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.

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.

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.

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.

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.

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.

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.

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.