Full-scale Fire Resistance Tests Research Articles

Similarity analysis of the fire-resistant behaviour of partially encased composite columns in different scales

As full-scale fire resistance tests commonly involve considerable expense and require specialized experimental apparatus, scale specimens are being employed in many investigations focusing on the performance of structural members under fire exposure. However, since the inherent thermal properties of materials are commonly independent of the geometrical scale factors, it is necessary to analyze the similarity among the thermal responses of scale specimens and their corresponding prototype in advance, in order to generalize the experimental conclusions to practice. In this context, the similarity of the fire-resistant behaviour of partially encased concrete (PEC) columns, a sort of structural member that is widely used in building and industrial structures, in different geometrical scales was studied in this work. A finite element model was developed and verified based on existing experimental results, and then used for the parametric studies. The similarities of the transient temperature fields, deformation states and the fire-resistant durations of the PEC columns with restrained thermal elongation in different scales were analyzed, which indicates that the mathematical relationship between the time-scale factor and the geometric scale factor in the classical similitude theory needs to be improved for such structural members with complex cross-sections. A modified time-scale equation was therefore proposed to ensure the fire endurance prediction accuracy of scale PEC models for the corresponding prototypes under fire, with the proportion of steel in the cross-section (steel ratio) and the aspect ratio well-considered, which could facilitate the temperature-related experiments and analyses of PEC structural members in the future.

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.

Fire Resistance of Fire-Protected Reinforced Concrete Beams Strengthened with Externally Bonded Reinforcement Carbon Fibre-Reinforced Polymers at the Full Utilisation Degree.

The fire resistance of reinforced concrete (RC) beams strengthened with externally bonded reinforcement carbon fibre-reinforced polymers (EBR CFRP) depends on the load level and degree of strengthening. Design guides for this type of structure recommend strengthening limits to prevent collapse of the structure due to vandalism, damage or fire. In practice, however, it is not uncommon to exceed the proposed limits. This necessitates protection of the CFRP adhesive against high temperatures, namely glass transition temperature levels. This paper presents the results of 10 full-scale experimental fire resistance tests of reinforced concrete beams with EBR CFRP strengthening, with and without fire protection and under various load levels including full utilisation. It was demonstrated that in cases where CFRP strengthening was not needed to carry load in an accidental fire scenario, test specimens with and without it achieved the same fire resistance. It was also proven that in cases where CFRP failure influenced the failure of the entire beam, fire protection was crucial for maintaining the beam's load-bearing capacity and its thickness had to be substantial. A fire resistance rating of over 4 h was achieved, nevertheless.

Bench-scale fuel fire test for materials of rechargeable energy storage system housings

The fire behaviour of electric vehicles (EVs) differs from that of vehicles with combustion engines. Especially the rechargeable energy storage system (REESS) requires special fire protection measures. The fire behaviour of materials for REESS housings plays an important role in the fire resistance of such systems. Full-scale fire resistance tests like gasoline pool fire tests on complete REESS according to the UNECE-R100-8E standard are mandatory for EVs. However, these tests are not applicable for materials used for REESS housings in the material and process development state, due to the high material demand and production costs of the REESS. Standard tests like the limiting oxygen index test, UL94-V test or cone calorimeter test are insufficient to analyse the fire behaviour of thermoplastic and thermoset materials in a gasoline pool fire. This paper describes a bench-scale fuel fire test including several test criteria to evaluate materials for REESS housings on a laboratory scale. This bench-scale fire test is demonstrated on two case studies: fibre-reinforced thermoset plates and thermoplastic sandwich structures.

Modeling evaluation for fire resistance design of rail car floor assembly

This paper is prepared to report the engineering practice by a Chinese railcar manufacture in a railcar design process for a Metro system in U.S. The fire resistance of rail car floor systems is considered as one of the important fire protection features on the railcars operated in U.S., which provides fire separation between the equipment installed under the floor and the passengers insider railcar. In this study, a pragmatic approach was developed to numerically evaluate the fire resistance of rail car floor assemblies and provide insights for necessary design modifications. Finite element analysis (FEA) was applied to assess the fire resistance performance of a rail car floor assembly designed for a metro railway system in the U.S. An optimization algorithm was applied to obtain the thermal properties of intumescent coating. FEA analysis results were applied to assist the design modifications so that the floor assembly successfully satisfies the current requirement and passes the ASTM E119 fire resistance test. The FEA modeling details and heat transfer analysis results are presented. It is also shown that the model predictions agree conservatively well with the full-scale fire resistance test data.

Numerical study and proposal of new design equations for steel decking concrete slabs subjected to fire

This paper presents a numerical study on structurally continuous steel decking concrete slabs subjected to fire. This is an important subject for improving the fire design methods of this type of elements. Slabs with tension, compression and/or both steel reinforcement types have been tested. The results of twelve full-scale slab fire resistance tests carried out by the authors have been used in the calibration of the numerical models. Despite the compression rebars being more thermally protected, the use of tension rebars proved to be a good design solution, because just from the initial 5 min of fire, a detachment of the steel deck was registered. In this sense, slabs without tension rebars performed like a non-reinforced concrete slab. The detachment of the steel decking suggests that this type of slabs should not be fire designed as a composite element. There is no interaction between the steel decking and the concrete just from the beginning of the fire exposure. Nevertheless, when the steel decking detaches and stops contributing to the mechanical resistance of the slab, it continues to work as a thermal barrier. Another important conclusion is that the simple calculation method of EN 1994–1-2 needs an update for taking into account these phenomena. A new methodology for the mechanical and thermal design of these slabs in case of fire is proposed.

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.

Modeling the fire-induced spalling in concrete structures incorporating hydro-thermo-mechanical stresses

This paper presents a numerical approach for predicting spalling in concrete structural members under fire conditions. The proposed approach evaluates spalling by taking into account the stresses generated due to pore pressure, thermal gradients, and structural loading under fire conditions. This approach is incorporated as a spalling sub-model into a macroscopic finite element based model that is capable of tracing the thermo-mechanical response of RC beams from pre-cracking stage to collapse under fire conditions. The analysis predictions, namely temperature, deflection, and extent of spalling are compared against the measured values from full-scale fire resistance tests on RC beams made with different concrete types of varying strengths. Results from the analysis indicate that pore pressure induced stresses are the primary trigger, though thermal and mechanical stress levels exert influence on the occurrence of spalling. Further, the level of spalling significantly influences fire resistance of concrete beams under severe fire exposures, and neglecting fire-induced spalling can lead to un-conservative fire resistance predictions in certain scenarios, specifically in the case of high strength concrete (HSC) and ultra-high performance concrete (UHPC) beams.

An Experimental Study on Fire Resistance Performance of a Bended Type Cladding Column System

As buildings are growing higher and larger, more composite structures have been used. However, the steel member used for composite structure tends to rapidly lose its strength at elevated temperatures. For this reason, it is required to apply a fire resistance mechanism, but it is difficult to implement because of the cost and technical limitations in the case of fire-resistant paint. In case of fireproof spray coat, scattering phenomena, poor work conditions for wet application, and construction delay are the main challenges to be addressed. In this study, a full-scale fire resistance test of non-fire resistant cladding column was conducted in accordance with KS F 2257-7. According to the test results, the specimens CC-01, CC-02, and CC-03 failed to meet the requirements for a 3-hour fire resistance rating because of the joint deformation and less cover thickness, while CC-04, CC-05, and CC-06 with increased thickness and reinforced joints satisfied the requirements for a 3-hour fire resistance rating.

Fire Resistance Testing of a Timber-Glass Composite Beam

Glass structures have been increasingly utilised in modern construction for decades with load-bearing walls or facades as the most common elements. However, the use of glass beams has recently been given more attention but its application as load-bearing elements has been limited by the low tensile resistance, its brittle behaviour during failure and concerns of its performance in case of fire. Parts of these aspects can be covered by using Timber-Glass composites beams, with timber flanges and a glass web. Previous research and practical application show high potential for this type of composites in ambient temperatures but its performance in fire has not yet been assessed and thus not completely understood. This study describes what to our knowledge is the first full scale fire resistance tests of Timber-Glass composites beams. These tests results are also analysed using finite-element simulations in order to understand the mechanisms of failure during the tests. It was shown that adding a timber flange to a glass web can have severe complications for the fire resistance, however, there are many possible ways to circumvent these issues.

Full-scale fire resistance tests of steel and plasterboard sheathed web-stiffened stud walls

Light gauge steel-framed (LSF) walls, commonly made with lipped channel studs and gypsum plasterboard sheathing, are increasingly being used in low to mid-rise buildings. Improvements have been made with respect to fire, wind/seismic and energy performance of LSF walls with the use of improved stud sections, wall configurations, different sheathing members, and insulation materials. Although the provision of sheet steel as sheathing has been found to improve the in-plane shear capacity of LSF walls, its effects on the fire performance of load bearing walls remain unknown. Three full-scale ISO 834 standard fire tests were conducted in this study to investigate the fire performance of axially loaded gypsum plasterboard and steel sheathed LSF walls made with web-stiffened studs. The results revealed that compared to the commonly used lipped channel stud, the web-stiffened stud is capable of withstanding a 57% greater axial compression load, yet yield the same fire resistance level (FRL), when sheathed only with two layers of gypsum plasterboard. Under the selected load ratio, the addition of steel sheathing caused only marginal improvements in the stud temperature development, resulting in minor improvements to the FRL of load bearing walls. However, the axial load bearing capacity improvement caused by the inclusion of steel sheathing allowed the web-stiffened stud to withstand a 10% greater axial compression load compared to the plasterboard only wall.

Study on Water Based Ultra-thin Fire Resistive Coating for Steel Structure and the Fire Resistance Test

A water based ultra-thin fire resistive coating for steel structure was researched. The coating was coated on I40b I-beam with APP as the main flame retardant and titanium dioxide as filler. The full-scale fire resistance test was carried out according to the China standard GB 14907-2002. The results shows that the resistive of the water based steel structure fire resistive coating can reach 1.2h when the thickness is about 2mm. Related research shows that water based steel structure fire resistive coating can be used as an effective fire-resistant material for steel structure.

Nonlinear Structural Analysis of Fire-Exposed Reinforced Concrete Column

A nonlinear structural analysis is presented for reinforced concrete (RC) columns exposed to fire. The analysis includes two steps: the first step is the calculation of the temperature distribution in concrete members, and the second the determination of the mechanical response due to elevated temperature and applied loading. In the thermal analysis, the effect of moisture is taken into account. The use of the computer program for evaluating the response of a RC column from the initial preloading stage to collapse, due to fire, is illustrated. The validity of the numerical model used in the program is verified by comparing the predictions from the computer program with measured results from full-scale fire resistance tests. The computer program can be used to predict the fire resistance of RC columns for any values of the significant parameters, such as load level, section dimensions, column length, concrete strength, concrete cover, aggregate type and reinforcement ratio.

화재에 노출된 콘크리트 세그먼트 온도거동 특성에 관한 실험적 연구

최근 한국에서는 해저터널 시공계획이 발표되면서 쉴드터널의 콘크리트 라이닝 내화성능 확보방안에 관한 중요성이 제기되고 있다. 쉴드터널 내부에 시공되는 철근콘크리트 세그먼트는 토압이나 수압 등 하중을 지지하는 구조부재로 압축강도가 40 MPa 이상의 고강도 콘크리트를 사용하고 있어 특별한 내화대책이 없을 경우에는 화재로 인해 세그먼트에 상당한 피해가 예상되며 아울러 폭렬에 의한 단면손실 및 철근 강도의 손실로 터널 붕괴로까지 이어질 가능성이 높다고 판단된다. 따라서 본 연구에서는 쉴드터널 콘크리트 구조물의 화재안전성 향상에 기여할 수 있도록 실대형 터널 세그먼트 내화실험의 화재손상범위와 EFNARC(European Federation of Producer and Applicators of Specialist Product for Structures)에서 제시하고 있는 터널 콘크리트 세그먼트의 내화성능평가 실험방법에 따른 내화실험 화재손상범위를 비교하여 실험방법에 따른 콘크리트 세그먼트의 화재거동 특성을 평가하였다. As the plan to subsea tunnels was announced in Korea, how to secure fire-resistance of the concrete linings in shield tunnels has been emerging as an important issue. Reinforced concrete segment used inside of shield tunnels is structural member which resists loads such as earth pressure or hydraulic pressure. Since high-strength concrete having compressive strength of over 40 MPa is used, significant damage to the segment is foreseeable upon a fire unless elaborate measures are taken against a fire. Therefore, in this study to find how to improve safety of concrete structure in shield tunnels, damage range observed from full-scale fire resistance test was compared with that observed from fire resistance test provided by the EFNARC (European Federation for Specialist Construction Chemicals and Concrete Systems) and the behaviors of concrete linings in the fire tests were evaluated.

Fire resistance characterisation of hemp fibre reinforced polyester composites for use in the construction industry

This paper presents research pertaining to the fire performance of natural fibre reinforced polymer composites (NFRP). Hemp fibre has been selected as representative of natural fibres used for reinforcement in NFRPs. The fire performance has been examined by a bench scale test method which provides an indicative assessment of the likely performance in full-scale fire resistance tests which are required for materials to meet building standards in the UK. It has been verified in this research that hemp fibres contribute to a thermally resistant char layer in polyester composites. There is an increase in thermal resistance of the char layer at high temperatures with an increase in fibre volume fraction. Ignition is delayed with an increase in fibre volume above 25%. Mechanical degradation occurs at relatively low temperatures which may be associated with the decomposition of hemicellulose and lignin. The desirability of NFRPs in terms of fire performance increases with an increase in fibre volume fraction and material thickness. Untreated hemp fibre reinforced polyester composites in this study have been characterised as having poor fire resistance and would not be expected to pass a full scale fire resistance test in their current state.

An approach to account for tie configuration in predicting fire resistance of reinforced concrete columns

High strength concrete (HSC) columns exhibit lower fire resistance, as compared to conventional normal strength concrete columns, due to occurrence of fire induced spalling and faster degradation of strength and stiffness properties of concrete with temperature. Fire resistance tests on HSC columns have shown that fire performance of HSC columns can be enhanced through bending the ends of ties at 135° into the concrete core, instead of bending the ties at 90°. This paper presents an analytical approach to model the effect of tie configuration on fire resistance of reinforced concrete (RC) columns. The proposed approach is based on seismic design principles and involves calculation of force acting on ties by evaluating effective stresses resulting from pore pressure, mechanical strain and thermal expansion. The resulting force acting on ties is compared against temperature (time) dependent bond strength (at the tie–concrete interface) to evaluate the failure of ties. The proposed tie sub-model is built into an existing macroscopic finite element based fire resistance analysis computer program that is capable of tracing the fire response of reinforced concrete (RC) columns in the entire range of behavior. The predictions from the model are compared against the full-scale fire resistance tests on RC columns to demonstrate the validity of the proposed approach in evaluating the beneficial effect of 135° tie configuration. The validated model is applied, through case studies, to quantify the effect of tie configuration on fire resistance of reinforced concrete columns. Results from numerical studies clearly show that HSC columns with 135° bent ties exhibit higher fire resistance than those HSC columns with 90° bent ties.

A simplified approach for fire-resistance design of steel-concrete composite beams

In this paper, a simplified approach based on critical temperature for fire resistance design of steel-concrete composite beams is proposed. The method for determining the critical temperature and fire protection of the composite beams is developed on the basis of load-bearing limit state method employed in current Chinese Technical Code for Fire safety of Steel Structure in Buildings. Parameters affecting the critical temperature of the composite beams are analysed. The results show that at a definite load level, section shape of steel beams, material properties, effective width of concrete slab and concrete property model have little influence on the critical temperature of composite beams. However, the fire duration and depth of concrete slab have significant influence on the critical temperature. The critical temperatures for commonly used composite beams, at various depth of concrete and fire duration, are given to provide a reference for engineers. The validity of the practical approach for predicting the critical temperature of the composite beams is conducted by comparing the prediction of a composite beam with the results from some fire design codes and full scale fire resistance tests on the composite beam.

Fire Resistance Performance Analysis of Reinforced Concrete Members Using Galerkin Finite Element Method

A research project is currently being conducted to develop and implement a 2D nonlinear Galerkin finite element analysis for reinforced concrete structures subjected to high temperature. Algorithms for calculating the closed-form element stiffness for a triangular element with a fully populated material conductance are developed. The validity of the numerical model used in the program is established by comparing the prediction from the computer program with results from full-scale fire resistance tests. Details of fire resistance experiments carried out on reinforced concrete slab, together with results, are presented. The results obtained from experimental test indicated that the proposed numerical model and the implemented codes are accurate and reliable. The changes in thermal parameters are discussed from the point of view of changes of structure and chemical composition due to the high temperature exposure. The proposed numerical model takes into account time-varying thermal loads, heat fluctuates due to the convection and radiation, and temperature- dependent material properties. Although, this study considers codes standard fire for reinforced concrete slab, any other time-temperature relationship can be easily incorporated.

Galerkin 유한요소법을 이용한 철근콘크리트 슬래브의 열전달해석 및 실험

이 연구는 실험과 병행 화재에 노출된 철근콘크리트 구조물의 갤러킨 유한요소해석 방법을 제시하였다. 이 방법은 비선형·비정상 온도분포해석에 관한 것으로 2차원 삼각형 요소에 대한 해석기법을 구축하였다. 해석기법의 검증을 위하여 실규모 철근콘크리트 슬래브에 대한 내화실험을 실시하였으며, 실험 결과와의 비교를 통해 해석기법의 유효성을 확인하였다. 또한 콘크리트 부재의 내화성능에 대한 실험 결과를 분석하였다. 변수분석에서는 화재규모, 콘크리트의 온도의존성 열적특성값, 콘크리트의 함수율이 콘크리트의 내화성능에 미치는 영향을 평가하였다. 이 연구에서 구축된 수치해석모델은 다양한 화재규모와 대류, 복사 경계조건, 재료의 온도의존성 열적특성값을 자유롭게 고려할 수 있다. 또한 이 논문에서는 콘크리트 슬래브를 대상으로 표준화재곡선을 대상으로만 분석하였지만 관련된 철근콘크리트 기둥 골조 해석에 용이하게 사용될 수 있을 것으로 판단되었다.

Performance in fire of FRP-strengthened and insulated reinforced concrete columns

This research investigates the fire performance of one circular and one square reinforced concrete column strengthened with a fibre reinforced polymer (FRP) wrap and covered with a unique supplemental fire protection system. An experimental full-scale fire resistance test was conducted at the National Research Council of Canada. The insulated and strengthened FRP wrapped columns were exposed to the ULC-S101 standard fire and both columns obtained fire endurance ratings of over 4 h. Details of the fire endurance experiment on both columns are described in this paper. Additionally, numerical models developed specifically for circular and square columns are validated against the experimental results.