model, and the bending stiffness and bending capacity of the simply supported beams after exposure to the fire were calculated. The test sample results were similar to the experimental results of the simply supported beams exposed to fire for 60, 90, and 120 min, which demonstrated the feasibility and effectiveness of the proposed method. Finally, a three‐step method for fire damage identification suitable for RC continuous beams was developed based on the FA‐SVM identification network. An example calculation analysis of three‐span continuous beams was performed, and the results demonstrated accuracy of the identification results. The identification sample magnitude was significantly reduced using this method, which can be conveniently used in practical engineering applications. [ABSTRACT FROM AUTHOR]

This article analyzes gypsum board dehydration effect on heat conductivity and deformation of multi-layered mechanical structures subjected to temperature changes. Specially designed structures (fire doors) consisting of steel sheets with stone wool and gypsum insulating layers in between were heated in furnace for a specified period of time of not less than 60 min. Temperature versus time curves and deformations of multi-layered structures were obtained. Experimental results were verified by numerical simulation. Experimental data was found to be in good agreement with numerical simulation results. The percent differences between door temperatures from simulation and fire test don't exceed 9 %. This shows that thermal behavior of such multi-layered structures can be investigated numerically avoiding time-consuming and expensive fire tests. The data obtained allowed to calculate convective heat transfer coefficient of gypsum board, which was fitted into multi-layered mechanical structure. It was found that it is more advantageous to place gypsum layer in the middle of the structure rather than closer to the fire source in order to cool the structure more efficiently during fire. [ABSTRACT FROM AUTHOR]

The paper presents results of numerical simulation and fire tests of multi-layered structures carried out under real fire conditions. It has been shown that fire test carried out according to ISO 834 standard differs from fire test conducted under real fire conditions. A new fire test methodology has been proposed. It is suggested to use real fire temperatures during fire tests to avoid accidents and allow occupants to evacuate the building safely. The ISO fire test standard should be improved visibly. Structural solutions to reduce temperatures and temperature deformations of multi-layered structures during fire are also reviewed. It was established that the gypsum layer should be placed in the middle of multi-layered structure in order to cool the structure more efficiently during fire. [ABSTRACT FROM AUTHOR]

This article presents the details of a fire test on eight prestressed reactive powder concrete (RPC) beams cured with 150°C hot air. The test specimens varied in load ratio, cover thickness of tendons, bonded and unbonded tendons, and partial prestressing ratio. The thermal fields, deflection behavior, effective prestress, fire endurance, failure modes, and crack patterns of the beams were observed and recorded, revealing that no obvious fire‐induced spalling occurred on the prestressed RPC beams. The fire test results indicate that the failure of prestressed RPC beams was driven by direct fire exposure and fracture of tendons and longitudinal rebars after generation of wide cracks in the beams. In extreme fire, prestressed RPC beams that were under‐reinforced at ambient temperature may fail as low‐reinforced beams. Fire resistance of the prestressed RPC beams dramatically improved with a decrease of load ratio and increase of cover thickness of tendons. Bonded prestressed RPC beams showed superior performance over equivalent unbonded prestressed RPC beams in fire. The whole‐scale transferring effect of prestress loss in unbonded beams should be considered for fire resistance performance design based on structural systems. [ABSTRACT FROM AUTHOR]

The influence of elevated temperatures on mechanical behavior of glued laminated timber beams is examined on the basis of tensile tests. Dog bone samples prepared from beams exposed to fire of variable duration were categorized with respect to the type and position of the failure crack, type and number of discontinuities such as knots, and the level of browning. The acquired experimental results suggest that the wood variability and the effect of growth discontinuities are probably more significant than the effect of elevated temperatures. To support this conclusion, further study is currently under way, exploring samples from the second series of the fire tests. [ABSTRACT FROM AUTHOR]

Plate thermometer (PT) that consists of a thin metal plate and a layer of inorganic insulation material attached to the backside of the metal plate has been used to calculate the incident radiant heat flux by other researchers. However, the incident radiant heat flux is often underestimated using PT as the heat loss from the metal plate is not appropriately reflected in the calculation. Especially when PT is placed in low ambient temperature conditions or in a heating phase, the underestimation becomes more significant. Besides the heat loss effect, some PT properties such as surface emissivity and thermo-physical properties as well as errors of temperature measurements affect the accuracy of incident radiant heat flux calculations. In the current study, a new incident radiant heat flux calculation method is proposed to overcome the aforementioned inaccuracies. The temperature that a thermally thin metal element should ideally achieve with a perfectly insulated back surface is correlated with the actually measured surface temperature under known heat fluxes for calibration. From this correlation, a set of equations to calculate the incident radiant heat flux is derived for a mixed radiation/convection environment. For validation, the incident radiant heat fluxes calculated from the proposed method and measured from a commercially available Schmidt-Boelter type total heat flux gauge were compared and a good agreement was observed. [ABSTRACT FROM AUTHOR]

This study investigates the effect of environmental moisture conditions on the calculated incident radiant heat flux (irradiance) by plate thermometers (PT). Alterations were made to the moisture content of the PT insulation layers to achieve these conditions. Irradiance was calculated using a pre-determined equation based on fully insulated conditions and validated using a Schmidt-Boelter radiometer. The study consisted of two phases; (i) investigating the effect of preheating PT to the accurate irradiance, (ii) investigating the effect of moisture in the PT on the measurement of irradiance. Calculated irradiance agreed with measured for preheated PT, but not with unheated PT. Four representative moisture conditions were identified for phase two, whereby samples were equilibrated at 0, 45, 65, and 98 wood moisture equivalent (%WME). No noticeable difference identified between measured and calculated irradiance was detected within 0-65%WME. PT with 98%WME showed a difference between the irradiance as the moisture inside the PT insulation absorbed energy from the PT to vaporize. Therefore, using preheated PT with any %WME under 65 is recommended to obtain accurate enough irradiance measurements. The result can use to improve determining the fire spread mechanisms and accurate measurements of irradiance in outdoor fires such as informal settlements fires. [ABSTRACT FROM AUTHOR]

The uniform‐load fire behaviors of four full‐scale integral composite beams with superposed slabs were tested, considering the post‐cast‐slab thickness, shear‐connector spacing, and precast‐slab overlap length on the steel‐beam upper flange. The concrete temperature distribution along the slab thickness, the temperature of the rebar inside the slab, the temperature distribution along the steel‐beam height, the bending stiffness, and the overall integrity of the superposed slabs and steel beam were studied. ABAQUS simulations of the temperature‐field and deformation behaviors of the composite beams with superposed slabs under coupled thermal and mechanical loading were performed. No damage to the post‐cast and precast slab bonding interface during the heating process was apparent. The post‐cast joint had no obvious influence on the structure, which could still bear loads. The composite‐beam temperature field and bending stiffness were not significantly affected by the bonding interface of the new and old concrete and the post‐cast joint. Overall, the post‐cast slab thickness and shear‐connector spacing predominantly influenced the composite‐beam fire resistance. The experiment and numerical results agree well, verifying the numerical‐model validity and feasibility. [ABSTRACT FROM AUTHOR]

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This paper attempts to disclose the damage mechanism of reinforced concrete plate-column structures under room temperature and fire. Several tests were carried out to record the law of crack development on the plate surface under room temperature. The infrared detection technology was adopted to observe how cracks develop under fire. The acoustic emission (AE) signals at different positions of the specimen were monitored by the AE techniques. Coupled with the macroscopic test phenomena, several characteristic parameters collected by the AE system, namely, cumulative number of events, event rate, energy rate and b-value, were analyzed in details. The results show that: the cumulative number of events was active in the loading, heating and cooling stages; the crack density and the change of internal forces could be derived from the trend of event rate; the local energy changes of the specimen could be deciphered from the curves of energy rate and b-value, making it possible to judge if a component has reached the failure state; the specimen suffered the most severe damage, when the AE parameters suddenly changed; AE monitoring enables the early warning of fire to reinforced concrete plate-column structure; infrared detection technology is suitable for real-time monitoring of crack development under high temperature. [ABSTRACT FROM AUTHOR]

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Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department 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.)

Copyright of Bautechnik is the property of Wiley-Blackwell 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.)

In order to obtain the degree of damage in reinforced concrete (RC) beams exposed to fire, using the equivalent fire exposure time as the damage index, a new method of damage identification based on the support vector machine technology was proposed. Firstly, the feasibility analysis was conducted based on finite element models of simply supported beams. Thereafter, four RC simply supported beams were designed for fire test and vibration test, which were used to amend the finite element model and the SVM-based identification method. Fire tests were carried out on 4 beams for 60, 90, 120, and 150 min, respectively. During and after the fire tests, structural modal information were recorded. The first two order modal information, as SVM input paraments, was used to predict the equivalent fire exposure time based on SVM. The predicted results were very close to the actual fire exposure time. The residual bearing capacities of the beams after fire were calculated according to the predicted fire exposure time, which were close to experimental results. It indicated that the equivalent fire exposure time as the output parameter for damage identification was reliable. Finally, on the basis of damage identification method for simply supported beams, a new three-step positioning method was established for identifing the degree of damage in continuous beams. The method was applied to a thress-span continuous beam. The numercial situlation results revealed that the three-step positioning method was accurate. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department 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.)