Purpose Portland-limestone cement (PLC) is a low-carbon, green alternative binder that can substitute for ordinary Portland cement (OPC) to support the development of eco-friendly infrastructure solutions. The building's energy consumption and strength retention efficiency can be improved by effectively enhancing the cementitious matrix properties of the rendering materials. Design/methodology/approach In this study, the residual mechanical strengths and microstructure of OPC and PLC mortars before and after exposure to elevated temperatures of up to 800 °C were experimentally investigated. Tested specimens were prepared using 0%, 5%, 10% and 15 wt.% of limestone as a replacement for OPC. The fire-resistance performance of the prepared rendering mixtures was evaluated through their residual strengths, X-ray diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Findings Based on the results, the mechanical properties of all mortars improved at 250 °C, due to internal autoclaving and pore pressure effects. At 800 °C, the major phases observed in OPC and PLC mortars were calcium silicate and quartz. Large wollastonite and gehlenite crystalline phases were observed in PLC mortars; thus, the matrix structure was severely damaged, and this damage was more pronounced in PLC mortars. Originality/value Several studies have concentrated on this area, and numerous investigations into the fire-resistance performances of cement-based mortars have been reported. Nevertheless, limited investigations focused have focused on the residual strengths of rendering mortars made with PLC as a sustainable alternative to Portland cement; and therefore, have not been acknowledged to date.
Purpose In this experimental investigation, the high-yield strength-deformed-steel (HYSD) and glass-fibre-reinforced-polymer (GFRP) rebars were employed to assess the bond behaviour at RT, 1000ºC, 2000ºC and 3000ºC. Natural river sand has been completely replaced with manufactured sand (MS) in the production of concrete, wherein it was observed that, the residual compressive strength decreases as the temperature increases. Based on ultrasonic pulse velocity (UPV) test results, the quality of concrete can be categorised from “Excellent to Good”. The bond strength of HYSD bar specimens reveals higher values compared to specimens with GFRP bars at RT, 1000ºC, 2000ºC and 3000ºC. The specimens with HYSD bars show lower slippage when compared to specimens with GFRP bars at elevated temperatures and the pullout failures have been noticed for the specimens at elevated temperatures. Based on experimental investigation, the mathematical equations have been suggested for predicting the bond stress at high temperatures. Design/methodology/approach The mix design has been conducted in line with IS 10262:2019 following material characterization. The samples were cast in the prescribed mix ratios and cured for 28 days. After curing, the samples were then dried for 48 h to remove any moisture and prevent cubes from spalling during heating. The samples were placed in an electrical furnace of 10000ºC capacity and heated to the desired temperatures for 2 h. The specimens were cooled to room temperature (RT) in the furnace, and non-destructive testing such as UPV and rebound hammer tests were performed to evaluate the quality of the post-heated specimens. The compression and pullout tests were performed to evaluate the post-heat mechanical behaviour. The analysis and interpretation of results were performed to examine the behaviour of specimens exposed to sustained elevated temperatures, and conclusions were drawn at the end of the research. Findings The specimens with HYSD bars reveal greater bond strength than specimens with GFRP bars at each interval of temperatures. The maximum slippage was observed for the specimens with GFRP bars at 3000ºC. This indicates increase in slip with rise in temperatures. Originality/value The bond strength of HYSD bar samples is higher than that of GFRP bars at RT, 1000ºC, 2000ºC and 3000ºC. At higher temperatures, specimens with HYSD bars exhibit lesser slippage than specimens with GFRP bars, and pullout failures were observed. Based on experimental data, mathematical formulae for estimating bond stress at high temperatures have been proposed.
Purpose This study aims to clarify the influence of the internal autoclave effect and cooling-induced thermal shock on the residual mechanical capacity and constitutive behavior of fire-exposed self-compacting concrete (SCC).Design/methodology/approach C35 SCC specimens were exposed to different target temperatures ranging from 20 degrees C to 700 degrees C and then subjected to two cooling regimes: natural cooling and water cooling. Residual compressive strength, failure morphology, surface damage characteristics and uniaxial stress-strain behavior were investigated. A Modified Popovics-based constitutive model was further calibrated to describe the post-fire mechanical response of SCC under different cooling regimes.Findings The results show that the dense matrix of SCC promotes moisture entrapment and hydrothermal reactions at intermediate temperatures, leading to a strength rebound of approximately 8.1%-9.9% at 300 degrees C in the naturally cooled specimens. Water cooling induces severe thermal shock, resulting in surface cracking, corner spalling and greater residual strength loss at high temperatures. The proposed constitutive model captures the degradation of peak stress, peak strain and curve shape with good accuracy.Originality/value This study provides experimental evidence for the coupled hydrothermal-mechanical response of SCC after fire exposure and proposes a calibrated constitutive model for post-fire residual capacity assessment of SCC structures subjected to different cooling conditions.
Purpose This study investigates the fire performance of Type F plasterboard-encased steel columns under standard fire exposure conditions, addressing a research gap regarding fall-off behaviour in column protection systems. Six full-scale 203 & times; 203 & times; 52 kg/m steel columns, three with single-layer 15 mm protection (60-min target) and three with double-layer 30 mm protection (120-min target), were tested under sustained axial loading. The research quantifies fall-off temperatures and times for Type F plasterboard, providing empirical data to support advanced numerical modelling and structural fire engineering design calculations.Design/methodology/approach Six full-scale steel column specimens from three manufacturers were tested in a column furnace under ISO 834 standard fire exposure with sustained axial loading (60-66% of ambient capacity). Columns were 3.4 m tall and box-encased in Type F plasterboard, using proprietary steel framing systems. Temperature measurements included thermocouples in the furnace, on the steel surface, and on the plasterboard rear face. The tests measured heat transfer, mechanical stability, fall-off time/temperature, and failure mechanisms.Findings Single-layer systems (15 mm Type F) achieved fire resistance exceeding 60 min, with plasterboard fall-off at 785-795 degrees C after 81-94 min. Double-layer systems (2 & times; 15 mm Type F) exceeded 120-min targets, with first-layer fall-off at 755-790 degrees C after 135-155 min. Load-bearing failures occurred before fall-off in all cases, with steel temperatures ranging from 570 to 620 degrees C. Therecommended design limiting temperature of 550 degrees C was exceeded in every specimen prior to structural failure, demonstrating the conservatism of simplified design methods. Fall-off resulted from coupled thermal degradation and mechanical deformation of loaded columns, distinguishing columns from wall/ceiling assemblies.Research limitations/implications The testing programme was limited to a single column section (203 & times; 203), reducing applicability to other sizes; smaller sections would heat faster due to higher surface area-to-volume ratios and may require separate analysis. Load ratios (0.60-0.66) represent standard fire scenarios but do not explore the effects of eccentricity or second-order effects. Temperatures between plasterboard layers were not measured due to concerns regarding system protection. Validated finite element models could enable extrapolation to untested configurations and design optimisation tools.Practical implications The research provides fire engineers with evidence-based fall-off temperature ranges for Type F plasterboard, enabling them to calibrate advanced numerical models with greater confidence. Designers can now account for realistic protective performance durations in structural fire design calculations. Single-layer 15 mm Type F systems reliably exceed 60-min ratings; double-layer systems exceed 120 min, offering flexibility in retrofit and lightweight construction applications. The findings validate that conservatism in simplified design methods (using 550 degrees C critical temperature) remains justified. Practitioners could reference these benchmarks when developing system-specific fire-resistance performance predictions for commercial applications.Social implications Understanding the performance of plasterboard-encased columns at elevated temperatures improves the overall building fire safety. More accurate fire-resistance predictions enable safer, code-compliant design of steel-frame buildings, particularly in mid-rise residential and commercial construction. The research supports evidence-based regulatory standards and performance-based design approaches, allowing for protection optimisation and cost reduction while maintaining adequate safety margins.Originality/value This research provides the first comprehensive experimental quantification of fall-off temperatures for Type F plasterboard-encased steel columns under sustained axial loading, a critical gap in the literature. Previous studies have largely focussed on the fire performance of light steel frame wall and ceiling assemblies. This work demonstrates that protection failure is a coupled thermo-mechanical phenomenon influenced by structural deformation. The empirical dataset from six full-scale specimens across three manufacturers provides robust benchmarks for validating advanced numerical models. The findings advance structural fire engineering beyond simplified design methods by characterising realistic protective performance, enabling more accurate fire resistance predictions and supporting evidence-based regulatory standards for steel-frame construction.
Purpose Concrete structural members in high-temperature industrial environments are susceptible to thermal cracking and performance degradation. This study aims to evaluate the thermo-mechanical behavior and reliability of glass fiber-reinforced concrete (GFRC) beams exposed to elevated temperatures using finite element-based probabilistic assessment.Design/methodology/approach RC beams incorporating glass fibers at volume fractions of 0.5%, 1.0%, 1.5% and 2.0% were numerically investigated under thermal exposure levels ranging from 25 degrees C to 600 degrees C. A total of 20 beam models were developed in ABAQUS using cohesive zone modeling (CZM) to simulate crack initiation and propagation. Several structural responses were evaluated and probabilistic analysis was conducted to estimate failure probability under thermal loading conditions.Findings Results indicate that incorporation of 1.5% glass fiber provides the optimum structural response. Compared with conventional RC beams, GFRC beams exhibited an increase of approximately 30-35% in load capacity at crack initiation and a 20-28% increase in mid-span deflection capacity at ambient temperature. Fracture energy increased from 0.10 N/mm in control beams to approximately 0.22 N/mm in fiber-reinforced beams, resulting in a reduction in crack width from 0.102 mm to 0.051 mm. The reliability index increased from beta = 1.9 for control beams to beta = 2.6 for beams containing 1.5% fibers, while the probability of failure decreased from 18% to 6% after thermal exposure.Originality/value This study provides a comprehensive numerical framework integrating CZM and reliability-based analysis to assess the high-temperature performance of GFRC beams, offering valuable insights for fire-resistant structural design in industrial applications.
PurposeThis study aims to systematically investigate the post-fire mechanical behavior of 630 MPa thermomechanically rolled reinforcing bars subjected to elevated temperatures and different cooling regimes. By combining tensile testing, microstructural analysis and comparative evaluation, the study seeks to clarify temperature-dependent degradation mechanisms, quenching-induced hardening effects and the role of cooling history. Empirical prediction models are further developed to support practical post-fire assessment and engineering decision-making for high-strength reinforcement in reinforced concrete (RC) structures.Design/methodology/approachA comprehensive experimental program was conducted on 630 MPa thermomechanically rolled reinforcing bars exposed to temperatures ranging from 150 degrees C to 1,000 degrees C. Specimens were heated under controlled conditions and subsequently cooled using air cooling, furnace cooling or water quenching to simulate realistic post-fire scenarios. Uniaxial tensile tests were performed after cooling to ambient temperature to evaluate residual mechanical properties. Microstructural observations were used to interpret temperature- and cooling-dependent mechanical responses, and empirical models were developed for post-fire strength prediction.FindingsThe results indicate that 630 MPa reinforcing bars retain most of their mechanical performance below 550-600 degrees C, while pronounced strength degradation occurs beyond this threshold due to recovery and recrystallization. Cooling history plays a critical role at high temperatures: air and furnace cooling lead to progressive softening and ductility enhancement, whereas water quenching induces significant strength hardening accompanied by severe ductility loss. The elastic modulus remains relatively insensitive to temperature and cooling conditions. Empirical prediction models provide reliable estimates within 150-850 degrees C but should not be extrapolated beyond this range.Originality/valueTo the best of the authors' knowledge, this study provides one of the first systematic post-fire experimental datasets for 630 MPa thermomechanically rolled reinforcing bars, a material increasingly used in modern RC structures but rarely addressed in existing fire research. Unlike most previous studies on plate-type high-strength steels, the work highlights the combined effects of temperature and cooling history on small-diameter rebars, particularly quenching-induced hardening and embrittlement. The proposed empirical models and engineering-oriented assessment framework offer practical value for post-fire evaluation and decision-making.
PurposeFire disasters pose severe threats to concrete beam bridges, potentially causing rapid performance degradation or collapse. This study aims to investigate the residual mechanical performance and load-bearing capacity of a hollow slab beam bridge in China following a specific fire accident. The primary objective is to accurately assess the post-fire structural safety by establishing a reliable temperature-damage mapping relationship. Furthermore, the study seeks to determine if the damaged bridge still meets serviceability limits to guide necessary maintenance, load restrictions, or strengthening measures.Design/methodology/approachBased on post-disaster field investigations, fire-affected zones were classified by temperature exposure. PyroSim software was used to simulate the spatial temperature distribution throughout the combustion process. The model's accuracy was validated by comparing simulated results with in-situ measurements and European standard material strength reductions. Subsequently, ABAQUS finite element analysis was employed to calculate the structure's mechanical response under a 35-ton vehicle load. The analysis focused on comparisons of mid-span deflection, reinforcement stress, and ultimate bearing capacity before and after the fire exposure.FindingsResults indicate that temperatures exceeding 800 degrees C caused concrete compressive strength reductions of over 60%. The simulation aligned well with actual data, validating an average material strength reduction factor of 0.844. Under a 35-ton fleet load, the bridge exhibited a mid-load deflection of 25.4 mm and an eccentric-load deflection of 26.7 mm-approximately 6-7 times the pre-fire values. With reinforcement stress increasing by 150%, the analysis confirms that the structure no longer meets the normal service limit state, urgently requiring structural intervention.Originality/valueThis study bridges the gap between theoretical fire modeling and practical engineering assessment by analyzing a real-world fire accident on a hollow slab bridge. It establishes a comprehensive workflow integrating field investigation, PyroSim fire dynamics, and ABAQUS structural analysis. Uniquely, the research validates the temperature-damage mapping relationship using both in-situ measurements and material strength tests. The findings provide critical quantitative reference data for the residual bearing capacity of hollow slab bridges, offering valuable guidance for post-disaster safety assessment, load restriction strategies, and structural rehabilitation in similar infrastructure projects.
PurposeThis paper aims to investigate the behavioral response of medium-span composite steel-concrete bridge girder subject to various short duration, localized fires. It employs the usage of coupled computational fluid dynamics (CFD) model and the finite element analysis (FEA) modeling to accurately examine the structural response during and after fire exposer. The study aims to expand the current understanding of localized fires by varying the fire's location and intensity, while simultaneously assuming a short burning time.Design/methodology/approachThe study adopts a numerical approach to investigate the thermos-mechanical response of a structure exposed to elevated temperatures. A coupled CFD-FEA framework was used to analyses the structures' behavior during and after fire. The models' parameters were complimented by already performed experimental results. The numerical results were validated by using simple theoretical calculations and already established numerical models.FindingsThe findings provide insight into the structural response of composite steel-concrete bridge girder during and after fire exposure. The results indicate that the load-bearing capacity is significantly influenced by the fire's location and intensity. In the case of mild fires, structural deflection remains limited, suggesting the feasibility of post-fire repair. Furthermore, the analysis demonstrated that creep strain can be neglected in case of short duration fires. Additionally, the study quantifies the cross-sections deformation in relation to time allowing for a deeper understanding of heating and cooling effects on the structure.Research limitations/implicationsA limitation of the study is the study lacks experimental validation for the FEA models. Therefore, researchers are encouraged to perform further tests on the proposed propositions and expand the database of structural responses to short fires.Practical implicationsThe paper provides a comprehensive example of advanced fire analysis of a bridge structure, offering a solid framework that can be replicated. By documenting the full modeling process and results, the paper contributes to the widening of the database of structural responses under elevated temperatures and supporting future research and improvement of design guidelines.Originality/valueThis paper provides new insights into the effects of short duration, localized fires on composite steel-concrete bridge structure. It additionally examines the influence of creep strain effects and air-cooling rate of steel.
PurposeLoad-bearing fire rating is essential for maintaining the structural integrity of light steel frame (LSF) walls during fire events. While most studies examine single-sided fire exposure, two-sided exposure, relevant in some internal wall scenarios, remains underexplored. This study investigates the impact of both side fire exposure on the load-bearing fire rating of LSF walls under various fire conditions.Design/methodology/approachThis research employs finite element modelling (FEM) to simulate the structural and thermal response of LSF walls under two-sided fire exposure. The models were calibrated and validated using experimental data from previous studies to ensure accuracy. Parametric studies were conducted to evaluate the effects of plasterboard thickness, number of layers, cavity insulation and load ratios under varying fire scenarios including standard, prolonged, rapid and hydrocarbon fires.FindingsThe results reveal that two-sided fire exposure significantly reduces the load-bearing fire rating of LSF walls compared to single-sided exposure. Under rapid and hydrocarbon fire conditions, the fire rating was reduced by up to 72%. Conversely, standard and prolonged fires resulted in lower reductions. The degradation in performance varies with construction configuration and exposure type, indicating that certain wall assemblies are more vulnerable under both side fire exposure.Originality/valueThis study provides the first comprehensive computational investigation into LSF wall performance under two-sided fire conditions. The findings highlight critical gaps in current design practices, emphasizing the need for revised fire safety assessments for internal walls potentially exposed to both side fire scenarios. Designers and engineers can use these insights to improve fire resistance strategies in buildings using LSF systems.
PurposeThis study aims to systematically investigate the compressive stress-strain behavior of desert sand mortar (DSM) after exposure to elevated temperatures ranging from 100 degrees C to 700 degrees C. The research specifically evaluates the influence of the desert sand replacement ratio (DSRR) to isolate the intrinsic "matrix effect" of desert sand on thermal stability, independent of coarse aggregate interference.Design/methodology/approachPrismatic DSM specimens were prepared using Maowusu desert sand at six replacement ratios (0%-100%) and cured for 28 days. Samples were subjected to a 4 degrees C/min heating regime and tested under displacement-controlled uniaxial compression (0.006 mm/s) to capture complete stress-strain curves. The thermo-mechanical response was quantified through microstructural analysis (XRD/SEM) and the development of a modified Popovics-type constitutive model.FindingsExperimental results indicate that a DSRR of 40% optimizes peak stress and elastic modulus. A strength rebound occurs at 200 degrees C due to C-S-H gel densification and "internal autoclaving," followed by linear degradation beyond 300 degrees C. DSM retains 15-30% higher residual strength at 700 degrees C compared to conventional mortar. The proposed constitutive and empirical models achieve high accuracy, with mean square percentage errors below 15% and R2 values exceeding 0.96.Originality/valueThis work provides the first comprehensive thermo-mechanical dataset for DSM, establishing a quantitative foundation for the fire-resistant design of desert-sand-based cementitious materials. It reveals the intrinsic degradation mechanisms of the mortar phase, offering essential input parameters for the multi-scale numerical modeling of desert sand concrete structures.
PurposeUltra-high-performance alkali-activated concrete (UHP-AAC) has emerged as a low-carbon alternative to ordinary Portland cement-based ultra-high-performance concrete; however, its mechanical and dynamic performance after fire exposure remains insufficiently understood. Limited information exists regarding stiffness degradation, stress-strain evolution and dynamic response of steel-fiber UHP-AAC subjected to elevated temperatures. This study aims to evaluate the residual mechanical, stiffness and dynamic properties of steel-fiber-reinforced UHP-AAC exposed to temperatures between 200 and 600 degrees C.Design/methodology/approachCube and beam specimens were heat-cured, oven-dried and subjected to controlled thermal exposure at a heating rate of 5 degrees C/min with a 2-h retention at peak temperature. Residual performance was evaluated through compressive, flexural, stress-strain and impact-based dynamic frequency testing.FindingsResults indicate negligible strength loss at 200 degrees C, followed by progressive degradation, with compressive strength and natural frequency decreasing by approximately 49 and 45%, respectively, at 600 degrees C. Stiffness degradation occurred more rapidly than strength loss, accompanied by increased peak strain and reduced flexural capacity.Originality/valueThese findings provide insight into the thermal degradation mechanisms of UHP-AAC and demonstrate its potential as a fire-resilient, sustainable structural material, while highlighting the importance of stiffness-based post-fire assessment methods.
PurposeThis study investigates the fire resistance of encased steel tube prestressed concrete (ESPC) beams, addressing the critical challenge of prestressed systems losing strength under elevated temperatures. Conventional prestressed beams are vulnerable to fire due to prestress loss, rapid thermal penetration and spalling. Limited research has explored how load ratio, tendon cover thickness and partial prestressing ratio (PPR) collectively influence thermo-mechanical performance.Design/methodology/approachA combined experimental and analytical program was conducted, including full-scale fire exposure tests and validated finite element simulations. The study systematically varied load ratios (eta = 0.25-0.5), tendon cover thicknesses (45 mm and 70 mm) and PPR values (0.5-0.75). Key response parameters such as deflection, stiffness degradation, cracking patterns, torsional behavior and ultimate failure modes were examined up to 600 degrees C.FindingsResults revealed that a higher load ratio (eta = 0.5) significantly enhanced fire resistance by sustaining internal force equilibrium and delaying failure. Thinner covers (45 mm) accelerated thermal ingress but mitigated explosive spalling, whereas thicker covers (70 mm) effectively protected tendons, extending beam stability. PPR exerted a strong influence, with higher ratios (0.75) accelerating cracking and reducing ductility, while optimized combinations of eta, tendon cover and PPR improved residual strength and energy absorption. Balanced prestressing and confinement were shown to enhance torsional stiffness and ductility, yielding superior fire resilience.Originality/valueThis work provides the first integrated evaluation of ESPC beams under fire, establishing clear correlations between thermal degradation and mechanical response. By offering design-oriented recommendations on prestressing configuration, tendon cover and PPR optimization, the study advances structural fire engineering and guides the development of fire-safe prestressed systems.
PurposeChina has developed new fire-resistant steel grades, particularly Q420FR and Q460FR. Evaluating the residual mechanical properties of these steels after fire exposure is essential for post-fire damage assessment and potential structural reuse. This study aims to investigate the post-fire mechanical behavior of Q420FR and Q460FR steels over a wide temperature range.Design/methodology/approachExperimental tensile tests were conducted on Q420FR and Q460FR steel specimens exposed to temperatures ranging from ambient conditions to 800 degrees C, followed by natural air cooling. The residual elastic modulus, yield strength, ultimate tensile strength and ultimate strain were systematically evaluated. The test results were compared with those of other structural steels reported in the literature. Based on the experimental data, constitutive equations were proposed to predict the post-fire mechanical properties of the two steels. A reliability analysis was performed to assess the validity of the proposed models.FindingsThe results indicate that both Q420FR and Q460FR steels exhibit limited degradation in mechanical properties at temperatures up to 600 degrees C. Beyond this threshold, exposure temperature has a pronounced influence on residual strength and ductility. Compared with conventional structural steels, Q420FR and Q460FR demonstrate superior strength retention and deformation capacity after high-temperature exposure. The proposed constitutive equations show good agreement with experimental results and provide conservative predictions of post-fire strength and stiffness.Originality/valueThis study provides a comprehensive experimental evaluation of the post-fire mechanical properties of Q420FR and Q460FR steels and establishes validated constitutive models for predicting their residual performance. The findings offer valuable guidance for post-fire assessment, design and reuse of fire-resistant steel structures.
PurposeThis study investigates the synergistic degradation effects of high-temperature exposure and subsequent freeze-thaw cycles on the mechanical behavior of steel fiber-reinforced reactive powder concrete (RPC). It aims to quantify the residual mechanical properties and mass loss of RPC under these combined environmental stressors.Design/methodology/approachRPC specimens containing steel fiber volume fractions of 1.5%, 2.0% and 2.5% were subjected to thermal treatments up to 600 degrees C, followed by freeze-thaw cycles ranging from 0 to 300. The study employed a systematic experimental design to measure residual compressive strength, surface damage and mass loss.FindingsResults indicate that moderate heating (=350 degrees C) enhances strength due to internal autoclaving, while temperatures above 400 degrees C lead to significant microstructural degradation. Freeze-thaw cycles exacerbated this damage, especially after high thermal exposure. Steel fibers effectively mitigated coupled damage, with 2.0% content providing the optimal balance of strength and durability.Originality/valueThis research addresses the limited understanding of RPC durability under coupled fire and freeze-thaw stressors. Based on the experimental data, an empirical model was developed to predict residual compressive strength, providing a tool for assessing structural performance in cold regions after thermal exposure.
PurposeThe purpose of this study is to develop and validate a temperature-indexed Concrete Damage Plasticity (CDP) model to analyze the thermo-mechanical behavior of reinforced concrete beams, slabs and columns under fire exposure. By integrating temperature-dependent material properties, this research aims to provide a comprehensive approach for evaluating the degradation of mechanical properties, including damage and strain, at elevated temperatures. The findings contribute to enhancing fire safety design practices, supporting Sustainable Development Goal (SDG) 9 (industry, innovation and infrastructure) and SDG 11 (sustainable cities and communities), by improving structural resilience to fire hazards.Design/methodology/approachThis study employs a temperature-indexed CDP model to simulate the thermo-mechanical behavior of reinforced concrete beams, slabs and columns exposed to fire. Numerical simulations are conducted using finite element analysis to assess the degradation of mechanical properties such as stress, strain and damage evolution under varying temperature conditions up to 800 degrees C. Experimental data are used to validate the model's predictions. The approach integrates temperature-dependent material properties, providing a comprehensive framework for understanding the structural response to fire and offering insights for enhancing fire-resistant design in concrete structures.FindingsThe findings of this study demonstrate that the temperature-indexed CDP model accurately predicts the thermo-mechanical behavior of reinforced concrete beams, slabs and columns under fire exposure. The model effectively captures the degradation of mechanical properties, including damage and plastic strain, at temperatures up to 800 degrees C. Numerical simulations align well with experimental data, showing strong predictive capability, although minor discrepancies are observed at higher temperatures, particularly in deflection and strain. The research underscores the importance of refining temperature-dependent material properties for more accurate simulations of concrete behavior in extreme fire conditions.Originality/valueThis study provides a novel approach by developing and validating a temperature-indexed CDP model for assessing the thermo-mechanical behavior of reinforced concrete under fire exposure. The model integrates temperature-dependent material properties, offering a comprehensive framework for simulating the degradation of concrete's mechanical properties across various structural elements. The originality lies in the model's ability to accurately predict damage, strain and stress evolution at elevated temperatures, filling a critical gap in structural fire safety design. This research advances fire-resistant infrastructure design, supporting more resilient and sustainable urban structures, contributing to SDG 9 and SDG 11.
Purpose- This study aims at investigating the fire performance of pultruded Glass Fiber-Reinforced Polymer (GFRP) slabs under combined elevated temperatures (20-200 degrees C) and mechanical loading. It provides new insights into how support conditions, fire exposure sides and load ratios affect structural behavior - an area with limited quantitative analysis in the current literature. Design/methodology/approach- Finite element (FE) models are developed in ABAQUS temperature-dependent orthotropic properties and validated against previous experimental deflection-temperature curves with <10% deviation. A parametric study was then conducted to investigate the impact of support types (pinned vs fixed), fire exposure (bottom-only vs three-sided) and applied load ratios on the midspan deflection and failure thresholds. Findings- Temperature-induced deflection increased sharply near the glass transition temperature. Fixed supports improved fire resistance by 40-60% over pinned supports. Failure temperatures declined significantly with rising load ratios (from 190 degrees C at 0.25 P to 30-60 degrees C at 0.75 P). Three-sided fire exposure showed faster stiffness loss and thermal softening. Originality/value- This study provides quantitative insights into the combined effects of mechanical loading and elevated temperatures on the structural performance of pultruded GFRP slabs. The findings provide practical engineering guidance for boundary condition selection, span optimization and offer validation data for advanced FE models that incorporate realistic fire scenarios and time-dependent material degradation.
PurposeThis study is to investigate the thermal behavior of steel columns exposed to different localized vehicle fire scenarios in parking structures.Design/methodology/approachA computational fluid dynamics (CFD) simulation of vehicle fires was conducted using Fire Dynamics Simulator (FDS), followed by thermal analysis of the steel columns using ABAQUS. A one-way coupling approach was employed, where the adiabatic surface temperature (AST) output from FDS was applied as a boundary condition in the thermal model of ABAQUS. The fire simulation and transient thermal analysis coupling method were validated by comparing the predicted steel column temperatures with results from previous experimental studies, demonstrating strong consistency.FindingsTo assess the thermal response of steel columns, three key parameters were considered: different floor heights (2.5 m, 3.0 m and 4.0 m), various fire scenarios and different numbers of burning vehicles. The results indicate that flame impingement resulting from differences in storey height primarily influences the temperature at the upper portions of the columns. However, this does not lead to substantial increases in the overall temperature of the steel columns. Furthermore, simulation results show that even when a single vehicle fire propagates to ignite two adjacent vehicles, the maximum temperature of the steel columns remains relatively low.Originality/valueThis numerical study first presents an investigation into the thermal behavior of steel columns subjected to various vehicle fire scenarios, with particular emphasis on fire impingement effects across different storey heights.
PurposeCorroded reinforced concrete (RC) structures are exposed to fire during their service lives. This study aims to examine the effects of stirrup corrosion, fire exposure duration, shear-span ratio and concrete cover thickness on the shear strength and energy dissipation capacity of RC beams.Design/methodology/approachIn total, 12 RC beams were fabricated, and accelerated corrosion tests were performed on the stirrups, after which they were subjected to an International Organization for Standardization 834 standard fire. Finally, the residual shear strength was determined using four-point loading tests.FindingsThe test results indicated an alteration in the failure modes of the concrete beams owing to the combined effects of stirrup corrosion and fire. When exposed to fire for 2 h or with a stirrup corrosion degree exceeding 5%, the load-bearing capacity of the RC beam decreased by more than 30%. Similarly, the energy dissipation capacity was affected by the stirrup corrosion and fire; a stirrup corrosion degree of 12% resulted in a 33% decrease in the energy dissipation capacity after one hour of fire exposure. Finally, an updated approach for determining the shear capacity is proposed.Originality/valueThese findings provide a valuable empirical foundation for evaluating the remaining shear behavior of in-service corroded RC beams subjected to high temperatures.
PurposeThe purpose of this study is to investigate the performance and durability of commonly used construction and building materials when subjected to elevated temperatures. The research aims to understand the degradation behavior and assess key physical and mechanical properties post-fire exposure, which are crucial for designing thermally resilient and fire-safe structures.Design/methodology/approachThis study evaluates six widely used masonry units - clay brick, fly ash brick, cement brick, autoclaved aerated concrete (AAC) block, porotherm block and solid concrete block - under fire conditions based on International Organization for Standardization 834 standard fire curves. The materials were exposed to heating durations of 1 and 2 h. Parameters such as dry and wet density, water absorption, compressive strength, porosity, mass loss and residual strength were comprehensively analyzed before and after fire exposure.FindingsThe results reveal significant variation in fire performance across different materials. Clay bricks retained the highest residual strength (74.4%) and exhibited the lowest porosity increase (1.8%) after 2 h of heating, indicating superior fire resilience. Fly ash bricks, while initially strong (11.48 MPa), suffered a 47.7% strength loss post-fire. Cement bricks showed a high mass loss (35.7%) and strength reduction (37.6%), limiting their post-fire reuse. AAC blocks displayed the highest water absorption (26.2%) and porosity (8.75%), compromising their structural reliability after exposure. Porotherm blocks showed a balanced performance with moderate strength loss (27.6%) and good thermal stability, suggesting suitability for fire-prone environments. Solid blocks, though dense, experienced the greatest strength degradation (52.3%) and porosity increase (8.88%), indicating poor thermal durability.Originality/valueThe novelty of this work lies in its holistic experimental comparison of both traditional and modern masonry units under standardized fire conditions. By integrating mass loss, residual strength and porosity as post-fire durability indicators, the study offers valuable insights for material selection in fire-prone and safety-critical structures. These findings also serve as a foundation for sustainability assessment and life cycle-based decision-making in resilient construction.
PurposeConventional plasterboard linings impose a hard limit on the fire resistance of light steel frame (LSF) walls because gypsum rapidly degrades at high temperature. This study analyses whether substituting those linings with 3D-printed concrete (3DPC) can enhance load bearing fire rating (LFR) and insulation fire rating (IFR) under both standard and severe hydrocarbon fire exposures.Design/methodology/approachEighty-eight finite-element models simulated LSF walls combining steel lipped channels and 3DPC facings. Parameters varied were 3DPC thickness (25-100 mm), cavity-insulation type (rockwool or glass fibre) and infill ratio (20-100%). Critical outputs were time to reach steel temperatures of 320 degrees C, 490 degrees C and 640 degrees C (load ratios 0.6, 0.4, 0.2) and time to 160/200 degrees C on the unexposed face.FindingsReplacing 25 mm panels (IFR = 18 min in hydrocarbon fire) with 100 mm 3DPC panels extended insulation fire resistance beyond the 240-min analysis window; under the standard curve, 50 mm panels already sustained the 0.2 load ratio for over four hours. Rockwool increased IFR by up to 55% and added more than 60 min to LFR. Regression models linking thickness, fill, fire severity and insulation type achieved R2 values to 0.992.Originality/valueThis is the first systematic investigation of 3DPC-LSF walls under both rapid-rise hydrocarbon and standard fires. It supplies design-ready regression models and shows that 3DPC walls = 50 mm, especially with rockwool, deliver multi-hour structural and insulation fire resistance, up to 50% higher than plasterboard, making them a viable, fire-robust alternative for fire-safe LSF construction.
