Performance of steel moment‐resisting beam‐supporting column transfer structures under fire

This paper investigates the structural fire response of steel beam‐supporting column transfer structures. Two three‐story (Case 1) and seven‐story (Case 2) structures with different span lengths are designed first to withstand gravity and seismic loads. All the structural members are also designed to meet their required fire resistance ratings based on the ISO834 fire. The structural vulnerability is then evaluated under two fire scenarios: the natural fire as a uniform and the traveling fire as a nonuniform temperature distribution inside the structures. The fire loads are applied to the first story of the structures where the structural irregularity is evident. The natural fires are determined based on Eurocode 1 and based on different opening ratios of 0.04, 0.067, 0.08, 0.12, and 0.16 to provide different duration of the heating phase. The results indicate that under the uniform fire scenarios, Case 1 collapses after 134 min under the opening ratio of 0.04. As well, Case 2 collapses under the opening ratios of 0.04, 0.67, and 0.08 at 95, 142, and 160 min, respectively. The results also show that under the nonuniform fire with a size of 25%; Case 1 collapses at 89 min, and Case 2 collapses at 93 min. Although it is believed that the cases studied should logically remain stable under possible fire scenario, the results indicate that this is not a true presumption. The results of this study provide beneficial information about structural fire response of beam‐supporting column transfer structures as an important structural irregularity.     

Behavior of moment‐resisting tall steel structures exposed to a vertically traveling post‐earthquake fire

An investigation is performed on a 10‐story moment‐resisting steel structure designed to the Life Safety level of performance of the Federal Emergency Management Agency (FEMA) 356 code by exposing it to post‐earthquake fire (PEF). The fire curve is accounted for using the natural fire method, and the fire is subjected to the floors vertically in three different scenarios: (a) fire initiated from the first floor, (b) fire initiated from the fourth floor and (c) fire initiated from the seventh floor. A delay of 5 minutes and 25 minutes are considered for spreading the fire between the floors. To make a comparison between the results, a concurrent fire is also considered for the fire analysis. The results indicate that the PEF resistance of the frame exposed to the concurrent fire and the 5 minutes delay is much lower than that with a delay of 25 minutes. The results also show that subjecting the frame to a delayed fire of 25 minutes leads to the collapse of the frame during cooling phase, whereas in the other scenarios, the frame collapses during heating phase. As a result, more considerations need to be implemented in the codes on top of that for the PEF itself and that is the appropriate rate of spread of fire between floors. Copyright © 2013 John Wiley & Sons, Ltd.     

非均匀受火下约束型钢混凝土柱力学性能研究

为了解不同受火条件下型钢混凝土柱截面温度场,同时考察受火方式、火灾荷载比、荷载偏心率、约束刚度比等参数对型钢混凝土柱抗火性能的影响,进行了14个包括四面、三面、相对两面、相邻两面、单面受火条件下轴向约束型钢混凝土柱的抗火性能试验。试验结果表明：受火面数量、受火方位对 型钢混凝土柱截面温度分布有显著影响,升温时间相同时,四面受火、三面受火、两面受火、单面受火试件截面相同位置处所经历的最高温度依此降低;距试件表面距离相同时,型钢翼缘外侧受火面温度比型钢腹板外侧受火面温度略高。受火方式、火灾荷载比、荷载偏心率、约束刚度比对升降温全过程下型钢混凝土柱轴向变形和轴力发展有显著影响,试件受热膨胀变形和降温压缩变形随受火面数的增多而增大;轴向膨胀变形随火灾荷载比的增大而减小,随荷载偏心率的增大而增大;荷载比越大,试件由轴向拉伸状态转为轴向压缩状态的时间越短,压缩程度越高。定义试验实测轴力与初始施加轴力的比值为轴力变化系数,四面受火、三面受火、两面受火、单面受火时,试件升降温后期的轴力变化系数依此递减,轴力变化系数峰值随荷载偏心率和轴向约束刚度比的增大而增大,随火灾荷载比的增大而减小。     

超薄膨胀型钢结构防火涂料防腐性能的研究

介绍了钢材的腐蚀及防腐机理,研究了以对丙烯酸树脂进行复合改性为基料,研制出的一种既具有高效防火隔热性能,又具有优异防腐蚀性能的超薄膨胀型钢结构防火涂料的防腐性能。     

Numerical modelling of load bearing light gauge steel frame wall systems exposed to realistic design fires

Fire safety has become an important part in structural design due to the ever increasing loss of properties and lives during fires. Conventionally the fire rating of load bearing wall systems made of Light gauge Steel Frames (LSF) is determined using fire tests based on the standard time–temperature curve in ISO834 (ISO 834-1, 1999 [1]). However, modern commercial and residential buildings make use of thermoplastic materials, which mean considerably high fuel loads. Hence a detailed fire research study into the fire performance of LSF walls was undertaken using realistic design fire curves developed based on Eurocode parametric (ENV 1991-1-2, 2002 [2]) and Barnett's BFD (Barnett, 2002 [3]) curves using both full scale fire tests and numerical studies. It included LSF walls without cavity insulation, and the recently developed externally insulated composite panel system. This paper presents the details of finite element models developed to simulate the full scale fire tests of LSF wall panels under realistic design fires. Finite element models of LSF walls exposed to realistic design fires were developed, and analysed under both transient and steady state fire conditions using the measured stud time–temperature curves. Transient state analyses were performed to simulate fire test conditions while steady state analyses were performed to obtain the load ratio versus time and failure temperature curves of LSF walls. Details of the developed finite element models and the results including the axial deformation and lateral deflection versus time curves, and the stud failure modes and times are presented in this paper. Comparison with fire test results demonstrate the ability of developed finite element models to predict the performance and fire resistance ratings of LSF walls under realistic design fires.     

钢结构性能化抗火设计的初步设想

指出了现行规范在实际应用中的不足，提出了钢结构性能化抗火设计方法的基本框架。讨论了钢结构抗火设计的总体目标、功能目标和性能要求。该方法可充分考虑不同业主及不同建筑结构抗火设计的不同要求，同时确保火灾发生后建筑物内人员的安全及结构抗火设计的最优综合经济指标。并探讨了钢结构性能化抗火设计需解决的关键问题。     

Load-temperature-deformation behaviour of partially protected steel columns in fires

In recent years many tests have been carried out to assess the fire resistance of steel members at elevated temperatures. These tests are very expensive to undertake and the results obtained for similar tests carried out in different furnaces can vary quite considerably. Analytical methods have been developed for determining the fire resistance of steel members but these are often only concerned with predicting the collapse condition and may not allow the behaviour of the member to be fully analysed as the temperature increases. A finite element program (ELTEMP) has been developed by the authors to assess the behaviour of steel columns at elevated temperatures. The effects of temperature gradients over the cross-section, such as occurs, for instance, in the case of members built into fire-resistant masonry walls, are included. The validity of the program has been checked by comparing results obtained from ELTEMP with those from actual fire resistance tests for both uniform and nonuniform temperature distributions. The comparisons show that ELTEMP generally gives good correlation with test results. Two small-scale model tests undertaken for this purpose are described.     

装配式钢结构建筑消防问题及解决方案

以某实际工程为例,分析了装配式钢结构体系建筑消防设计中存在的主要问题。对装配式钢结构体系建筑的主要建筑构件,包括钢柱、钢桁架楼板、非承重墙等开展耐火性能试验研究。结合装配式钢结构体系的特点及现行规范的要求,对该类建筑中楼板空腔及竖向管道的防火封堵等进行了探讨并提出了相应的解决方案。     

钢结构箱形柱与梁异型节点抗剪承载力分析

基于对钢结构箱形柱与梁异型节点形式及受力性能的分析,建立异型节点域的受剪计算模型,并推导节点域在压弯情况下的抗剪承载力计算公式。通过对箱形柱与工字梁和箱形梁异型节点模型的低周反复加载试验,研究轴压比和核心区高度对节点域抗剪承载力的影响,得到节点域的剪力-剪应变滞回曲线;从试验模型的滞回曲线可以看出,异型节点域以剪切变形为主,且具有良好的延性和抗剪承载能力。试验结果与计算分析表明,节点域在小核心区发生剪切屈服,提出的节点域抗剪承载力计算公式与试验结果比较吻合。     

CA and RVM combined method for predicting collapse of vertical irregular mid-rise cold-formed steel structures under strong earthquake

为提高竖向不规则多层轻钢龙骨复合剪力墙结构强震倒塌预测精度，对已有细胞自动机(cellular automata，CA)方法进行改进。通过增加邻居细胞数目，采用结构归一化Pushover分析后的层间位移定义细胞状态值。在此基础上，采用相关向量机(relevance vector machine，RVM)代替已有相似区域匹配准则，得到CA与RVM的联合预测方法。采用联合法和已有CA法，预测竖向不规则多层轻钢结构在强震作用下倒塌时的层间位移(倒塌判别准则为强震作用下多层轻钢结构层间位移角分别超过2.0%、3.5%、4.0%)，并将预测结果与非线性时程分析结果对比。结果表明：联合法以弹塑性阶段特征值作为细胞状态值，且选用RVM建立细胞状态值与结构倒塌时层间位移的非线性关系，可准确预测竖向不规则多层轻钢结构倒塌时的层间位移，较原有CA方法预测精度明显提高。     

竖向不规则多层轻钢结构强震倒塌预测的细胞自动机与相关向量机联合法

为提高竖向不规则多层轻钢龙骨复合剪力墙结构强震倒塌预测精度,对已有细胞自动机(cellular automata,CA)方法进行改进。通过增加邻居细胞数目,采用结构归一化Pushover分析后的层间位移定义细胞状态值。在此基础上,采用相关向量机(relevance vector machine,RVM)代替已有相似区域匹配准则,得到CA与RVM的联合预测方法。采用联合法和已有CA法,预测竖向不规则多层轻钢结构在强震作用下倒塌时的层间位移(倒塌判别准则为强震作用下多层轻钢结构层间位移角分别超过2.0%、3.5%、4.0%),并将预测结果与非线性时程分析结果对比。结果表明：联合法以弹塑性阶段特征值作为细胞状态值,且选用RVM建立细胞状态值与结构倒塌时层间位移的非线性关系,可准确预测竖向不规则多层轻钢结构倒塌时的层间位移,较原有CA方法预测精度明显提高。     

钢结构抗火安全研究现状与发展趋势

火灾引起的高温严重降低建筑钢材的强度和刚度,从而造成钢结构损伤、严重破坏甚至倒塌。20世纪90年代人们开始重视钢结构抗火理论研究,2001年美国“9·11”事件引起了世界各国对钢结构抗火问题的高度关注。结构抗火学科经过几十年的发展,已形成系统的抗火理论和设计方法,文章介绍火灾引起钢结构破坏的原因,论述结构抗火设计原则的发展过程,归纳近年来钢结构抗火研究的重大进展,指出钢结构抗火的重要发展趋势,供有关研究者参考。     

轻型钢结构建筑火灾痕迹特性分析

以单跨门式刚架结构为例，从轻钢结构建筑的材料性能、结构特点入手，依据火灾发生、发展规律，阐述了轻钢结构建筑火灾特有的弯曲变形痕迹、倒塌牵拉方向性痕迹、轻质围护材料火灾表面痕迹、微观金相火灾痕迹形成机理和勘查中的证明作用。     

基于规范与数值模拟的钢结构抗火计算对比研究

对GB 51249-2017《建筑钢结构防火技术规范》中的关键条文进行解读,并基于规范与数值模拟实验进行钢结构抗火计算的对比研究.结果表明:规范对静定结构中的三面、四面受火的钢构件适用性好;对于超静定结构中的三面、四面受火钢构件,适用性有待进一步研究.     

Development of realistic design fire time-temperature curves for the testing of cold-formed steel wall systems

Fire resistance rating of light gauge steel frame (LSF) wall systems is obtained from fire tests based on the standard fire time-temperature curve. However, fire severity has increased in modern buildings due to higher fuel loads as a result of modern furniture and light weight constructions that make use of thermoplastics materials, synthetic foams and fabrics. Some of these materials are high in calorific values and increase both the spread of fire growth and heat release rate, thus increasing the fire severity beyond that of the standard fire curve. Further, the standard fire curve does not include a decay phase that is present in natural fires. Despite the increasing usage of LSF walls, their behavior in real building fires is not fully understood. This paper presents the details of a research study aimed at developing realistic design fire curves for use in the fire tests of LSF walls. It includes a review of the characteristics of building fires, previously developed fire time-temperature curves, computer models and available parametric equations. The paper highlights that real building fire time-temperature curves depend on the fuel load representing the combustible building contents, ventilation openings and thermal properties of wall lining materials, and provides suitable values of many required parameters including fuel loads in residential buildings. Finally, realistic design fire time-temperature curves simulating the fire conditions in modern residential buildings are proposed for the testing of LSF walls.     

浅谈钢结构抗火计算方法

对钢结构抗火设计的意义、建筑室内火灾的发展与温度变化进行了介绍，主要对钢结构在火灾条件下反应分析的有限元方法及其研究成果进行综述，并且指出了钢结构高温设计分析的发展方向。     

某会所不规则钢框架结构设计研究

随着建筑功能及造型的要求不断提高,不规则建筑大量涌现.某会所采用多层不规则钢框架结构,设计中考虑了多种方法优化结构方案;本文以该会所为例,对不规则框架结构的设计方法进行了探讨,阐述了该结构的结构体系、计算分析结果以及节点、基础等关键部分的设计.     

火灾全过程中高层钢框架结构抗连续性倒塌性能及控制措施

建筑内部火灾的发生、发展过程较为复杂,采用标准升温曲线会造成过于保守或偏于不安全的结果。为研究火灾升降温全过程中三维部分铰接钢框架结构（周边刚接、内部铰接）的抗连续性倒塌性能,分析火灾场景、防火等级和支撑布置对结构倒塌的影响。研究表明：钢框架结构是否倒塌主要受升温段持续时间的影响,倒塌模式呈现明显的侧移式和下沉式特点,倒塌时间可偏保守地取为钢柱温度达到550 ℃时对应的时刻,结构受火的严重程度与其构件的防火等级有关,较高的防火等级可以防止结构在升温段发生倒塌,但也可能导致结构在降温段倒塌;为防止框架梁端在升温段和降温段发生断裂,梁端受拉承载力应分别不低于梁屈服荷载的30%和100%。在实际设计中,建议在顶层整层布置水平支撑体系,并在周边和内部布置竖向支撑体系,以防止结构发生倒塌;建议在确定结构的耐火等级时,应考虑可能发生的火灾场景,尤其要重视“长时-低温受火”的危险性。     

Behavior of vertically irregular structures near mines: Comparison of responses under seismic and mine blast-induced ground motion

Due to architectural and functional considerations, buildings with irregular configurations are frequently constructed with rapid urbanization. During a seismic or blast activity, the performance of a building depends on various factors like adequate lateral strength, stiffness, ductility, regularity, and the extent of simplicity in the configuration. The irregular distributions of the stiffness, mass, and strength in the plan and height of the building create irregularity within the structures. The purpose of this study is to understand the nature of response under seismic ground motion and that obtained from ground vibration generated due to mine blasts if such buildings are situated near mines. This study also emphasizes on identifying the critical location of stress concentration of the structures under both seismic and mine blast-induced ground motion. Base shear, fundamental natural periods, mode shapes, and member forces for a few buildings with typical irregular configurations and similar buildings with regular counterparts are obtained. Nonlinear dynamic analysis has been carried out on irregular buildings for confirming the trends in behavior observed from linear dynamic analysis. Since the mine blasts take place sequentially, the study also aims to prescribe a suitable delay interval between such series blasts to minimize the vulnerability of vertically irregular seismic structures to the possible extent.     

火灾高温下耐火保护钢梁设计荷载的分析

研究了火灾高温环境下耐火保护钢梁温度和结构的变化,运用有限元软件ANSYS模拟不同涂料厚度的耐火保护钢梁在标准温升模型、慢速和快速温升BFD模型3种温升曲线下,荷载作用不同时的最大挠度值,并与Robertson-Ryan准则中的最大挠度值比较,确定耐火保护钢梁的设计荷载值。结果表明,采用标准火灾模型代替自然火灾模型确定的设计荷载是不安全的;钢梁最高温度越高,设计荷载越低;随着涂料增厚,温升速率的改变对设计荷载值的影响逐渐明显。