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Methods for Prediction of Steel Temperature Curve in the Whole Process of a Localized Fire in Large Spaces  [PDF]
Zhang Guowei,Zhu Guoqing,Yuan Guanglin,Huang Lili
Mathematical Problems in Engineering , 2014, DOI: 10.1155/2014/238515
Abstract: Based on a full-scale bookcase fire experiment, a fire development model is proposed for the whole process of localized fires in large-space buildings. We found that for localized fires in large-space buildings full of wooden combustible materials the fire growing phases can be simplified into a fire with a 0.0346?kW/s2 fire growth coefficient. FDS technology is applied to study the smoke temperature curve for a 2?MW to 25?MW fire occurring within a large space with a height of 6?m to 12?m and a building area of 1?500?m2 to 10?000?m2 based on the proposed fire development model. Through the analysis of smoke temperature in various fire scenarios, a new approach is proposed to predict the smoke temperature curve. Meanwhile, a modified model of steel temperature development in localized fire is built. In the modified model, the localized fire source is treated as a point fire source to evaluate the flame net heat flux to steel. The steel temperature curve in the whole process of a localized fire could be accurately predicted by the above findings. These conclusions obtained in this paper could provide valuable reference to fire simulation, hazard assessment, and fire protection design. 1. Introduction With the increasing public demand for building space and architectural aesthetics, more and more large-space public service buildings have emerged in the city, such as large-scale gymnasiums, large convention centers, and opera houses. These large-space buildings in general feature wide spans, unique styles, and mostly steel structures. Although steel structural components have good strength under normal atmospheric temperature, when a fire occurs, the heat thus generated may greatly influence the material properties of the steel structural components, in particular mechanical properties. Especially when the temperature of the steel structural component exceeds 550°C, the ordinary structural steel will lose most of its strength, thus resulting in partial or even whole building collapse. Therefore, the stability of steel structure in a fire has become an important research direction in prevention and mitigation of buildings fires, and the temperature distribution of steel components in a fire is a key issue for stability analysis of steel structure [1–6]. Thus numerous methods for predicting steel temperature development have been proposed. In the developed methods, the heat that steel receives is classified into thermal radiation and heat convection between steel members and hot smoke. These relationships are depicted in (1). As can be seen from (1), thermal

LIAO Guangxuan,HU Longhua,

力学与实践 , 2008,
Abstract: Based on fire plume models, the smoke temperature above the fire source at different heights was predicted for typical fire scenarios of Beijing National Stadium of Olympics 2008. The strength and modulus of elasticity of steel under different temperatures were considered to determine the critical temperature value. Accordingly the fire hazard region for steel structures in Beijing National Stadium of Olympics 2008 was determined to be with in 10.2\,m above the seats.
Experimental and numerical analysis on high strength steel extended endplate connections in fire

- , 2018, DOI: 10.3969/j.issn.1001-0505.2018.01.021
Abstract: 对1个Q690和2个Q960高强钢外伸式端板连接节点进行高温550 ℃ 下的足尺模型试验研究和有限元模拟分析,并将试验结果与采用欧洲现行钢结构设计规范EN 1993-1-8的计算结果及有限元分析结果进行对比.结果表明,550 ℃时,Q690和Q960高强钢端板连接节点的承载力分别为常温时的45%和46%,初始转动刚度为常温时的57%和65%,但转动能力分别为常温时的1.43倍和1.66倍.EN 1993-1-8中基于普通钢端板连接节点常温力学性能所提出的组件法可直接用于预测高强钢端板连接节点火灾下的失效模式和承载能力,但初始转动刚度的计算公式并不适用,且采用EN 1993-1-8关于保障节点转动能力的相关要求对高强钢端板连接节点进行抗火设计偏于保守.有限元模型可准确模拟该端板连接节点火灾下的弯矩转角关系和失效模式.
The full-scale experimental study and the simulation analysis on the mechanical behaviors of one Q690 and two Q960 high strength steel endplate connections at the elevated temperature 550 ℃ were carried out.The experimental results were compared with the results calculated according to the current European steel structure design code EN 1993-1-8 and the finite element analysis results. The results show that at 550 ℃, the plastic moment resistance of Q690 and Q960 high strength steel endplate connections are 45% and 46% of those at ambient temperature, and the initial rotational stiffness are 57% and 65% of those at ambient temperature, respectively. However, the rotation capacity of Q690 and Q960 high strength steel endplate connections are 1.43 and 1.66 times that at ambient temperature. The component method in EN 1993-1-8 proposed based on the connections made of mild steels at ambient temperature can be used to calculate the plastic resistance and predict the failure mode of the high strength steel endplate connections in fire, but it is not suitable to predict the initial rotational stiffness. The suggestion about the rotation capacity of the connections proposed in EN 1993-1-8 is too conservative for high strength steel endplate connections in fire. The finite element models can accurately simulate the moment-rotation relationships and the failure modes of the connections in fire
Fire experiment and residual strength of steel-concrete composite girders

- , 2016, DOI: 10.3969/j.issn.1001-0505.2016.02.019
Abstract: 完成了3根试验梁的火灾试验,测试了钢-混组合梁受火时的温度场、挠度变形和裂缝分布情况,并对受火后的3根试验梁分别展开静载试验,实测了其剩余承载力和破坏形态.基于高温后混凝土强度表达式和温度场分布函数,推导出高温后的混凝土受压区高度计算公式.结果表明,恒载作用下,3根试验梁的竖向挠度随受火时间的增长而明显增加.简支T梁和箱梁的顶板混凝土未见明显裂缝,连续箱梁负弯矩区的顶板混凝土出现数条横向贯通裂缝,裂缝宽度随构件受火时间的增长而增大.箱梁的混凝土顶板温度上升较慢,其耐火性能优于T梁.所提的剩余承载力计算方法具有良好的精度.
The fire experiments of three test beams were accomplished. The temperature field, the deflection deformation and the cracking distribution of the steel-concrete composite girders exposed to fire were tested. And the residual strengths and the failure modes of these three test beams under static loads were measured. The calculation formula of the compressive zone depth of concrete after fire was deduced based on the strength expression of concrete after fire and the temperature distribution function.The results indicate that the vertical deflections of the three test beams under dead loads in fire increase as the time goes on. The simple supported T-beam and the box girder have no obvious crack at the top of concrete. But as for the continuous box girder, several cut through cracks are observed at the top of concrete in the hogging moment area and the widths of these cracks increase as the time goes on. The temperature at the top of the box girder rises slowly, resulting in better fire resistance compared with the T-girder. The proposed calculation method for the residual strength has high accuracy

LONG QiweiInstitute of Metal Research,Academia Sinica,Shenyang,

金属学报 , 1985,
Abstract: The temperature dependence of fracture toughness of materials seems to haveanalogy to that of yield strength.This similarity for low-carbon steel has beenapproached on the basis of the plastic work loss at the crack tip.Both obey theexponential law and are in agreement with experiment.The availability to enquirefor the temperature dependence of fracture toughness for certain materials otherthan low-carbon steel from that of yield strength has been also discussed.
Measurement of Breakdown Electric Field Strength for Vegetation and Hydrocarbon Flames  [PDF]
Kago Ernest Maabong, Kgakgamatso Mphale, Douglas Letsholathebe, Samuel Chimidza
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2018, DOI: 10.4236/jemaa.2018.103004
Abstract: A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.
Analysis of the Strength of a Reinforced Concrete Compressive Column under the Temperature of Fire  [cached]
Aidas Jokūbaitis,Arnoldas ?neideris
Science – Future of Lithuania , 2012,
Abstract: The article discusses principles calculating resistance of a reinforced concrete column to fire. The paper provides column calculation models, the main characteristics of materials and characteristic stress set points applying finite element program SolidWorks. A comparative analysis of stresses in the cross-section of the reinforced concrete column and the reinforced concrete column strengthened with a metallic shell is made.
Numerical analysis of composite steel-concrete beams in ambient temperature and in fire situation  [cached]
Larissa Degliuomini Kirchhof,Jorge Munaiar Neto,Maximiliano Malite,Roberto Martins Gon?alves
Semina : Ciências Exatas e Tecnológicas , 2005,
Abstract: This paper presents three-dimensional numerical models of steel-concrete composite beams with full interaction (no slip between concrete slab and steel beam) using a non-linear procedure. The threedimensional numerical models must be capable of predicting the response of composite beam at ambient temperature and in fire situation with accuracy. The computer program ABAQUS 6.3-1, based on Finite Element Method, was used to analyze the numerical modeling. The accuracy of the models is demonstrated through the results obtained, which are compared with the experimental results presented in other works. The reported results, when compared to experimental data, demonstrate that the numerical models elaborated with shell finite elements show better performance when compared to the results of the numerical models elaborated with solid finite elements.
Fire resistance performance on restrained high strength Q460 steel beams

- , 2015, DOI: 10.11835/j.issn.1674-4764.2015.02.009
Abstract: 为了研究约束高强度Q460钢梁的抗火性能,在已有约束钢梁分析理论的基础上,引入残余应力,提出了约束钢梁的抗火性能分析方法,并采用普通强度约束钢梁试验数据对分析方法进行了验证。考虑高强度Q460钢材高温下力学性能参数,利用所提出的方法分析了约束高强度Q460钢梁的抗火性能,并与普通强度Q345钢梁进行了对比。对影响约束高强度Q460钢梁的抗火性能参数进行了分析,包括荷载比、残余应力、轴向约束刚度、转动约束刚度和受火方式等。研究表明:所提出的分析方法准确可靠,高强度Q460钢梁抗火性能与普通强度钢梁具有较大的区别,高强度Q460约束钢梁的抗火性能明显优于普通强度约束钢梁。荷载比、轴向约束刚度、转动约束刚度、受火方式对高强度Q460约束钢梁有较大影响。
In order to study the fire resistance of restrained high strength Q460 steel beam,the residual stresses were introduced to analyze the fire resistance of restrained steel beam. The method was validated by experiment conductedon restrained mild steel beams. Fire resistance of restrained high strength Q460 steel beams was analyzed and compared with that of restrained mild Q345 steel beams and parameters affecting the fire resistance of restrained high strength Q460 steel beams were studied The parameters included load ratio,residual stress,stiffness of axial restraint,stiffness of rotational restraint and fire exposure mode. The results showed that the innovative method proposedwas accurate and reliable; the fire resistance of restrained high strength Q460 steel beam was much better than mild steel beam and the former. Load ratio,stiffness of axial restraint,stiffness of rotational restraint and fire exposure mode had significant influence on fire resistance of restrained Q460 steel beam.
Investigations on the impact strength of constructional high-strength Weldox steel at lowered temperature  [PDF]
W. Ozgowicz,E. Kalinowska-Ozgowicz
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: The paper presents the results of investigations concerning the impact strength of thick steel plates at lowered temperature obtained by industrial smelting of micro-alloyed steel of the type S1100QL (Weldox 1100) and S1300QL (Weldox 1300) with a yield strength of 1100-1300 MPa.Design/methodology/approach: The main methods used for these researches were the impact test Charpy V at lower temperatures, and metallographic observations. The tested samples at lower temperature have also been analyzed fractographically.Findings: The influence of the chemical composition and technology of production on the structure and mechanical properties of the investigated kinds of steels have been determined, as well as their ductility temperature of transition into the brittle state.Research limitations/implications: A large dispersion of intermetallic precipitated phases restricted considerably the possibility of their metallographic identification. This latter one will be done in the next stage of basic investigations.Practical implications: A wide range of practical applications of Weldox 1100 and Weldox 1300 sheet plates is warranted by both their high impact strength, especially at lower temperatures, and lower ductility transition temperature.Originality/value: It has been found that the degree of refinement of the martensitic structure and dispersion of secondary precipitations, mainly carbides and niobium nitrocarbides affect considerably the change of the impact strength within the investigated range of temperature from ambient temperature to minus 150°C.
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