Standard Fire Tests Research Articles

Pożarowe analizy konstrukcji w aspekcie zjawisk fizycznych obserwowanych podczas prób jednoosiowego rozciągania stali

Metody obliczeń konstrukcji budowlanych w pożarze powinny umożliwiać dokładną analizę i uwzględniać specyficzne właściwości ogrzewanych materiałów, na przykład nieliniowe pełzanie metali. Teoretyczne rozważania na temat konstrukcji metalowych w pożarze mogą być weryfikowane, a także uzupełniane wynikami badań materiałowych i badań ogniowych. Badania materiałów konstrukcyjnych w podwyższonej temperaturze mają na celu przede wszystkim wyznaczenie charakterystyk wytrzymałościowych i termicznych. Wyniki typowych badań ogniowych określają natomiast reakcję elementu wydzielonego z konstrukcji budowlanej na ogrzewanie zgodne z normową krzywą „temperatura-czas”. Normowe uproszczenia rzeczywistych sytuacji pożarowych wynikają między innymi z ograniczonych możliwości badań laboratoryjnych.

Fire Behavior of Full-Scale CFRP-Strengthened RC Beams Protected with Different Insulation Systems

In this paper, a series of experimental studies conducted to investigate the fire behavior of insulated full-scale carbon-fiber-reinforced polymers (CFRP)-strengthened reinforced concrete (RC) beams is presented. Four CFRP-strengthened RC beams, respectively insulated with a thick coating system, ultrathin coating system and calcium silicate board system, were tested under ISO834 standard fire exposure. The test results revealed that satisfactory fire endurance for CFRP-strengthened concrete beams can be obtained with the protection of the three systems. The major role of fire insulation materials is to delay the failure of adhesive in the early stage and reduce the performance degradation of concrete and internal reinforced bars after the bond failure of the CFRP–concrete interface. In addition, it was indicated that effective anchorages of CFRP and reasonable anchoring constructions of the insulation system played important roles in ensuring the fire-resistant capability of CFRP-strengthened concrete beams. Further, a detailed finite element model was developed as an alternative to the standard fire test. The predicted temperature and deflection results were in good agreement with the measured ones. Based on the case studies, insulation thickness, insulation thermal conductivity, CFRP amount and load ratio were proven to be the main influences of the fire resistance of insulated CFRP-strengthened beams.

Fire-resistant capacity of RC structures considering time-dependent creep strain at elevated temperature

This paper introduces a numerical evaluation of the fire-resistant capacity of reinforced concrete structures. On the basis of a time-dependent temperature distribution across a section determined from a transient heat transfer analysis considering heat conduction, convection and radiation, a layered fibre section method is adopted to take into account the non-linear material properties depending on the temperature. Furthermore, non-mechanical strains of concrete and steel such as thermal strain, transient strain and creep strain, which increase with elevated temperature variation induced by fire, are implemented into the formulation. Numerical results for structural members are compared with experimental data obtained from standard fire tests to investigate the influence of non-mechanical strains at elevated temperature. Beyond the member level, frame structures exposed to fire are also analysed to evaluate the influence of fire on statically indeterminate structures exposed to practical fire conditions. Finally, consideration of the change in material properties induced by elevated temperature in design practice is emphasised through correlation studies between the resisting capacities evaluated by the introduced numerical algorithm and those determined by the design code EN 1992-1-2.

Hydrocarbon time–temperature curve under airjet perturbation: An in situ method to probe char stability and integrity in reactive fire protection coatings

Intumescent coatings are the present-day state-of-art techniques to protect steel structures and other structural materials from fire hazards. Thermal insulation properties of such protective materials are normally deduced from standard fire tests, however, with least reference to char integrity and strength. This work proposes a simple and resourceful in situ experimental protocol to evaluate char strength of intumescent coatings on steel panels during hydrocarbon time–temperature fire test (at about 1200°C). It is based on in-process monitoring the physical integrity, mechanical stability, and thermal insulation capacity of fully developed char under a stream of air (airjet) before steel plate reaches its critical temperature. A bench-scale furnace designed in our laboratory to reproduce hydrocarbon fire scenario (UL1709) was upgraded to simulate air turbulence to impact the char strength. Silicone- and epoxy-based coatings on steel panels were tested under these conditions. Silicone-based coatings are found to have several interesting advantages over the latter. Furthermore, this protocol was extended to investigate the compositional influence on char strength in a set of silicon-based coatings.

PE 이종강관의 소방용 배관 적용성에 관한 실험적 연구

본 연구는 현재 사용하고 있는 소방용 배관의 부식으로 인하여 발생하는 수계소화설비의 문제를 해결하기 위하여 개발한 Polyethylene (PE) 이종강관을 수계소화설비배관으로 적용할 수 있는지를 파악하기 위한 실제 화재시험을 수행하였다. 개발된 이종배관에 대한 관련시험기준이 없어 국내외 기술자료 및 시험기준을 비교분석하여 적합한 화재시험기준을 선정하여 PE 이종강관의 성능을 분석하였다. 따라서 본 배관의 성능시험에 채택한 화재시험기준은 합성수지배관과 금속배관의 두 가지의 화재시험기준을 적용하였고 총 6차례의 화재실험을 실시하여 배관성능을 평가하였다. 소방용합성수지배관의 시험기준을 적용한 1, 2차의 화재시험결과 이음쇠와 배관에서 파손이나 변형이 없었으며 5분간 내압시험을 실시한 결과에서도 누수가 없었다. 금속배관시험기준을 적용한 화재실험은 총 4회를 실시하였으며 1, 2차 실험은 습식설비를 모사한 것으로 화재시험결과는 PE 이종강관에서 누설이나 파열이 발생하지 않았으며 또한 PE 재질의 이탈 등 손상이 발생되지 않음을 확인하였다. 단, 건식설비를 모사한 3, 4차의 화재시험결과 소화수가 방출되기 이전에 PE 이종강관에서 파열, 변형 등의 손상이 발생하였다. 따라서 실험결과 습식설비를 모사한 화재시험의 경우 PE 이종강관의 융착성, 변형, 파손 등 배관의 성능에 이상이 없음을 확인하였다. In this study, to determine whether it is possible to apply Polyethylene (PE) compound pipe, which was developed to solve the problem caused by the corrosion of the fire protection piping currently in usein water based fire extinguishing systems, we performed an actual mockup fire test. Since no test standard was available related to the developed compound pipe, we compared and analyzed domestic and international technical materials and test standards and selected suitable fire test standards to evaluate the performance of the PE compound pipe. we applied two fire test standards to the PE compound pipe, viz. those for CPVC and metallic pipes, and conducted a total of 6 experiments to evaluate its performance. According to the results of the first and second fire tests based on the test standard for the CPVC pipe, neither the fitting nor the piping was damaged or deformed and no leakage was observed in the pressure test, which was performed for 5 minutes. For the fire test based on the metallic pipe test standard, a total of 4 experiments were conducted. The first two experiments were conducted to simulate the wet piping system. In the results of this fire test, neither leakage nor rupture was observed from the PE compound pipe and no damage was caused, such as the secession of the PE material. However, in the next two experiments, which simulated the dry system, the PE compound pipe suffered damage and rupture, including deformation before the fire fighting water was discharged. Therefore, we found that the piping performance of the PE compound pipe did not undergo any deterioration, including fusion, deformation, or damage, in the wet piping system simulated fire test.

Robustness assessment of a generic steel fire-protected moment-resisting frame under travelling fire

Due to their vulnerability to high temperatures, steel structures are typically protected against fire by insulation materials, as recommended by fire codes. The fire resistance rating of a protected member is determined based on a standard fire test, which simulates post-flashover fire conditions. Empirical evidence has shown that fires in large open-plan compartments do not burn uniformly, and a method called “traveling fire” has been introduced in previous research to simulate the effects of spreading fires. An investigation is performed here to examine the robustness of a generic four-story moment-resisting steel structure with one-hour fire resistance rating subjected to travelling fire. Various fire sizes are considered: 12.5, 25, 50 and 100% of the floor area. The results show that while no collapse occurs during the 12.5, 50 and 100% fire sizes, the structure collapses under the 25% fire size at 85 min due to the inability of the system to transfer the load after one of the columns buckles. This seems to be in contradiction with traditional belief that a fire covering a larger portion of the floor plan would reduce the safety margin. The investigation performed underlines that the fire protection of structures based on the standard time-temperature curve does not necessarily provide adequate resistance under travelling fires. With the lack of adequate fire regulations codified for large compartments, more research is required before arriving at a better understanding of the application of travelling fire to large compartments.

Thermal and mechanical transient behaviour of steel doors installed in non‐load‐bearing partition wall assemblies during exposure to the standard fire test

SUMMARYIn this paper, the authors present experimental results and observations of four full‐scale standard fire tests on single‐leaf steel doors and steel frames installed in 3 × 3 m non‐load‐bearing partition walls. Three full‐scale fire tests were performed on steel doors installed in lightweight partition walls constructed by using steel C‐section studs with gypsum boards fixed on both sides. Two lightweight walls incorporated Rockwool cavity insulation, while the third lightweight wall was constructed without cavity insulation. The fourth fire test involved a steel door installed in a masonry partition wall. While the steel door leaf and door frames were identical in all four full‐scale tests, only the steel door installed in the masonry wall achieved the desired fire resistance rating of 30 min. The integrity criterion for fire resistance was determined for the scenario when the door opened away from the furnace. The duration of fire resistance according to the integrity criterion was found to be 38, 25 and 19 min for the same door when installed in masonry wall, uninsulated lightweight wall and insulated lightweight wall respectively. For the thermal insulation criterion of fire resistance, the scenario of the door opening into the fire was found to be the most onerous. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

강재보용 내화피복의 내화성능 평가단면에 대한 고찰

강구조용 내화피복은 내화성능평가를 통하여 내화구조로 인정을 받아야 사용할 수 있는데 기둥용 내화피복은 4면, 보용 내화피복은 3면을 가열하여 내화성능을 평가한다. 4면이 균등하게 가열되는 기둥과 달리 3면이 가열되는 보의 경우 비가열면인 상부의 온도가 가열면의 온도와 차이가 있을 것이 예상된다. 보용 내화피복 내화성능 평가시 비가열면의 온도도 포함되는데 비가열면의 온도가 부재의 온도와 유의한 차이가 있다면 온도측정 부위에 대한 신중한 검토가 필요할 것이다. 이에 본 논문에서 내화구조로 인정된 보용 내화피복의 내화성능시험결과를 분석하여 보용 내화피복 내화성능 평가단면의 타당성을 살펴보고자 한다. It is necessary to obtain a fire resistance certification in order to use Fire Protection Coating in Korea. According to the fire test standards, columns have four heating sides and beams have three. In comparison with columns which are heated four sides equally, beams have three exposed sides and one unexposed up side. So the question arises as to there were the differences between the temperature of up side and others of beams in fire test. The purpose of this study is to consider the positions of thermocouples for beams through a comparative analysis of the temperature data obtained from fire certification tests.

Fire Resistance of Timber Panel Structures Under Standard Fire Exposure

Timber panel construction using Cross-Laminated Timber (CLT) or Laminated Veneer Lumber (LVL) panels have been developed for cost and construction efficiencies in the building industry. The increased use of timber as a sustainable construction material in buildings is expected to expand the forest industry and increase carbon stock. Heavy timber structural elements with sufficient load bearing capacity could be used in tall buildings. However, sufficient data are not yet available to understand the structural and thermal behaviors of domestic timber panel elements with cross laminations/layers when they are exposed to fire. In this study, fire testing data for timber panels are obtained and the charring characteristics and failure modes of structural elements under standard fire exposure are investigated to develop a simple method for estimating the fire resistance of timber panels. Toward this end, a series of experiments consisting of heating tests and load bearing tests for walls in furnaces with various experimental parameters was conducted. The experimental parameters considered include the adhesive type, thicknesses of laminations and panels, wood species, fire protection, and applied loads of the panels. Experiments without loading showed that CLT and LVL panels and joints of panels with 135 mm thickness showed sufficient thermal insulation and integrity over 90 min in standard fire tests. Smoke leakage from the joints of the timber panels was observed in the early stage of the fire tests because of a lack of air-tightness. Delamination of almost all charred layers glued with an API adhesive was observed in fire tests of CLT panels; however, delamination of LVL and CLT panels with a RPF adhesive was limited. The estimated charring rates of a Japanese cedar CLT panel with API and RPF adhesives were 0.78 mm/min and 0.66 mm/min at 260°C, respectively. The charring rate of LVL panels was ∼0.6 mm/min at 260°C, less than that of CLT panels. The load bearing capacity of timber walls subjected to one-sided fire exposure depended on the buckling strength under the eccentric load caused by asymmetric charring. A prediction method based on the Secant formula was presented to estimate the buckling strength in fire tests. An equation that considered the effect of the degradation of elasticity at high temperatures and eccentricity of loading provided the approximate buckling strength of the timber panel specimens in the fire tests.

A 3D finite element model for predicting the fire behavior of hollow-core slabs

A nonlinear finite element three-dimensional model is presented and validated in this work against standard fire tests. The aim is to develop a numerical tool in order to study the behavior of prestressed Hollow Core (HC) slabs in the event of fire. A sequentially coupled approach is considered in order to perform the thermo-mechanical analysis at an affordable computational cost. The model includes the effect of prestress and a realistic constitutive inelastic behavior of concrete, for both tension and compression. It takes into account the temperature dependency of the material properties, and thus the crack patterns due to bending, shear, thermal cracking and longitudinal cracking are reproduced. The model is validated by comparing the simulation results with 11 real fire resistance tests on single elements, obtaining satisfactory results in terms of both failure mechanism and failure time. Finally, the suitability of using the simple calculation models existing in the European codes (Eurocode 2, EN 1168) for the verification of the HC resistance in fire situation is discussed. In particular, the numerical results are compared to the simple calculation model given in the EN 1168.

Performance criteria for the fire safe use of thermal insulation in buildings

Building design can be considered as a multi-objective optimisation problem, in which many criteria are considered for determining the most favourable solution. The application of optimisation techniques requires the design criteria to be quantifiable, which sets the baseline for the application of performance-based designs. Sustainability has become the main driver in the built environment during recent decades, with energy efficiency becoming the foremost design criteria and appropriately quantified. By contrast, the approach taken for fire safety is much simplistic, relying on a series of prescriptions based on material classification and “pass–fail” criteria defined in standard fire tests. This results in deficiencies in identification of fire hazards and undermines any attempt at design optimisation. A redefinition of the failure criteria framework based on fundamental understanding of the material behaviour, including the heat transfer controlled processes governing the onset of pyrolysis, can provide a performance-based methodology for the fire safe use of insulation materials in buildings. The different hazards from insulation materials in fire are identified and a set of criteria are defined to identify likely failure modes. A series of highly instrumented large-scale experiments of a construction system involving a common combustible material are referenced to demonstrate the proposed methodology.

Thermal performance of load‐bearing walls made of cold‐formed hollow flange channel sections in fire

SummaryTypical load‐bearing light gauge steel frame (LSF) walls are made of conventional lipped channel section studs and gypsum plasterboards. Current research at the Queensland University of Technology is investigating the effects of using new thin‐walled stud sections on the fire‐resistant rating of LSF walls, in particular, the use of hollow flange channel (HFC) sections. A sound knowledge on the thermal performance of these LSF walls is essential, but expensive and time‐consuming nature of fire tests has acted as a barrier. In this study, finite element models were developed to predict the thermal performance of load‐bearing LSF walls made of HFC section studs exposed to fire on one side. The developed models were validated using the results of five full‐scale standard fire tests of LSF walls. They were then extended to perform a parametric study where the effects of stud dimensions, geometries, spacings and wall configuration were evaluated. The hot and cold flange time‐temperature profiles of HFC studs were developed as a function of the aforementioned parameters, which can be used to predict the fire resistance ratings of LSF walls. This paper presents the fire tests, and the details of the developed finite element models and the thermal performance results of LSF walls made of HFC studs. Copyright © 2015 John Wiley & Sons, Ltd.

FIRE RESISTANCE PERFORMANCE OF CELLULAR STEEL BEAM (CSB) AT ELEVATED TEMPERATURES

Cellular steel beam (CSB) is getting more and more popular to be used as the main structural member for steel building structure in the United Kingdom (UK). Despite quite costly to erect and assemble a steel structure member compared to concrete, it has several advantages in terms of lightweight material, higher strength, easy to assemble and aesthetic value. Even though the use of CSB is quite significantly positive, the negative side also needs to be addressed. Any steel structures are prone to fire exposure scenario. The strength of CSB will be significantly decreased when exposed to elevated temperature due to fire. Large deformation from experimental procedure will be clearly seen after the time-temperature curve reach critical stage. Vierendeel bending mechanism and web-post buckling are some of the drawbacks of the CSB at elevated temperature. In this paper, general purpose ABAQUS Finite Element (Version 6.14) on large deformation of protected and unprotected CSB at elevated temperature is proposed. Performance based approach is introduced to validate the numerical analysis with the experimental results from the available Compendium of UK Standard Fire Test Data produced by British Steel Corporation Research Services, Swinden Laboratories, UK.

Temperatures and thermal boundary conditions in reverse channel connections to concrete filled steel sections during standard and natural fire tests

The paper presents fire test and numerical simulation results of temperature distributions in reverse channel connections to concrete-filled tubular columns during standard and natural fire tests. The experiments included a furnace fire test with the composite frame subjected to increasing fire temperature according to the ISO 834 standard time–temperature curve and two natural fire tests in a full-scale structure including a cooling phase. These fire tests examined the effects of fire protection, different connection locations and different connection dimensions. Temperatures at different connection components were recorded. The recorded connection component temperatures were simulated by using the SAFIR fire engineering software to calibrate the thermal boundary conditions in different connection components. From the numerical simulation results, it has been concluded that radiation to the inner surfaces of the reverse channel and the adjacent part of the column tube is only from the gas volume bounded by these surfaces. A lower flame emissivity value than the standard value should be used. For simplicity, a value of εf=0.1 is proposed. Also a lower value of the convective heat transfer coefficient of 10W/m2K can be used in the connection area.

Investigating the Properties of Fireproofing Materials for an Advanced Design of Equipment Protection

Fire scenarios in process industry have a high potential to cause severe asset damage. Fireproofing is a consolidated technique for passive fire protection for units and supporting structures. Since several materials are available for passive fire protection, it is important to choose the best solution for the protected equipment and critical fire scenarios. Current practice in rating fireproofing materials does not provide sufficient information about the protection granted to process equipment: for example, the ‘time-to-failure’ of pressurized vessels protected by fireproofing materials cannot be predicted from the results of standardized fire tests. This study investigates the key properties (e.g. density, geometrical structure, thermal degradation and thermal conductivity) of representative fireproofing materials, in order to better understand the elements underlying the actual protection performance. An experimental activity was focused on the definition of fundamental models to describe the thermo-physical properties of the materials. The investigation cast the foundations of a better understanding of the dynamics underlying the effective design for passive fire protection, identifying the criticalities and limits of the alternative fireproofing options. The changes in the physical properties of materials during fire exposure were confirmed to play a major role on the protection performance. Such effects could not be accounted for complex geometries by conventional simplified approaches alone: thus, the proposed approach paves the way for a safer and more cost effective design of passive fire protection systems.

The Reduced Cross Section Method Applied to Glulam Timber Exposed to Non-standard Fire Curves

Timber is an desired material for structural applications due to its green credentials and attractive external appearance. Fire safety design of timber structures is largely limited to considering the exposure of elements to the standard fire, to which timber demonstrates exceptional resilience. This paper reports on a series of tests which were carried out with the intention of exploring the impact of non-standard fires on timber elements. Because of the natural variation in timber elements, the tests and the resulting analysis of the test results were conceived and designed in such a way that as much information about the statistical distribution of the response of the elements as possible could be obtained. The resulting testing programme comprised four furnace fire tests, each of eight loaded timber beams, with three different temperature time curves: two standard fire tests, one long-cool parametric fire and one short-hot parametric fire. The reduced cross section method for structural calculations is extended in this paper to parametric fire exposures, and the results of the tests are compared with this method. It is shown that the thickness of the zero-strength layer is dependent on the temperature time curve to which the timber is exposed in the furnace and that the 7 mm zero-strength layer prescribed in EN 1995-1-2 may be un-conservative for members in bending. For the cases studied, the zero-strength layer thickness in bending is shown to be around about 15 mm under standard fire exposure and 16 mm under exposure to a long cool parametric fire. Conversely, the zero-strength layer is only 8 mm deep under exposure to a short hot parametric fire. This has implications for the design of timber elements not only for parametric fire exposure in enclosures, but also perhaps for the use of timber elements in large open structures such as halls or arenas where more localised fire exposure or travelling fire exposure may be expected.

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.

Buckling length determination of concrete filled steel tubular column under axial compression in standard fire test

The structural behavior of the column under fire becomes essential since it concerns the safety of buildings and people inside in case of fire event occurs. The standard fire tests were usually used to evaluate the resistance of the members under fire. This paper presents a method to determine the buckling length that was used to predict the resistance of the concrete filled steel tubular (CFST) column under axial compression in standard fire test. In this method, the fourth-order differential equation was used to develop the analytical model. Various boundary conditions of the column at working condition, e.g. fixed–fixed, fixed–pinned, and pinned–pinned, were considered in this analytical model. Design formulae and charts were developed to determine the buckling lengths that considered varying flexural stiffness along the column height in fire. Temperature-independent buckling lengths were also proposed to further simplify the fire resistance design procedure. To establish the validity, the determined fire resistance of CFST columns based on the analytical and proposed buckling lengths were compared with test results in literature and predictions based on empirical buckling lengths.

Thermo-mechanical analysis of a fire door for naval applications

In this work, the thermo-mechanical response of fire doors for naval application is considered. In order to evaluate their behaviour, fire doors must undergo a standardized fire test. A realistic simulation of the heating process can be useful during the design phase in order to reduce the number of prototypes to be constructed and tested. In this work, a finite element model is developed with the aim of capturing the qualitative behaviour of the fire door and its supporting frame. Two different types of thermal analysis are considered: (1) transient analysis and (2) steady-state analysis. A non-linear mechanical analysis predicts the displacement field that occurs at the end of the heating phase. The adopted model is validated through a comparison with experimental measurements obtained during standard fire tests, confirming that the proposed approach can be a valid tool for the prediction of the thermo-mechanical performance of a naval fire door.

Experimental and Numerical Study of Fire Resistance of Composite Beams

In this paper, the standard fire resistance test under load and associated numerical study were carried out to evaluate the fire resistance of unprotected partially encased beams and slimfloor beams. The temperature evolution and the deflection increase of the composite beam specimens were investigated and the effects of the key behavioral parameters including the load ratio, the reinforcement, and the fire exposure were analyzed. The test results showed that the temperature rise of the partially encased beams and slimfloor beams is considerably slow compared to the conventional H-shape composite beams. Up to at least 90 minutes, the reinforcements in the partially encased composite beams maintained below the temperature at which the cold steel strength is sustained. Unprotected partially encased beams and slimfloor beams in the experimental program achieved the fire resistance more than 2 hours according to the limiting deflection criteria. This implies that unprotected partially encased beams and slimfloor beams can be very promising alternatives to enhancing the fire resistance of steel beams. This study also conducted the fully coupled thermal-stress analysis by using the commercial code ABAQUS to the thermal and structural behaviour of composite beams in fire. The numerical predictions provide acceptable correlations with the experimental results. Keywords - Partially encased beam, Slimfloor beam, Fire resistance test under load, Coupled thermal-stress analysis, Fire resistance