Effect of increased charring on the narrow side of rectangular timber cross‐sections exposed to fire on three or four sides

Owing to the influence of two‐dimensional heat transfer, fire tests and heat transfer calculations show that charring on the narrow side of rectangular timber cross‐sections may be considerably greater than charring on the wide side. For timber members unprotected throughout the time of fire exposure as well as members initially protected from fire exposure, it is shown by calculation, that the relationship between charring on the narrow side and time is nonlinear. In order to take into account increased charring on the narrow side of timber members a section factor k_s was determined. By calculation it is shown that bending moment resistance is only insignificantly influenced by the effect of two‐dimensional heat transfer and the factor k_s can therefore be neglected, making the fire design of timber members easier. Copyright © 2011 John Wiley & Sons, Ltd.     

Mass loss and flammability of insulation materials used in sandwich panels during the pre‐flashover phase of fire

Nowadays, buildings contain more and more synthetic insulation materials in order to meet the increasing energy‐performance demands. These synthetic insulation materials have a different response to fire. In this study, the mass loss and flammability limits of different sandwich panels and their cores (polyurethane (PUR), polyisocyanurate (PIR) and stone wool) are studied separately by using a specially designed furnace. Expanded polystyrene and extruded polystyrene are tested on their cores only. The research has shown that the actual mass loss of synthetic and stone wool‐based cores is comparable up to 300 °C. From 300 °C onwards, the mass loss of PUR panels is significant higher. The mass losses up to 350 °C are 7%, 29% and 83% for stone wool, PIR and PUR respectively, for the influenced area. Furthermore, delamination can be observed at exposure to temperatures above 250 °C for the synthetic and 350 °C for the mineral wool panels. Delamination occurs due to the degradation of the resin between core and metal panels and the gasification of the (PUR) core. The lower flammability limits have been established experimentally at 9.2% m/m (PUR) and 3.1% m/m (PS). For PUR, an upper limit of 74% was found. For PIR and mineral wool, no flammability limits could be established. Copyright © 2017 John Wiley & Sons, Ltd.     

Experimental fire analysis of steel‐to‐timber connections using dowels and nails

The paper describes and discusses the results of an extensive testing programme on the structural behaviour of timber connections under ISO‐fire. The results of reference tests performed at normal temperature are also presented. From the variety of timber connections multiple shear steel‐to‐timber connections with dowels and slotted‐in steel plates and connections with steel side plates and annular ringed shank nails were experimentally studied. Particular attention was given to the analysis of the efficiency of different strategies in order to increase the fire resistance of the timber connections. The test results showed that unprotected multiple shear steel‐to‐timber connections with dowels designed for normal temperature reached a fire resistance of about 30 min. A reduction of the load level applied during the fire did not lead to a significant increase of the fire resistance. By increasing the side timber members as well as the end distance of the dowels by 40 mm the connections reached a fire resistance of more than 70 min. Connections protected by timber boards or gypsum plasterboards showed a fire resistance of around 60 min. Thus, from a fire design point of view these strategies were favourable in order to increase the fire resistance of the connections significantly. Unprotected connections with steel side plates and annular ringed shank nails failed already after about 12 min due to large deformations of the nails and the steel side plates directly exposed to fire. By protecting the steel side plates using an intumescent paint the fire resistance of the connections was increased to around 30 min. The test results enlarged the experimental background of timber connections in fire significantly. Copyright © 2009 John Wiley & Sons, Ltd.     

Fire performance of closed‐cell charring insulation materials in plasterboard‐insulation assemblies

This paper presents an experimental study on the fire performance of two types of plastic charring insulation materials when covered by a plasterboard lining. The specific insulation materials correspond to rigid closed‐cell plastic foams, a type of polyisocyanurate (foam A) and a type of phenolic foam (foam B), whose thermal decomposition and flammability were characterised in previous studies. The assemblies were instrumented with thermocouples. The plasterboard facing was subjected to constant levels of irradiation of 15, 25, and 65 kW m^?2 using the heat‐transfer rate inducing system. These experiments serve as (1) an assessment of the fire behaviour of these materials studied at the assembly scale and (2) an identification of the fire hazards that these systems pose in building construction. The manifestation of the hazards occurred via initial pyrolysis reactions and release of volatiles followed by various complex behaviours including char oxidation (smouldering), cracking, and expansion of the foam. Gas‐phase conditions may support ignition of the volatiles, sustained burning, and ultimately spread of the flame through the unexposed insulation face. The results presented herein are used to validate the insulation “critical temperature” concept used for a performance‐based methodology focused on the selection of suitable thermal barriers for flammable insulation.     

Small-scale assessment method for the fire resistance of historic plaster system and timber structures

The primary protection against the charring of timber is ensured by protection materials. Today, there are only a limited number of materials given in design codes as fire protection materials for timber. Historic surface finish materials such as plasters have rarely been studied with respect to fire; no design values exist in the current fire part of Eurocode 5. Full-scale fire testing is costly to assess the fire performance of material combinations, thus this study presents a useful tool that is specifically tailored to evaluate the fire protection ability of materials in small-scale. A review of conducted tests demonstrate that the cone heater of a cone calorimeter is a dependable device to estimate the charring performance of protected timber specimens as the test results approximate the ones obtained from furnace tests. This work contributes to the assessment of fire resistance performance of various combinations and types of plaster systems found in existing timber buildings that often require an individual approach for an adequate fire risk analysis and design decisions to meet current fire safety regulations with respect to the load-bearing capacity and compartmentation of building structures. Increased knowledge on the fire protection performance of traditional plasters is believed to facilitate their wider use in timber buildings, primarily to preserve their significance as part of the cultural built heritage.     

Fire characteristics of steel members coated with nano‐enhanced polymers

Polymeric coatings applied to masonry infill walls have been demonstrated to provide protection against blast. Steel frames may be embedded in these walls to improve the structural characteristics of the building. During the process of retrofitting the walls with blast protection polymeric coatings, the steel frame may be fully or partially coated with these materials to provide adequate anchorage of the retrofit system to the frame and to avoid global failure of walls subjected to blast loading. The development of a blast‐resistant coating for masonry walls that safeguards all structural elements in a fire would provide buildings with protection against explosions and a fire following the blast, as well as against ordinary building fires. This paper uses a numerical tool based on the particle finite element method to evaluate the melting and dripping of nano‐enhanced polymeric coatings applied on steel members embedded within masonry walls. Viscosity measurements were performed to obtain needed parameters for the simulations. Polyurea nanocomposite residues showed a minimum in viscosity with temperature, possibly caused by cross‐linking and charring. Model results for the polyurea residue with the lowest value of minimum viscosity showed that the coating remained attached, although there was some flow that caused a chunk of material to break off from an overhang. Copyright © 2013 John Wiley & Sons, Ltd.     

Predicting the fire resistance of timber members loaded in tension

The paper presents a numerical model for predicting the fire resistance of timber members. Fire resistance is evaluated in a two‐step process implemented in the Abaqus finite element code: first, a time‐dependent thermal analysis of the member exposed to fire and then a structural analysis under a constant load are performed. The structural analysis considers the reduction in mechanical properties (modulus of elasticity and strength) of timber with temperature. The analysis terminates when the member can no longer redistribute stresses from the hottest to the coldest parts, leading to structural failure. The model was used to simulate fire tests carried out on specimens made from laminated veneer lumber loaded in tension. Experimental data in terms of temperature, charring depth, displacement and failure time were compared with the numerical results obtained by assuming the thermal properties and degradation of mechanical properties with temperature as suggested by Eurocode 5, showing an overall acceptable approximation. The fire resistance of the timber member was then predicted depending upon the applied tensile loads using the numerical model and analytical formulas. The proposed finite element model can be used to predict the fire resistance of timber structures as an alternative to expensive and complicated experimental tests. Copyright © 2012 John Wiley & Sons, Ltd.     

A model to predict fire resistance of non‐load bearing wood‐stud walls

The author has developed a series of computer models to predict the fire resistance of wood‐framed walls and floors. The models utilize two‐dimensional heat‐conduction equations and thermo‐physical property data to describe heat transfer through the assemblies. The model for wall assemblies WALL2D, the basic version of the wall model, has already been published in Fire and Materials. Recently, WALL2D has been extended to WALL2DN to analyse heat transfer through insulated walls and walls that experience openings at the joints between adjacent sheets of gypsum board. Since gypsum board shrinks at high temperatures, the joints between adjacent sheets of gypsum board open. Hot fire gases, thereby, enter the openings and heat the edge of the gypsum board and wood studs. The new model WALL2DN simulates the joint opening and describes the resultant effect of openings. The model also calculates heat transfer through insulation in the stud cavity and depicts the effect of insulation on the fire resistance of non‐load bearing wall assemblies. Insulation selected in WALL2DN is glass‐fibre insulation, rock‐fibre insulation, polystyrene foam and polyurethane foam. When walls are exposed to fire, the insulation in the cavity shrinks (and/or melts) and an empty space appears at the interface between insulation and gypsum board. The model simulates this shrinking behaviour of insulation in the cavity. Finally, the model was validated by comparing the predicted results to those from full‐scale standard fire‐endurance tests. Copyright © 2003 John Wiley & Sons, Ltd.     

Charring rates and temperature profiles of wood sections

A research project was carried out at the Swiss Federal Institute of Technology (ETH) to study the fire behaviour of hollow core timber slabs and timber‐concrete composite slabs. This paper describes the main results of the basic fire behaviour of timber measured in the study. The first part of the analysis looks at the charring rate of timber. In the second part a new calculation model for the temperature development in wood members exposed to the standard ISO‐fire is presented and compared with the fire test results. Copyright © 2003 John Wiley & Sons, Ltd.     

Experimental investigation of acid environment influences on load‐bearing performance of pin‐connected continuous glass‐fiber‐reinforced polyphenylenesulfide composites

In this study we aimed to investigate the load‐bearing performance of pinned connections in corrosive environment. Experimental results are presented for the effect of acid environment on load‐bearing performance of pin‐connected continuous glass‐fiber‐reinforced polyphenylenesulfide composites. Chemical corrosion was also observed as an important environmental factor which affected the load‐bearing performance remarkably. Specimens were exposed to hydrochloric acid in order to find the durability of glass‐fiber‐reinforced plastics in hostile environments. An attempt is made to explain this phenomenon. The failure formation of material was affected by exposure time to HCl. Consequently, after the material has been exposed to acidic environment for 16 weeks, there were ∼93 and 95% performance decrease in the final failure load and first failure load, respectively. POLYM. COMPOS., 2010. © 2008 Society of Plastics Engineers     

The charring rate and charring depth of bamboo scrimber exposed to a standard fire

To better understand the charring properties of bamboo scrimber, a standard fire test was conducted to examine the effect of moisture content, exposure time, and grain direction on the charring rate of bamboo scrimber. The bamboo scrimber specimens were exposed to fire on one side with furnace temperatures following the requirements of ISO 834. The experimental results indicated the charring depth decreased as moisture content increased from 6% to 18%. Due to the thermal insulation of the char layer of bamboo scrimber, the charring rate decreased non‐linearly as the fire exposure time increased from 10 to 40 minutes. The charring rate of bamboo scrimber parallel to grain was approximately 1.23 times that perpendicular to grain. The non‐linear equation to express the charring rate of bamboo scrimber with moisture content, exposure time, and grain direction was established by regression analysis of the test data. The temperature of the char front was approximately 280°C, determined by heat transfer analysis of the 3‐dimensional finite element method model. Compared with different timber species in the literature and in standards, bamboo scrimber has better fire performance and a lower charring rate.     

Heat transfer model for a cementitious‐based insulation with moisture

The lack of actual thermal properties of fire insulation materials lead to erroneous temperature prediction of protected structural steel members. For cementitious‐based fire insulations, moisture held in the pores significantly alters the thermal response of the material. In this study, a heat transfer model is proposed to accurately predict the thermal response of cementitious‐based fire insulations. The effects of the moisture and the decomposition of calcium hydroxide are incorporated in the thermal properties of the selected insulation material. The model was validated against the thermal response of the material obtained experimentally using the finite element programme abaqus (LAF Group, Sydney, NSW, Australia). Copyright © 2013 John Wiley & Sons, Ltd.     

玻璃棉及其制品的应用

玻璃棉及其制品是理想的吸声材料,同时也是高效的节能材料。本文通过玻璃棉的化学成分、主要性能指标等的论述,指出了玻璃及其制品的性能特点及应用,同时也指出了建筑绝热保温材料是建筑节能的物质基础。     

Residual response of fire‐damaged high‐strength concrete beams

This paper presents results from an experimental study on residual capacity of fire‐damaged high‐strength concrete (HSC) beams. Four reinforced concrete (RC) beams, fabricated with HSC, were first subject to structural loading and fire exposure with a distinct cooling phase and then loaded to failure upon cooldown to ambient conditions to evaluate residual capacity. Temperatures, deflections, and spalling in the beams were monitored during heating and cooling phases of fire exposure. Further, residual capacity, strains at critical section, and crack patterns (failure mode) of fire‐damaged beams were recorded during residual capacity tests. Results from experiments indicate that the load level during fire exposure, duration of heating phase, rate of cooling, extent (type) of spalling, and duration of postcooling storage influence residual deformations and also residual capacity of RC beams. Further, fire‐damaged HSC beams can recover 40% to 70% of their flexural capacity with respect to their room temperature design capacity provided they survive the entire duration of fire exposure.     

Mechanical properties of fire‐damaged glass‐reinforced phenolic composites

Changes to the mechanical and physical properties of a glass‐reinforced resole phenolic composite due to intense radiant heat and fire are investigated. Fire testing was performed using a cone calorimeter, with the composite exposed to incident heat fluxes of 25, 50, 75 or 100 kW/m² for 325 s and to a constant flux of 50 kW/m² for different times up to 1800 s. The post‐fire tensile and flexural properties were determined at room temperature, and these decreased rapidly with increasing heat flux and heat exposure time due mainly to the chemical degradation of the phenolic resin matrix. The intense radiant heat did not cause any physical damage to the composite until burning began on exposure to a high heat flux. The damage consisted of cracking and combustion of the phenolic matrix at the heat‐exposed surface, but this only caused a small reduction to the mechanical properties. The implication of the findings for the use of glass‐reinforced resole phenolic composites in load‐bearing structures for marine craft and naval ships, where fire is a potential hazard, is discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

Fire performance of charring closed‐cell polymeric insulation materials: Polyisocyanurate and phenolic foam

Results are presented from 2 series of ad hoc experimental programmes using the cone calorimeter to investigate the burning behaviour of charring closed‐cell polymeric insulation materials, specifically polyisocyanurate (PIR) and phenolic (PF) foams. These insulation materials are widely used in the construction industry due to their relatively low thermal conductivity. However, they are combustible in nature; therefore, their fire performance needs to be carefully studied, and characterisation of their thermal degradation and burning behaviour is required in support of performance‐based approaches for fire safety design. The first series of experiments was used to examine the flaming and smouldering of the char from PIR and PF. The peak heat release rate per unit area was within the range of 120 to 170 kW/m² for PIR and 80 to 140 kW/m² for PF. The effective heat of combustion during flaming was within the range of 13 to 16 kJ/g for PIR and around 16 kJ/g for PF, while the CO/CO₂ ratio was within 0.05 to 0.10 for PIR and 0.025 to 0.05 for PF. The second experimental programme served to map the thermal degradation processes of pyrolysis and oxidation in relation to temperature measurements within the solid phase under constant levels of nominal irradiation. Both programmes showed that surface regression due to smouldering was more significant for PF than PIR under the same heat exposure conditions, essentially because of the different degree of overlap in pyrolysis and oxidation reactions. The smouldering of the char was found to self‐extinguish after removal of the external heat source.     

Uncertainties in modelling heat transfer in fire resistance tests: A case study of stone wool sandwich panels

Modelling fire performance of building fire barriers would allow optimising the design solutions before performing costly fire resistance tests and promote performance‐based fire safety engineering. Numerical heat conduction analysis is widely used for predicting the insulation capability of fire barriers. Heat conduction analysis uses material properties and boundary condition parameters as the input. The uncertainties in these input parameters result in a wide range of possible model outcomes. In this study, the output sensitivity of a heat conduction model to the uncertainties in the input parameters was investigated. The methodology was applied to stone wool core sandwich panels subjected to the ISO 834 standard fire resistance temperature/time curve. Realistic input parameter value distributions were applied based on material property measurements at site and data available in literature. A Monte Carlo approach and a functional analysis were used to analyse the results. Overall, the model is more sensitive to the boundary conditions than to the material thermal properties. Nevertheless, thermal conductivity can be identified as the most important individual input parameter.     

Semiconductor‐assisted self‐cleaning polymeric fibers based on zinc oxide nanoparticles

Self‐cleaning polymeric fibers have been successfully prepared by depositing ZnO nanoparticle onto wool and polyacrylonitrile (PAN) fibers with good compatibility and significant photocatalytic self‐cleaning activity using the sol‐gel process at ambient temperature. scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller surface area analysis, and thermogravimetric analysis have been adopted as the characterization techniques. Transmission electron microscopy studies revealed presence of zinc oxide nanoparticles with 10–15 nm in size. Brunauer‐Emmett‐Teller measurement showed surface area of 48 m²/g for the ZnO nanoparticles. Photocatalytic activity of the self‐cleaning materials were tested by measuring the photo‐assisted degradation of methylene blue (MB) and eosin yellowish (EY) under ultraviolet‐visible illumination. The results indicate that both of the ZnO‐coated polyacrylonitrile and ZnO‐coated wool fibers acquire photocatalytic activity toward dyes degradation. The photocatalytic activity of the treated fibers is maintained upon several numbers of photodegradation cycles. This facile and cheap preparation technique can be also applied to new polymeric fabrics to produce self‐cleaning materials for industrial application. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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

In 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.     

Temperature analysis of steel structures protected by intumescent paint with steel claddings in fire

It is of great interest to understand the stabilization effect of steel structures by steel claddings in fire. Structural fire analysis using finite-element method, including temperature analysis and structural analysis, is important to investigate the stabilization effect. However, temperature-dependent thermal material data for the insulation layer of sandwich panels and the intumescent paint for fire protection of steel sections are still scarce. In this paper, the available thermal properties of these materials from the literature are summarized, and 2D and 3D temperature analyses were carried out for steel sections with steel claddings, such as sandwich panels with mineral wool and polyisocyanurate (PIR) cores and trapezoidal sheeting with mineral wool insulation. The analysis results were compared with the fire tests conducted in European research project STABFI (Stabilization of Steel Structures by Steel Claddings in Fire). The study shows reasonable accuracy of modeling using existing thermal material data for temperature-dependent insulation properties and thermal data for intumescent paint, for intumescent coatings (IC) protected steel beam with mineral wool sandwich panel and trapezoidal sheeting claddings. Larger discrepancy between finite element (FE) prediction and test measurement was observed for the case of sandwich cladding with PIR core. Gaps for further research were identified. The study also shows the heat sink effect of the steel section by sandwich panels with a mineral wool core. Therefore, it is recommended that the sandwich panels should be included in the thermal analysis model for steel sections with sandwich claddings.