Standard Fire Resistance Test Research Articles

Full-scale hybrid fire test in real-time with multiple degree of freedom

To experimentally assess the fire resistance of civil structures, testing whole structures is very costly but the standard tests on individual structural elements can sometimes be too simplistic, regarding their boundary conditions. Hybrid fire testing offers a promising solution to these limitations, but performing such tests is technically challenging and few full-scale tests have been conducted. Current approaches rely on high-performance sensors and actuator systems, as well as assumptions about the stiffness of the tested element. This paper presents the detailed methodology and results of a full-scale, real-time test with 3 degrees of freedom on a concrete beam. The use of an adaptive controller allowed for maintaining stability and achieving reasonable precision despite the use of relatively low-precision sensors, regular hydraulic actuators, and no assumptions about the tested element’s stiffness. The comparison with the same element tested using a standard fire resistance test demonstrates the usefulness of this technique in achieving a more accurate representation of the performance of the tested element in realistic conditions.

Study on mechanical properties and fire resistance of porous ceramic silicone rubber

AbstractPorous ceramic silicone rubber (PCSR) has an excellent ablative resistance because of its strong carbon layer structure after burning. However, as a marine sealant material, it also needs to have better mechanical properties for better application. In this study, PCSR composites were prepared by compounding with different additives and different viscosity base adhesives, and their fire resistance, tensile properties, and bond strength of multiple substrates at different temperatures were investigated and compared. When the ratio of 20,000 to 80,000 viscosity matrix adhesive is 3:7, the material prepared by adding deketoxime crosslinker and silane coupling agent containing amino and epoxy groups together can reach more than 1.4 MPa tensile shear strength at 150°C. Sintering experiments have shown that PCSR composites can still maintain the strength and integrity of the carbon layer structure, and the results of the A‐60 standard fire resistance test for cable and pipe penetration devices have shown that marine PCSR sealants can effectively prevent flame propagation.

Thermal response of high-speed train multi-layer composite floor structure: Experimental and numerical analysis

This study examines the issue of fire resistance in multi-layer composite floor structures for high-speed trains. A standard test was conducted to evaluate the thermal insulation and integrity of the structure, and a 1-D numerical simulation model was established to calculate the fire resistance accurately. The fire resistance test results show that the aluminum profiles and glass wool played an important role in the fire resistance of the high-speed train floor structure. The upper surface temperature of the glass wool remained below 150 °C during the initial 30 min of the fire test, and the glass wool maintained its structural integrity for an additional 4.33 min after the aluminum profile was burnt through. This study validates the established model by comparing the simulation results with the standard structural fire resistance test result. The floor temperature distribution from the numerical simulation is consistent with the experimental results, and the error in integrity and thermal insulation is only 2.6 % and 5.4 % compared with the experimental value.

Evaluating fire resistance of timber columns using explainable machine learning models

The global attention to using timber products as sustainable construction material urges careful assessment of their performance against different hazards, particularly fire. However, the current methods prescribed by design codes for evaluating the fire resistance of timber components tend to underpredict the outcomes of standard fire resistance tests, and lack interpretability due to the use of semi-empirical equations. This study develops explainable data-driven models to predict fire resistance of timber columns using geometry- and material-related properties based on a comprehensive experimental database. Nine different single and ensemble-based machine learning algorithms were trained, and their performance was optimized through rigorous hyperparameter tuning and feature selection. The best models were then interpreted using partial dependence and Shapley plots to infer the underlying relationship between fire resistance and column properties. Lastly, the models’ predictive capabilities were compared to available prescriptive equations. The results show that a random forest-based model provides the best performance with an average ratio of predicted to observed fire resistance of 1.03 on the test set. The random forest prediction is mainly governed by column capacity at ambient temperature, and to a lesser degree, columns’ cross-section dimension. In addition, the partial dependence plots indicate that the effect of density, modulus of elasticity, length, and compressive strength on fire resistance was not notable. Finally, while the considered prescriptive equations consistently underpredict fire resistance, the random forest model provides a consistently accurate and balanced prediction.

Full-scale fire resistance tests of lightweight steel framed floor systems

As cold-formed steel profiles are increasingly used for load-bearing structural systems, their fire design requires specific attention due to their thin-walled nature and high slenderness. In some specific applications such as in storage hall floor systems, these structures are used without sheathing or thermal protection on the fire-exposed side. Yet, there is a lack of data from fire resistance tests on full-scale load-bearing thin-walled steel structures, especially with directly exposed steel. This article describes two standard fire resistance tests on full-scale light gauge steel frame floors made of cold-formed steel lipped channel girders and joists topped by chipboard panels. The experimental program was designed to investigate the fire resistance of the unprotected girders. A specificity of this program was that the girders were subjected to a low load level to probe the ability to achieve without passive fire protection a 30-min fire resistance rating typical for storage hall structures in the Czech Republic. The absence of protection resulted in differences in thermal gradients and bracing compared to common fire tests, as well as a very low degree of utilization leading to an expected failure temperature higher than 800 °C. The results showed that the two floors remained stable during the 30 min with limited deflections, but failed the deflection rate criteria after 24 and 22 min, respectively. Comparison is provided with the calculation methods from the Eurocodes. The presented results provide new data on the response of full-scale, unprotected cold-formed steel floor systems subjected to fire, which can be used to calibrate numerical models and fire design methods outside of the range currently covered by the codes.

Experimental Study on the Structural Performance of Reinforced Truss Concrete Composite Slabs during and after Fire

Standard fire resistance tests and post-fire tests on residual mechanical properties were carried out on two four-edge simply supported reinforced truss concrete two-way composite slabs with wide seam splicing (“integral seam”) and close seam splicing (“separated seam”), and the effects of the different splicing forms on the mechanical properties of the reinforced truss concrete composite slabs during and after exposure to high temperatures were explored. The results indicate that there are significant differences in terms of crack developments, moisture loss times on the slab surface, spalling characteristics of the bottom of the slab and cross-section temperature gradients of concrete and steel reinforcement along the thickness direction between the wide seam spliced reinforced truss concrete composite two-way slab (referred to as “S1 composite slab”) and the close seam spliced reinforced truss concrete composite two-way slab (referred to as “S2 composite slab”) in the fire test. This is mainly due to differences in the splicing forms and structural measures of the prefabricated base slabs at joints, which led to changes in the heat transfer path at the joints. As the temperature at the close seam can be released quickly, the stiffness recovery of the S2 composite slab is significantly greater than the stiffness weakening due to the thermal hysteresis of the concrete, so the deflection of the S2 composite slab recovers immediately after the fire stops. Overall, both the S1 and S2 composite slabs exhibit two-way high temperature deformation characteristics. The post-fire residual static load tests show that the static load-carrying capacity of the S1 composite slab is 12.08% higher than that of the S2 composite slab and the ultimate displacement is 8.74% lower than that of the S2 composite slab. It is appropriate to calculate the residual load capacities of the S1 and S2 composite slabs after the fire as a one-way slab.

Numerical and Experimental Analysis of Fire Resistance for Bulkhead and Deck Structures of Ships and Offshore Installations

Investigating the loss of integrity (E) in cabin walls and decks, as well as the role of insulation capabilities, holds significant implications for preventing serious human, economic and environmental damage caused by the ignition of cabins in ships and ocean platforms due to fires and explosions. In this study, the fire resistance of A-60 class ship bulkheads and decks was evaluated through two groups of standard fire resistance tests. In the first test, the steel structure side of the bulkhead was exposed to the fire, while in the second test, the mineral wool and L-shaped stiffeners side of the deck was exposed to the fire. Numerical material models for steel and mineral wool were established based on standards, and the temperature distribution and structural deformation were simulated using Abaqus. The results showed a good correlation with the experimental data. The maximum and average temperature increases on the unheated surface of the bulkhead during the standard fire resistance test were 158 °C and 136 °C, respectively. The corresponding values for the deck were 176 °C and 138 °C. Upon the conclusion of the experiment, the maximum displacement deformation in the direction towards the furnace from the center of the cabin wall was 54 mm, and from the center of the deck, the maximum displacement deformation towards the furnace was 28 mm. This research can provide guidance for the design of fire-resistant ship compartment structures.

Post-earthquake fire performance of fire door sets

This paper presents the results of an experimental cyclic and fire test program to investigate the fire performance of fire door sets after experiencing simulated earthquake damage. The earthquake damage mimics that of a 35-story tall residential benchmark building subject to design earthquake intensity level, inducing an inter-story drift of 57 mm. Three earthquake-damaged 90-min rated fire door sets were subject to displacement controlled quasi-static cyclic loading test at ambient temperature and then to standard fire resistance tests. Results of cyclic load tests at ambient temperature reveal severe distortion of the fire door frames and excessive gaps, notably at top corners. Results of the subsequent standard fire resistance tests show that the fire resistance of the damaged fire door sets decreased by as much as 70%. The reduction can be attributed to large gaps due to the distorted door geometry after seismic loading, substantial loosening of the door hinges and damaged intumescent seals around the door. Maximum gap measurement of 8 mm between the door and door frame is considered as the threshold above which the fire compartment is compromised, and fire door set replacement is necessary.

Comparison of a Standard Fire-Resistance Test of a Combustible Wall Assembly with Experiments Employing Pre-defined Heat Release Curves

Comparison of a Standard Fire-Resistance Test of a Combustible Wall Assembly with Experiments Employing Pre-defined Heat Release Curves

Comparative energy analysis from fire resistance tests on combustible versus noncombustible slabs

SummaryStandard fire resistance tests have been used in the design of structural building elements for more than a century. Originally developed to provide comparative measures of the level of fire safety of noncombustible products and elements, the recent resurgence in engineered timber construction raises important questions regarding the suitability of standard fire resistance tests for combustible structural elements. Three standard fire resistance floor tests (5.9 m × 3.9 m in plan), one on a concrete slab and two on cross‐laminated timber (CLT) slabs, were undertaken to explore some of the relevant issues. The fuel consumption rate within the furnace was recorded during these tests, and the energy supplied from this was determined. An external fuel supply (from natural gas supplied to the furnace) equating to approximately 3 MW was recorded throughout the concrete test, whereas this was about 1.25 MW throughout the CLT tests. The total heat release rate was calculated using carbon dioxide generation calorimetry; this yielded values of approximately 1.75 MW during the CLT tests (ie, an additional energy contribution of approximately 0.5 MW from the timber). This demonstrates that considerably more energy input (by about 1.25 MW) was needed to heat the system when the test sample was noncombustible. A further series of six large‐scale compartment fire experiments (6 m × 4 m × 2.52 m) was undertaken to further explore comparative performance of combustible versus noncombustible construction when the external fuel load is kept constant and is governed by more realistic compartment fire dynamics. For a fuel‐controlled case, the peak temperatures in the compartment with an unprotected CLT ceiling were approximately 200°C higher than in the compartments with a concrete ceiling, whereas for a ventilation‐controlled case, the compartment with a CLT slab ceiling displayed a burning duration that increased by approximately 15 minutes. Potential implications for standard fire resistance testing of combustible specimens are discussed.

Development and application of a simulation approach for fire and structure interaction of concrete members subject to spalling

SummaryThis paper describes the development and illustrates the use of an approach to model the mechanical performance of a concrete bridge and its structural components exposed to fire and subject to spalling. The work is motivated by some recent fire incidents that involved concrete bridges, the poor state of an increasing number of bridges throughout the United States (which makes them more vulnerable to fire damage), and the lack of design codes and standards that adequately protect bridges against fire. An important objective of the work is to develop a method to predict spalling that captures the principal physical and chemical phenomena but is simple enough so that it can be implemented in a 3‐D structural simulation. The first step in the approach involves using a hydrothermal model to determine if and at what temperature spalling occurs for a specified concrete mix (defined by its composition, type of aggregate, water‐cement ratio, porosity, permeability, etc), free moisture content, and heating rate. The second step uses the resulting “critical spalling temperature” in a coupled thermal and mechanical analysis to determine how spalling affects the performance of the concrete member. The approach is illustrated for two standard fire resistance tests conducted on posttensioned concrete slab systems reported in the literature. The paper concludes with a list of recommendations for additional work to improve the predictive capability of the heat and mass transfer and structural models and to address several challenges with the implementation of the spalling criteria in the structural model.

Fire technical properties of intumescent and ablative fire resistant glass

Conventional glass materials are weak spots in building fires, and fire codes requires installing fire-resistant glass in specified places. Apart from assessing fire resistance of glass panels by standard tests, there are no universal standards in fire-resistant glass specifications. In standard fire resistance tests, the most relevant performance criteria of fire-resistant glass are integrity, insulation, and radiation. The chemical compositions of the glass products, which depend on the manufacturing method and the required fire resistance standards, are not listed in glass specifications. This article provides an attempt to use calculation method for calculation fire resistance of some types of insulated fire-resistant glass, and describe some specific defects of alkali-silicate gel filled glass. It is shown that recently developed ablative fire resistant glass has some advantage.

Fire resistance and burnout resistance of reinforced concrete columns

This paper quantifies the resistance to complete burnout of reinforced concrete columns under fire exposure. It adopts a new metrics to complement the fire resistance rating that captures the specific effects of the cooling phase and characterizes explicitly the ability of a structural member to survive burnout. The analysis is performed on a dataset of 74 standard fire resistance tests on columns. Finite element modeling is applied first to reproduce the standard tests. The obtained ratio between the computed and experimental fire resistance has an average value of 0.95 with a standard deviation of 0.29. Then, finite element modeling is used to analyze the 74 columns under ‘standardized’ natural fire comprising a cooling phase. The effects of cooling are carefully incorporated in the materials laws including thorough consideration of irreversibility of properties and explicit modeling of transient creep. An iterative computational procedure is applied to subject each column to increasing durations of fire exposure until finding the shortest standardized fire that cannot be survived until burnout, from which the burnout resistance metrics is defined. The duration of this shortest fire increases approximately linearly with the fire resistance of the columns, but with a factor smaller than one, revealing an increased propensity to delayed failure in columns with longer fire resistance. Finally, a simple equation is formulated to estimate the burnout resistance from the fire resistance. Such equation can support design for complete burnout which has benefits for safety of fire brigades and first responders, as well as for property protection and resilience of the built environment.

Experimental study on the onset of swelling for thin intumescent coatings

Intumescent coatings (also known as reactive coatings) are widely used to protect load-bearing steel structural elements during fire. Upon heating, these initially thin coatings swell to form a low density, highly insulating foamed char that insulates steel substrate. Within the context of modern fire safety engineering design of steel structural systems, thermal insulation during fire may be key for assuring that steel does not reach ‘critical’ temperatures that may yield local structural instability and/or progressive failure (i.e. global instability).Traditionally, the fire performance of intumescent coatings is typically based on compliance (and to some extent their performance) to the standard fire resistance test in furnace, where single coated elements are exposed to the standard temperature-time curve. Numerous research studies have emphasised the influence of heating conditions on the onset of swelling and the overall effectiveness of intumescence. Moreover, some studies have shown that slow growing fires or low heating regimes may cause an incomplete swelling of the intumescent coating, or even melting or delamination. Consequently, the onset of swelling of is key for assuring its effectiveness in providing thermal insulation to the steel substrate during fire. Past researchers have shown that the onset of swelling occurs for temperatures in the range of 200-300°C. There are limited research studies that have look at the effects of varied, non-standard heating regimes on the onset or effectiveness of swelling of thin intumescent coatings.The study presented herein investigates the onset of swelling for a commercially available thin intumescent coating exposed to a wide range of heating regimes. Experiments are performed by using radiant panels and controlling incident radiant heat flux at the exposed surface of coated steel samples. This allows for the direct and precise control of the thermal boundary conditions at the exposed surface of tested samples. The onset of swelling criteria were defined in two ways: (1) visual observation of swelling during heating or (2) time-history of the protected steel temperature.The outcomes of this work aim at yielding a sound understanding of the true effectiveness of thin intumescent coatings. Experimental results mainly show that onset of swelling is directly influenced by the heating regime and it occurs for test samples heated at constant incident radiant heat flux above 20 kW/m2. The onset of swelling for the tested thin intumescent coating occurs for steel temperatures between 150 and 300°C and ‘mean coating temperature’ between 350 and 450°C. However, the steel temperature at onset of swelling is inversely proportional to the amount of constant incident heat flux at the exposed surface of tested samples, while the ‘mean coating temperature’ is directly proportional. As a conclusion, the time-history of net heat flux at the exposed surface of tested samples is not the only parameter that governs the onset of swelling for thin intumescent coatings.

Technical note - Thermal exposure of wood in standard fire resistance tests

1 Abstract Recently, standard fire resistance testing has been questioned for combustible products. A part of the comments address the thermal boundary conditions and the different thermal exposure of combustible products in comparison to incombustibles. These comments are evaluated in this technical note. To compare heat flux measurements of combustibles and incombustible products when tested in a furnace, furnace tests were performed. The furnace was controlled by plate thermometers to follow the EN 1363/ISO 834 standard temperature-time curve. It could be proven that (a) the heat flux measurements at the specimens surface behind the plate thermometer (PT) are not higher than in front of the PT. The reason for this is most likely that no flaming combustion is possible near the surface due to the low oxygen content typically for a furnace. It could be further shown (b) that the heat flux measurements when combustibles are tested follow the trend reported in literature for incombustibles. Further, (c) that the lower burner fuel used in furnaces is due to the contribution of the specimen (ca. 30% in the presented tests) and due to the lower thermal inertia (ca. 20% in the presented tests). Finally it can be concluded that the thermal exposure of combustibles and incombustibles is equivalent in furnaces simulating a ventilation controlled fire development for a pre-defined duration.

Timber under real fire conditions – the influence of oxygen content and gas velocity on the charring behavior

PurposeThe purpose of this study is to investigate the influencing factors on the charring behaviour of timber, the char layer and the charring depth in non-standard fires.Design/methodology/approachThis paper summarizes outcomes of tests, investigating the influences on the charring behavior of timber by varying the oxygen content and the gas velocity in the compartment. Results show that charring is depending on the fire compartment temperature, but results show further that at higher oxygen flow, char contraction was observed affecting the protective function of the char layer.FindingsIn particular, in the cooling phase, char contraction should be considered which may have a significant impact on performance-based design using non-standard temperature fire curves where the complete fire history including the cooling phase has to be taken into account.Originality/valueUp to now, some research on non-standard fire exposed timber member has been performed, mainly based on standard fire resistance tests where boundary conditions as gas flow and oxygen content especially in the decay phase are not measured or documented. The approach presented in this paper is the first documented fire tests with timber documenting the data required.

Motivation, drivers and barriers for a knowledge-based test environment in structural fire safety engineering science

Structural fire testing has traditionally relied on the use of the standard fire resistance test (i.e. furnace test) for assuring regulatory compliance of structural elements and assemblies, and in many cases also for developing the scientific understanding of structural response to fire. Conceived in the early 1900s and fundamentally unchanged since then, the standard testing procedure is characterized by its high cost and low repeatability. A novel test method, the Heat-Transfer Rate Inducing System (H-TRIS), resulting from a mental shift associated with controlling the thermal exposure not by temperature (e.g. temperature measured by thermocouples) but rather by the time-history of incident heat flux, was conceived, developed, and validated within the scope of the work presented in this paper. H-TRIS allows for experimental studies to be carried out with high repeatability, imposing rationally quantifiable thermal exposure, all at low economic and temporal cost. This works aims at demonstrating that a rational, and practical, understanding of the fire performance of structural systems during real fires is unlikely to be achieved only by performing additional standard fire resistance tests. Hence, H-TRIS presents an opportunity to help promote an industry-wide move away from the contemporary pass/fail and costly furnace testing environment.

Behaviour of non-loadbearing tabique wall subjected to fire – Experimental and numerical analysis

Tabique construction is one of the most used traditional building techniques and it can be found almost everywhere in Portugal with special incidence in the northeast region. Tabique construction elements can be described as a timber structure filled on both sides with an earth-based render. Tabique elements can be found in ancient buildings, from simple construction as rural dwellings to more urban sophisticated ones. This paper presents a study of the behaviour of tabique walls, concerning its fire resistance. Therefore, an experimental analysis was performed using tabique wall panel specimens. Such wall panels were made in pine wood with an earth-based render finishing. In order to assess the thickness effect of the earth-based render on the fire resistance of the wall, three specimens with different render thicknesses of 15mm, 10mm and 5mm were tested in a fire-resistance furnace according to the ISO 834 [1] standard fire curve. Fire resistance is a measure of the ability of a building element to resist a fire, usually the time for which the element can meet appropriate criteria during exposure to a standard fire resistance test. By this way it is possible to increase the safety of people and property. Two performance criteria were verified which are the integrity and the insulation. In addition, a numerical model was also developed in order to assess the tabique wall behaviour under fire conditions, which was validated using the obtained experimental results.

Parameter estimation approach to the thermal characterization of intumescent fire retardant paints

Intumescent paints are widely used as passive fire retardant materials in the building sector. They swell on heating to form a highly insulating char, protecting steel members. Intumescent coatings for use in buildings are typically certified according to the standard cellulosic fire resistance test. This test is expensive, often non-representative of realistic fire conditions, and not enough versatile to gather detailed performance information on the response of reactive coatings. A promising approach, that could offer a helpful tool to the engineering community involved in fire safety, is found in the modelling of the behaviour of the intumescent coating. Under this approach, the knowledge of the equivalent thermal conductivity of the intumescent material is a fundamental issue, since it represents the main parameter that allows predicting the thermal protecting capability of the layer. The purpose of this paper is to optimize an estimation procedure intended to the restoration of the equivalent thermal conductivity of intumescent layers. The thermal stress is activated by the action of a cone calorimetric apparatus, while the estimation procedure is based on the inverse heat conduction problem approach under steady state assumption, where the temperature values measured at some locations inside the layer during the expansion process are used as input known data. This procedure was successfully applied to steel samples protected with an intumescent paint; the estimated equivalent thermal conductivity of the layer results to temperature dependent while the initial thickness of the paint does not seem to have a great effect.

Thermal modelling of gypsum plasterboard assemblies exposed to standard fire tests

SummaryGypsum plasterboards are widely used for compartmentation and for retarding the spread of fire in buildings. Although numerous heat transfer studies have been conducted, literature indicates there are extensive differences in the thermal properties used in these studies. Comprehensive experimental and numerical analyses have been conducted to elucidate the leading factor in the ablation of a gypsum board system when it is exposed to the standard fire resistance test. A methodology based on both simultaneous thermal analysis and computational modelling is proposed to understand the behaviour of a gypsum plasterboard when the boundary temperature increases quickly as one side of the wall is subjected to the standard ISO 834. Finally, four different wall assemblies made of a commercial fireproof plasterboard system are exposed to the standard test. The temperature on the unexposed face is examined to validate the computational model of the plasterboard. Copyright © 2015 John Wiley & Sons, Ltd.