Fire Research is an Open-Access journal publishing scholarly articles, surveys, and original contributions on the domain of fire science and engineering. Fire Research topics include, but are not limited to: fire dynamics, fire chemistry and physics, material properties at high temperatures, structural fire performance, measurement and test methods, fire detection and suppression, active/passive fire protection methods, human behavior in case of fire, organization and management of fire safety, decision analysis and operations research in fire problems, fire risk assessment methods, fire in industrial buildings and explosions, forensic investigation, wildland/urban interface fires, wildland fires. This journal is fully Open Access, it has no submission fee and no article processing charge. All papers are immediately published as soon as they have been accepted, by adding them to the "current" volume's Table of Contents. Looking for rapid publication? Fair peer-review? Immediate indexing? Submit your paper to our journal!
PAGEPress Scientific Publications, Pavia, Italy
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Structural fire performance of restrained composite columns made of concrete-filled square and circular hollow sections
Most of the previous studies on concretefilled steel hollow section columns at high temperatures addressed the effect of depth-tothickness ratio, column slenderness, initial applied load level, load eccentricity, and local buckling of concrete-filled steel tubes on the fire resistance of these columns. For this reason, it important and required to study the influence of the axial and rotational restraint on the buckling behavior of these types of columns subjected to fire. The results of a series of fire resistance tests on these types of columns inserted in a steel frame are presented and discussed in this paper. The primary test parameters taken into account were column slenderness, type of section geometry, and axial and rotational restraint level imposed by a surrounding steel frame to the columns. The specimens were then uniformly exposed to the ISO 834 standard fire curve, and the critical time (fire resistance), failure temperature distribution and respective failure modes were assessed. Finally, the results of this research study showed most of all that the fire resistance of identical semi-rigid ended columns may be not significantly affected by the stiffness of the surrounding structure but, on the contrary, their post-buckling behavior may be affected.
Copyright (c) 2016 João Paulo C. Rodrigues, Luís Laím, Helder D. Craveiro
Buckling behavior of cold-formed steel columns at both ambient temperature and simulated fire conditions
Cold-formed steel (CFS) profiles with a wide range of cross-section shapes are commonly used in building construction industry. Nowadays several cross-sections can be built using the available standard single sections (C, U, Σ, etc.), namely open built-up and closed built-up cross-sections. This paper reports an extensive experimental investigation on the behavior of single and built-up cold-formed steel columns at both ambient and simulated fire conditions considering the effect of restraint to thermal elongation. The buckling behavior, ultimate loads and failure modes, of different types of CFS columns at both ambient and simulated fire conditions with restraint to thermal elongation, are presented and compared. Regarding the buckling tests at ambient temperature it was observed that the use of built-up cross-sections ensures significantly higher values of buckling loads. Especially for the built-up cross-sections the failure modes were characterized by the interaction of individual buckling modes, namely flexural about the minor axis, distortional and local buckling. Regarding the fire tests, it is clear that the same levels of restraint used in the experimental investigation induce different rates in the generated restraining forces due to thermal elongation of the columns. Another conclusion that can be drawn from the results is that by increasing the level of restraint to thermal elongation the failure of the columns is controlled by the generated restraining forces, whereas for lower levels of restraint the temperature plays a more important role. Hence, higher levels of imposed restraint to thermal elongation will lead to higher values of generated restraining forces and eventually to lower values of critical temperature and time.
Copyright (c) 2016 Hélder David Craveiro
Load carrying capacity of partially encased columns for different fire ratings
Partially encased columns have significant fire resistance in comparison with steel bare columns. However, it is not possible to assess the fire resistance of such members simply by considering the temperature of the steel. The presence of concrete increases the mass and thermal inertia of the member and the variation of temperature within the cross section, in both the steel and concrete components. The annex G of EN1994-1-2:20051 allows to calculate the load carrying capacity of partially encased columns, for a specific fire rating time, considering the balanced summation model. New formulas will be proposed to calculate the plastic resistance to axial compression and the effective flexural stiffness. These two parameters are used to determine the buckling resistance. The finite element method is used to compare the results for the elastic critical load and the load carrying capacity of partially encased columns for different fire ratings of 30 and 60 min. This work compares the results from both solution methods, provides the validation of the three-dimensional model and demonstrates that a new design curve should be used for the buckling analysis of partially encased columns.
Behavior of cellular beams protected with intumescent coatings
A new engineering practice in modern buildings is to use beams with web openings to allow the passage of services within the depth of the beam instead of underneath the beam. As the web post failure may occur before the section reaches the limiting temperature, usually an increase in the fire protection may be required for members with web openings in comparison to its equivalent solid section. The aim of this work is to present an experimental study of unloaded solid and cellular beams with circular holes in fire conditions with and without intumescent fire protection. These preliminary tests results are the basis for generating an elemental multi-temperature analysis needed to assess cellular beams with intumescent protection and give experimental results for calibration of further numerical simulations. The experimental results show that, considering the same nominal fire protection thickness, one can obtain a higher fire resistance time for solid beams when compared with cellular beams. The tests performed, with different hole diameters and web-post widths, points that to achieve the same fire resistance time, a cellular beam will need a higher fire protection compared to an equivalent solid beam. Also, a special care is needed when the intumescent coating is applied around the hole to avoid the intumescent contraction, applying for example an over coating.
Copyright (c) 2017 Brahim Lamri, Luis Mesquita, Kada Abdelhak, Paulo Piloto
Analytical study on lateral torsional buckling of partially encased beams under ISO834 fire exposure
European standard EN1994-1-2:2005 provides tabulated values and simplified calculation models for assessing fire resistance of composite beams, but does not consider the design checks against lateral torsional buckling under fire. This research presents an analytical method to calculate the buckling resistance moment of laterally unrestrained partially encased beams in fire conditions. The proposal applies a reduction factor for lateral torsional buckling in fire design condition to the moment resistance of the homogenised section at time t, determined by EN1994-1-2:2005. Two finite element models capable to simulate the thermal and mechanical behaviour of partially encased beams are also presented, including the validation against fire tests conducted by Piloto et al. Based on these models, a numerical analysis of partially encased beams with the same geometry and material properties as used in experimental tests is presented, evaluating different load levels when exposed to standard fire ISO834:1999. The numerical results of fire resistance according to standard EN1363- 1:2012 and the numerical ultimate time, when beams suffer instability, are used to validate the proposal, using experimental and analytical heating result according to EN1994-1-2:2005.
Copyright (c) 2017 Ana Belén Ramos-Gavilán, Paulo Gonçalves Piloto, Luis Ribeiro Mesquita
On the ductility of bolted steel joints at ambient and elevated temperatures
Beam-to-column joints must be ductile enough to sustain plastic deformation without premature failure when the moment resistance of the joint is less than the moment resistance of the connected beam. In order to prevent premature failure, the Eurocode 3 imposes that the rotation capacity of a joint must be checked if the design moment resistance of the joint is less than 1.2 times the design plastic moment resistance of the connected beam. The Eurocode 3 gives a simple rule for the rotation capacity of bolted joints, based on the assumption that joints designed with that rule are ductile enough to prevent premature failure of the bolts. This paper analyses the Eurocode 3 ductility rule and shows that this rule is in certain cases unsafe and can lead to brittle failure of joints. An alternative rule is proposed for beam-to-column bolted joints at ambient and elevated temperatures.
Copyright (c) 2017 Fernando Gomes, João Paulo C. Rodrigues
In 2017 Portugal was devastated by forest fires that destroyed more than 500 thousand hectares and claimed at least 112 lives. The country was plagued with a severe drought that raised the risk of fire and was caught by two prominent episodes of extreme conditions: one in mid-June and another in mid-October that caused the greatest damages.
Copyright (c) 2018 Domingos Xavier Viegas
Reliability on timber columns under fire situation
Timber structures in fire situation are subject to intrinsic uncertainties from the material and the actions on the structure and their probabilistic behavior has not being studied exhaustively. In this paper, four limit state equations using the reduced cross-section method are developed for timber columns in fire situation. The security criteria taken into account in these equations are the compression, the lateral stability and the combined bending and compression, according to the NBR 7190:1997 standard. The structural reliability analysis of five simply supported timber columns with rectangular cross-section in fire situation and different base and height ratios where performed using the first order reliability method. The overall probability of failure of the column was obtained by associating the failure criteria in a series system. The reliability behavior of the different base to height ratios was evaluated, leading to different results for the distinct ratios and the criteria used. Also, a sensitivity analysis was performed indicating the timber charring rate as the most important random variable in the reliability analysis for these limit state equations.
Copyright (c) 2018 Auro Cândido Marcolan Júnior, Poliana Dias de Moraes
Modelling the influence of crowd control railings on the Kiss nightclub evacuation
Fires in crowded gathering places such as nightclubs generate imminent risks to people’s lives, as supported by historical facts. Building evacuation is defined as fundamental to prevent the occurrence of a tragedy. In the Kiss nightclub fire, many people could not reach the exit because of the controlling rails positioned in front of exit doors, as pointed-out by firefighters and survivors. This study aimed to evaluate the influence of these barriers in the escaping of Kiss nightclub, using computerassisted simulation. Four simulations were run, considering two types of capacity, each one with and without the rails. As preliminary analyses, the simulations presented a reduction of nearly 50% of the total time for the nightclub evacuation without the rails, confirming the barriers as a factor that considerably increased evacuation time of the nightclub occupants.
Copyright (c) 2018 Guilherme Günther Hennemann, Augusto M. Gil, Fabrício L. Bolina, Eduardo E.C. Rodrigues, Bernardo F. Tutikian, George C.B. Braga
Effect of radiation inside square hollow section under moderate non-symmetric fire
The temperature calculation of hollow steel sections at elevated temperatures is a well-documented and standard procedure. Through this standard procedure, the temperature can be calculated by assuming a uniform gas temperature all around the section, which is called a symmetric fire in this paper. Embedding in surrounding structures or connecting to another steel member results in non-symmetric heat distribution in the member. This non-symmetricity of the surrounding temperature may cause surface- to-surface heat radiation inside the member, thus affecting the steel section temperature distribution. This effect is considered in this paper by adopting analytical and finite element method analysis.
Copyright (c) 2018 Jolanta BÄ…czkiewicz, Sami Pajunen, Markku Heinisuo
Natural fire tests in a dormitory with fire protected furniture
This article presents a full-scale fire experiment carried out in a dormitory bedroom in the city of Recife, Pernambuco, Brazil. The experiment was recorded by thermal and conventional cameras, and temperatures were measured at 24 different points within the environment, making it possible to observe the dynamics and behavior of the fire in detail. Among the objects in the dormitory were two identical bedside tables, one of which was coated with intumescent paint. Particular attention was paid to the behavior of this piece of furniture, which, despite being in direct contact with the flames for more than 20 minutes, did not completely burn. Similar experiments are rare in Brazil and in Latin America as a whole, especially with the use of furniture and locally built structures. Understanding the dynamics of this fire, which very closely resembles many local cases, is therefore important to generate data on thermal behavior and overall understanding of the phenomenon. Regarding the specially-treated piece of furniture, its performance was found to be satisfactory, suggesting that such a protective process for furniture may help inhibit the spread of similar fires.
Copyright (c) 2018 Cristiano Corrêa, George Cajaty Braga, Roberto Ryanne Ferraz de Menezes, José Jéferson Rêgo e Silva, Roberta Tabaczenski, José do Carmo Bezerra Junior, Tiago Ancelmo Pires de Oliveira
Thermal and structural analysis of a fuel storage tank under an adjacent pool fire
This work reports the modeling and computational implementation of heat transfer processes that take place from a source tank to a target tank in a tank farm, focusing on the thermal field that develops at the target tank. Pool fire with gasoline burning is modeled at the source, in which the flame is represented by a two-layer solid flame model. A rigorous heat transfer model is implemented together with a Computational Fluid Dynamics model for the fuel storage. This process yields the temperature field in the target tank. Such thermal fields are subsequently employed as input in a structural analysis of the target tank to compute displacements and stresses and to assess possible structural damage. For the case studied, the results show that a steady-state process is reached in less than an hour, with temperatures in the order of 400°C at elevations above the fuel level stored in the target tank, whereas much lower temperatures are computed on the zone in contact with fuel. Displacement jumps are seen to occur at the fuel level and at the junction between the cylinder and a fixed roof.
Copyright (c) 2018 Susana N. Espinosa, Rossana C. Jaca, Luis A. Godoy
Graphical tool for assessing the critical temperatures of steel beams and columns in fire
In a fire situation, the temperature in which the ultimate limit state of the structural element is reached is called critical temperature. It is very laborious to determine it. The aim of this work was to create a graphical tool to allow quick determination of the critical temperature of I shaped columns and beams without local buckling. The method used was based on the Brazilian standard and using AcoInc software developed by the authors. The result was a tool whose similarity was not found in the literature. The use of the tool developed in this study simplifies the use of the standardized design method. One conclusion to be highlighted is one in which constants values of the critical temperature, generally accepted in practice, may be unsafe.
Copyright (c) 2018 Valdir Pignatta Silva, Arthur Ribeiro Melão, Igor Pierin
Performance of intumescent coatings in cone calorimeter and open pool fires
Accidental fire is a major concern in terms of safety of infrastructures and human lives. With the technological advancement, several novel methods are developed for minimizing the damages caused by the fire. One of the methods is to paint the base metals/ material with fire retardant coatings which can increase the lead time so that economic destruction and loss of human lives can be avoided. In this work, the performance of the intumescent coating (passive type fire retardant coatings) is studied with the help of cone calorimeter and open pool diesel fire as sources of heat. The transient temperature distribution for bare Stainless Steel 310 plate suggests that the cone calorimeter experiments alone cannot suffice for mimicking real life conditions. Comparison of the behavior of the available paints in cone calorimeter and open pool fire confirms that the performance of intumescent coatings in cone calorimeter is very different from that in open pool fire. The safe initial thickness of the intumescent coating is a function of heat release rate of the source. The effective thermal conductivity of the intumescent coatings is evaluated using one dimensional conduction heat equation with constant boundary temperature condition.
Copyright (c) 2019 Saket Singh, Sumit Shivani, Sudheer Siddapureddy, Siddini Venkatesh Prabhu
Thermal properties of fired clay bricks from waste recycling. A review of studies
The large waste volumes globally generated have increased environmental awareness, promoting waste recycling as a sustainable construction material. This study presents a review of researches that analyze the thermal behavior of eco-friendly clay bricks incorporating organic and mineral waste materials as an addition. Many of these works also provide data related to the composition of the material, and its physical, micro-structural and mechanical characteristics. Most of eco-friendly clay units increase the porosity of the ceramic, improving the energy efficiency of masonry enclosures, reducing the clay content and the energy consumption during the fire process. The positive effects of lightweight ceramics are an opportunity to improve the fire resistance inside green buildings.
Papers from the 5th CILASCI Congress: Reviews and Articles
Proposal of new expressions for the calculation of section factor on structural steel columns in contact with walls
The fire resistance of a steel column is highly affected by the contact between the columns and the walls, leading in general to a favorable effect due to the reduction of temperatures. However, it leads to the Thermal Bowing effect, which is not more than a differential heating in the steel cross sections, causing an inversion of bending moments and an inversion of the deflections of the column. Thus, it is necessary to accurately assess the evolution of the temperature field in the cross section of the steel elements in contact with walls. In Eurocode 3 part 1-2, the structural design of steel elements in fire situation is performed with expressions for the calculation of the section factor of steel profiles, but different cases of positioning the columns and the surrounding walls could be considered as causing extremely high thermal gradients. In this paper, a new approach for the calculation of section factors for cases not included in table 4.2 of Eurocode 3, part 1- 2 are presented. This was achieved using numerical models with finite element modelling with the ABAQUS program, varying the cross-section of the columns, orientation of the web in relation to the walls, and the position and thickness of the walls, to achieve the desired section factors.
Thermo-structural analysis of reinforced concrete beams
The objective of this study is to simulate the behavior of reinforced concrete beams in fire situation. In order to achieve this objective, advanced numerical formulations were developed, implemented and evaluated. When exposed to high temperatures, the properties of the material deteriorate, resulting in the loss of strength and stiffness. To achieve the goal, two new modules within the Computational System for Advanced Structural Analysis were created: Fire Analysis and Fire Structural Analysis. The first one aims to determine the temperature field in the cross section of structural elements through thermal analysis by using the Finite Element Method (FEM). The second was designed to perform the second-order inelastic analysis of structures under fire using FEM formulations based on the Refined Plastic Hinge Method coupled with the Strain Compatibility Method. The results obtained of the nonlinear analyses of two reinforced concrete beams under high temperature were compared with the numerical and experimental solutions available in literature and were highly satisfactory. These results also showed that the proposed numerical approach can be used to study the progressive collapse of other reinforced concrete structures in fire situation and extended to the numerical analysis of composite structures under fire condition.
Computational System for Advanced Structural Analysis
Influence of different merging angles of pedestrian flows on evacuation time
The growing number of fires and other types of catastrophes occurring at large events highlights the need to rethink safety concepts and also to include new ways to optimize buildings and venues where events are held. Although there have been some attempts to model and simulate the movement of pedestrian crowds, little knowledge has been gathered to better understand the impact of the built environment and its geometric characteristics on the crowd dynamics. This paper presents computer simulations about pedestrians’ crowd dynamics that were conducted based on the Social Force Model. The influence of different configurations of pedestrian flows merging during emergency evacuations was investigated. In this study, 12 designs with different merging angles were examined, simulating the evacuation of 400 people in each scenario. The Planung Transport Verkehr (PTV, German for Planning Transport Traffic) Viswalk module of the PTV Vissim software (PTV Group, Karlsruhe, Germany) program was adopted, which allows the employment of the Social Force approach. The results demonstrate that both symmetric and asymmetric scenarios are sensitive to the angles of convergence between pedestrian flows.
Mechanical analysis of a portal steel frame when subjected to a post-earthquake fire
Although current design code can manage the separate action of a fire or an earthquake, which causes a significant threat to the human life and to the integrity of the structures, the dual effect of a Post- Earthquake Fire (PEF) stands as a major hassle to designers and rescuers alike. Algerian seismic design code, RPA99v2003, with no exception does not consider the possibility of a subsequent fire after an earthquake, whose effect can significantly weaken the steel frame and destroy its fire protection. This paper presents the evaluation of the fire resistance for a two-storey steel portal frame, damaged by an earthquake simulated through spectrum response of Chlef, scaled three in the Algerian Seismic Code. First, the design of the steel structure considers seismic actions by a static nonlinear analysis. Second, it is followed by a fire analysis using an ISO834 standard fire model, considering that the structure is partially damaged. The finite element simulation and numerical analysis of the structure in post-earthquake fire condition yield the bilinear capacity curve at ambient temperature and the variation of local and global displacement at high temperature. A final comparison of the damaged (PEF) and undamaged (FIRE) frames subjected to the different fire scenarios is done.
Synthesis of silica nanoparticles to enhance the fire resistance of cement mortars
Silica nanoparticles are known to enhance the strength and durability of cementitious materials, due to their nanofilling effect and their high pozzolanic reactivity. They also have the potential to improve their thermal properties and fire resistance. However, these improvements are highly dependent on the nanoparticles’ characteristics. In this work, silica nanoparticles were prepared by sol-gel reaction and a design of experiments with four factors was used to conclude about the parameters that have more influence in the synthesis of these nanoparticles and, thus, optimize this process and the particles’ properties. Using a lower ethanol/water, higher hydrolysis and condensation time and higher volume of catalyst, the smallest particle size was obtained (118 nm). The effect of the incorporation of these silica nanoparticles into cement mortars was studied in terms of density and thermal conductivity of these mortars, after curing at room temperature. The presence of silica nanoparticles led to an increase in density and decrease of thermal conductivity. The mortars were also exposed to high temperature, which originated a significant reduction (~50%) in their thermal conductivity.
VIRGILE project: The concept of virtual fire resistance facility for the assessment of construction products performance
Construction industries products have to satisfy fire safety regulation, including technical approvals in fire resistance, by tests in accredited laboratories. Fire resistance tests lay down on a complex protocol, in which full size samples are settled in large furnaces able to reproduce severe time-dependent fire curves. The full-scale mounting and the cost of such tests could be a constraint for their development. In that context, the concept of virtual facility has been developed by Efectis during the VIRGILE project. The use and development of numerical simulation tools are an interesting complement to the fire tests. The developed tool aims to model a fire resistance test including interaction between sample and fire test facility. The virtual facility allows to better analyze and evaluate a large number of technical alternatives in order to find the most efficient technical and economical solutions. Moreover, numerical simulations may improve the testing conditions including thermal stress control and metrology. This paper presents an overview of the main results and applications achieved during the VIRGILE project in ten years.