Structural Fire Behaviour Research Articles

Influence of end restraint strength on the structural fire behavior and deterioration mechanism of RC frame beams

AbstractThe end restraint strength of the reinforced concrete (RC) beams under the fire conditions may greatly influence the inner force redistribution and the structural behavior of the beams, even the stability of the whole structure. The structural fire behavior of two full‐scale frame beams with different end restraint strength under load were studied based on experiment and simulation. The temperature field, reinforcement strain, beam deflection, end axial displacement, and rotation angle of the structure during the whole heating and cooling process were measured. The influence of end restraint strength on the structural behavior was analyzed. The results show that the vertical displacement, axial force, end bending moment, and angular displacement first increase rapidly, then decrease gradually and become stable in the whole process; the lateral displacement increases first and then stabilizes; the change of axial and rotational deformations appeared to be non‐proportional with the corresponding restraining forces, reflecting that the axial and the rotational restraint strength at the ends of the beams decreased with the rise of temperature. The restraining strength of beams that submitted to fire globally decreased faster, and leading to a severe fire response and an earlier failure of the structure. The analysis results and the conclusions will supply scientific basis for the fire‐resistance design and safety evaluation on complex structures.

Fire behaviour of damaged wood–steel–wood beam connections retrofitted with self-tapping screws — experimental study

This experimental study aimed to investigate the structural fire behaviour of damaged glulam beam connections retrofitted using self-tapping screws (STS). Four full-size glulam beam-end bolted connections with wood–steel–wood connection configurations using four or six bolts arranged in two different bolt patterns were examined. All connections were retrofitted using STS after being deliberately damaged through physical testing until failure. In a subsequent stage, the retrofitted connections were experimentally tested under standard fire exposure while subjected to the maximum design load of the weakest, undamaged, unreinforced connection configuration. The influence of the application of STS in terms of preventing wood-splitting propagation and maintaining reasonable fire resistance for the retrofitted connections was experimentally investigated and proven in this study. Results show that the retrofitted glulam beam connections maintained a minimum of approximately 67% of the failure time of identical but undamaged, unreinforced connections under standard fire exposure.

Developing customized fuel models for shrub and bracken communities in Galicia (NW Spain)

Geospatial fire behaviour and fire hazard simulators, fire effects models and smoke emission software commonly use standard fuel models in order to simplify data collection and the inclusion of complex fuel scenarios. These fuel models are often mapped using remotely sensed data. However, given the great complexity of fuelbeds, with properties that vary widely in both time and space, the use of these standard fuel models can greatly limit accurate fuel mapping. This affects fuel hazard assessment, fuel reduction treatment plans, fire management decision-making and evaluation of the environmental impact of wildfire. In this study, we developed unique customized fire behaviour fuel models for shrub and bracken communities, by using k-medoids clustering analysis based on both fuel structural characteristics and potential fire behaviour. We used an original database of 722 destructive sample plots in nine different shrub and bracken communities covering the entire distribution area in Galicia (NW Spain), one of the regions in Europe most affected by forest fires. Measurements of cover, height and fuel fractions loads differentiated by size and vegetative state (live or dead) were used to estimate the potential rate of fire spread with five different models including fireline intensity, heat per unit area and the flame length for each sampling site and considering extreme environmental conditions. The optimal number of clusters was established by combining practical knowledge about the shrubland communities under study and their associated fire behaviour, with maximization of the mean value of the silhouette variable and minimization of the within-cluster sum of squares. The structural characteristics of the medoids derived from the analysis were associated with each of the proposed customized fuel models. Finally, a simple dichotomous classification based only on shrub height was developed to enable construction of spatially explicit fuel model maps based on remotely sensed data. Thus, the methodology applied allows generation of a more realistic representation of fuel distribution in the landscape, based on fuel structure measurements of natural regional ecosystems rather than on the use of standard models. We believe that the proposed methodology is generally applicable to communities composed of other shrub and fern species in different biogeographical regions.

Burnout resistance of concrete‐filled steel tubular (CFST) columns under realistic fire conditions

AbstractIn this paper, we investigate the structural behaviour of concrete‐filled steel tubular (CFST) columns under various fires. Our contribution is based on two fire scenarios in modelled FDS with subsequent 3D FE numerical analysis (Abaqus), where material properties are defined for heating and cooling using user subroutines. Our goal is to examine the burnout resistance of CFST columns under different realistic fire scenarios involving varying number of burning cars.The loss of compressive strength of concrete due to high temperature is irreversible. Hence, the burnout resistance is affected by the field of the highest temperatures reached inside the column. Moreover, the pre‐existing load affects the deformation of the column during heating and influences the post‐fire behaviour. The analysis is performed in several steps: first, results from the CFD models are extracted and appropriately mapped, then the heat transfer analysis between fire and solid is performed, and the resulting temperature history of the CFST column is calculated. Subsequently, a mechanical analysis is performed, where (1) the column is loaded, (2) the analysis of the column's structural fire behaviour is carried out, (3) if the column sur‐vives burnout, then in the last step, it is loaded until failure.

Material characterisation tests of ultra‐high‐strength steels S960QL and S1100M under natural fire conditions

AbstractFire hazards represent one of the most important threats to the built environment with serious economic consequences for society and most dangerous threats to life. Fire engineering is the key discipline to improve fire safety in the building environment in a cost‐effective manner. Comprehensive knowledge of the material behavior is the basis for a thorough understanding and a realistic modeling of the structural fire behavior of steel structures. For state‐of‐the‐art buildings with increasing requirements, the utilization of high‐strength steels is favorable, as they can contribute to resource and energy efficiency due to their good strength‐to‐weight ratio. Modern production processes enable the production of structural steels with very high nominal yield strengths. For those ultra‐high‐strength steels there are currently no experimental results available regarding the material behavior in case of fire and the post fire residual strengths. The paper provides experimental data of the first test program regarding the constitutive material behavior of ultra‐high‐strength steels of grades S960QL and S1100M in the case of fire, taking into account the entire fire progress including the heating and cooling phases and the post fire range.

Structural-fire responses forecasting via modular AI

This study analyses the structural response of an aluminium reticulated roof structure that is constructed at Sichuan Fire Research Institute (Sichuan, China), and to be tested in fire. The structural fire behaviour under 960 localised fire scenarios is considered first, and then used to construct a database for training a modular artificial intelligence (AI) system for real-time forecasting. The system consists of several AI models, each of which predicts the displacement at a specific monitoring point. These individual predictions are then combined to generate a comprehensive forecast of the global structural-fire behaviour. The individual AI model utilized is a Long Short-Term Memory Recurrent Neural Network (LSTM RNN). The modular design allows different models to be modified or added as needed, making the system flexible and adaptable, and improving the accuracy and reliability of the predictions. The results demonstrate the effectiveness of the modular AI approach in accurately forecasting fire-induced structural collapses as indicated by the sensitivity the local models can have. The key objective of this research is to help to make informed decisions and prioritize efforts to minimize the risk of structural collapse in fire.

Hybrid fire collapse simulation of reinforced concrete structures under localized fires

The safety of extensive reinforced concrete (RC) buildings under sudden fire scenarios is of particular concern nowadays. Localized fires may bring serious damage and even collapse to the RC bearing structures, causing huge casualties and economic losses. However, due to the limitations of test facilities, technology, and high costs, etc., full-scale and even reduced-scale structural fire tests have been very limited. The recent development of numerical techniques instead of challenging physical tests has provided exciting prospects for refinement of structural fire behavior prediction. This paper is therefore focused on a hybrid fire collapse simulation method through performing damage analysis of the locally fire-heated components and collapse simulation of the remaining major structure. The damage and failure behavior of the fire-exposed substructure is simulated based on an energy-based elastoplastic damage model for concrete at elevated temperatures. While the resulting deformation and collapse of the rest main structure is modeled by conventional collapse analysis. The key to the hybrid simulation is the coordination of internal forces and deformations between the substructure and the main structure. The developed method allows for an integrated simulation of the whole process from high temperature damage of materials to fire destruction of local components and to the collapse of the entire RC structure.

Structural Stability Verification for Steel Beam‐columns in Fire ‐ a Consistent Approach with Ambient Temperature Rules

AbstractSteel structures are characterized by a slender design, which makes stability verifications particularly important. While the design methods for steel members at ambient temperatures have been continuously developed and revised for the second generation of Eurocode 3, the method for elevated temperatures in prEN 1993‐1‐2 is still based on the corresponding rules of ENV 1993‐1‐1 of 1992. This leads to a divergence of methodology for ambient and elevated temperatures and to unnecessarily complex design methods for the engineering practice. Therefore, a harmonization of design models for ambient temperature and fire design is desirable.This paper presents a theoretical and numerical study on the stability behaviour of steel members at elevated temperatures. The structural fire behaviour of steel beams, columns and beam‐columns, i.e. flexural buckling under pure compression, lateral torsional buckling under major axis bending and spatial buckling of members under combined bending and axial compression has been investigated. Based on results available in the literature as well as an extensive numerical parametric study, reduction factors and interaction factors were determined. The new reduction and interaction factors were used to develop a design model for the member stability verification in fire that follows the format of FprEN 1993‐1‐1. Thus, engineering practice is provided with a harmonized verification method for steel members in bending and compression for ambient temperature and fire design.

Review and discussion on fire behavior of bridge girders

This paper presents an overview on fire behavior of bridge girders mainly including prestressed concrete (PC) bridge girders and steel bridge girders. The typical fire accidents occurred on bridges are illustrated and, the seriousness of posing threats to bridge structures resulted from increasing traffic fires, specially intense hydrocarbon fires generated from petrol-chemicals, is highlighted. The current researches, embracing high-temperature properties of constituent materials, prestress state, measurement in fire tests, numerical methods, structural fire resistance, and so forth, taken on coping with problems existing in fire behavior and structural fire behavior in bridge girders are reviewed and discussed. Further, strategies for enhancing fire resistance of bridge girders followed with failure criterion and mode in types of bridge structures are provided. Future research area along with emerging trends in structural fire behavior of bridge girders is also recommended for mitigating fire hazards occurred on bridge girders. Herein, it can be attained a conclusion from review and discussion that prestressed concrete bridge girders with thin webs, specially T-shaped bridge girder, are prone to unstable under fire exposure conditions. High-strength concrete utilized in prestressed concrete bridge girders is vulnerable to spalling at elevated temperature. Steel-truss bridge girder present a more significant fragility to fire exposure compared than other steel bridge girders. • Fire behavior of bridge girders is reviewed and discussed. • Seriousness of bridge fires is highlighted. • Strategies for enhancing fire resistance of bridge girders are provided. • Fire resistance in types of bridge girders is investigated and presented. • Steel-truss bridge girders are significantly vulnerable to fire damage.

Load ratio effects on the structural fire behaviour of glass fibre‐reinforced polymer‐reinforced concrete beams with mid‐span bar lap splices – Experimental study

AbstractFibre‐reinforced polymer (FRP)‐reinforced concrete members have been gaining attention as an alternative to conventional steel‐reinforced concrete members due to their advantageous characteristics. A few to mention are excellent resistance to corrosion, high strength‐to‐weight ratio, and reduced maintenance cost in the long term. Nevertheless, FRPs are often limited in use mainly due to fire safety considerations since they can encounter significant deprivation of strength and bond with concrete in fire conditions. This paper presents the results of an experimental study aimed to investigate the effects of the applied load level on the structural behaviour of glass fibre‐reinforced polymer (GFRP)‐reinforced concrete beams having mid‐span bar lap splices when exposed to standard fire. Two 2750‐mm long beams with cross‐sectional dimensions of 300 mm wide × 350 mm high were exposed to elevated temperatures that followed the CAN/ULC‐S101 standard fire time–temperature curve while being subjected to a load level equivalent to 85% of the beam ultimate design load. The experimental results of the two beams were compared to those obtained for identical beams but subjected to a lower load level that is equivalent to only 40% of the beam's ultimate design load. Results show that the increased load level (slightly more than double the load ratio) unexpectedly did not impact the fire resistance time of the GFRP‐reinforced concrete beams but affected other structural responses of the beam, such as its midspan deflections and cracking patterns.

The Collapse of World Trade Center 7: Revisited

The catastrophic events of September 11, 2001, stand out as a major motivation for research on improving the understanding of structural behaviour in fire. These events included the first complete collapse of a tall steel framed structure solely due to fire. World Trade Center 7 (WTC7) was a 47-storey office building within the WTC complex that collapsed due to a fire initiated by debris from the collapse of WTC1. In the following years, detailed investigations were carried out by expert teams to pinpoint the cause of the progressive failure of WTC7. Each of the expert teams analysed the fire and structure and made varying conclusions with regards to the mechanisms responsible for initiating and propagating the collapse of the building. This paper revisits the collapse of WTC7 and its investigation, and then explores the hypothesis that a potential hydrocarbon fire may have compromised the large transfer structure within the mechanical space of the building. This is done via two OpenSees finite element models. The first model explores the thermomechanical response of the mechanical floors to a potential diesel fire, and the second investigates the response of the structure to a failure caused by that fire. The outcome of the analyses shows that it is feasible that a mechanical room fire could lead to a failure in the transfer structure, which would then result in the loss of support to at least two columns within the building core. The failure of these columns may unbrace the eastern-most core columns and precipitate in the failure of the structure as observed on 9/11.

Finite element model for the steel-polymer composite floor filled with phase-change amorphous polymers at elevated temperatures

In this study, a steel-polymer composite floor filled with PU, an amorphous polymer with irregular polymer chains, was introduced. Because these sandwich-type floors have significant structural performance at ambient temperatures, actual buildings in Korea selected them as floor members. In addition, the fire behavior of composite floors has been investigated in several studies. However, it is highly complicated to define an analytical model for the behavior of the floors owing to the phase changes of the amorphous polymers. Therefore, a finite element model considering the phase change of the polymers is proposed in this study. The proposed model considers the composition of the polymers depending on the phase changes at elevated temperatures, as defined by material and furnace heating tests. Next, several factors, such as porosity, volumetric expansion of polymer gasification, and phase-change temperatures, were investigated to model the material properties. The analysis results from the proposed model considering the factors were compared with the furnace heating tests to obtain reliability. Porosity generally influences the structural fire behavior of composite floors, whereas the volumetric expansion of gasification partially influences the structural fire behavior after gasification. In addition, the entire phase-change temperatures provide information on the structural fire behavior depending on each characteristic, and the gasification temperature particularly provides information on the start time for large expansion owing to gasification. Finally, the fundamental behavior of the composite floors at elevated temperatures is defined by the investigations, and this can be used to predict the structural fire behavior of new steel-polymer composite floors filled with new amorphous polymers that will be improved or have different properties with finding the factors to derive the thermal expansion coefficients.

EXPERIMENTAL STUDY ON BEHAVIOR OF UNPROTECTED FOAMED CONCRETE FILLED STEEL HOLLOW COLUMN UNDER FIRE

Reduction in self-weight and achievement of full fire resistance requirements are some of the important considerations in the design of high-rise structures. Lightweight concrete filled steel tube (CFST) column provides an alternative method to serve these purposes. Recent studies on lightweight CFST columns at ambient temperature have revealed that foamed concrete can be a beneficial and innovative alternative material. Hence, this study investigates the potential of using foamed concrete in circular hollow steel columns for improving fire resistance. A series of nine fire test on circular unfilled hollow and foamed concrete filled hollow section column were carried out. ISO 834 standard fire exposure test were carried out to investigate the structural response of these columns under fire. The main parameters considered are load level and foamed concrete density; foamed concrete density used are 1500 kg/m3 and 1800 kg/m3 at 15%, 20%, and 25% load level. All the columns tested are without any external fire protection, with concentrically applied load under fixed-fixed boundary conditions. The columns dimension was 2400 mm long, 139.7 mm diameter and steel tube thickness of 6 mm. The fire test result showed that foamed concrete increases the fire resistance of steel hollow column up to an additional 16 minutes. The improvement is more at load level above 15%, and the gain in fire resistance is about 71% when 1500 kg/m3 density foamed concrete is used. Generally, foamed concrete filled steel hollow column demonstrate a good structural fire behavior, based on the applied load and foamed concrete density. Also, inward local buckling was averted by filling the steel hollow column with foamed concrete. General method for composite column design in Eurocode 4 adopted to calculate the axial buckling load of 1500 kg/m3 foamed concrete filled columns. These type of columns can be used for structures like airports, schools, and stadiums; taking the advantage of exposed steel for aesthetic purpose and high fire resistance. It can also be used for high rise structures; taking advantage of high fire resistance and reduction in self-weight of a structure.

Experimental analysis of cross-laminated timber rib panels at normal temperature and in fire

The results of an experimental programme on the structural behaviour, fire behaviour, and fire resistance of CLT rib panels are presented. The floor system consists of cross-laminated timber (CLT) plates rigidly bonded to glued-laminated timber ribs by means of screw-press gluing.The experimental programme comprised ultimate-load tests at normal temperature as reference tests and full-scale fire resistance tests on four cross-sections. In addition to the reference tests, shear tests of the glue line between CLT plate and glued-laminated timber rib were performed for analysis of the cross-sections’ composite action.The results of the reference tests show good agreement with results based on the simplified method according to EN 1995-1-1 [1] and its final draft of CLT design [2]. The importance of the glue line’s quality was confirmed. The fire resistance tests show results on the safe side compared to predictions of the fire behaviour according to EN 1995-1-2 [3] and its actual draft [4]. However, the fire resistance was underestimated due to conservative assumptions about the composite cross-section’s structural behaviour.The experimental programme addressed the fire behaviour and fire resistance of CLT rib panels currently not covered in standards. The project’s overall aim is the development of design rules in fire for EN 1995-1-2.

Experimental fire testing of large‐scale glass fibre‐reinforced polymer‐reinforced concrete beams with mid‐span straight‐end bar lap splices

SummaryAdopting glass fibre‐reinforced polymer (GFRP) rebars as a replacement of conventional steel reinforcement in different infrastructure applications is mainly attributed to its corrosion resistance and considerable lightweight‐to‐high strength ratio. However, the use of FRP rebars in construction is still limited due to the degradation of its mechanical properties at elevated temperatures. The experimental work presented in this paper aimed to investigate the structural fire behaviour of concrete beams reinforced with GFRP bars having lap splices at the beam mid‐span. Four identical 2750‐mm long concrete beams with cross‐sectional dimensions of 300 mm × 350 mm were experimentally examined under four‐point flexure bending. A 60‐mm thick concrete cover was used on the bottom, front and back sides of all beams. Two beams were tested as control specimens in ambient condition, while the other two beams were exposed to standard fire while subjected to a transverse load equivalent to 40% of the beam ultimate design moment. Experimental results show that concrete beams sustained the applied loads for a minimum of 53 minutes in standard fire conditions. Also, both test beams failed due to slippage of the spliced bars when the temperature measured at the top of the middle bar approached its glass transition temperature.

Experimental and numerical analysis on the structural fire behaviour of three-cell hollowed concrete masonry walls

Masonry is one of the oldest and most traditional materials in building construction. Nevertheless, the knowledge on the structural fire behaviour of masonry elements is not yet well consolidated. The literature on the load-bearing capacity of masonry walls in case of fire showed an enhanced performance of these elements, however the lack of normative documents, characterization of material properties at high temperatures and experimental results, for calibrating and validating the numerical models, indicates the need of further research. A research study on the structural fire behaviour of three-cell hollowed concrete masonry walls subjected to fire is presented based on results of experimental and numerical studies. First, several loadbearing capacity tests at high temperatures and fire resistance tests on the walls, were carried out in order to assess their behaviour, critical times, failure modes and temperature distribution. The specimens were built with three cell concrete blocks and M10 mortar and were then subjected to an in-plane serviceability load during test. The temperatures, loads and displacements were measured. Second, finite element models were developed and validated with the experimental results. The experimental and numerical results were also compared with the ones given by EN1996-1–2 provisions.

Assessing fire frequency and structural fire behaviour of England statistics according to BS PD 7974-7

Contemporary structural fire statistics are fundamental in engineering design practice to evaluate likelihood and consequence of fire for different property types, and to investigate how different safety measures impact fire spread. British Standard PD 7974-7:2003 has recently been updated using USA fire statistics; this paper compares PD 7974-7:2003 to current England statistics (named UK statistics) using one public and one Home Office dataset. PD 7974-7:2003 overestimates fire frequency with values up to 5 times greater than the ones found in UK and USA. When fire frequency is plotted against total floor space, for different property types, power laws with positive or negative exponent and polynomial functions provide better approximations of the data than the current codes. Average area damage from PD 7974-7:2003 has been compared to fire and total damage from UK datasets where fire size is usually well confined to room of origin at 20% of fires based on the publicly available dataset. When fires exceeding specific areas of damage are considered, PD 7974-7:2003 usually overestimates fire damage and underestimates total damage, with more damage evident when sprinklers are absent compared to when they are present.

Thermo-mechanical analysis of reinforced concrete slab using different fire models

Coupled thermo-mechanical analysis of reinforced concrete slab at elevated temperatures from a fire accounting for nonlinear thermal parameters is carried out. The main focus of the paper is put on a one-way continuous reinforced concrete slab exposed to fire from the single (bottom) side as the most typical working condition under fire loading. Although contemporary techniques alongside the fire protection measures are in constant development, in most cases it is not possible to avoid the material deterioration particularly nearby the exposed surface from a fire. Thereby the structural fire resistance of reinforced concrete slabs is mostly influenced by a relative distance between reinforcement and the exposed surface. A parametric study with variable concrete cover ranging from 15 mm to 35 mm is performed. As the first part of a one-way coupled thermo-mechanical analysis, transient nonlinear heat transfer analysis is performed by applying the net heat flux on the exposed surface. The solution of proposed heat analysis is obtained at certain time steps of interest by a-method using the explicit Euler time-integration scheme. Spatial discretization is done by the finite element method using a 1D 2-noded truss element with the temperature nodal values as unknowns. The obtained results in terms of temperature field inside the element are compared with available numerical and experimental results. A high level of agreement can be observed, implying the proposed model capable of describing the temperature field during a fire. Accompanying thermal analysis, mechanical analysis is performed in two ways. Firstly, using the guidelines given in Eurocode 2 - Part 1-2 resulting in the fire resistance rating for the aforementioned concrete cover values. The second way is a fully numerical coupled analysis carried out in generalpurpose finite element software DIANA FEA. Both approaches indicate structural fire behavior similar to those observed in large-scale fire tests.

Structural fire performance of wood-steel-wood bolted connections with and without perpendicular-to-wood grain reinforcement

PurposeIn fire condition, the time to failure of a timber connection is mainly reliant on the wood charring rate, the strength of the residual wood section, and the limiting temperature of the steel connectors involved in the connection. The purpose of this study is to experimentally investigate the effects of loaded bolt end distance, number of bolt rows, and the existence of perpendicular-to-wood grain reinforcement on the structural fire behavior of semi-rigid glued-laminated timber (glulam) beam-to-column connections that used steel bolts and concealed steel plate connectors.Design/methodology/approachIn total, 16 beam-to-column connections, which were fabricated in wood-steel-wood bolted connection configurations, in eight large-scale sub-frame test assemblies were exposed to elevated temperatures that followed CAN/ULC-S101 standard time-temperature curve, while being subjected to monotonic loading. The beam-to-column connections of four of the eight test assemblies were reinforced perpendicular to the wood grain using self-tapping screws (STS). Fire tests were terminated upon achieving the failure criterion, which predominantly was dependent on the connection’s maximum allowed rotation.FindingsExperimental results revealed that increasing the number of bolt rows from two to three, each of two bolts, increased the connection’s time to failure by a greater time increment than that achieved by increasing the bolt end distance from four- to five-times the bolt diameter. Also, the use of STS reinforcement increased the connection’s time to failure by greater time increments than those achieved by increasing the number of bolt rows or the bolt end distance.Originality/valueThe invaluable experimental data obtained from this study can be effectively used to provide insight and better understanding on how mass-timber glulam bolted connections can behave in fire condition. This can also help in further improving the existing design guidelines for mass-timber structures. Currently, beam-to-column wood connections are designed mainly as axially loaded connections with no guidelines available for determining the fire resistance of timber connections exerting any degree of moment-resisting capability.

Elevated temperature performance of restrained stainless steel beams

This paper reports the results of a numerical investigation into the response of axially restrained austenitic stainless steel beams in fire, where in addition to the degradation of strength and stiffness at elevated temperatures, the influence of thermally induced stresses, are also included. The finite element (FE) programme ABAQUS has been used to model austenitic stainless steel welded I-section beams of different axial end restraint stiffness subjected to fire. The FE models are firstly validated against a selection of literature test data, which are shown to accurately capture the effects of restrained thermal deformations with a high degree of accuracy, and then used to perform parametric studies to further explore the structural behaviour in fire. A simplified analytical model for predicting the restraint axial force-temperature response is presented and validated against the numerically obtained results. The numerical models and the simplified analytical model allow the influence of frame continuity to be explicitly considered in design of stainless steel members in fire to quantify the required strength and ductility demands on connections for catenary action to develop. Comparisons with carbon steel beams demonstrate that while austenitic stainless steel beams show similar stages of behaviour in fire, they are capable of withstanding higher temperatures prior to the onset of catenary action, while developing similar levels of maximum tensile catenary force to carbon steel beams, despite the higher thermal expansion of the material.