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

2018 ◽  
Vol 9 (3) ◽  
pp. 222-236 ◽  
Author(s):  
Joachim Schmid ◽  
Alessandro Santomaso ◽  
Daniel Brandon ◽  
Ulf Wickström ◽  
Andrea Frangi
Keyword(s):  
Oxygen Content ◽  
Gas Flow ◽  
Fire History ◽  
Gas Velocity ◽  
Protective Function ◽  
Content Type ◽  
Char Layer ◽  
Standard Fire ◽  
Timber Member ◽  
Cooling Phase

Purpose The 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/approach This 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. Findings In 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/value Up 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.

Fire performance, including the cooling phase, of structural glued laminated timber beams

2016 ◽  
Vol 7 (4) ◽  
pp. 349-364 ◽  
Author(s):  
H. Kinjo ◽  
T. Hirashima ◽  
S. Yusa ◽  
T. Horio ◽  
T. Matsumoto
Keyword(s):  
Temperature Distribution ◽  
Maximum Load ◽  
Strength Reduction ◽  
Fire Performance ◽  
Load Bearing ◽  
Content Type ◽  
Standard Fire ◽  
Glued Laminated Timber ◽  
Charring Rate ◽  
Cooling Phase

Purpose Based on heating tests and load-bearing fire tests, this paper aims to discuss the charring rate, the temperature distribution in the section and the load-bearing capacity of structural glued laminated timber beams not only during the heating phase during a 1-h standard fire in accordance with ISO 834-1 but also during the cooling phase. Design/methodology/approach Heating tests were carried out to confirm the charring rate and the temperature distribution in the cross-section of the beams. Loading tests under fire conditions were carried out to obtain the load-deformation behavior (i.e. the stiffness, maximum load and ductility) of the beam. Findings The temperature at the centroid reached approximately 30°C after 1 h and then increased gradually until reaching 110-200°C after 4 h, during the cooling phase. The maximum load of the specimen exposed to a 1-h standard fire was reduced to approximately 30 per cent of that of the specimen at ambient temperature. The maximum load of the specimen exposed to a 1-h standard fire and 3 h of natural cooling in the furnace was reduced to approximately 14 per cent. In case of taking into consideration of the strength reduction at elevated temperature, the reduction ratio of the calculated bending resistance agreed with that of the test results during not only heating phase but also cooling phase. Originality/value The results of this study state that it is possible to study on strength reduction in cooling phase for end of heating, timber structural which has not been clarified. It is believed that it is possible to appropriately evaluate the fire performance, including the cooling phase of the timber structural.

Simulation of charring depth of timber structures when exposed to non-standard fire curves

2018 ◽  
Vol 9 (1) ◽  
pp. 63-76 ◽  
Author(s):  
Jean-Christophe Mindeguia ◽  
Guillaume Cueff ◽  
Virginie Dréan ◽  
Gildas Auguin
Keyword(s):  
Fire Resistance ◽  
Experimental Studies ◽  
Thermal Exposure ◽  
Performance Based Design ◽  
Analytical Models ◽  
Content Type ◽  
Char Layer ◽  
Wooden Structure ◽  
Standard Fire ◽  
A Performance

Purpose The fire resistance of wooden structures is commonly based on the calculation or measurement of the char layer. Designers usually estimate the char layer at the surface of a structural element by using analytical models. Some of these charring models can be found in regulations, as Eurocode 5. These analytical models, quite simple to use, are only reliable for the standard fire curve. In that case, the design of the structure is qualified as “prescriptive-based design” and can lead to oversizing the structure. Optimization of a structure can be achieved by using a “Performance-based design”, where realistic fire scenarios are taken into account by means of more or less complex models [parametric fires, two-zones models, computational fluid dynamics (CFD)]. For these so-called “natural fires”, no model for charring is available. The purpose of this paper is to present a novel methodology for applying a performance-based design to a simple timber structure. Design/methodology/approach This paper presents the development of a numerical model aiming to simulate the thermal transfer and charring in wood, under any type of thermal exposure, including non-standard fire curves. After presenting the physical background, the model is calibrated and compared to existing experimental studies on wood samples exposed to different fire curves. The model is then used as a tool for assessing the fire resistance of a common wooden structure exposed to standard and non-standard fire curves. Findings The results show that the fire resistance is obviously dependent on the choice of the thermal exposure. The reliability of the model is also discussed and the importance of taking into account particular reactions in wood during heating is underlined. Originality/value One aim of this paper is to show the opportunity to apply a performance-based approach when designing a wooden structure. It shows that more knowledge of the material behaviour under non-standard fires is still needed, especially during the decay phase.

Finite element analysis of lightweight concrete-filled LSF walls exposed to realistic design fire

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Irindu Upasiri ◽  
Chaminda Konthesingha ◽  
Anura Nanayakkara ◽  
Keerthan Poologanathan ◽  
Gatheeshgar Perampalam ◽  
...  
Keyword(s):  
Lightweight Concrete ◽  
Fire Exposure ◽  
Fire Performance ◽  
Content Type ◽  
Design Fire ◽  
Standard Fire ◽  
Heating And Cooling ◽  
Cooling Phase ◽  
Concrete Filling ◽  
Design Fires

PurposeLight-Gauge Steel Frame (LSF) structures are popular in building construction due to their lightweight, easy erecting and constructability characteristics. However, due to steel lipped channel sections negative fire performance, cavity insulation materials are utilized in the LSF configuration to enhance its fire performance. The applicability of lightweight concrete filling as cavity insulation in LSF and its effect on the fire performance of LSF are investigated under realistic design fire exposure, and results are compared with standard fire exposure.Design/methodology/approachA Finite Element model (FEM) was developed to simulate the fire performance of Light Gauge Steel Frame (LSF) walls exposed to realistic design fires. The model was developed utilising Abaqus subroutine to incorporate temperature-dependent properties of the material based on the heating and cooling phases of the realistic design fire temperature. The developed model was validated with the available experimental results and incorporated into a parametric study to evaluate the fire performance of conventional LSF walls compared to LSF walls with lightweight concrete filling under standard and realistic fire exposures.FindingsNovel FEM was developed incorporating temperature and phase (heating and cooling) dependent material properties in simulating the fire performance of structures exposed to realistic design fires. The validated FEM was utilised in the parametric study, and results exhibited that the LSF walls with lightweight concrete have shown better fire performance under insulation and load-bearing criteria in Eurocode parametric fire exposure. Foamed Concrete (FC) of 1,000 kg/m3 density showed best fire performance among lightweight concrete filling, followed by FC of 650 kg/m3 and Autoclaved Aerated Concrete (AAC) 600 kg/m3.Research limitations/implicationsThe developed FEM is capable of investigating the insulation and load-bearing fire ratings of LSF walls. However, with the availability of the elevated temperature mechanical properties of the LSF wall, materials developed model could be further extended to simulate the complete fire behaviour.Practical implicationsLSF structures are popular in building construction due to their lightweight, easy erecting and constructability characteristics. However, due to steel-lipped channel sections negative fire performance, cavity insulation materials are utilised in the LSF configuration to enhance its fire performance. The lightweight concrete filling in LSF is a novel idea that could be practically implemented in the construction, which would enhance both fire performance and the mechanical performance of LSF walls.Originality/valueLimited studies have investigated the fire performance of structural elements exposed to realistic design fires. Numerical models developed in those studies have considered a similar approach as models developed to simulate standard fire exposure. However, due to the heating phase and the cooling phase of the realistic design fires, the numerical model should incorporate both temperature and phase (heating and cooling phase) dependent properties, which was incorporated in this study and validated with the experimental results. Further lightweight concrete filling in LSF is a novel technique in which fire performance was investigated in this study.

scholarly journals Influence of center gas supply device on gas–solid flow in COREX shaft furnace through DEM–CFD model

2020 ◽  
Vol 18 (5-6) ◽  
Author(s):  
Heng Zhou ◽  
Shuyu Wang ◽  
Binbin Du ◽  
Mingyin Kou ◽  
Zhiyong Tang ◽  
...  
Keyword(s):  
Gas Flow ◽  
Shaft Furnace ◽  
Middle Zone ◽  
Cfd Model ◽  
Gas Velocity ◽  
Gas Distribution ◽  
Particle Segregation ◽  
Solid Flow ◽  
Corex Shaft Furnace ◽  
Gas Supply

AbstractIn order to develop the central gas flow in COREX shaft furnace, a new installment of center gas supply device (CGD) is designed. In this work, a coupled DEM–CFD model was employed to study the influence of CGD on gas–solid flow in COREX shaft furnace. The particle descending velocity, particle segregation behaviour, void distribution and gas distribution were investigated. The results show that the CGD affects the particles descending velocity remarkably as the burden falling down to the slot. Particle segregation can be observed under the inverse ‘V’ burden profile, and the influence of CGD on the particle segregation is unobvious on the whole, which causes the result that the voidage is slightly changed. Although the effect of CGD on solid flow is not significant, the gas flow in shaft furnace has an obvious change. Compared with the condition without CGD, in the case with CGD, the gas velocity is improved significantly, especially in the middle zone of the furnace, which further promotes the center gas distribution. Meanwhile, the pressure drop in the furnace with the installation of CGD is increased partly.

Experimental study on fire resistance of a full-scale composite floor assembly in a two-story steel framed building

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Lisa Choe ◽  
Selvarajah Ramesh ◽  
Xu Dai ◽  
Matthew Hoehler ◽  
Matthew Bundy
Keyword(s):  
Natural Gas ◽  
Fire Resistance ◽  
Full Scale ◽  
System Level ◽  
Compartment Fire ◽  
Content Type ◽  
Standard Fire ◽  
Fire Experiment ◽  
The Usa ◽  
Floor System

PurposeThe purpose of this paper is to report the first of four planned fire experiments on the 9.1 × 6.1 m steel composite floor assembly as part of the two-story steel framed building constructed at the National Fire Research Laboratory.Design/methodology/approachThe fire experiment was aimed to quantify the fire resistance and behavior of full-scale steel–concrete composite floor systems commonly built in the USA. The test floor assembly, designed and constructed for the 2-h fire resistance rating, was tested to failure under a natural gas fueled compartment fire and simultaneously applied mechanical loads.FindingsAlthough the protected steel beams and girders achieved matching or superior performance compared to the prescribed limits of temperatures and displacements used in standard fire testing, the composite slab developed a central breach approximately at a half of the specified rating period. A minimum area of the shrinkage reinforcement (60 mm2/m) currently permitted in the US construction practice may be insufficient to maintain structural integrity of a full-scale composite floor system under the 2-h standard fire exposure.Originality/valueThis work was the first-of-kind fire experiment conducted in the USA to study the full system-level structural performance of a composite floor system subjected to compartment fire using natural gas as fuel to mimic a standard fire environment.

Characterizations and Process Parameters of Titanium Dioxide Thin Film by RF Sputtering

2013 ◽  
Vol 22 ◽  
pp. 9-21 ◽  
Author(s):  
Chii Rong Yang ◽  
Tun Ping Teng ◽  
Yun Yu Yeh
Keyword(s):  
Thin Films ◽  
Oxygen Content ◽  
Flow Rate ◽  
Gas Flow ◽  
Deposition Time ◽  
Photocatalytic Performance ◽  
Oxidation Process ◽  
Rf Sputtering ◽  
Rf Magnetron Sputtering ◽  
Oxygen Ratio

In this study, we successfully combined RF magnetron sputtering of a pure Ti metal target and one-stage oxidation process with a wider oxygen ratio (10%-90%) and total sputtering flow rate (16-24 sccm) to produce TiO2thin films on a glass substrate. The crystallization, morphology, roughness, and thickness of the thin films were examined using XRD, HR-FESEM, AFM, and a profilometer. Subsequently, the photocatalytic performance was examined using a spectrometer and video tensiometer. The experimental results show that the TiO2thin films with a majority of anatase and higher roughness exhibit superior photocatalytic performance; the total sputtering gas flow rate of 18 sccm and oxygen content at 10% is the optimal option. Finally, an empirical formula to correlate the film thickness with deposition time was conducted for the sputtering flow rate of 18 sccm and the oxygen content of 10%.

Characterizations of Zinc Oxynitride Powders Prepared Under Ammonia Gas Flow

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1523-1526 ◽  
Author(s):  
Takashi Sakamoto ◽  
Ryoji Saki ◽  
Toshihiro Moriga ◽  
Kei Ichiro Murai ◽  
Ichiro Nakabayashi
Keyword(s):  
Band Gap ◽  
Oxygen Content ◽  
Lattice Constant ◽  
Gas Flow ◽  
Optical Band Gap ◽  
Zinc Powder ◽  
Ammonia Gas

The anti-bixbyite-type zinc oxynitrides Zn 3( N1-xOx ) 2-y could be prepared by directly nitriding zinc powder under ammonia gas flow. Oxygen content x and amount of anion deficiency y decreased with increasing nitriding period at [Formula: see text]. Zn 3( N0.91O0.09 )1.98 could be obtained after the 168 hours of nitridation at [Formula: see text]. Reduction of both x and y, especially x, enhanced the lattice constant and reduced optical band gap of the oxynitride.

scholarly journals Important Late-Stage Symbiotic Role of theSinorhizobium melilotiExopolysaccharide Succinoglycan

2018 ◽  
Vol 200 (13) ◽  
pp. e00665-17 ◽  
Author(s):  
Markus F. F. Arnold ◽  
Jon Penterman ◽  
Mohammed Shabab ◽  
Esther J. Chen ◽  
Graham C. Walker
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Late Stage ◽  
Sinorhizobium Meliloti ◽  
Antimicrobial Action ◽  
Protective Function ◽  
Content Type ◽  
Early Stages ◽  
Symbiotic Interactions ◽  
Legume Symbiosis

ABSTRACTSinorhizobium melilotienters into beneficial symbiotic interactions withMedicagospecies of legumes. Bacterial exopolysaccharides play critical signaling roles in infection thread initiation and growth during the early stages of root nodule formation. After endocytosis ofS. melilotiby plant cells in the developing nodule, plant-derived nodule-specific cysteine-rich (NCR) peptides mediate terminal differentiation of the bacteria into nitrogen-fixing bacteroids. Previous transcriptional studies showed that the intensively studied cationic peptide NCR247 induces expression of theexogenes that encode the proteins required for succinoglycan biosynthesis. In addition, genetic studies have shown that someexomutants exhibit increased sensitivity to the antimicrobial action of NCR247. Therefore, we investigated whether the symbiotically activeS. melilotiexopolysaccharide succinoglycan can protectS. melilotiagainst the antimicrobial activity of NCR247. We discovered that high-molecular-weight forms of succinoglycan have the ability to protectS. melilotifrom the antimicrobial action of the NCR247 peptide but low-molecular-weight forms of wild-type succinoglycan do not. The protective function of high-molecular-weight succinoglycan occurs via direct molecular interactions between anionic succinoglycan and the cationic NCR247 peptide, but this interaction is not chiral. Taken together, our observations suggest thatS. melilotiexopolysaccharides not only may be critical during early stages of nodule invasion but also are upregulated at a late stage of symbiosis to protect bacteria against the bactericidal action of cationic NCR peptides. Our findings represent an important step forward in fully understanding the complete set of exopolysaccharide functions during legume symbiosis.IMPORTANCESymbiotic interactions between rhizobia and legumes are economically important for global food production. The legume symbiosis also is a major part of the global nitrogen cycle and is an ideal model system to study host-microbe interactions. Signaling between legumes and rhizobia is essential to establish symbiosis, and understanding these signals is a major goal in the field. Exopolysaccharides are important in the symbiotic context because they are essential signaling molecules during early-stage symbiosis. In this study, we provide evidence suggesting that theSinorhizobium melilotiexopolysaccharide succinoglycan also protects the bacteria against the antimicrobial action of essential late-stage symbiosis plant peptides.

scholarly journals Practical method to predict the axial capacity of RC columns exposed to standard fire

2018 ◽  
Vol 9 (4) ◽  
pp. 266-286 ◽  
Author(s):  
Salah F. El-Fitiany ◽  
Maged A. Youssef
Keyword(s):  
Concrete Strength ◽  
Practical Method ◽  
Simple Method ◽  
Rc Columns ◽  
Content Type ◽  
Natural Fire ◽  
Rc Structures ◽  
Axial Capacity ◽  
Standard Fire ◽  
Structural Engineers

Purpose Existing analytical methods for the evaluation of fire safety of reinforced concrete (RC) structures require extensive knowledge of heat transfer calculations and the finite element method. This paper aims to propose a rational method to predict the axial capacity of RC columns exposed to standard fire. Design/methodology/approach The average temperature distribution along the section height is first predicted for a specific fire scenario. The corresponding distribution of the reduced concrete strength is then integrated to develop expressions to calculate the axial capacity of RC columns exposed to fire from four faces. Findings These expressions provide structural engineers with a rational tool to satisfy the objective-based design clauses specified in the National Code of Canada in lieu of the traditional prescriptive methods. Research limitations/implications The research is limited to standard fire curves and needs to be extended to cover natural fire curves. Originality/value This paper is the first to propose an accurate yet simple method to calculate the axial capacity of columns exposed to standard fire curves. The method can be applied using a simple Excel sheet. It can be further developed to apply to natural fire curves.

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