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Due to the large increase in human population, the need for more buildings and other amenities is widening. Concrete is considered one of the most abundant and popular materials used in the structure and construction fields. It is known as a composite mix composed of cement and aggregates including fine and coarse and water. Despite its good properties, its capability to be formed in different shapes and its ability to resist severe conditions, concrete will struggle with the presence of extremely high temperatures. So, different types of concrete must be found to resist those challenging conditions. Refractory concrete can be considered a good choice to be used in places exposed to elevated temperatures and severe conditions. Mainly, refractory concrete is made up of ordinary Portland cement replacement well known as refractory cement, specific types of fine and coarse aggregates and are known as refractory or temperature-bearing aggregates and water. To the best authors' knowledge, review papers about refractory concrete are rare. For this reason, more than 65 papers were consulted including many recently published. This review describes the different types of materials used in refractory concrete. Furthermore, the different fresh, hardened, structural, durability and thermal properties of refractory concrete are also included such as slump, density, compressive strength, flexural strength, tensile strength, modulus of elasticity, ultrasonic pulse velocity, shrinkage, mass loss, porosity, water absorption, damage level and thermal conductivity. [ABSTRACT FROM AUTHOR]

The effects of the exposure to elevated temperatures on the mechanical performances of a PBO FRCM (fabric reinforced cementitious matrix) composite system, consisting of polypara-phenylene-benzo-bisthiazole (PBO) fiber meshes embedded into an inorganic mortar, widely used in the strengthening of existing degraded reinforced concrete structures, are analyzed and discussed in the paper. The residual tensile properties of PBO FRCM composites and the residual bond properties of PBO FRCM-to-concrete are analyzed through the results of an experimental investigation conducted on specimens subjected to heating-cooling regimes at temperatures ranging from 20°C to 300°C, and then tested at ambient temperature (20°C). Direct tensile (DT) tests on PBO FRCM coupons and direct single lap shear (DS) tests on PBO FRCM-concrete elements were performed. The parameter varied was the target temperature value, namely 20°C, 100°C, 200°C, and 300°C. Test results are reported in terms of cracking stress, tensile strength, ultimate tensile strain, uncracked and cracked elasticity moduli, failure mode, bond strength, and corresponding slip values. The obtained results are evidence that the effects of exposure at the target temperatures were different for each mechanical parameter. Significant reductions of the values measured at ambient temperature were observed only at 300°C. Temperature-dependent relationships for both tensile and bond mechanical parameters, useful for thermo-mechanical simulations and fire design of reinforced concrete structures strengthened with PBO FRCM composites, are also defined. Finally, the results of a comparative analysis between the experimental results described in the present paper and those available in the literature are reported and discussed. [ABSTRACT FROM AUTHOR]

The influence of elevated temperatures and strain rate on the mechanical and structural properties of steel 42CrMo4 were analysed experimentally in this paper. The experiments were based on uniaxial tension and compression tests at high temperatures between 700 °C and 1100 °C and strain rates in the range 0.0018–0.1 s−1. The influence of temperature and strain rate on yield stress, strain to fracture, hardness, structural changes, and fracture characteristics were analysed. The non-uniformity of deformations obtained at different values of the strain rate and temperature were also analysed. Analysis by scanning electron microscopy showed the ductile behaviour of the material. The degree of damage in the material caused by the presence of cavities increased with increasing deformation temperature. For all the presented deformation conditions, the formation of the fracture through the ductile fracture mechanism resulted from localized necking and the coalescence of microvoids. By increasing the deformation temperature and reducing the strain rate, the fracture behaviour of 42CrMo4 steel can be improved. [ABSTRACT FROM AUTHOR]

In this paper, the modified Ramberg-Osgood constitutive equations for calculating the stress-strain of steel at elevated temperatures using the parameters determined based on the transient state tensile test results achieved at the Helsinki University of Technology are verified. This is done by numerically comparing the global and local buckling capacities of I-shaped steel members incorporating the modified Ramberg-Osgood model along with the material model given in the fire section of Eurocode EN1993-1-2. For this purpose, a numerical model using the ABAQUS software was developed. Then, nonlinear analyses with imperfections (GMNIA) were performed to compare the buckling capacities of the steel columns and beams of four different hot-rolled cross-sections (IPE160, IPE180, HE100B, HE500B), made of steel grade S355, at three different temperatures (400°C, 500°C, 600°C). The results showed that adopting the modified Ramberg-Osgood model can lead to the same buckling capacities resulting when using the EN1993-1-2 material model for steel temperatures of less than 400°C. However, adopting this model for 600°C overestimates the buckling capacities in most cases. [ABSTRACT FROM AUTHOR]

The cyclic performance of structural steels after exposure to various elevated temperatures and cooling-down methods was experimentally investigated in this paper. Four types of frequently used structural steels were tested including Chinese mild steel Grade Q235, Chinese high-strength steel Grade Q345, and Chinese stainless steel Grade S304 and S316. A total of eighty specimens were prepared using three different heating–cooling processes before being subjected to cyclic loads. The post-fire basic features and hysteretic performances of the four types of structural steels exposed to various target temperatures (100–1000 °C), heat soak times (30 min or 180 min) and cooling-down methods (natural air or water) were recorded and discussed. The results show that all the tested structural steels prepared using different heating–cooling treatments exhibited proper ductility and energy dissipation capacity, while the heat soak times and cooling-down methods had a definite effect on their energy dissipation capacity; no Masing phenomenon was found in the tested structural steels. Finally, a set of skeleton curves were proposed for the four types of structural steels under cyclic loading based on the Ramberg–Osgood model, which could serve as the foundation for the seismic capacity evaluation of steel structures after a fire. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations on the cross-sectional behavior and compressive capacities of aluminum alloy channel section stub columns after exposure to fire. A testing program was performed, including heating tests, postfire material tests, geometric imperfection measurements, and 16 stub column tests. The testing program was followed by a numerical modeling program. Finite-element models were developed to simulate the test responses and conduct parametric studies to obtain additional numerical data. The obtained test and numerical data were analyzed and adopted to perform design analyses, in which the applicability of the relevant room-temperature design rules in the American, European, and Australian/New Zealand codes to the postfire design of aluminum alloy channel sections under compression were examined. The results of the design analyses reveal that all three examined design codes yield excessively conservative and scattered predictions of postfire strengths, owing to the neglect of significant postfire material strain hardening. Then, a new design approach was proposed by rationally considering the material strain hardening. The new proposal was found to offer greatly improved design accuracy and consistency compared to the American, European, and Australian/New Zealand codes, especially for aluminum alloy channel sections after exposure to elevated temperatures above 400°C. [ABSTRACT FROM AUTHOR]

The fireproof design of geopolymers through adjusting multi-component metallurgical solid wastes has attracted increasing attention, due to their potential low carbon emission, cost effectiveness, and role in environmental conservation. Herein, the effects of silica fume (SF) on the microstructure and mechanical properties of alkali-activated slag/FA (fly ash) pastes subjected to elevated temperatures (150, 500, 850, and 1200 °C) are investigated to clarify whether or not SF has a positive role in the mechanical strength of the slag/FA (slag/FA = 30:70, wt.%) geopolymer during building fires. The results show that the replacement of FA with 10 wt.% SF (silica fume) promotes the increasing pore volume with a diameter of 0.2~3 μm, leading to an increase in the compressive or flexural strength below 850 °C, "right shifts" of the endothermic peak, and uniform and compact fracture surfaces. Meanwhile, gehlenite and labradorite are generated after exposure above 850 °C. The bloating effect of the SF-containing sample occurs at 1200 °C, leading to a greater deformation due to the further restructuring of the amorphous geopolymer chain N–A–S–H or N–(Ca)–A–S–H composed of [SiO4]4− and [AlO4]5−. This paper explores an effective approach to improving geopolymers' fireproof performance by adjusting the formulation of solid waste. [ABSTRACT FROM AUTHOR]

The objective of this paper is to to ascertain the reliable mechanical properties of cold-formed Q345 steel at elevated temperatures while considerting the effects of tensile strain rate and specimen width. This paper presents an experimental study on the mechanical properties of cold-formed Q345 steel at temperatures ranging from 20°C to 800°C tested with two specimen widths and three tensile–strain rates, namely 0.06/min , 0.6/min , and 1.2/min. Tensile specimens were fabricated from a steel plate with a nominal thickness of 2.5 mm and tensile tests were carried out to determine the stress–strain relationship, yield strength, tensile strength, and elastic modulus. The test results showed that the tensile–strain rate has a maximum influence of 9% on yield and tensile strength at 600°C and the specimen width has a maximum influence of 14% on yield and tensile strength at 400°C. The maximum influence of the tensile–strain rate and specimen width on the elastic modulus is 18% and 12% respectively at 500°C. The necking phenomenon is less noticeable at temperatures below 300°C but is clearly observed at temperatures above 300°C. The comparison of the test results with predictions obtained from design standards (EC3, AISC, and AS4100) indicates a good agreement on the yield and tensile strength, but the magnitudes of elastic modulus obtained from the test are considerably higher than those obtained from the design standards. Based on averaged values of the test results associated with different tensile–strain rates and specimen widths, predictive equations were proposed to determine the mechanical properties of cold-formed Q345 steel at elevated temperatures. [ABSTRACT FROM AUTHOR]

Results of experimental testing of the shot peened steel C55 specimens are presented in this paper. The aim was to establish behaviour of the compressive residual stresses induced by the shot peening at elevated temperatures; namely their stability in terms of temperature and time. Experimental work included verification of the tested material chemical composition, heat treatment (austenitization at 820 °C ± 5 °C for 30 minutes, cooling in the Durixol V70 oil at 20 °C ± 5 °C, high tempering at 450 °C ± 5 °C for 120 minutes, followed by cooling in air), tensile tests according to EN 10002-1 standard, hardness (HRC) measurements, shot peening with parameters Almen intensity 12A and coverage of 100 %, at the incidence angle close to 90° with respect to the specimen surface. The residual stresses state was evaluated by the X-ray diffraction measurement. It was concluded that the elevated temperature of 130 °C and after exposure of 100, 500 and 1000 hours, did not cause a significant decrease in compressive residual stresses. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the fatigue properties of C17200 alloy under the condition of quenching aging heat treatment at high temperatures, and to provide a design reference for its application in a certain temperature range. For this purpose, the tensile and rotary bending fatigue (RBF) tests were carried out at different temperatures (25 °C, 150 °C, 350 °C, and 450 °C). The tensile strength was obtained, and relationships between the applied bending stress levels and the number of fatigue fracture cycles were fitted to the stress-life (S-N) curves, and the related equations were determined. The fractured surfaces were observed and analyzed by a scanning electron microscopy (SEM). The results show that the RBF fatigue performance of C17200 alloy specimens is decreased with the increase in test temperature. When the temperature is below 350 °C, the performance degradation amplitudes of mechanical properties and RBF fatigue resistance are at a low level. However, compared to the RBF fatigue strength of 1 × 107 cycles at 25 °C, it is decreased by 38.4% when the temperature reaches 450 °C. It is found that the fatigue failure type of C17200 alloy belongs to surface defect initiation. Below 350 °C, the surface roughness of the fatigue fracture is higher, which is similar to the brittle fracture, so the boundary of the fracture regions is not obvious. At 450 °C, due to the further increase in temperature, oxidation occurs on the fracture surface, and the boundary of typical fatigue zone is obvious. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced polymer (CFRP) has been used widely in the strengthening of steel structures. Steel/CFRP systems being subjected to elevated temperatures is realistic in summer climate events in many countries, which leads to the degradation of the bond performance between CFRP and steel. Therefore, it is critical to study the bond behavior of the CFRP/steel system under elevated temperature. This paper investigates the mechanical performance of CFRP/steel adhesively bonded double strap joints under different temperatures. Thirty CFRP/steel double strap joints were tested to failure under temperatures between 10 °C and 90 °C. It was found that the joint failure mode changed from adherend failure to debonding failure as the temperature was approaching glass transition temperatures. In addition, the ultimate load and joint stiffness decreased significantly under temperatures near to and higher than glass transition temperatures. Based on the experimental results, a model is proposed to predict the bond stress of the CFRP/steel under different temperatures. [ABSTRACT FROM AUTHOR]

Knowledge of elevated-temperature mechanical properties of structural steel is essential for accurate evaluation of structural behavior in a fire. As a result, various test procedures have been adopted to obtain the stress–strain behavior and to establish elevated-temperature mechanical properties of structural steel suitable for structural-fire applications. This paper provides a critical review of steady-state and transient-state temperature material tests, the two common methods of characterizing the mechanical behavior of structural steel subjected to fire. The main focus in this review is the thermal creep of steel and how it is modeled in each material test. It is indicated that these two test methods result in rate-dependent stress–strain curves, in which creep effects are implicit in the behavior of steel at elevated temperatures. Alternatively, steady-state temperature creep tests allow for the explicit consideration of thermal creep in the form of isochronous stress–strain curves. It is shown that creep can result in significant time- and temperature-dependent reductions in the strength of structural steel in fire and that the adopted method of characterizing the stress–strain behavior of steel for structural-fire engineering applications can lead to underestimation of creep effects depending on the applied stress, temperature, and steel grade. [ABSTRACT FROM AUTHOR]

Due to the large increase in human population, the need for more buildings and other amenities is widening. Concrete is considered one of the most abundant and popular materials used in the structure and construction fields. It is known as a composite mix composed of cement and aggregates including fine and coarse and water. Despite its good properties, its capability to be formed in different shapes and its ability to resist severe conditions, concrete will struggle with the presence of extremely high temperatures. So, different types of concrete must be found to resist those challenging conditions. Refractory concrete can be considered a good choice to be used in places exposed to elevated temperatures and severe conditions. Mainly, refractory concrete is made up of ordinary Portland cement replacement well known as refractory cement, specific types of fine and coarse aggregates and are known as refractory or temperature-bearing aggregates and water. To the best authors’ knowledge, review papers about refractory concrete are rare. For this reason, more than 65 papers were consulted including many recently published. This review describes the different types of materials used in refractory concrete. Furthermore, the different fresh, hardened, structural, durability and thermal properties of refractory concrete are also included such as slump, density, compressive strength, flexural strength, tensile strength, modulus of elasticity, ultrasonic pulse velocity, shrinkage, mass loss, porosity, water absorption, damage level and thermal conductivity.

The paper presents the experimental results of the mechanical behavior of Ti-5Al-2.5Sn alloy at high strain rates and elevated temperature. Flat smooth and notched specimens with notch radii of 10 mm, 5 mm, and 2.5 mm were used. The experimental studies were carried out using the high-velocity servo hydraulic test machine Instron VHS 40/50-20. The samples were heated with flat ceramic infrared emitters on average between 60 s and 160 s. The temperature control in the working part of specimens was carried out in real time using a chromel-alumel thermocouple. The digital image correlation (DIC) method was employed to investigate the evolution of local fields in the gauge section of the specimen. Data on the influence of stress triaxiality on the ductility of Ti-5Al-2.5Sn alloy were obtained under tension with strain rates ranging from 0.1 to 103 s−1 at a temperature of 673 K. It was found that, at 673 K, the ductility of Ti-5Al-2.5Sn alloy increases with the increasing strain rate for both smooth and notched specimens. [ABSTRACT FROM AUTHOR]

This paper summarizes preliminary results of an experimental investigation on the creep behavior of transverse welded lap joints at elevated temperatures. The aim of this study is to quantify the time-to-failure for transverse welded lap joints exposed to high temperatures. In this study, two series of experiments were conducted. In the first series, the specimens were heated to target temperatures and then loaded to failure to estimate the peak load P that the specimens could sustain at each target temperature. In the second series, after the specimens were heated to the test temperatures, fractions of the peak load P were applied rapidly and kept constant throughout the test. Through the combination of these two series of experiments, the effect of load and temperature on the time-dependent or creep behavior of transverse welded lap joints was studied. The experimental results show that, for temperatures greater than 450°C, transverse welded lap joints undergo excessive deformation due to creep, and that creep effect becomes more significant as load and temperature increase. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on web crippling behaviour of cold-formed stainless steel square and rectangular hollow sections (SHS and RHS) at elevated temperatures. A total of 21 web crippling tests were conducted under the Interior Two-Flange (ITF) loading condition as codified in ASCE/SEI 8–22 Specification at various temperatures up to 800 °C. Tensile flat and corner coupon tests were conducted to obtain the material properties of the cold-formed stainless steel SHS and RHS at various temperatures corresponding to those pre-set in the web crippling tests. Details of the test specimens, setups and procedures are comprehensively documented in this paper. Furthermore, the specimen temperatures together with the test results, including failure modes, web crippling strengths and load-deformation curves are fully reported. The obtained test results were used to evaluate the suitability of codified web crippling design provision as per ASCE/SEI 8–22, where reduced material properties were used in calculating the web crippling strengths at elevated temperatures. In addition, the test results were also compared with the predictions obtained from existing design rules in literatures for cold-formed stainless steel SHS and RHS at elevated temperatures. Moreover, reliability analyses were conducted to assess the reliability levels of these design provisions. It is demonstrated that the available web crippling design provisions can provide generally conservative and reliable strength predictions, and therefore are deemed suitable for predicting the web crippling strengths of cold-formed stainless steel SHS and RHS at elevated temperatures. • This investigation serves as the first test programme to study web crippling behaviour of CFSS sections at elevated temperatures. • Flat and corner coupon tests were conducted to obtain material properties at various temperatures. • A total of 21 web crippling tests were conducted under ITF loading condition with temperatures up to 800°C. • Test results are reported and existing web crippling design provisions are also assessed. [ABSTRACT FROM AUTHOR]

• South Africa is not spared from the adverse effects of climate change which alters the ecosystem and have a ripple effect on food security. • This paper reviewed the impacts of climate change on the phenology, physiology, and economic benefits of wild fruits and vegetables in South Africa. • The possible productivity of wild fruits and vegetables was evaluated with spatial-based data through land use/land cover which showed that South Africa had varied vegetation and land cover dynamics. • There is a need to develop cultivation strategies for edible wild fruits and vegetables to expand knowledge and create options in utilizing the wild species. • This will boost the country's economy, help to improve diet, and can play a crucial role in food security. Overdependence on exotic plant species constitutes a major setback for the consumption of wild fruits and vegetables among South Africans. The country is not spared from the adverse effects of climate change which play a substantial role in altering the ecosystem and have a ripple effect on food security. Wild fruits and vegetables have been identified to be underutilized despite the country's struggle in nourishing its population. This paper reviewed the impacts of climate change on the phenology, physiology, and economic benefits of wild fruits and vegetables in South Africa. Furthermore, spatial-based data was used to evaluate the possible productivity of wild fruits and vegetables through land use/land cover (LULC) assessment. The result showed that South Africa had varied vegetation and land cover dynamics. For example, Northern Cape and Western Cape Provinces are dominated by shrubland and barren land, thus unsuitable for fruit and vegetable production. In contrast, Limpopo, North-West, Mpumalanga, Gauteng, Free State, some parts of KwaZulu-Natal and Eastern Cape Provinces are covered with grassland and cultivated areas which made them good for vegetable farming and potential ground for wild fruit and vegetable cultivation. Thus, there is a need to develop cultivation strategies for edible wild fruits and vegetables with known nutritional characteristics to expand knowledge about nutritional benefits and options in utilizing the wild species. This will boost the country's economy, help to improve diet, and can play a crucial role in food security. [ABSTRACT FROM AUTHOR]

This paper presents the latest research findings investigating RC members' residual load–slip response to combined damage caused by corrosion and fire. The idea is to simulate an accidental fire in old or aging structures situated in an aggressive environment such as along the coastlines. The research involved evaluating the response of an RC bond exposed to corrosion and subsequently to elevated temperatures. Pullout bond tests were carried out on cylindrical bond specimens as per standard recommendations following the exposure to accelerated corrosion and elevated temperatures at steady state. Specimens were corroded in the range (2%–20%) as mass loss followed by exposure to elevated temperatures to achieve the steady state (200°C–800°C). The residual load–slip response is examined with the aid of displacement-controlled pullout tests. A set of LVDTs equipment was used to precisely obtain the ultimate bond strength and the steel bar's slip relative to the concrete. The study presents distinct load–slip response curves depicting the overall load–slip mechanism of an RC bond. The results indicate significant changes in the load–slip response due to the two nonlinear phenomena's superimposition. The bond strength degradation and the load–slip response have been modeled to predict RC members' bond behavior exposed to corrosion–temperature interaction. [ABSTRACT FROM AUTHOR]

This paper studies the role of volume, spacing, and configuration of lateral reinforcement on the axial load resisting capacity of reinforced concrete (RC) columns at elevated temperatures. Short RC columns were tested under combined thermal and compressive loading conditions. Columns with different confinement reinforcement volumes, two different lateral reinforcement configurations, and three different lateral reinforcement spacing values were tested as a part of this study. The test results indicate that lateral reinforcement passing through the core of the column is more effective than rectangular lateral reinforcement placed at the perimeter in improving the fire performance of RC columns. Two different numerical approaches, namely, finite element-based approach in combination with a concrete plasticity model and fiber-based sectional analysis approach along with concrete confinement models available in the literature were used to simulate the axial compression behavior of RC columns at elevated temperatures. It was established that some of the popular confinement models developed for ambient temperature conditions could also be used to model the confinement effect at elevated temperatures. Further, a parametric study was conducted to study the role of lateral reinforcement on a broader set of column parameters. It was established that the confinement effect is generally more pronounced at elevated temperatures than at room temperature. [ABSTRACT FROM AUTHOR]

This paper reports on studies relating to the unstressed residual compressive strengths of geopolymer pastes that are heated up to 800 °C, behavior of reactive powder concrete before and after exposure to elevated temperatures and thermal behavior of novel reactive powder geopolymer-based concretes. For this purpose, 10 geopolymer pastes and three reactive powder concrete mixtures were tested for residual strengths. Gladstone fly ash was used as the primary binder for both geopolymer pastes and reactive powder geopolymer concretes. In addition, four novel reactive powder geopolymer concrete mixes were prepared with zero cement utilization. While reactive powder concretes achieved the highest seven-day compressive strengths of approximately 140 MPa, very poor thermal behavior was observed, with explosive spalling occurring at a temperature of ca. 360 °C. The reactive powder geopolymer concretes, on the other hand, displayed relatively high thermal properties with no thermal cracking at 400 °C, or visible signs of spalling and very mild cracking in one case at 800 °C. In terms of the strength of reactive powder geopolymer concrete, a maximum compressive strength of approximately 76 MPa and residual strengths of approximately 61 MPa and 51 MPa at 400 °C and 800 °C, respectively, were observed. [ABSTRACT FROM AUTHOR]

Background: Accurate evaluation of life-limiting failure behavior is a prerequisite to ensure the successful design and application of ceramic matrix composites (CMCs). Objective: To investigate life-limiting failure behavior of CMCs, it is necessary to evaluate the in-plane shear strength. Methods: In this paper, the in-plane shear strength (IPSS) of two-dimensional carbon fiber reinforced silicon carbide matrix (2D C/SiC) composites at elevated temperatures in air was studied by a modified Iosipescu method. A simplified Iosipescu loading configuration without mechanical connections or a fastening assembly was proposed. Results: According to finite element analysis, an almost pure in-plane shear stress field and an in-plane shear failure mode were obtained. The modified Iosipescu method was adopted to evaluate the IPSS of 2D C/SiC at room temperature (RT), 800 °C, and 1000 °C. The in-plane shear failure mode was observed, and the IPSSs were obtained. Based on the microstructure analysis, the release of the tensile stress at elevated temperatures can account for the increase in the IPSS from RT to 800 °C. The decrease in the IPSS from 800 °C to 1000 °C may have resulted from the oxidation of carbon fibers. Conclusions: The modified Iosipescu method can be used to measure the in-plane properties of CMCs. This study may be beneficial to reveal the failure mechanisms and guide the design of CMCs. [ABSTRACT FROM AUTHOR]

In this paper, a numerical investigation on the global buckling capacity of the axially compressed steel columns with hot-rolled I crosssection at elevated temperatures is presented. Geometrically and materially non-linear finite element model and the ABAQUS software were used to determine the buckling resistance. The numerical ABAQUS model was validated using experimental results available in the literature, and then the validated numerical model was used to generate a database of load-carrying capacity. The parametric study covered three different cross-section classes (class 1, 2 and 3), ten different non-dimensional slenderness ̄λ = 0.5, 0.6, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.0), three different temperatures (400°C, 500°C, 600°C), and two stress-strain constitutive relations including (the nonlinear material model adopted in the European guidance for structural fire design EN1993-1-2, and a Bilinear material model), with and without residual stress. The influence of the model parameters on the load capacity of steel columns at elevated temperatures was evaluated. The results of the parametric study were compared with the results of the simplified calculation model presented in EN1993-1-2. [ABSTRACT FROM AUTHOR]

This paper studied the effect of elevated temperatures on the compressive strength of alkali-activated fly ash (so-called geopolymer) with the addition of calcium aluminate cement (CAC). In the elevated temperature tests (600 and 800 °C), the unstressed test method was adopted. Taguchi analysis was used to study the effect of three parameters (considered in mix design) on the hot strength. These parameters include the replacement ratio of fly ash by CAC, molarity of sodium hydroxide solution, and alkaline solution to fly ash ratio. The first parameter was found to be the most influential factor. XRD, TG/DSC and SEM techniques were then carried out to investigate the effects of the CAC content on the high-temperature performance of the geopolymer. The phase transformation taking place during the heat exposure was found to affect the compressive strength in the hot state directly. The retained strength of the optimal geopolymer mortar at 600 °C was around 2.5 times higher than that of ordinary Portland cement mortars with a similar original strength level. [ABSTRACT FROM AUTHOR]

This paper presents key findings of an experimental program performed to examine the rate-dependent behavior of weld material in transverse welded lap joints at elevated temperatures under steady-state thermal conditions. The data are intended to support the development of models of welded connections for structural-fire engineering applications. Two different loading rate scenarios (fast and slow) were incorporated in the experiments to evaluate the loading rate effect on the strength and deformation capacity of welded connection test specimens at ambient and elevated temperatures. Retention factors for the weld material under both slow and fast loading rates were computed and compared with those available in the literature. Results from this study indicate that the loading rate has a significant effect on the strength and deformation capacities of transverse welded lap joints for temperatures greater than 450°C. [ABSTRACT FROM AUTHOR]

This paper studies the role of confining reinforcement on the compression behavior of axially loaded reinforced concrete (RC) columns at elevated temperatures. To demonstrate, experimental tests are conducted on 10 RC stub columns, each with a cross-sectional dimensions of 230×230 mm and a length of 860 mm. Two different concrete mixes (M30 and M50) exposed to varying combinations of two different heating durations (140 and 200 min) and two different volumes of confining reinforcement (0.25% and 2.14% by volume) are used in these tests. A length of approximately 500 mm at the middle of the column is heated for the desired duration and then loaded concentrically in compression until failure. The tests reveal that an increase in the amount of confining reinforcement significantly improves the axial load–carrying capacity of RC columns at elevated temperatures. These tests are also simulated using finite element (FE)–based heat transfer and stress analyses. The numerical simulations predict the time-temperature (t-T), axial load-deformation behavior, and the failure mode reasonably well. The numerical simulations are further used to understand the role of the confining reinforcement on the confinement pressure in the RC columns. [ABSTRACT FROM AUTHOR]

The quasi-static properties (strength and stiffness) of polymer matrix composites (PMC's) exhibit significant temperature dependence in tension. Part I of the present paper introduced a new model enabling the computations of the strength and stiffness of PMC's in tension as an explicit function of temperature. In the second part, this model was used to model the behavior of unidirectional PMC's (AS4/PPS) in end-loaded bending. A new set of stress-rupture experiments was performed on the amorphous composite in bending in order to complete the data available in the literature (based on semi-crystalline composite). A model enabling the computation of the rupture life of the bent specimen as a function of temperature and applied load was established. The theoretical simulations were successfully compared to a set of 7 independent end-loaded bending experiments. This paper demonstrates the validity and the ease of integrating the polymer stiffness-temperature model in mechanics of composite materials, and completes the theoretical and experimental basis for the modeling of the end-loaded behavior of PMC's. [ABSTRACT FROM AUTHOR]

This paper presents the behavior of axially loaded steel columns subjected to thermal gradients through their cross sections. Experimental tests were conducted on full-scale wide-flange steel columns with W8 × 35 and W14 × 53 sections made from standard grade 50 steel. The experimental investigations confirmed that variations in fire protection thickness had significant influence on the thermal gradient developing through the steel cross section. Thermal gradient along the flanges caused bowing of column specimens toward the hotter side. Thermal bowing introduced second-order moments and adversely affected stability, leading to failure of column specimens by inelastic flexural column buckling. The experimental behavior and results were compared with those obtained from detailed nonlinear finite-element analyses of the tested specimens. These nonlinear finite-element models utilized standard (temperature-dependent) material properties, and reasonably predicted the axial load-temperature-deformation behavior and failure temperature of column specimens subjected to nonuniform heating. [ABSTRACT FROM AUTHOR]

Experimental evidence demonstrates the complexity of beam-to-column connections at elevated temperatures and its performance has been identified in association with instability of steel members or steel-framed structures. This paper presents a research work on the inelastic behavior of a sub-framed structure at high temperatures, adopting a component-based model to represent restraints to steel members, then produced by finite element simulation, to demonstrate performance of sub-framed structures at elevated temperatures. The finite element simulation demonstrates that instability of steel members in a sub-framed structure is associated with temperature-dependent material properties (e.g. strength or deformation) of bolted connections at the ends of steel members. In addition, connection failure mechanism is very much dependent on connection components already identified, and their strength and ductility. Instability of steel members in catenary action has also been discussed for high temperatures in this paper. [ABSTRACT FROM AUTHOR]

A mathematical model using the fiber approach is presented in this paper for quantifying the strength and fire-resistance of eccentrically loaded slender concrete-filled steel tubular (CFST) columns with rectangular sections incorporating the interaction of local and global buckling. The model utilizes the thermal simulator to ascertain the temperature distribution in cross-sections, and the nonlinear global buckling analysis to predict the interaction responses of local and global buckling of loaded CFST slender columns to fire effects. The initial geometric imperfection, air gap between the concrete and steel tube, tensile concrete strength, deformations caused by preloads, and temperature-dependent material behavior are included in the formulation. The computational theory, modeling procedure and numerical solution algorithms are described. The computational model is verified by existing experimental and numerical results. The structural responses and fire-resistance of CFST columns of rectangular sections exposed to fire are investigated. The mathematical model proposed is demonstrated to be an efficient computer simulator for the fire-performance of slender CFST columns loaded eccentrically. [ABSTRACT FROM AUTHOR]

This paper presents the effects of various slag contents on the residual compressive strength and physical properties of ambient air-cured fly ash-slag blended geopolymers after exposure to various elevated temperatures up to 800°C. The results showed an increasing trend in the compressive strength of ambient air-cured geopolymers with increase in the slag contents after exposure to 400 and 600°C temperatures. This trend deviated, however, at 800°C. Nevertheless, all the geopolymers showed reductions in control compressive strength at ambient temperature after exposure to elevated temperatures. The reductions were much higher at 600 and 800°C compared to 400°C. All the geopolymers exhibited significant damage in terms of cracking after exposure to a temperature of 800°C compared to 400 and 600°C and significant damage occurred at slag contents of 15-30%. Scanning electron microscopic (SEM) images of the above geopolymers also showed higher porosity at 800°C compared to 400 and 600°C. Traces of calcite/calcium silicate hydrate (CSH) peaks are observed in the X-ray diffraction (XRD) analysis of fly ash-slag geopolymers, and the intensity of those peaks increased with increases in slag contents. After exposure to elevated temperatures, the calcite/CSH peaks disappeared and new phases of nepheline and gehlenite were formed at 800°C in all the fly ash-slag geopolymers. [ABSTRACT FROM AUTHOR]

Recycled crumb rubber is a material created by grinding and commutating used tyres. There is no doubt that the increasing piles of tyres create environmental concerns. The long term goal of this paper is to find a means to dispose of the crumb rubber in lightweight self-compacting concrete (SCC) and still provide a final product with good engineering properties. This paper has considered replacement of natural normal-weight aggregates with crumb rubber aggregates and lightweight scoria aggregate together with the addition of macro fibres which provides a sustainable alternative which assists in minimizing the environmental damages associated with the disposal of waste tyres. Also, the purpose of this study is to determine the effect of fibres on fresh and mechanical properties in additional to the performance of the concrete after exposure to elevated temperatures. Investigation has been performed after concrete exposure to both room and elevated temperatures. Fibre reinforcement were added to a control mix containing 80% replacement of traditional coarse aggregate with lightweight scoria aggregate and 20% replacement of traditional fine aggregate with crumb rubber aggregate. Steel and polypropylene (PP) fibres were explored so as to ascertain the benefits each fibre can provide through a range of temperatures. Nine mixes were prepared; a control mix and four mixes per each fibre with increasing fibre addition. Chemical admixture dosages were adjusted so as to achieve the desired slump flow. Experimental program investigated the fresh properties of the SCC through slump flow, slump flow T500 and J-ring tests. Mechanical properties were investigated after 28 days curing, standard 100 × 200 mm cylinder specimens were subjected to compressive and indirect tensile tests after exposure to 25, 100, 300, 600 and 900 °C. Compiled results will be compared to those of the control mix. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the mechanical properties of sixty A4-70 and A4-80 stainless steel bolts under steady-state temperatures ranging from 20 to 900 °C. The material responses at elevated temperatures of the parent materials, SUS316 and SUS316Ti stainless steels (also known as EN 1.4401 and EN 1.4571 steels), and of fire-resistant bolts are included for comparisons. The tensile strength degradation of stainless steel bolts in fire are found to be reasonably close to those specified by Eurocode 3 Part 1.2 for their parent materials, but the Young's modulus degradation is not so robust. At temperatures lower than 650 °C, the stainless steel bolts retain their 0.2% proof strength better than their parent materials. Importantly, in the temperature range of 500 to 900 °C the stainless steel bolts retain their tensile strength, Young's modulus and 0.2% proof strength better than fire-resistant bolts (BOLTEN110N-FR to JSSII-09 standard). Based on the experimental data, reduction factors for tensile strength, Young's modulus and 0.2% proof strength are derived in this paper for stainless steel bolts at elevated temperatures. [ABSTRACT FROM AUTHOR]

This paper deals with the experimental study of the response of refractory concrete mixture to gradual thermal loading, up to 1000 °C. A binding system based on calcium aluminate cement (CAC) modified by the partial replacement of metakaolin was used. Short ceramic fibers were applied in a dose of 4% by volume in the studied mixture. Material transformations due to thermal loading were monitored in terms of residual mechanical, fracture and basic physical properties-compressive strength, flexural strength, fracture energy, dynamic modulus of elasticity, and bulk density in the study. The results obtained corresponded well with the mineral transformations monitored using the thermogravimetric analysis performed on the binder paste. Residual values of compressive and flexural strength were approximately 40% of the initial values after exposure to a temperature of 1000°C; however, the dominant part of the total loss was monitored up to 400°C, due to decomposition of the hydrates. Fiber employment contributed considerably to the resistance against thermal loading up to 400°C, which was demonstrated by the fracture energy results (a loss of 25% was monitored). An additional increase of the temperature load led to micro crack propagation, which was obvious in the results of dynamic modulus of elasticity determination, in which the short fiber incorporation was noticeably limited. [ABSTRACT FROM AUTHOR]

An experimental study on the flexural behaviour of six fibre-reinforced lightweight aggregate concrete (FRLWAC) one-way slab strips under ambient and elevated temperatures is presented in this paper. Two slabs, one simply-supported and one continuous, were loaded to failure at ambient temperature as references for the fire tests, while another simply-supported and three continuous slabs with varying degrees of design moment redistribution were loaded and exposed to elevated temperatures until failure. The ambient tests showed that the steel fibre addition prevents premature flexural-compression failure commonly observed in lightweight aggregate concrete structures. The rotations of FRLWAC plastic hinges were concentrated in a single crack under ambient temperature and a few cracks under fire exposure. The fire tests revealed significant moment redistribution towards the hogging moment area in the continuous slabs due to restrained thermal-induced deflection. Furthermore, the reinforcement configuration that catered for moment redistribution towards the hogging area was found to enhance the fire resistance of continuous FRLWAC slabs. A fibre-reinforced concrete (FRC) plastic hinge model, based on the rigid-body rotation concept, was proposed and validated. This model predicts the moment-rotation behaviour of FRC hinges at ambient temperature and the fire resistance of FRLWAC one-way slabs with good accuracy. • Six FRLWAC slab specimens were tested at ambient temperature and fire conditions. • Test parameters are fire exposure, continuity and design moment redistribution. • The plastic hinge rotation in FRLWAC concentrates on one crack at ambient and a few cracks under fire. • Moment redistribution towards the hogging area improves fire resistance of FRLWAC slabs. • A plastic hinge model for predicting moment-rotation and fire resistance of FRLWAC slabs is proposed. [ABSTRACT FROM AUTHOR]

Welding is commonly used in the construction of steel connections in the United States (U.S.). Thus, accurate characterization of weld behavior at elevated temperatures is critical for designing and evaluating the performance of steel structures exposed to fire. This paper presents results from an experimental study in which steady-state tensile tests of butt-welded steel plate coupons made from ASTM A36 steel and E70 electrode were conducted at temperatures ranging from ambient laboratory temperature (20 °C) to 800 °C. Retention factors for elastic modulus, yield strength, and ultimate strength were produced from the data and compared with those values specified for structural steels and fillet welds in U.S. and European design codes and standards. While the elastic modulus retention factors specified in the American Institute of Steel Construction (AISC) 360–22 Specification for Structural Steel Buildings were found to be conservative, the yield strength and ultimate strength factors recommended by AISC were found to be nonconservative for welds heated to temperatures between 400 °C and 800 °C. In addition, tensile fractures of the coupons, which predominately occurred in the base metal away from the heat-affected zone, were observed to occur within the weld at temperatures of 500 °C and 800 °C. • Mechanical properties of butt-welded steel coupons tested at elevated temperature. • Retention factors for elastic modulus, yield strength, and ultimate strength. • Welded steel connection performance in fire. [ABSTRACT FROM AUTHOR]

Reliable deformation measurement is required for proper quantification of fire performance of concrete structures. Predictive capability of models for many critical properties, including Young’s moduli, stress-strain relationships and load-induced thermal strains, is first and foremost dependent on such reliable deformation capturing. This paper first presents a state-of-the-art review of existing methods for capturing deformation of concrete structures at elevated temperatures. Key merits, limitations and challenges associated with each measuring technique are discussed. It is shown that existing testing facilities and measuring instruments generally do not allow reliable direct measurement of deformation and strain of high-temperature concrete. As a result, the deformation has typically been captured either indirectly or outside the heated zones, inevitably introducing additional uncertainty and errors that are difficult to be adequately quantified. On the basis of that review, the paper details a new test set-up for reliable non-contact full-field deformation capturing of concrete structures at high temperatures using 3D Digital Image Correlation technique. Key features of the new setup that enable to successfully address major challenges of thermal boundary condition, thermal stability of speckle pattern, contrast of image and hot air movement are presented; together with evidences giving confidence to the reliability of such set-up. With its combined advantages of reliable full-field deformation capturing and thermal boundary conditions on test specimens, the new set-up allows to generate required reliable data on performance of concrete at elevated temperatures, thereby facilitating the development of effective rational fire design and analysis of concrete structures. [ABSTRACT FROM AUTHOR]

Platinum plays a crucial role in the superior high-temperature oxidation resistance of Pt-modified nickel aluminide (PtAl) coatings. However, PtAl coatings usually serve in thermo-mechanical coupling environments. To investigate whether Pt contributes to the high-temperature mechanical properties of PtAl coating, stress rupture tests under 1100 °C/100 MPa were performed on PtAl coatings with varying Pt contents. The different coatings were obtained by changing the thickness of the electroplated Pt layer, followed by a diffusion heat treatment and the aluminizing process in the present work. The results of the stress rupture tests indicated that an increasing Pt content resulted in a significant decrease in the stress rupture life of PtAl-coated superalloys under 1100 °C/100 MPa. Theoretical calculations and microstructural analysis suggested that an increased coating thickness due to the Pt content is not the main reason for this decline. It was found that the cracks generated close to the substrate in high-Pt-coated superalloys accelerated the fracture failure. [ABSTRACT FROM AUTHOR]

This paper presents a parametric study for the bending stiffness of mineral wool (MW) sandwich panels subjected to a bending load. The MW panels are commonly used as wall panels for industrial buildings. They provide excellent insulation in the case of fire. In this research, the performance of sandwich panels is investigated at both ambient and elevated temperatures. To reach that goal, a finite element (FE) model is developed to verify simulations with experimental results in normal conditions and fire case. The experimental investigation in the current paper is a part of STABFI project financed by Research Fund for Coal and Steel (RFCS). The numerical study is conducted using ABAQUS software. Employing simulations for analysis and design is an alternative to costly tests. However, in order to rely on numerical results, simulations must be verified with the experimental results. In this paper, after the verification of FE results, a parametric study is conducted to observe the effects of the panel thickness, length and width, as well as the facing thickness on the bending stiffness of MW sandwich panels at normal conditions. The results indicate that the panel thickness has the most significant effect on the bending stiffness of sandwich panels.

This paper presents the temperature dependence of the mechanical properties of structural high-strength low-alloy (HSLA) ASTM A709 Gr50 steel (En10025: S355 JO; DIN: ST 52-3U). Engineering stress-strain diagrams at lowered and elevated temperatures are presented. Creep responses for selected constant stresses at selected temperatures are also presented and are fit with a rheological model. Additionally, a relation between impact toughness and fracture toughness is proposed and is validated using results from notch impact tests on a Charpy pendulum impact machine. [ABSTRACT FROM AUTHOR]

Structural lightweight concrete (LWC) has recently acquired research importance because of its good thermal insulation properties. However, there is a lack of knowledge about its thermal properties at elevated temperatures. The thermal properties, such as thermal conductivity and specific heat, of porous LWC vary depending on the aggregates, air voids, and moisture content of the LWC in question. To study these effects, in this paper, we measured the thermal properties of three types of structural LWCs at different temperatures, combining different characterization techniques, namely, differential scanning calorimetry (DSC), laser flash analysis (LFA), and modified transient plane source (MTPS). Bulk density and porosity were also evaluated. Specific heat is analyzed by the DSC technique from 20 to 1000 °C and the MTPS technique from 20 to 160 °C. Thermal conductivity is studied using MTPS and LFA techniques at temperatures ranging from 20 to 160 °C and 100 to 300 °C, respectively. The results indicate that the thermal properties of LWC are highly affected by moisture content, temperature, and porosity. For LWC, the current Eurocodes 2 and 4 assume a constant value of specific heat (840 J/kg°C). This research reveals variability in temperatures near 150, 450, and 850 °C due to endothermic reactions. Furthermore, for low temperatures, the higher the porosity, the higher the thermal conductivity, while, at high temperatures, the higher the porosity, the lower the thermal conductivity. Thus, Eurocodes 2 and 4 should be updated accordingly. This research contributes to a deeper understanding and more accurate prediction of LWC's effects on thermal properties at elevated temperatures. [ABSTRACT FROM AUTHOR]

High-strength steels (HSS) are produced using special chemical composition or/and manufacturing processes. Both aspects affect their mechanical properties at elevated temperatures and after cooling down, and particularly the residual strength and the ductility of the structural members. As HSS equates the design of lighter structural elements, higher temperatures are developed internally compared to the elements designed with conventional carbon steel. Therefore, the low thickness members, along with the severe effect of high temperature on the mechanical properties of the HSS, constitute to the increased vulnerability of such structures in fire. Moreover, the re-use and reinstatement of these structures are more challenging due to the lower residual mechanical properties of HSS after the cooling down period. This paper presents a review of the available experimental studies of the mechanical properties of HSS at elevated temperatures and after cooling down. The experimental results are collected and compared with the proposed material model (reduction factors) of EN1993-1-2. Based on these comparisons, modified equations describing the effect of elevated temperatures on the mechanical properties of HSS are proposed. Also, the post-fire mechanical properties of HSS are examined. A comprehensive discussion on the effect of influencing parameters, such as manufacturing process, microstructure, loading conditions, maximum temperature, and others is further explored. [ABSTRACT FROM AUTHOR]

A novel mechanical attachment for conducting in-plane biaxial tensile test is provided in this paper. In this attachment, the conversion of force from an external actuator into two pairs of orthogonal forces is achieved by specially designed trapezoidal blocks. By using trapezoidal blocks with different inclination angles, biaxial tensile tests of six different tensile ratios can be performed. A heating device is designed for the attachment to conduct thermal biaxial tensile tests. The heating device adopts a combination of the induction heating technology and the conduction heating method. With the developed mechanical attachment and the heating device, the forming limit curves (FLC) of DP590 sheets at ambient temperature, 300 °C, 400 °C and 500 °C are determined using biaxial tensile tests. A classical Nakazima test procedure at ambient temperature is carried out to establish a reference FLC for the material, and the reference FLC is further used to evaluate the results from biaxial tensile tests. Furthermore, an anisotropic GTN model based on Yld2000-3d yield criterion is calibrated by inverse identification procedures and applied to predict the localized necking and fracture for DP590 sheets under biaxial tensions.

Material properties at corner parts of cold-formed sections are different from their flat counterparts. Currently, there is lack of investigation into corner material properties of cold-formed stainless steel sections at elevated temperatures. This paper presents a careful experimental study on corner material properties of cold-formed lean-duplex stainless steel (LDSS) sections at elevated temperatures. The corner coupons were extracted from rectangular hollow sections (RHS) cold-formed from grade EN 1.4162 LDSS strips. Tensile corner coupon tests were conducted by using steady state test method for temperatures up to 850℃. The full-range stress-strain curves at 12 different temperatures were obtained with key material properties derived. The corner coupon test results were compared with flat coupon test results previously reported in the literature. The comparison results demonstrated that the material strengths at corner parts of cold-formed RHS generally deteriorated more severe than their flat counterparts at elevated temperatures, especially for temperatures exceeding 550℃. The obtained reduction factors were compared with design values codified in current EN 1993-1-2. New design curves to predict the deterioration of corner material properties of cold-formed LDSS RHS at elevated temperatures were proposed. A constitutive model was proposed to predict the stress-strain relationship of the corner coupon specimens. It is shown that the proposed reduction factors and stress-strain model can be used to predict the corner material properties of cold-formed LDSS RHS at elevated temperatures. The impact of elevated temperature history on corner material properties of cold-formed LDSS RHS was also explored. • Corner material properties of cold-formed lean-duplex stainless steel sections at elevated temperatures were studied. • Effects of exposed temperature ranged from 20 to 850 °C and elevated temperature history were investigated. • Existing design rules are assessed by comparing test results. • Design curves to predict corner material properties are proposed. • A constitutive model to predict stress-strain curves at elevated temperatures is proposed. [ABSTRACT FROM AUTHOR]

Steel bolted connections are critical structural components that can initiate progressive collapse at ambient and elevated temperatures. High-strength bolts are highly vulnerable members due to rapid strength degradation at high temperatures. This paper presents a numerical study on the ductile fracture of the frequently used Grade 8.8 and 10.9 structural bolts under tension, shear, and combined forces at 20–700 °C. True stress–strain curves have been defined up to fracture for both grades. The fracture parameters have been calibrated by a total of four experiments: two tensile and shear tests for each grade. The ductile fracture models with proposed fracture parameters have been further validated by pretensioned shear tests at elevated temperatures. The relationship between equivalent strain and triaxiality was investigated based on the numerical results. In general, equivalent plastic strain values become larger with increasing temperature. The fracture analysis with given ductile fracture parameters estimates the test results with reasonable accuracy under all failure modes. The fracture model can be used in numerical analysis to investigate the ductile failure of the high-strength bolted connections at ambient and elevated temperatures. Furthermore, the influence of displacement at fracture values on the results was investigated by a three-bolted inclined shear test. • A ductile fracture model is proposed for Grade 8.8 and 10.9 bolts up to 700°C. • The proposed fracture model agrees well with the validation test results. • Fracture models given in literature are compared for bolts at elevated temperatures. • A linear relation is seen in PEEQ and stress triaxiality in tensile tests. • In general, the ductility of bolts increases with temperature rise. • The fracture at displacement value effect is not found significant under shear load. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the mechanical properties of 1860 MPa twisted wire strands and the load capacity of hot casting sockets at elevated temperatures. The stress-strain curves of the strands at the temperature in 20 °C to 600 °C range are reported, and the elastic modulus, yield strength, ultimate strength, ultimate strain and rupture strain are obtained and compared to EC2 and other existing studies. The failure mode, load capacity, failure displacement and critical temperature of the sockets at the temperature in 20 °C to 440 °C range are acquired. The test results show that 1860 MPa twisted wire strands have significantly improved ductility in necking stage after 200 °C, which is underestimated in EC2. The strands with hot casting sockets rupture before 180 °C, and are pulled out from the sockets after 230.5 °C. The load capacity drops after 150 °C, and the failure displacement dropped after 300 °C, indicating significant influence of the sockets on the fire resistance. Based on thick-walled cylinder model, calculation methods are proposed to determine the bonding strength and load capacity of the strand with hot casting sockets. The prediction of the failure modes and load capacity agrees well with test results. The parametrical analysis by the calculation methods shows that the load capacity of the strands with sockets increases as the embedded length or internal diameter of socket increases, or the diameter of the strands decreases in a limited range. For fire protection, it is recommended to keep the socket temperature under the critical temperature in accordance with load ratio. • Mechanical properties of 1860 MPa twisted wire strands at elevated temperatures are presented. • A novel stress-strain model of high-strength twisted wire strands is proposed. • The load capacity of hot casting sockets at elevated temperatures is presented. • The critical temperature of hot casting socket as a function of load ratio is proposed. • An analytical method is proposed to determine the bonding strength of the strand with hot casting sockets. [ABSTRACT FROM AUTHOR]

• The proposed analytical method can predict the ultimate bearing capacity of RC slabs and composite slabs in fire. • An equation for the elliptical boundary is determined, and the temperature has a minor influence on the ellipse. • The numerical model can simulate the thermo-mechanical behaviours of RC slabs and composite slabs at elevated temperatures. • The numerical simulation demonstrates that TMA progresses from the boundary to centre. • l /10 and l /8 are recommended as the failure criteria of RC slabs and composite slabs in fire conditions, respectively. Slabs can take full advantage of tensile membrane action (TMA) in fire conditions to improve the ultimate bearing capacity. This paper proposed a novel analytical method to determine the ultimate bearing capacity of both reinforced concrete slabs and composite slabs at elevated temperatures, considering the influence of TMA. In this analytical model, a well-defined equation for the elliptical boundary of the TMA region is reasonably determined, and the enhancement of TMA is derived from a series of force and moment equilibria. The analytical method shows a good agreement with the test results. The analytical analysis reveals that while increasing temperature has little effect on the geometry of the membrane action region, it significantly influences the enhancement of ultimate load due to the temperature-induced stress redistribution in the slab. In addition, the membrane action predicted by the analytical method aligns well with that predicted by the numerical method. The development of TMA progresses from the boundary of ellipse to centre, according to the stress distribution predicted by numerical analysis. Finally, with the aid of test results and numerical results, span/10 and span/8 are suggested as the failure criteria for reinforced concrete slabs and steel-concrete composite slabs in fire conditions, respectively. [ABSTRACT FROM AUTHOR]

Reducing the environmental footprint of concrete is one of the most effective methods to mitigate climate change since cement production contributes to about 8 % of global CO2 emissions. This paper presents an experimental investigation into the strength and flexural performance of reinforced concrete (RC) beams incorporating natural aggregate (NA), recycled concrete aggregate (RCA), and reclaimed asphalt pavement concrete (RAP) at normal and elevated temperatures. The NA was replaced by RAP at three replacement ratios of 40 %, 60 % and 80 %. Additionally, there were four mixes of 80 % RCA-20 % RAP, 60 % RCA-40 % RAP, 40 % RCA-60 % RAP, and 20 % RCA-80 % RAP. A total of 16 beams (L: 1400 mm, W: 150 mm, H: 250 mm) and 128 cylinders (H: 200 m, D: 100 mm) were tested to evaluate the flexural capacity and material strength. Eight RC beams were tested after exposure to a temperature of 600 °C for 3 h. The compressive strength, ultimate flexural load, and mid-span deflection were measured. The results showed that temperature has an adverse effect on the s compressive strength, flexural load capacity, and deflection of RC beams. Specimens made with the RAP and RCA combination showed a significant loss in their load-carrying capacity under elevated temperature by (55 %–65 %), while the temperature effect was relatively less severe in specimens made with high RAP replacement of NA. Increasing the RAP percentage increased the reduction of flexural capacity in RCA-RAP mixes by (3 %–10 %), while in NA-RAP mixes, the effect is similar except for 60 % RAP, which has a smaller reduction compared to 40 % and 80 % RAP.

The use of Ti6Al4V components in the aerospace industry has increased in the past years s. Jet engine components made of Ti6Al4V such as compressor blades and exhaust ducts, as well as landing gear, hydraulic systems, and many airframe parts, are exposed to different temperatures while in service, which may affect their mechanical properties. Compressor blades are exposed to temperatures up to 400 °C, exhaust ducts up to 300 °C, and hydraulic systems in the range of −50 °C–135 °C, while landing gears and many airframe structures are exposed to temperatures in the range of −50 °C–70 °C. Therefore, it is of great importance to determine their stability at different temperatures. The results of a study aimed at investigating the effect of elevated temperatures on the mechanical properties and microstructures of DMLS Ti6Al4V(ELI) alloy are presented and discussed in this paper. A DMLS EOSINT M290 machine was used to manufacture test specimens, which were then machined to comply with ASTM E8 for tensile tests. Thereafter, tensile tests were carried out at different test temperatures till fracture. Fractography was then used to study the characteristics of the fracture surfaces. The results obtained in this work showed that temperatures between 175 °C and 325 °C have a significant effect on the mechanical properties and microstructures of the alloy.

During the last decades, traffic loads by heavy vehicles have increased due to requirements of the current society and this fact has to be considered when the state of existing bridges is evaluated. Many concrete structures, for instance lateral cantilevers of highway boxgirder bridges, can be strengthened on the upper side with Externally Bonded (EB) Carbon Fiber Reinforced Polymer (CFRP) strips in order to increase their load-bearing capacity in flexure. These additional reinforcements can be applied as an unstressed or prestressed system. The main objective of this paper is to analyze the influence of elevated temperatures for instance due to the application of warm mastic asphalt on the bond between the concrete substrate, the epoxy resin layer, and the externally prestressed bonded CFRP strip. Background of the study is a non-mechanical anchorage system for prestressed composite strips known as the gradient anchorage. A literature review collecting the most important experimental works performed in this field together with an own experimental investigation performed at Empa is presented in this paper. Besides, an analytical linear elastic model has been proposed to study the behavior of such prestressed systems after the releasing stage. [ABSTRACT FROM AUTHOR]

Current design rules for the member capacities of cold-formed steel columns are based on the same non-dimensional strength curve for both fixed and pinned-ended columns at ambient temperature. This research has investigated the accuracy of using current ambient temperature design rules in Australia/New Zealand (AS/NZS 4600), American (AISI S100) and European (Eurocode 3 Part 1.3) standards in determining the flexural–torsional buckling capacities of cold-formed steel columns at uniform elevated temperatures using appropriately reduced mechanical properties. It was found that these design rules accurately predicted the member capacities of pin ended lipped channel columns undergoing flexural torsional buckling at elevated temperatures. However, for fixed ended columns with warping fixity undergoing flexural–torsional buckling, the current design rules significantly underestimated the column capacities as they disregard the beneficial effect of warping fixity. This paper has therefore recommended the use of improved design rules developed for ambient temperature conditions to predict the axial compression capacities of fixed ended columns subject to flexural–torsional buckling at elevated temperatures within AS/NZS 4600 and AISI S100 design provisions. The accuracy of the proposed fire design rules was verified using finite element analysis and test results of cold-formed lipped channel columns at elevated temperatures except for low strength steel columns with intermediate slenderness whose behaviour was influenced by the increased nonlinearity in the stress–strain curves at elevated temperatures. Further research is required to include these effects within AS/NZS 4600 and AISI S100 design rules. However, Eurocode 3 Part 1.3 design rules can be used for this purpose by using suitable buckling curves as recommended in this paper. [ABSTRACT FROM AUTHOR]