Axial strength of cold-formed thin-walled steel channels under non-uniform temperatures in fire

This paper presents the results of a numerical investigation into the axial strength of cold-formed thin-walled channel sections (columns) under non-uniform high temperatures in fire. The non-uniform temperature distributions are based on the results of a thermal analysis of thin-walled stud panels carried out by the authors. The general finite-element package ABAQUS is used to obtain strengths of columns with different lengths at different fire exposure times. To aid development of a hand calculation method of column strength in fire, the accuracy of using two ways of simplifying the non-uniform temperature distribution is investigated. The ambient temperature design method for cold-formed thin-walled columns in Eurocode 3 Part 1.3 (EN1993-1-3, Eurocode 3: design of steel structures, Part 1.3: general rules, supplementary rules for cold formed thin gauge members and sheeting, European Commission for Standardisation, Brussels, 2001) is modified to take into account the change in the strength and stiffness of steel at elevated temperatures and thermal-bowing effects. The results of this design method are compared to the ABAQUS simulation results.     

冷弯薄壁槽钢-混凝土组合梁受火试验研究

对5个冷弯薄壁槽钢-混凝土组合梁试件进行在ISO-834标准火灾下的受火试验。试验中考虑了荷载水平、防火涂层厚度和槽钢截面高度等参数的影响。试验结果表明：荷载水平、防火涂层厚度和槽钢截面高度是影响组合梁抗火性能的主要因素,其他因素影响很小;在ISO-834标准火灾下,以跨中挠度δ=l/25作为组合梁达到耐火极限的判别标准是合适的;填充混凝土可有效提高组合梁的整体刚度和延性,使其在高温下直至破坏仍可保持完整性,没有出现高温局部屈曲现象;在槽钢上直接涂刷防火涂层不能保证其与槽钢表面的紧密结合,需要改进组合梁的防火涂层施工工艺;试验结果验证了有限元分析结果的正确性。     

Experimental study on the performance of a load-bearing steel stud gypsum board wall assembly exposed to a real fire

The National Institute of Standards and Technology (NIST) and the Center for Better Living (CBL) have formed an international collaboration to assess the performance and failure mechanisms of gypsum wall assemblies under real fires/furnace conditions. In an effort to compile an experimental database necessary to validate models that could be used to predict their performance and ultimate failure under various design fires, a full scale test was conducted in the Large Fire Laboratory (LFL) at NIST. This paper provides a valuable experimental data set on the performance of a full scale loaded gypsum steel stud assembly exposed to an intense full scale compartment fire.     

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.     

A simple method to predict temperature development in a protected steel member exposed to localized fire in large spaces

Temperature development is a key issue for fire protection of steel structures. However, until now, there has been little systematic approach to predict the steel temperature development during the whole process of a localized fire in large spaces. The smoke temperature development in large spaces is different from that in normal enclosure fires as they have lower maximum temperatures and non‐uniform temperature distributions. In the present study, a whole process prediction method for the development of smoke temperatures in a large space localized fire is proposed. The prediction method accurately reflects the temperature curves (in the growing, fully developed and decay phases) and the uniform temperature distribution in large space localized fires. Based on basic heat transfer principles and the proposed smoke temperature development model, a new relationship is proposed to predict the temperature development in a protected steel member exposed to localized fire in large spaces. There is only one variable, t (time), in the proposed relationship, and thus, it is very simple to implement in evaluating temperatures, and it accurately reflects the development of the whole fire process (growing, fully developed and decay phases). Copyright © 2016 John Wiley & Sons, Ltd.     

冷弯型钢房屋墙体立柱临界屈曲荷载能量解

冷弯薄壁型钢低层住宅房屋体系的墙体一般由墙体密立柱、墙面围护材料组成 墙面材料不仅是建筑的需要 ,同时也能在一定程度上对墙体立柱提供有效的支承作用 通过简化推导 ,建立起了考虑墙板的支承效应时墙体立柱的力学模型 ,并在弹性范围内 ,分别利用Rayleigh Ritz法推导出了墙体立柱两端简支、两端固定、一端固定一端自由和一端简支一端固定等 4种典型边界条件下墙体立柱的整体屈曲临界荷载 ,并将其转化成为常规形式的表达式 ,可供设计、研究参考     

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。     

Behaviour and design of restrained steel column in fire, Part 3: Practical design method

This paper presents a practical design method for calculating the buckling and failure temperatures of restrained steel column under axial load or combined axial load and bending moment based on the results of extensive numerical parametric studies. Design equations for unrestrained columns in fire are adopted to calculate the buckling temperature of a restrained column by including the additional compression axial force due to restraint thermal elongation. The cross-section yield axial strength-plastic bending moment interaction curve is employed when calculating the failure temperature of restrained column. Results from the proposed method are compared with ABAQUS simulation for different cases. For the restrained column under axial load only, the buckling and failure temperatures calculated by the simplified method agree well with predictions by ABAQUS. For the restrained column under combined axial force and bending moment with realistic parameters, the buckling and failure temperatures predicted by the proposed method also agree well with ABAQUS predictions.     

房屋加层中钢丝网架夹心板的应用及设计

介绍钢丝网架夹心板在加层工程中用在楼（屋）面时的原理、附加钢筋（丝）的计算方法及施工程序。指出了加层工程中,采用框架承重钢丝网架夹心板作墙体是优化设计。     

钢管混凝土柱防火保护的计算

以厦门国际旅游客运码头联检大楼为实例,通过对钢管混凝土柱耐火极限值的计算,确定钢管混凝土柱进行防火保护的问题。     

Temperature fields for fire resistance analysis of structures exposed to natural fires in large space buildings

Temperature fields analysis is an essential work to evaluate the behavior of structures in fires. Large space buildings are mostly highly populated or high‐fire load places with high fire risks. So it is a research focus to predict the temperature fields of large space fires accurately. In this study, a full‐scale physical experiment on fires in large spaces has been conducted. The results show that the temperature distribution of natural fires in large spaces is nonuniform. With regard to the evolution laws of the temperature fields of natural fires in large spaces, the author developed a new temperature field prediction model for large spaces. The new model has been compared with the well‐known Li G Q model and the Xue S D model. Based on the comparative analysis, the new model can predict the change laws of the temperature fields with time in the whole fire process and reflect the gradual attenuation of temperature fields in the fire during the decay phase better. In the meantime, this new model developed by the authors can be used to structural analysis exposed to fires in large space buildings.     

Optimising design decision-making for steel structures in fire using a hybrid analysis technique

Steel structures can be protected against the effects of fully-developed fires by the use of sprayed on materials, board systems and intumescent paints, etc. or by using sufficiently large unprotected elements. This paper presents how optimum decisions for the protection of steel structures in fires can be achieved in a performance-based design environment, given conflicting structural fire design decision criteria and multidisciplinary fire design stakeholder views. In particular, a novel hybrid analysis approach is proposed for combining stakeholder views on the different fire protection options and the numerical outcomes of structural fire analysis. As for the stakeholder views, reference is made to benefits and costs criteria priorities for assessing competing options resulting from a previous study from the same authors. The fire protection structural performance is numerically and probabilistically assessed according to a parametric study. The proposed approach is exemplified by making reference to a limit state structural fire design of single steel elements. A synthesis and ranking technique is then applied to integrate the qualitative results obtained in terms of benefits and costs priority scores; and the quantitative measures of failure probabilities and costs for the different fire protection options. The results show that the ranking technique accounts for multidimensionality in synthesising the structural fire design decision problem. The results also show that intumescent paints and board systems are the most cost-effective options in different stakeholder influence scenarios, given a general selection of steel structural fire protection. The hybrid technique is proposed to support an optimal and cost-effective structural fire design decision-making for buildings in a performance-based design environment.     

A design model for stainless steel box columns in fire

A study of stainless steel cold-rolled box columns at elevated temperatures is presented, which is a part of an on-going RFCS project “Stainless Steel in Fire”, 2004-2007. Experimental results of six, class 4, stub columns at elevated temperature, tested by Ala-Outinen [Members with Class 4 cross-sections in fire: Work package 3, ECSC project stainless steel in fire. Contract no. RFS-CR-04048, Espoo, Finland; 2005], were used to evaluate the finite element (FE) model. The FE analysis obtained using the commercially available software, ABAQUS, shows that the critical temperature was closely predicted. Further, a parametric study was performed using the same numerical model. This was a basis to check the quality of prediction of a newly proposed improvement for design rules of class 4 cross-sections in fire according to EN 1993-1-4 [Eurocode 3 - Design of steel structures — Part 1-4: General rules — Supplementary rules for stainless steels, CEN; 2006] and EN 1993-1-2 [Eurocode 3: Design of steel structures — Part 1.2: General rules — Structural fire design, CEN; 2005].     

超大空间火灾钢构件危险性分析简化方法

确定350℃为高大空间钢结构耐火的临界安全温度,提出了高大空间钢结构坍塌风险评估方法。基于热平衡方程建立了受火钢构件温升计算方法,方法中包含了火源辐射对钢构件的热作用、烟气辐射对钢构件的热作用以及烟气热对流对钢构件的热作用。分析某钢结构仓库内部发生15 MW火灾时,屋面钢结构的稳定性。结果表明,建筑面积小于6 000 m2且建筑高度小于8m的高大空间钢结构内部发生15 MW火灾时,屋面钢结构存在坍塌风险。     

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.     

A new design method for stainless steel columns subjected to flexural buckling

The objective of this paper is to develop a design method for stainless steel columns subjected to flexural buckling. In this method, the strength curve for every type of stainless steel in common use is generated by using the base strength curves and a slenderness conversion formula. A validated finite element model is employed to generate the strength curves for different types of stainless steels. According to the strain hardening exponent n in the Ramberg-Osgood material model, cluster analysis is conducted to separate these strength curves into two groups. In each group, one type of material parameter is selected as the base material and the corresponding strength curve is expressed in the form of a modified Perry formula that serves as the base strength curve. A slenderness conversion formula is derived for any two stainless steel columns with the same section type and boundary conditions, but with different types of stainless steel. Based on the base strength curves and the slenderness conversion formula, the strength curve for every type of stainless steel in common use can be generated. The predictions of the proposed method show a good agreement with the results of the finite element analysis.     

A data analysis method for detecting wall thermal resistance considering wind velocity in situ

To improve the accuracy of data analysis methods for the field measurement of wall thermal resistance, a method considering wind velocity is presented through an analysis of both surface heat flux and temperature samples. This analysis method takes the wall heat transfer of linear system into account, simplifying the first order differential equation of wall transient response based on the nodes of the interior and exterior wall surfaces. An approximate solution has been proposed in the form of time domain interpolation. By applying the weighted residual method for the approximate solution, the data analysis method about temperature, heat flux, and wind velocity can be achieved.A transient heat transfer model of a wall was established applying the infinite difference method, by which the proposed analysis method was validated in this paper. Additionally, the heat flow meter experiment platform considering wind velocity was built, on which the proposed method, the mean method and the dynamic analysis method suggested by the international standard ISO 9869 were applied to the test wall under different wind velocities. The wall thermal resistance value obtained in our proposed method has proven to be in better agreement with that obtained for a steady state.     

复杂空间钢结构整体性防火分析的系统方法研究

复杂空间钢结构建筑的飞速发展为结构防火分析和设计带来了新的挑战。在分析现有规范和性能化设计方法中结构防火设计不足的基础上,基于火灾科学、结构工程、计算机模拟等多个学科领域的知识和研究成果,立足于复杂空间建筑的整体防火性能模拟与分析的理论研究和实际应用,建立空间整体结构火灾-结构耦合分析模型和系统集成方法,提出复杂空间结构整体性防火分析的系统分析模型,并进行实例研究。该系统分析模型综合考虑实际火灾的发展蔓延过程以及火灾对结构体系的影响,研究建筑火灾中火场状况与空间结构体系之间的相互关系,对大空间建筑在各种火灾场景下的结构反应进行仿真模拟,从而进行整体性系统化的分析和评估。本课题的研究在理论分析的基础上为结构整体防火分析提出了新的手段和思路,可为我国建筑防火研究和建筑防火设计、消防救援、应急预案制定等工程实际应用提供有益的参考。     

冷弯薄壁型钢自冲铆接受拉性能及设计方法研究

为将连接效率和工业化程度高的自冲铆接应用于冷弯薄壁型钢结构中,对84组薄壁钢自冲铆接进行了受拉性能试验;研究了钢板厚度、钢板厚度比、组合方式及铆钉长度对其受拉性能及破坏模式的影响;考察了现有自冲铆接抗拉强度计算方法及各国规范自攻螺钉受拉承载力计算方法的适用性;提出了自冲铆接的受拉承载力计算方法及基于容许强度法的设计方法。结果表明:钢板厚度比t₂/t₁是影响自冲铆接破坏模式的关键因素,当1≤t₂/t₁<1.5时,自冲铆接发生铆钉腿拔出下层钢板破坏,当t₂/t₁≥1.5时,发生铆钉头拉脱上层钢板破坏;钢板厚度和铆钉长度对自冲铆接受拉性能的影响显著,受拉承载力随两者的增加基本呈线性增加;钢板组合方式对自冲铆接受拉性能和破坏模式影响较大,薄板位于铆钉头侧能有效提高承载力及变形能力;由于计算值过于保守且考虑的破坏模式不全面,现有计算方法不适用于冷弯薄壁型钢自冲铆接;与现有方法相比,提出的自冲铆接受拉承载力计算方法能考虑更为全面的破坏模式,且其计算值精度更高、离...     

A method for determining fire accidental loads and its application to thermal response analysis for optimal design of offshore thin-walled structures

More than 70% of accidents that occur on offshore installations stem from hydrocarbon fire and explosion, and as they involve heat and blast effects, they are extremely hazardous with serious consequences in terms of human health, structural safety and the surrounding environment. To prevent further accidents, substantial effort has been directed towards the management of fire and explosion in the safety design of offshore installations. The aim of this paper is to present a risk-based methodology procedure to help determine the fire accidental design load of an offshore installation (AL Living Quarter) in association with the thermal response characteristics for structural optimisation. A probabilistic sampling approach with numerical fire simulations was taken to determine the fire accidental load. To determine the optimisation of the thin-walled structures of the living quarter, an A60 based on the results of thermal response analyses was conducted and the temperature distribution calculated. The analysis results suggest incorporating both the design and safety planning aspects of offshore Living Quarter.