胶合木结构螺栓连接耐火极限的试验

通过对胶合木构件螺栓连接的火灾试验,研究连接的侧材厚度、螺栓直径、螺栓数、端距、荷载水平、施加保护等参数对连接耐火极限的影响。结果表明:螺栓的直径和间距对耐火极限影响不大,而增加侧材厚度、降低荷载水平、增加连接端距能提高其耐火极限;需要对连接施加有效的保护才能达到规定的耐火极限。     

Fire effluent component yields from room‐scale fire tests

Estimation of the time available for escape (ASET) in the event of a fire is a principal component in fire hazard or risk assessment. Valid data on the yields of toxic smoke components from bench‐scale apparatus is essential to accurate ASET calculations. This paper presents a methodology for obtaining pre‐flashover and post‐flashover toxicant yields from room‐scale fire tests. The data are to be used for comparison with bench‐scale data for the same combustibles: a sofa, bookcases, and electric power cable. Each was burned in a room with a long adjacent corridor. The yields of CO₂, CO, HCl, HCN, and soot were determined. Other toxicants (NO₂, formaldehyde, and acrolein), whose concentrations were below the detection limits, were of limited importance relative to the detected toxicants. The uncertainty values were comparable to those estimated for calculations used to determine ASET and were sufficiently small to determine whether a bench‐scale apparatus is producing results that are similar to the real‐scale results here. The use of Fourier transform infrared spectroscopy was useful for obtaining toxicant concentration data; however, its operation and interpretation are not routine. The losses of CO, HCN, and HCl along the corridor were dependent on the combustible. Copyright © 2009 John Wiley & Sons, Ltd.     

Fire resistance of cold-formed steel framed shear walls under various fire scenarios

This paper presents results of large-scale experiments with varying levels of fire severity on lateral force-resisting systems commonly used in cold-formed steel framed buildings. Gypsum-sheet steel composite panel sheathed walls, oriented strand board sheathed walls, and steel strap-braced walls are examined. Postflashover fire conditions of two different intensities as well as 1 hour of fire exposure similar to that in a standard furnace qualification test are studied. Additionally, a full-scale furnished kitchen fire experiment is conducted for comparison. The results highlight differences in the thermal response and subsequent performance of the walls as well as differing sensitives of the walls to pre-damage, eg, that might occur during an earthquake. The results are part of a larger effort to provide fragilities for these wall systems in response to realistic fires for performance-based design.     

Comparative energy analysis from fire resistance tests on combustible versus noncombustible slabs

Standard fire resistance tests have been used in the design of structural building elements for more than a century. Originally developed to provide comparative measures of the level of fire safety of noncombustible products and elements, the recent resurgence in engineered timber construction raises important questions regarding the suitability of standard fire resistance tests for combustible structural elements. Three standard fire resistance floor tests (5.9 m × 3.9 m in plan), one on a concrete slab and two on cross-laminated timber (CLT) slabs, were undertaken to explore some of the relevant issues. The fuel consumption rate within the furnace was recorded during these tests, and the energy supplied from this was determined. An external fuel supply (from natural gas supplied to the furnace) equating to approximately 3 MW was recorded throughout the concrete test, whereas this was about 1.25 MW throughout the CLT tests. The total heat release rate was calculated using carbon dioxide generation calorimetry; this yielded values of approximately 1.75 MW during the CLT tests (ie, an additional energy contribution of approximately 0.5 MW from the timber). This demonstrates that considerably more energy input (by about 1.25 MW) was needed to heat the system when the test sample was noncombustible. A further series of six large-scale compartment fire experiments (6 m × 4 m × 2.52 m) was undertaken to further explore comparative performance of combustible versus noncombustible construction when the external fuel load is kept constant and is governed by more realistic compartment fire dynamics. For a fuel-controlled case, the peak temperatures in the compartment with an unprotected CLT ceiling were approximately 200°C higher than in the compartments with a concrete ceiling, whereas for a ventilation-controlled case, the compartment with a CLT slab ceiling displayed a burning duration that increased by approximately 15 minutes. Potential implications for standard fire resistance testing of combustible specimens are discussed.     

Sprinklered office fire tests

This paper presents data relating to the performance of sprinklers and detectors in real office fire situations. For sprinklers, these data are additional to that associated with the standardized testing used to determine the design delivery density and pressure requirements for various occupancy situations, and provide a useful insight into the effect of sprinklers on developing fires with various office situations. The data given in this paper include the times for activation of various types of sprinkler heads (normal and fast response), the efficacy of the systems as far as extinguishment is concerned, estimates of the maximum size of the fires prior to commencement of extinguishment and associated air temperatures at various locations within the office enclosures. Copyright © 2008 John Wiley & Sons, Ltd.     

Chemical changes in slabs of cast gypsum during standard tests of resistance to fire

A study was made of changes in composition occurring in slabs of cast gypsum when subjected to standard tests of resistance to fire. The temperature of the unfired surfaces of the specimens rose rapidly for ～55°c and then continued to rise but very much more slowly. Eventually, the temperature again began to rise rapidly and thermal failure occurred. In the cases of the thicker specimens tested, the increase in temperature during the period of slow rise was in the form of two steps separated by a period of faster heating. Observations were made on the composition of specimens heated to various extents. Dehydration was virtually complete at the beginning of the final rapid increase in temperature.     

高低温交替对涂料防火性能的影响

利用冷热循环法加速防火涂料的老化,采用小室法和酒精喷灯法分别研究了自制水性硅丙饰面防火涂料和3种市售水性防火涂料(包括丙烯酸、聚氨酯和苯丙防火涂料)在冷热循环前以及冷热循环15、30和45d后的质量损失、耐火时间及炭层高度。结果表明,4种涂料在冷热循环过程中的防火性能均逐渐下降。其中水性丙烯酸防火涂料在冷热循环45d后失去了阻燃作用;水性聚氨酯和水性苯丙饰面防火涂料在交替温度变化过程中的防火性能下降幅度较大,但仍高于国标;自制水性硅丙饰面防火涂料在45d交替温度变化过程中,防火性能变化不大,仍具有良好的阻燃作用。     

Fire performance of gusset connections in glue-laminated timber

This paper describes a comprehensive experimental investigation of the fire performance of nailed gusset connections between large glue-laminated timber members. Both plywood and steel gusset plates were investigated with a range of loaded and unloaded test methods. The principal conclusions are that unprotected gussets have poor fire performance, but that a layer of solid wood or gypsum plasterboard will provide at least one hour of fire protection to typical joints.     

Relationship between fire resistance and fire tolerance

Much of the information accumulated on the fire resistance of ‘dividing’ elements can be utilized in the design of buildings for fire safety, if the fire tolerance values are converted into fire resistance. Three methods of conversion, one based on the concept of equal temperature-time areas, the second on the concept of equal maximum temperatures, and the third, Law method, are critically examined and handy conversion tools presented. In the case of the ‘key’ elements of buildings, basing the fire safety design on fire resistance information is not recommended.     

Fire performance of bolted connections in laminated veneer lumber

This paper describes an investigation into the fire performance of bolted tensile connections in laminated veneer lumber (LVL) made from radiata pine. The capacity of the bolted connections depends on the embedment strength of the wood and on the yield moment of the bolts. The purpose of the research was to develop a prediction method for the time to failure of the connections when exposed to fire. An experimental investigation was carried out on the axial tensile strength of three types of bolted connections that utilized either wood or steel splice plates. Some specimens were tested at ambient temperatures while similar specimens were tested in fire conditions with a constant applied load. In addition, single‐bolted connections were tested under constant elevated temperature conditions to determine the embedment strength of the LVL. Connections with no steel plates, or with steel plates slotted between the timber members, performed better than those with exposed steel. A simplified design approach is proposed, using an extension of the Johansen formulae, such that the embedment strength of the LVL depends on the temperature in the bolt. Copyright © 2009 John Wiley & Sons, Ltd.     

Fast surface-temperature measurement for fire tests

A method of increasing the speed of measurement of surface temperature is described. This would possibly be suitable for improving the determination of temperature of the unexposed face of specimens subjected to a British 476 (part 8) fire-resistance test. A simple electronic circuit used in conjunction with a disc-mounted thermocouple allows ‘hot spots’ to be quickly identified. The technique may also find application in other similar standards such as ISO 834.     

Fire testing flat roofs and wall linings with point fire sources

In the spring of 1977 seven real scale fire tests on flat roofs and wall linings were carried out with relatively small fire loads to simulate the early stages of a fire. Tests with large fire loads had already been performed. Five tests were carried out on insulated corrugated steel roof decks with a fire-retardant EPS (expanded polystyrene) foam insulation of reduced flammability and one test with a non-combustible mineral-wool insulation. A seventh test was run to study the fire behaviour of corrugated asbestos cement roofs and wall linings with EPS foam insulations and fire loads of the same kind (wood cribs up to 200 kg) as before. The tests demonstrated both the advantages and the disadvantages of the different insulations for corrugated steel roof decks in case of fires before Flash-over.     

Fire modeling of an emerging fire suppression system

Self-contained fire extinguishers are a robust, reliable and minimally invasive means of fire suppression for gloveboxes. Test methodology has been developed (experiments and computations) to predict fire induced tube wall failure in small scale compartments such as gloveboxes. A small scale test apparatus has been developed to characterize tube wall temperature and breakage properties. Computational tools have been used to better understand experiments. The heat release rate and heat flux have been accurately predicted because the forward predicted temperatures closely matched the experimentally measured values. Data generated from computational modeling of fire phenomena helps to identify the limitations of self-contained fire extinguishers.     

Fabrication and characterization of melamine formaldehyde fibers with enhanced mechanical properties and high fire resistance by dry spinning

High-performance melamine formaldehyde (MF) fibers are successfully produced by innovatively utilizing dry spinning with high efficiency and low emission. Three ways are adopted to enhance the mechanical performance of MF fiber. First, MF resin is modified by introducing flexible chain segments into MF three-dimensional network and reducing the network crosslink density. Second, the energy dissipation capacity of the MF fibers is improved through constructing of hydrogen bond networks among modified MF resin, nano-SiO₂, and/or polyvinyl alcohol and forming interpenetrating network structures of modified MF resin and nano-SiO₂. Third, homogeneous and stable spinning solutions without phase separation are prepared, which can reduce interior defects of MF fibers. The chemical changes in the spinning solutions with increasing temperature and the rheology behavior of the solutions are investigated. In addition, the effects of fiber compositions on microstructure, morphology, and the properties of the MF fibers are also systematically studied. The prepared MF fibers possess high fire retardancy (i.e., limiting oxygen index >40%), thermal stability (i.e., T_max >360°C), and mechanical properties (i.e., tensile strength >2.5 cN/dtex).     

Australian fire tests in standards and regulations

Fire test methods cited in Australian regulations codes and specifications and the authorities promulgating them are reviewed. The pertinent regulations are generally drafted and administered by departments of the seven State governments, in some cases in reference to model codes developed by committees supported by the federal government to promote uniformity. The test methods, specifications and codes of practice are standardized by the Standards Association of Australia, an independent body with no statutory powers: the standards become mandatory when called up in legislation. Building materials and structures, consumer products, certain electrical components and children's nightwear are the main areas concerned with regulations that invoke fire test methods. The intent of the regulations and the test methods are discussed with particular emphasis on matters unique to Australia.     

Defining the thermal environment in fire tests

The ability of engineered systems to withstand a fire environment is usually demonstrated by test. Iterative design and experimentation historically has been used to develop these engineered systems. To optimize the engineered system, in instances where the cost of the prototype is high, the process of iterative redesign and testing may be infeasible. Consequently, in such instances it is desirable to predict the thermal performance of the engineered system analytically. In order to predict the thermal performance of the engineered system the thermal insult the test environment provides to a test unit must be quantified. To quantify the thermal insult, both temperature and heat flux measurements are necessary. However, as will be discussed, one of the major difficulties associated with conducting any type of fire test is making accurate measurements in both the fire and on the test unit. This paper discusses a number of measurement techniques. Due to the potential for errors in the measurements, the uncertainty in the measured parameters is emphasized.     

Modeling of NBS mattress tests with the harvard mark V fire simulation

NBS burned eleven mattresses made up with bedding in two different rooms, typical of a residential bedroom and a nursing home patient room, respectively. Seven of the mattresses flamed and burned vigorously, the other four were of a construction or so heavily flame-inhibited that they only smoldered. The burning behavior of the seven that flamed was modeled with the Harvard Mark V fire simulation. The experimental burn behavior for tests conducted in one room was well reproduced using only total weight of combustible, surface area and heat of combustion. Smoke production values were found to have little effect on the predicted behavior except for the smoke production itself. Fires in a second room, whose ventilation was intentionally restricted by the configuration of the adjoining space, could not be as well reproduced by the present, single-room fire model. During this study several changes were made to the simulation. The most significant change was the inclusion of mixing of the hot exiting fire gases with the cold incoming air. As a part of this, the inter-layer radiation exchange was reformulated to include the effect of smoke contamination of the lower layer. The reformulation of the radiation model has a marked effect on the predicted upper layer gas temperatures, generally improving the quality of the simulation.     

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.     

Fire resistance of hybrid building materials

In this work, an experimental procedure was conducted to investigate the effect of weight content of short E‐glass fibers on the degradation of flexural properties of a hybrid building material, when exposed to a direct gas (propane/butane) flame for varying time intervals. This experimental procedure is aiming on one hand to define the role that E‐glass fibers play on the degradation of the flexural properties of the materials tested, as well as to provide a sufficient quantity of experimental data which will allow to quantitatively predict the observed degradation of the aforementioned properties due to exposure to direct gas flame using the Residual Property Model (R.P.M.) developed by the first author and already successfully applied to a number of different materials subjected to a combination of different damage sources. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013