Evaluation of duct opening protection in two-hour fire walls and partitions

There is a continuing debate among fire protection specialists on the value and role of fire dampers in preventing fire spread via HVAC duct systems. It has been recognized that fire dampers are not required under all circumstances. For example, NFPA 90A,Standard for the Installation of Air Conditioning and Ventilation Systems, does not require the installation of fire dampers in ducts penetrating one-hour fire-rated walls and partitions. Additionally, there are circumstances where the closure of dampers may affect critical environmental air systems. In these situations, the value of fire dampers must be determined in terms of an overall risk assessment. It has been suggested that the role of fire dampers be considered in terms of the total building fire protection system, but a quantitative approach for such an assessment has been previously unavailable. In particular, there has been no data related to the performance of a duct system when subjected to a standard two-hour fire exposure. Gewain et al. have described an equivalency approach and full-scale fire test data for the protection of duct openings in two-hour fire-resistant walls and partitions. The objective of this paper is to review and summarize the equivalency rationale and test data and describe engineering methods available to apply an equivalency approach more generally. The approach was developed for situations where horizontal steel ventilation ducts penetrate fire-rated walls and partitions. The approach does not address smoke dampers or ducts containing combustible materials.     

Development of an Algorithm to Predict Vertical Heat Transfer Through Ceiling/Floor Conduction

This paper describes a new algorithm of the Consolidated Fire Growth and Smoke Transport (CFAST) fire model and compares the results with data from real-scale fire tests conducted aboard the ex-USS Shadwell, the U.S. Navy's Research and Development Damage Control Platform. The new phenomenon modeled in this work is the conduction of heat in the vertical direction. The Shadwell tests chosen for validation purposes were part of the Internal Ship Conflagration Control (ISCC) Program. The work focuses on four compartments of the ship that were vertically aligned. The temperatures of the compartments and the decks between them were compared with model predictions. The predictions were very close to the experimental results for all compartments, although the temperatures rise in the topmost compartment was barely above ambient.     

Fire tests of Magnesium Oxide board lined light gauge steel frame wall systems

Recently, Magnesium Oxide (MgO) board has been widely used in LSF wall systems because of its improved acoustic properties, impact resistance, structural strength and serviceability. However, their thermal properties and fire performance have not been fully investigated. Therefore, in this research study thermal properties of two different types of MgO boards available in Australia were measured and their fire performance was investigated using three full-scale fire tests of LSF walls lined with two types of MgO board. Although the tests were conducted on two different types of MgO boards with different configurations, the fire test results gave a fire resistance level (FRL) of 30 min, in which the failure was initiated by integrity of the board with either board cracking or board joint opening. This paper presents the details of the thermal property tests and the three full-scale fire tests, and their results. In addition, the effects of different MgO boards, joint configurations and compounds, noggings, screw fastening techniques and cavity insulation on the fire performance of LSF walls are also presented.     

Behavior of hollow clay brick masonry walls during fire. Part 2: 3D finite element modeling and spalling assessment

In the first part of this work [1], the fire behavior of masonry walls made with hollow fired-clay bricks was investigated experimentally. Several complex mechanisms occurred during firing are analyzed and identified. In particular, in cases of load-bearing walls, the local spalling of bricks is considered as an important factor governing the fire performance of masonry walls.In this second part, fired-clay masonry is investigated by theoretical approach with the finite element method in order to predict its behavior and its performance under fire exposure. For this purpose, a 3D numerical simulation is conducted with paying a particular attention to the spalling risks of alveolus bricks.     

Thermal bowing on steel columns embedded on walls under fire conditions

The contact of steel columns with building walls is responsible for huge thermal gradients within its cross-section during fire. Current regulatory codes for fire design of steel members provide a formulation to assess the load-bearing capacity of these members assuming uniform temperature through the cross-section; however, this is not what happens in the major part of the cases in real structures where the columns are embedded on walls. The walls on one hand will provide a temperature reduction on the columns, which is somehow favourable in terms of its fire resistance, on the other hand the differential heating on the columns cross-section may lead to unfavourable stresses (bending moments) responsible for instability (thermal bowing). Considering that the structural behaviour of columns is strongly dependent of the second order effects this is an important phenomenon which may lead to a significant reduction on its fire resistance. This paper presents the results of a numerical study to assess the influence of the differential heating on the fire design of steel columns. New interaction axial force–bending moment diagrams for non-uniformly heated H steel columns are proposed.     

Fire resistance of concrete-filled steel plate composite (CFSPC) walls

Concrete-filled steel plate composite walls (CFSPC walls) have recently emerged as promising alternatives to conventional reinforcement concrete shear walls due to the benefits of effective space use, less construction time/effort, and higher ductility. While the basic load carrying capacity and seismic performance of CFSPC walls have been receiving great attention, little work has been conducted so far on their fire performance. This paper aims to bridge the knowledge gap by performing 12 fire tests on CFSPC walls, where shear stud spacing, wall height, wall thickness, steel ratio, and fire scenario (uniform or single-sided fire) were considered as the main test parameters. For the uniform fire tests, the specimens exhibited reasonably good fire resistance, where the fire resistance time exceeded 2 h. Three dominating failure modes were observed, namely, local buckling of steel plates (LB), severe cracking (‘tearing’) of the weld along the corner line of the wall (WC), and global instability (GI). For the specimens subjected to single-sided fire, minor local buckling of the heated steel plate accompanied by tie bar failure in the buckled areas were observed, but no further load bearing failure was induced by the end of the heating process. The fire resistance time, which exceeded 2.5 h for the specimens exposed to single-sided fire, was governed by the ‘thermal insulation criterion’. After 2.5 h of heating, some specimens lost their thermal insulation capacity. Based on the test phenomena, preliminary design recommendations are proposed, and future research directions are also outlined.     

A two-dimensional numerical investigation of the oscillatory flow behaviour in rectangular fire compartments with a single horizontal ceiling vent

This paper presents a comparison of fire field model predictions with experiment for the case of a fire within a compartment which is vented (buoyancydriven) to the outside by a single horizontal ceiling vent. Unlike previous work, the mathematical model does not employ a mixing ratio to represent vent temperatures but allows the model to predict vent temperatures a priori. The experiment suggests that the flow through the vent produces oscillatory behaviour in vent temperatures with puffs of smoke emerging from the fire compartment. This type of flow is also predicted by the fire field model. While the numerical predictions are in good qualitative agreement with observations, they overpredict the amplitudes of the temperature oscillations within the vent and also the compartment temperatures. The discrepancies are thought to be due to three-dimensional effects not accounted for in this model as well as using standard ‘practices’ normally used by the community with regards to discretization and turbulence models. Furthermore, it is important to note that the use of the turbulence model in a transient mode, as is used here, may have a significant effect on the results. The numerical results also suggest that a linear relationship exists between the frequency of vent temperature oscillation (n) and the heat release rate ( ) of the type , similar to that observed for compartments with two horizontal vents. This relationship is predicted to occur only for heat release rates below a critical value. Furthermore, the vent discharge coefficient is found to vary in an oscillatory fashion with a mean value of 0.58. Below the critical heat release rate the mean discharge coefficient is found to be insensitive to fire size.     

Aircraft cargo compartment fire detection and smoke transport modeling

The US Federal Aviation Administration, along with other regulatory agencies, requires that cargo compartments on passenger carrying aircraft be equipped with fire detection and suppression systems. Current regulations require that the detection system alarms within 1 min of the start of a fire and flight tests are required to demonstrate compliance with these regulations. Due to the high costs of flight tests, extensive ground certification tests are typically conducted to ensure that the detection system will meet the time to alarm requirements during the flight tests. For the purpose of improving the detection system design and certification process, a transient computational fluid dynamics computer code for the prediction of smoke, heat, and gas species transport in cargo compartments has been developed. This simulation tool couples heat, mass, and momentum transfer in a body-fitted coordinate system in order to handle a variety of cargo bay shapes and sizes. Ideally, such a physics-based simulation tool can be used during the certification process to identify worst case locations for fires, optimum placement of detector sensors within the cargo compartment, and sensor alarm levels and algorithms needed to achieve detection within the required time. Validation of the model was completed, and comparison of the predicted results with the results obtained from full-scale fire tests in a variety of actual aircraft cargo compartments provides insight into the model capabilities.     

The behaviour of masonry walls subjected to fire: Modelling and parametrical studies in the case of hollow burnt-clay bricks

A thermo-mechanical model is adopted in order to investigate the fire behaviour of clay masonry walls. In this analysis, conductive, convective and radiative thermal transfers are considered together with local energy consumption due to phase changes. These latter are essentially initiated by both the vaporisation of adsorbed water and the chemical transformation of clay under rising temperatures. Therefore, experimental tests at both the material scale and the brick scale are performed in order to identify the parameters that characterise the thermo-hygral behaviour of clay. For this purpose, numerical simulations are carried out on the experimentally tested hollow bricks in order to determine by back analysis these material parameters. The thermal model being validated, the thermo-mechanical behaviour of a masonry wall subjected to fire, is thereafter investigated by adopting a full three-dimensional finite-element analysis. Numerical simulations results are compared to the experimentally measured ones in terms of both temperature and out-of plane displacement fields. In this analysis, it is shown that a non-linear elastic behaviour for bricks and mortar with temperature-dependent mechanical parameters is sufficient to retrieve the overall behaviour of thin masonry walls. Finally, a parametric study provides the influence of each material parameter on the fire behaviour of the partition walls.     

基于人工智能的外立面开口火溢流温度场预测

为了明确外立面构造形式对开口火溢流的影响,对不同外立面构造条件下的开口火溢流进行实验研究,并对外立面火灾温度场的实时预测进行探索.通过不同翼墙间距和进深条件下的外立面火灾实验构建外立面火灾预测数据库,并将其应用于人工智能方法—卷积神经网络的训练和验证,建立不同外立面构造形式下开口溢流火焰温度的实时预测模型,为外立面构造...     

The fire hazard of fibrous glass ducts—An evaluation

A series of fifty-seven fire tests was conducted to evaluate the significance of the combustible components of compositions used in the manufacture of fibrous glass ducts and to evaluate the fire spread potential of such ducts. These tests established that fibrous glass ducts are products of low combustibility comparable to several other products of low combustibility which are commonly classed as noncombustible, that with severe fire exposure much in excess of the available heat in the products themselves they can be made to burn, and that the likelihood of fire spread through the ducts to other areas is remote. Factory Mutual Research Corporation Note: Based on Factory Mutual Research Corp. Laboratory Report No. 15985 by J. A. Wilson, prepared for the National Insulation Manufacturers Association, Mr. Capron is currently employed by the Inland Steel Company.     

Behavior of steel-sheathed shear walls subjected to seismic and fire loads

A series of tests was conducted on six 2.7 m×3.7 m shear wall specimens consisting of cold-formed steel framing sheathed on one side with sheet steel adhered to gypsum board and on the opposite side with plain gypsum board. The specimens were subjected to various sequences of simulated seismic shear deformation and fire exposure to study the influence of multi-hazard interactions on the lateral load resistance of the walls. The test program was designed to complement a parallel effort at the University of California, San Diego to investigate a six-story building subjected to earthquakes and fires. The test results reported here indicate that the fire exposure caused a shift in the failure mode of the walls from local buckling of the sheet steel in cases without fire exposure, to global buckling of the sheet steel with an accompanying 35% reduction in lateral load capacity after the wall had been exposed to fire. This behavior appears to be predictable, which is encouraging from the standpoint of residual lateral load capacity under these severe multi-hazard actions.     

Predicting the Fire Dynamics of Exposed Timber Surfaces in Compartments Using a Two-Zone Model

There is an increasing desire to use more engineered timber products in buildings, due to the perceived aesthetics of timber and desire for more sustainable architecture. However, there are concerns about fire performance of these products especially in taller buildings. This has led to renewed research to understand the behaviour of timber surfaces in compartments exposed to fire. This paper describes a two-zone calculation model for determining the fire environment within a compartment constructed from timber products where varying amounts of timber are exposed on the walls and ceiling. A set of eight full-scale compartment experiments previously reported in the literature are used to assess the capability of the model. The fire load energy density in the experiments ranged from 92 MJ/m² to 366 MJ/m² comprising either wood cribs or bedroom furniture with the largest compartment having dimensions 4.5?×?3.5?×?2.5 m high with an opening 1.069 m wide?×?2.0 m high. The experiments were ventilation-controlled. It is shown that the model can be used to provide conservative predictions of the fire temperatures for compartments with timber exposed on the walls and/or ceiling as part of an engineering analysis. There are several limitations that are discussed including the need to consider the debonding of layers in the case of cross-laminated timber. It is recommended that further benchmarking of the model be done for different ventilation conditions and with engineered timber products where debonding does not occur. This will test the model under a wider range of conditions than examined in this paper.     

Fire exposure to exterior walls and flame spread on combustible cladding

A segment of the on-going research program on fire spread via exterior walls conducted at the Institute for Research in Construction of the National Research Council of Canada is described. The research includes full-scale experimental studies of fire exposure to exterior walls, fire hazards associated with the use of combustible materials, and the development of new test methods for assessing the flammability of combustible cladding. Correlations between the results of a new full-scale test and standard flame spread tests (Steiner tunnel test, radiant panel test, roof deck test) were investigated. A prototype of a reduced-scale test, the vertical channel test, is described. It was found that, at present, the full-scale test is the most appropriate method to evaluate the fire hazards of combustible wall assemblies.     

The modeling of fire spread in buildings by Bayesian network

Fire spread modeling is very important to fire safety engineering and to insurance industries involved in fire risk–cost analysis of buildings. In this paper, the Bayesian network is introduced. The directed acyclic graph of a fire spread model is presented. When the fire ignition location is known, the fire spread model based on the Bayesian network from the compartment of fire origin to another compartment can be built, and the probability of fire spread can be calculated by making use of the joint probability distribution of the Bayesian network. A specific application for an office building is presented for a case without sprinkler and one with sprinkler installed.     

Degradation of Out-of-plane Initial Stiffness of Steel-concrete Walls Exposed to Fire

Steel-concrete (SC) walls, as a main lateral resisting system in nuclear power plants, have serious fire resistance problem because of their exposed steel faceplates. The out-of-plane stiffness of SC walls will degrade when exposed to fire, which has significant influence on the mechanical performance of the composite walls and even the whole structure. In this paper, a finiteelement (FE) model was developed to simulate thermo-mechanical coupling behavior of SC walls exposed to fire. One conducted ISO-834 standard fire test and two reported thermal and mechanical loading tests were assembled to verify the developed FE model. Based on the validated FE model, numerical experiments of 15 SC walls in fire exposure durations of 0~3 h were conducted to investigate the effect of steel arrangement and geometrical size on the out-of-plane initial stiffness of SC walls under elevated temperatures. Numerical results indicate that the out-of-plane initial stiffness of SC walls under ambient temperature is mainly influenced by steel faceplate thickness and section depth, while the initial stiffness degradation under elevated temperature is mainly influenced by fire exposure duration or surface temperature of exposed steel faceplate. Then, two equations were proposed to predict the out-of-plane initial stiffness of SC walls exposed to fire. The predicted results agree well with the test and numerical results, which demonstrates that the proposed equations can be used to estimate the damage of SC walls in fire.     

Mechanical behaviour of full unit masonry panels under fire action

An analytical model is presented to predict the mechanical resistance of full unit masonry panels under combined compressive and bending stress, in the presence of a nominal fire acting on one side. Transitory thermal analysis of the panels is conducted, while accounting for the convection and radiation effects produced by the fire, to determine the collapse conditions for combined compression and bending; five strain field collapse configurations are considered. The numerical analyses, based on data drawn from European regulations EN 1996-1-2, permit the determination of the M-N crushing domains for brick and lightweight aggregate concrete masonry walls, with various thicknesses and exposure times to nominal fire. A numerical example demonstrates the applicability of the model, and a comparison with a set of experimental data on masonry panels demonstrates the efficiency of the model.     

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.     

Probabilistic simulation of fire endurance of a wooden beam

This paper presents a probabilistic simulation approach to assessment of the fire endurance of a wooden load-bearing beam in a fire. The approach introduces several novel modelling techniques developed by VTT, such as the probabilistic fire simulator which is an interface enabling to run fire simulation models in the Monte Carlo mode and the time-dependent event-tree method which enables to take into account the active fire safety measures such as detectors, first-aid fire fighting, sprinklers and fire brigade intervention. Also the simulation of the response to heat and the mechanical performance of the structure are carried out using the Monte Carlo technique. The charring rate of the wooden beam is calculated by a new model that includes explicitly the principal sources of uncertainties and variabilites. The results show explicitly the effectiveness of different fire safety measures in reducing the risk of structural failure.     

真实火灾下足尺冷成型钢复合剪力墙结构耐火性能试验研究

冷成型钢复合剪力墙结构采用冷成型钢管混凝土边柱、半刚性连接节点、组合楼盖体系和外填充式夹心组合墙体等构件,具有整体连接性强、抗震性能优越等优势.其耐火性能研究是该结构在我国推广应用的研究重点之一.为此,建造了3栋平面尺寸为7.2m×7.2m、层高3m的单层冷成型钢复合剪力墙结构模型房屋,并对其进行了不同火灾工况下的足尺...