Model fire tests on a beam‐to‐leg connection in an offshore platform topside

Beam‐to‐column connections are of great significance as they noticeably influence the mechanical behavior of structures at ambient and elevated temperatures. Observations from full‐scale fire tests confirm that connections play an important role on the resistance time of structural components in fire. Because of the high cost of elevated temperature tests, adequate experimental data on a broad range of connections are not available. One type of such connections is the I‐beam‐to‐circular tubular leg connections in offshore oil/gas platform topsides. Considering the high risk of fire events in offshore oil/gas platforms, our study focuses on the structural behavior of this type of connection at elevated temperatures. Eleven small‐scale experimental tests were conducted on a uniplanar welded steel I‐beam‐to‐tubular chord connection with external diaphragms to investigate their fire resistance capacity. Local strengthening and partial thermal insulating were separately introduced to the connection components. The results show that the external diaphragms play a considerably more important role on the connection fire response as compared with that for the vertical stiffeners. It is also found that the degradations in the connections' stiffness at elevated temperature might be closely correlated with the classical thermomechanical data on steel material. Copyright © 2013 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.     

Predicting the thermal response of timber structures in natural fires using computational ‘heat of hydration’ principles

The thermo‐physical response of timber structures in fire is complex. For this reason, debate still exists today as to the best approaches for simulating thermal response in fire using tools such as finite element analysis (FEA) modelling. Much of the debate is concerned with the thermal properties of timber, for example, conductivity, specific heat and density, at elevated temperature and how such properties should be implemented or interpreted in numerical calculations. For practitioners intending to use modelling as a fire design tool for timber buildings, guidance exists on the thermal properties of softwood in Annex B of EN 1995‐1‐2. These properties are limited for use under standard fire exposure conditions because of the way in which they were derived from calibration against focussed test data. As a result, they cannot be applied to non‐standard fires, which are more representative of real fires due to a combination of varying heating rates and the decay phase of fire development. The limitations of the standard fire test (and associated curve) are widely understood. As a result, much recent structures in fire research has focussed on the ‘performance based design’ of buildings subject to increasingly realistic fire conditions. Such an approach allows engineers to quantify the level of safety that can be achieved in a building should a fire occur. In addition, the design of buildings to withstand fires proportionate to the risks foreseen and also the geometry present results in better value buildings that are inherently more robust. For the same approaches and associated benefits to be realised for timber buildings, then a number of barriers must be overcome. The most obvious of these is engineers' ability to determine timber structure temperatures as a result of fires other than the standard fire curve. This however presents a number of challenges. Upon heating, the moisture bound within begins to evaporate, volatiles begin to flow from the heated surface and char forms. The rate of which these behaviours occur and the nature of the char that forms depends on a number of factors, but most notably the rate of heating. Upon cooling, the timber member continues to generate heat energy as the surface oxidises. As a result, any models intended to simulate temperature development must consider the relationship not only between temperature and thermo‐physical characteristics but also between heating rate and the process of heat generation. Many models have been developed for this purpose; however, they are extremely complex and are some way from being ready for implementation as design tools. This paper proposes implementing ‘heat of hydration’ routines, intended for the curing of concrete structures, to simulate the heating and cooling process in timber structures. Such routines are available in many commercial FEA software packages. The adoption of the hydration routines allows the heat generation process, as a result of oxidation, to be considered in parallel with solid phase heat transfer using apparent thermal properties. The approach is shown to be very effective in simulating temperature development in timber members subject to parametric design fires. The models developed are benchmarked against experiments conducted in the 1990s by SP Trätek. Predictably, a number of the heat generation parameters adopted are shown to depend on the fire dynamics considered. However, recommended parameters are given that provide an acceptable level of accuracy for most design purposes. Copyright © 2012 John Wiley & Sons, Ltd.     

Behavior of beams in bolted column‐tree frames at elevated temperature

Column‐tree moment resisting frames, as the efficient shop‐welded and field‐bolted structural systems, are used in many countries. Very limited research has been carried out on such systems under fire conditions. This paper presents experimental and numerical investigations of the behavior of beam and bolted splice connections in steel column‐tree moment resisting frames exposed to fire. Two full‐scale steel sub‐frames with different splice connections were tested under International Organization for Standardization (ISO 834) fire. The observation of thermal and structural fire behaviors including temperature histories, temperature deflection of the beam, temperature rotation of splice connections, and failure modes was investigated. The beam splice connection failed because of shear fracture of top bolts at temperatures beyond 750 °C, while beam underwent large deflections of more than span/20. In addition, detailed 3‐D finite element models were developed to simulate the structural behavior of the specimens in fire. Obtained numerical results from the finite element analysis successfully simulated the experimental fire test results. Copyright © 2015 John Wiley & Sons, Ltd.     

Fire losses in selected property classifications of non‐residential,commercial and residential wood buildings. Part 1: hotels/motels and care homes for aged

In an attempt to evaluate the adequacy of building code requirements for selected classifications of non‐residential, commercial and residential wood buildings, researchers at Forintek Canada Corp. have examined Canadian and American fire loss statistics and compared fire losses for the selected classifications of wood buildings with those for similar buildings of non‐combustible construction. They have also examined causal factors associated with fires in those structures, extent of flame and smoke spread, ability of sprinkler systems and building construction to minimize fire losses, and outcomes of fire events. Because of the volume of information that was analysed, the results are being reported through three separate papers. This, the first, presents the ‘big picture’ with respect to fire losses in the selected classifications of non‐residential, commercial and residential structures, and discusses in detail fire losses for hotel/motel properties and care homes for the aged. Copyright © 2006 John Wiley & Sons, Ltd.     

Numerical modelling of carbon fibre‐reinforced polymer and hybrid reinforced concrete beams in fire

Investigation on the fire resistance of fibre‐reinforced polymer (FRP) reinforced concrete (RC) is essential for increased application of FRP bars in the construction industry. Experimental tests for determining the fire resistance of RC elements tend to be expensive and time‐consuming. Although numerical models provide an effective alternative to these tests, their use in case of FRP RC structures is hindered because of the insufficient constitutive laws for FRP bars at elevated temperatures. This paper presents the details of a numerical modelling work that was carried out for simply supported carbon FRP (CFRP) and hybrid (steel‐FRP) bar RC beams at elevated temperatures. Constitutive laws for determining temperature‐dependent strength and stiffness properties of CFRP bars are proposed. Numerical models based on finite element modelling were employed for the rational analysis of beams using the proposed constitutive laws. The behaviour of concrete was simulated by means of a smeared crack model based on the tangent stiffness solution algorithm. The employed numerical models were validated against previous experimental results. The theoretical rebar stresses were calculated in both the FRP and steel bars, and the differences are discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Temperature distribution in a nailed gypsum-stud joint exposed to fire

Performance of wood-stud walls depends on the integrity of nailed connections between the sheathing and the framing members. The performance of nailed connections has been studied at room temperature, but the effects of intense thermal loads, such as those from fire, are still poorly understood. This study examines the temperature distribution within nailed joints exposed to fire; this information is essential in modeling strength and stiffness of connections in wall systems. The finite-element method was used to determine the effects of wood density, nail size, and type of gypsum board on temperature distribution within a set of connections. Temperature distributions were verified in nailed joints exposed in fire tests conducted in accordance with ASTM E119-88. The principal path of heat flow through the connection was along the nail, rather than directly through the interface between gypsum board and wood. Wood species, type of gypsum board, and nail length did not change temperature distribution significantly.     

Effect of temperature and cooling regime on mechanical properties of high‐strength low‐alloy steel

This paper presents results from experimental studies on the effect of temperature on mechanical properties of high‐strength low‐alloy ASTM A572 steel commonly used in structural members in bridges. A set of high‐temperature tensile strength tests and post‐temperature exposed residual strength tests is carried out on ASTM A572 steel coupons in 20–1000 °C temperature range. The residual strength tests on high‐temperature exposed steel coupons are carried out after subjecting the coupons to two methods of cooling, namely, air cooling and water quenching. Results from these tests indicate that temperature‐dependent strength and stiffness degradation in A572 steel follow the same trend as that of carbon steel but with some variations. A572 steel recovers almost 100% of its room temperature yield strength when heated to temperature up to 600 °C, regardless of the method of cooling, while the extent of strength degradation in coupons subjected to heating beyond 600 °C is dependent on heated temperature and method of cooling. Data generated in these tests are utilized to generate high‐temperature stress–strain and residual stress–strain response of A572 steel. These results are also utilized to propose temperature‐dependent strength, elastic modules, and residual strength reduction factors of A572 steel, which can be used in evaluating residual response of fire‐exposed steel structures. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Research on seismic resistance and mechanic behavior of reinforced lightweight aggregate concrete walls after high temperature

This study focused on the mechanical behavior of reinforced lightweight aggregate concrete (RLAC) walls under repeated horizontal loads after a standard temperature‐rising fire‐resistance test and compared the specimen walls' ultimate loads, yielding loads, cracked loads, stiffness, and ductility with those of reinforced normal‐weight aggregate concrete (RNAC) walls. Steel reinforcing bar spacing, aggregate types, wall widths, and high temperatures were variables in this study. The experimental results showed that, after the fire‐resistance test, the smaller the steel reinforcing bar spacing of RLAC walls, the higher the yield and ultimate loads, yet the worse the ductility and the hysteresis loop's energy, whereas the greater the width of the wall, the greater the stiffness and the higher the hysteresis loop's energy. The differences in terms of stiffness, ductility, and hysteresis between RLAC walls with and without the fire‐resistance test were insignificant, indicating that RLAC walls do not lose their basic mechanical behavior during a high‐temperature fire. RNAC walls showed, indeed, a significant downward trend for strength and hysteresis after the fire‐resistance test, but the decrease was much less clear for stiffness. Therefore, RLAC walls did show better seismic resistance than RNAC walls under the same testing conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

超薄膨胀型钢结构防火涂料烃类火试验研究

钢结构建筑属于循环结构形式,由于钢材耐火性能差,温度超过600℃,材料强度和刚度都显著降低,因此必须对钢结构建筑进行防火保护。超薄膨胀型钢结构防火涂料逐渐应用到民用建筑钢结构防火保护中,而且GB14907—2002对其耐火性能评价方法有了具体规定,但是对石化烃类火环境下的耐火性能没有提及。本研究依据GB14907—2002的规定,参照UL1709的实验方法,对烃类火下超薄膨胀型钢结构防火涂料的耐火性能进行了测试。根据试验情况主要考察了涂料的发泡倍数,试验结果表明发泡倍数指标可以作为该类涂料的一个参考指标,并且对烃类火下超薄膨胀型防火涂料的施工养护和粘结强度等提出了建议。     

Temperature of post‐flashover compartment fires—Calculations and validation

This paper describes and validates by comparisons with tests a one‐zone model for computing temperature of fully developed compartment fires. Like other similar models, the model is based on an analysis of the energy and mass balance assuming combustion being limited by the availability of oxygen, ie, a ventilation‐controlled compartment fire. However, the mathematical solution techniques in this model have been altered. To this end, a maximum fire temperature has been defined depending on combustion efficiency and opening heights only. This temperature together with well‐defined fire compartment parameters was then used as a fictitious thermal boundary condition of the surrounding structure. The temperature of that structure could then be calculated with various numerical and analytical methods as a matter of choice, and the fire temperature could be identified as a weighted average between the maximum fire temperature and the calculated surface temperature of the surrounding structure as a function of time. It is demonstrated that the model can be used to predict fire temperatures in compartments with boundaries of semi‐infinitely thick structures as well as with boundaries of insulated and noninsulated steel sheets where the entire heat capacity of the surrounding structure is assumed to be concentrated to the steel core. With these assumptions, fire temperatures could be calculated with spreadsheet calculation methods. For more advanced problems, a general finite element solid temperature calculation code was used to calculate the temperature in the boundary structure. With this code, it is possible to analyze surrounding structures of various kinds, for example, structures comprising several materials with properties varying with temperature as well as voids. The validation experiments were accurately defined and surveyed. In all the tests, a propane diffusion burner was used as the only fire source. Temperatures were measured with thermocouples and plate thermometers at several positions.     

Eurocode method for calculating the external steelwork temperature in fire; comparative studies

To design a steel structure in fire is necessary to know its temperature. Using the data from many experimental fire tests, Margaret Law estimated the maximum temperature in a compartment (natural fire), the external heat transfer to steel elements and the maximum temperature value for steel. The Eurocode adopted her method, with minor adjustments. The method is very calculation intensive—it involves about 60 equations—too many for a quick hand calculation. Besides, while a distinction is made between steel members engulfed and not engulfed in flame, the method is not clear about partially engulfed members. The authors developed the software ExteelFire to determine the maximum temperature of external steel structures for buildings in fire based on the Eurocode method including the determination of the temperature of the partially engulfed elements. Aiming to ascertain the level of safety of the Eurocode method, the results from ExteelFire and a numerical analysis performed using Smartfire (CFD software for the fire model) and Super Tempcalc (finite element method, FEM, software for the thermal analysis) were compared. Furthermore, results from ExteelFire and from two full‐scale experimental tests (Dalmarnock and Ostrava) were contrasted. Based on the comparisons, the Eurocode method is conservative. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance of a light timber‐framed compartment in natural fire subjected to lateral load

A common approach for designing buildings for lateral stability during and post‐fire in New Zealand is to ensure that a fire‐rated structure does not collapse when subjected to a nominal horizontal force. For external walls of residential buildings, which are required to resist a lateral load of 0.5 kPa, it is hypothesised that the adjacent unrated construction could provide sufficient support. A natural fire experiment has been conducted to evaluate the fire performance of a laterally loaded light timber‐framed compartment, with external dimensions of 4.33 m × 3.35 m and a stud height of 2.4 m constructed with a timber truss roof and plasterboard ceiling. During the experiment, the ceiling collapsed at 12 to 13 minutes, and the bottom chord of the roof truss failed in tension after 28 minutes which resulted in the fire‐rated wall losing its lateral stability at 28 minutes. The fire severity experienced in the compartment has been estimated to correspond to an equivalent time of 33‐minute exposure to a standard furnace time‐temperature. It is concluded that there is no need to provide nominal (additional) moment‐resisting fixity at the base of the fire‐rated wall when exposed to the standard fire for no more than 30 minutes.     

Ansätze zur numerischen Berechnung von Brandeinwirkungen auf Bauteile

Within the context of the preparation of fire safety certificates for industrial buildings methods of fire protection engineering are frequently used. Computational fluid dynamics represents instruments for these methods and is used for modeling and calculation of fire scenarios. In this paper a method of fire technological measurement, which is based on computational fluid dynamics and structural mechanics, was used for an industrial building. Unsteady temperature profiles were used as an input value for the building component calculation. The outcomes were finally used for the calculation of the equivalent length of fire, which is an important term to reckon the fire resistance rating of building components.     

Overall stability analysis of oversized steel‐framed buildings in a fire

Our present paper summarizes the shortcomings in the current fire‐resistant design of oversized steel structures and proposes a method for overall stability analysis of steel structures in the event of fire. The Fire Dynamics Simulator (FDS) software platform–based large‐eddy simulation technology can accurately reflect the environment in a fire scenario and correctly predict the spatial–temporal change in the smoke temperature field within an oversized space. Adopting the FDS software and finite element structural analysis (ANSYS) coupling can fundamentally overcome the natural defect of adopting the International Organization for Standardization (ISO) standard curve (or other indoor homogeneous temperature increase curves) that substitutes a point for the overview of a field. They reflect the structural additional internal force and internal force redistribution incurred by the gradient temperature difference of the spatial–temporal changing nonhomogeneous temperature field and both theoretically and technically realize the analysis of structural heat transfer and mechanical properties in a natural fire. Furthermore, a modified model to predict the steel temperature curve in localized fire is also proposed. The localized fire in large spaces can be treated as a point fire source to evaluate the flame thermal radiation to steel members in the modified model. Copyright © 2014 John Wiley & Sons, Ltd.     

Fire‐retardant hybrid thermosetting resins from unsaturated polyesters and polysilazanes

This introduces an organic–inorganic thermosetting hybrid resin system based on unsaturated polyester and polysilazanes. It shows the chemical modification of unsaturated polyester structures by end capping to enable the combination of both components. In general, halogen‐free unsaturated polyesters are not fire‐retardant and have to be equipped with additives. Fillers and intumescent additives are preponderantly used in today's fire‐retardant formulations. In contrast to these fire‐retardants, polysilazanes act as ceramizing agents. Polysilazanes are suitable fire‐retardants for resin transfer molding due to their low viscosity. Both burning behavior and glass transition temperature (T_g) are investigated as important application properties. In contrast to state‐of‐the‐art fire‐retardant formulations polysilazane‐based thermosetting hybrid resins burn with high intensity and fast extinction. Therefore, total heat and smoke emission is decreased. The formation of ceramic structures during burning results in high residual mechanical properties and a low mass loss. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40375.     

Numerical simulation of the fire behaviour of façade equipped with aluminium composite material‐based claddings—Model validation at intermediate scale

Increasing the energy performance of buildings is a crucial sustainable development objective. However, building features, products, mounting, and fixing of façade components have a large impact on fire safety. Authors in previous study performed façade fire propagation tests according to ISO13785‐1 on different combinations of ACM claddings and insulants. In this paper, simulations are performed to reproduce three of these tests. The model is validated with the aforementioned experimental results, including details in terms of thermal conditions in the system. This allows better understanding of the fire propagation on the overall system. Additional information, such as the relative contribution of the cladding and the insulant, are investigated numerically. The fire behaviour of each component of the overall system is thus validated. Simulations and tests performed show that the ACM cladding is the most important element driving the global fire behaviour of façade types considered. In particular, ACM‐PE–based cladding systems show large fire propagation whatever the insulant. This series of simulations is a part of a larger study including several steps of increasing complexity. Once the model for the fire behaviour of façade system is validated at intermediate scale, larger façade systems will be investigated numerically to evaluate the influence of scaling.     

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.     

Experimental study of the fire resistance of walls and floors constructed with steel studs and steel joists

Steel‐framed houses using light‐gauge steel as a structural member have been developed and constructed since the early 2000s as a new construction pattern in the low‐rise construction market in Korea. Generally, the steel frames consist of two major load‐carrying elements such as load‐bearing wall and floor construction made up of approximately 1.0‐mm cold‐formed light‐gauge steel and light‐weight boards. Therefore, the steel frames are very simple to construct and make the construction period shorter than the ordinary construction type or concrete‐based construction. In Korea, regardless of the construction material types, the building regulation requires 1‐h fire rating for apartment buildings of four stories or under. To meet the fire resistance, new models of load‐bearing wall and floor should be developed. From the fire test results, two layer gypsum boards of 12.5 mm in thickness reinforced with glass fiber were proven satisfactory to provide 1‐h fire resistance with load‐bearing wall and floor. Copyright © 2012 John Wiley & Sons, Ltd.