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.     

Thermal Performance of Composite Panels Under Fire Conditions Using Numerical Studies: Plasterboards, Rockwool, Glass Fibre and Cellulose Insulations

In recent times, light gauge steel frame (LSF) wall systems are increasingly used in the building industry. They are usually made of cold-formed and thin-walled steel studs that are fire-protected by two layers of plasterboard on both sides. A composite LSF wall panel system was developed recently, where an insulation layer was used externally between the two plasterboards to improve the fire performance of LSF wall panels. In this research, finite element thermal models of the new composite panels were developed using a finite element program, SAFIR, to simulate their thermal performance under both standard and Eurocode design fire curves. Suitable apparent thermal properties of both the gypsum plasterboard and insulation materials were proposed and used in the numerical models. The developed models were then validated by comparing their results with available standard fire test results of composite panels. This paper presents the details of the finite element models of composite panels, the thermal analysis results in the form of time–temperature profiles under standard and Eurocode design fire curves and their comparisons with fire test results. Effects of using rockwool, glass fibre and cellulose fibre insulations with varying thickness and density were also investigated, and the results are presented in this paper. The results show that the use of composite panels in LSF wall systems will improve their fire rating, and that Eurocode design fires are likely to cause severe damage to LSF walls than standard fires.     

Vereinfachtes Naturbrandmodell für die Brandschutzbemessung von Bauteilen und Tragwerken

Simplified natural fire model for the fire safety of components and structures In this contribution a simplified natural fire model is presented, which is based on a realistic design fire and was derived on the basis of extensive simulations with heat balance models. With so‐called real fire curves the temperature‐time curves of natural fires in multi‐storey residential and office buildings can be gathered realistically with a simple hand resp. spread sheet calculation. In contrast to the design with ISO 834 standard temperature‐time curve, the fire safety design according to Eurocode can be performed with the thermal action given by the real fire curves considering the existing boundary conditions (ventilation, fire load, geometry). The application of the method is demonstrated by means of an example.     

Fire performance of cold-formed steel wall panels and prediction of their fire resistance rating

Recent research at the Queensland University of Technology has investigated the structural and thermal behaviour of load bearing Light gauge Steel Frame (LSF) wall systems made of 1.15 mm G500 steel studs and varying plasterboard and insulation configurations (cavity and external insulation) using full scale fire tests. Suitable finite element models of LSF walls were then developed and validated by comparing with test results. In this study, the validated finite element models of LSF wall panels subject to standard fire conditions were used in a detailed parametric study to investigate the effects of important parameters such as steel grade and thickness, plasterboard screw spacing, plasterboard lateral restraint, insulation materials and load ratio on their performance under standard fire conditions. Suitable equations were proposed to predict the time–temperature profiles of LSF wall studs with eight different plasterboard-insulation configurations, and used in the finite element analyses. Finite element parametric studies produced extensive fire performance data for the LSF wall panels in the form of load ratio versus time and critical hot flange (failure) temperature curves for eight wall configurations. This data demonstrated the superior fire performance of externally insulated LSF wall panels made of different steel grades and thicknesses. It also led to the development of a set of equations to predict the important relationship between the load ratio and the critical hot flange temperature of LSF wall studs. Finally this paper proposes a simplified method to predict the fire resistance rating of LSF walls based on the two proposed set of equations for the load ratio–hot flange temperature and the time–temperature relationships.     

A parametric natural fire model for the structural fire design of multi-storey buildings

A parametric natural fire model is presented, which is derived on the basis of simulations with heat balance models for realistic natural design fires, taking into account the boundary conditions of typical compartments in residential and office buildings. These so-called iBMB parametric fire curves are formulated with the help of simplified empirical equations which can easily be used for structural fire design as part of a performance-based natural fire design concept. The iBMB parametric fire curves are checked and validated by comparison with results of different heat balance models and with published fire tests from different fire research laboratories. In addition, a natural fire test in a test room with ordinary office room furnishings has been performed which supports the parametric natural fire model presented here. The application of the iBMB parametric fire curves is demonstrated by means of an example.     

Assessment of the Use of Fire Dynamics Simulator in Performance-Based Design

This paper discusses a procedure for the use of fire modelling in the performance-based design environment to quantify design fires for commercial buildings. This procedure includes building surveys, medium-and full-scale experiments and computer modelling. In this study, a survey of commercial premises was conducted to determine fire loads and types of combustibles present in these buildings. Statistical data from the literature were analysed to determine the frequency of fires, ignition sources, and locations relevant to these premises. Based on the results of the survey and the statistical analyses a number of fuel packages were designed that represent fire loads and combustible materials in commercial buildings. The fuel packages were used to perform medium- and full-scale, post-flashover fire tests to collect data on heat release rates, compartment temperatures and production and concentration of toxic gases. Based on the experimental results, input data files for the computational model, Fire Dynamics Simulator (FDS), were developed to simulate the burning characteristics of the fuel packages observed in the experiments. Comparative analysis between FDS model predictions and experimental data of HRR, carbon monoxide (CO), and carbon dioxide (CO₂), indicated that FDS model was able to predict the HRR, temperature profile in the burn room, and the total production of CO and CO₂ for medium- and large-scale experiments as well as real size stores.     

Rapid prototyping a virtual fire drill environment using computer game technology

Conducting fire evacuation drills in modern buildings under realistic fire conditions can be difficult. Typical fire drills do not feature dynamic events such as smoke filled corridors, fires in unexpected places or blocked fire exits that require on the spot decisions from evacuees. One alternative is the use of virtual environments. Virtual environments can support the training and observation of fire evacuee behaviours in 3D virtual buildings. However complex virtual environments can be difficult to build. This paper explores how the reuse of computer game technology can aid in the rapid prototyping of virtual environments which can be populated with fire drill evacuation scenarios. Over a three week period, a single developer constructed a realistic model of a real world building to support virtual fire drill evaluations. While participants in a user study found the simulated environment realistic, performance metrics indicated clustering in the results based on participants’ previous gaming experience.     

Schutzzielorientierte brandschutztechnische Bemessung für mehrgeschossige Gebäude

Performance – based fire safety design of multi‐storey buildings. In most countries fire design of multi‐storey buildings is still based on the standard temperature‐time curve (ISO 834) which is supposed to cover real fire scenarios on the safe side. A fire safety design considering more realistic natural fires and the redundancies of entire structural systems is risk‐oriented as well as economical. Using international experience and test results and ongoing research of iBMB, a design fire is developed and so‐called real fire curves are derived. They serve as a basis for general calculation methods (according to the Eurocodes) which are able to grasp the real behaviour of structural systems in a fire. A probabilistic safety concept guarantees the necessary reliability of the design taking the probability of fire development, the boundary conditions of life safety and the uncertainties of the design parameters into account.     

Fire Resistance of Loadbearing Steel-Stud Wall Protected with Gypsum Board: A Review

With the increased use of cold-formed lightweight steel framing (LSF), there is growing demand for the proper assessment of its performance in building fires. In partnership with the North American steel industry, the National Research Council of Canada (NRC) is conducting an experimental and analytical study on the fire resistance of loadbearing cold-formed steel-framed wall and floor assemblies. As part of this collaboration, this literature survey summarizes the information available on the topics related to the fire resistance of loadbearing cold-formed steel-stud walls clad with gypsum board. The current practice of establishing their fire-resistance rating, based on full-scale furnace tests, is assessed. Previous experimental and analytical studies on the subject and on the thermal and mechanical properties of the constituent materials—steel, gypsum board, and insulation—at elevated temperatures are also discussed. Future research needs are identified in the context of recent performance-based fire safety engineering concepts.     

A computational study on the use of balconies to reduce flame spread in high-rise apartment fires

High-rise apartment fires are perhaps the most dangerous residential fires. Within high-rise buildings, flames and smoke can travel through ductwork, between interior walls, and up elevator shafts and stairwells. One of the fastest ways a fire spreads to other floors is along the exterior of the building due to open windows. Flame spread up vertical walls has been studied experimentally and computationally for years in the US and abroad. A numerical study has been undertaken to examine the reduction of vertical flame spread due to the presence of a balcony. The depth and geometry of the balcony greatly affects the vertical movement of fire. By varying the balcony depth and geometry, the aim of this study is to find an optimum configuration that reduces vertical fire spread on the external wall.     

Analysis of Changing Residential Fire Dynamics and Its Implications on Firefighter Operational Timeframes

There has been a steady change in the residential fire environment over the past several decades. These changes include larger homes, different home geometries, increased synthetic fuel loads, and changing construction materials. Several experiments were conducted to compare the impact of changing fuel loads in residential houses. These experiments show living room fires have flashover times of less than 5 min when they used to be on the order of 30 min. Other experiments demonstrate the failure time of wall linings, windows and interior doors have decreased over time which also impact fire growth and firefighter tactics. Each of these changes alone may not be significant but the all-encompassing effect of these components on residential fire behavior has changed the incidents that the fire service is responding to. This analysis examines this change in fire dynamics and the impact on firefighter response times and operational timeframes.     

住宅建筑火灾自动报警系统设计——解读《〈火灾自动报警系统设计规范〉图示》

通过国家建筑标准设计14X505-1《〈火灾自动报警系统设计规范〉图示》中关于住宅建筑火灾自动报警系统的内容,介绍如何应用GB 50116-2013《火灾自动报警系统设计规范》设计住宅建筑、住宅建筑群及住宅小区的火灾自动报警系统,重点解析住宅建筑火灾自动报警系统分类、总线短路隔离器、家用火灾报警控制器、火灾警报器、消防应急广播、可燃气体探测器等的设置要求。     

Assessing safety measures in residential buildings in Saudi Arabia

The incidence rate of fire in residential buildings in Saudi Arabia accounts for 69% of all building fires. A field assessment of current safety issues for residential buildings in Saudi Arabia is used to identify common safety deficiencies. The survey showed that most residents are ignorant many safety aspects in their homes. A safety audit checklist for assessing the effectiveness of safety measures in existing residential buildings is also presented. Based on these findings, a number of strategies for designers, local authorities, building owners and residents is suggested.     

The influence of travelling fires on a concrete frame

When building fires occur in large, open compartments they rarely burn uniformly across an entire floor plate of a structure. Instead, they tend to travel, igniting fuel in their path and burning it out as they move to the next fuel package. Current structural fire design methods do not account for these types of fires. This paper applies a novel methodology for defining a family of possible heating regimes to a framed concrete structure using the concept of travelling fires. A finite-element model of a generic concrete structure is used to study the impact of the family of fires; both relative to one another and in comparison to the conventional codified temperature-time curves. It is found that travelling fires have a significant impact on the performance of the structure and that the current design approaches cannot be assumed to be conservative. Further, it is found that a travelling fire of approximately 25% of the floor plate in size is the most severe in terms of structural response. It is concluded that the new approach is simple to implement, provides more realistic fire scenarios, and is more conservative than current design methods.     

高层建筑现状分析与其火灾预防对策探讨

针对目前高层建筑存在的各种隐患和问题,从高层建筑存在的火灾特点和火灾危险性入手,分析讨论了制约高层建筑消防安全的因素,提出了高层建筑火灾的防控对策,以期指导实践,从源头上预防火灾。     

Comparison of FDS Prediction of Smoke Movement in a 10-Storey Building with Experimental Data

In this study, the Fire Dynamics Simulator (FDS), a computational fluid dynamics (CFD) model developed by National Institute of Standards and Technology (NIST) is used to simulate fire tests conducted at the National Research Council of Canada (CNRC). These tests were conducted in an experimental 10-storey tower to generate realistic smoke movement data. A full size FDS model of the tower was developed to predict smoke movement from fires that originate on the second floor. Three propane fire tests were modelled, and predictions of O₂, CO₂ concentrations and temperature on each floor are compared with the experimental data. This paper provides details of the tests, and the numerical modelling, and discusses the comparisons between the model results and the experiments. The 10-storey experimental tower was designed to simulate the centre core of high-rise buildings. It includes a compartment and corridor on each floor, a stair shaft, elevator shaft and service shafts. Three propane fire tests were conducted in 2006 and 2007 to study smoke movement through the stair shaft to the upper floors of the building. The fire was set in the compartment of the 2nd floor. Thermocouples and gas analyzers were placed on each floor to measure temperature and O₂, CO₂ and CO concentrations. Comparisons in the fire compartment and floor of fire show that the FDS model gives a good prediction of temperature and O₂ and CO₂ concentrations. In the stair shaft and upper floors there are some small differences which are due to the effect of heat transfer to the stairs that was not considered in the model. Overall the study demonstrates that FDS is capable of modelling fire development and smoke movement in a high rise building for well ventilated fires.     

An experimental study on the temperature and structural behavior of a concrete wall exposed to fire after a high-velocity impact by a hard projectile

Projectiles, such as turbine blades, can be released in an accident and impact structures. Airplanes and other flying objects can also become impact projectiles. These impacts occasionally cause fire when fire loads, such as oil, fuel, and other combustible materials, are present. This study examines the thermal insulation performance of concrete plates and the structural fire behavior of load-bearing reinforced concrete walls that are exposed to fire after a high-velocity impact by a hard projectile. Impact and fire tests were carried out using small-scale concrete plates and reinforced concrete walls. The results show the influence of local damage and the advantage of short-fiber reinforced concrete subjected to impact loads and fire.     

Assessing safety measures in residential buildings in Saudi Arabia

The incidence rate of fire in residential buildings in Saudi Arabia accounts for 69% of all building fires. A field assessment of current safety issues for residential buildings in Saudi Arabia is used to identify common safety deficiencies. The survey showed that most residents are ignorant many safety aspects in their homes. A safety audit checklist for assessing the effectiveness of safety measures in existing residential buildings is also presented. Based on these findings, a number of strategies for designers, local authorities, building owners and residents is suggested.     

高层建筑消防隐患及防火监督对策研究

随着人们的生活水平和物质要求的不断提高,高层建筑中的可燃物数量也在不断地增加,这在一定程度上增加了高层建筑出现火灾的几率.在实际工作中需要加强对高层建筑消防隐患的全方位检查及研究,制定与之匹配的防火监督对策,减少高层建筑火灾发生的几率,从而推动我国建筑行业的持续性发展,为人们营造舒适、安心的居住环境.