A Round Robin of fire modelling for performance‐based design

Increased industrialization and aging infrastructure have resulted in leaks of hazardous chemicals, such as CO. Leak modeling is crucial to developing emergency response strategies. Therefore, we simulated the time to criticality (TTC), which is the time to reach the threshold limit for occupational exposure, of a CO leak. The basis of the study is a fire dynamics simulator, a computational fluid dynamics model that was used to investigate the movement of CO in various scenarios, including using different building layouts and areas, temperatures, and leak diameters. Multiple regression analysis was performed to obtain regression equations for the TTC as a function of the independent variables. Ultimately, we found that the type of dispersion varies with respect to the temperature-dependent density of CO, and, among the independent variables, the leak diameter had the strongest effect on the TTC. The regression equations with logarithmic conversion were validated and found to have higher accuracy than those without logarithmic conversion. The findings provide useful information for developing emergency response plans regarding leak size in the case of hazardous chemical leakage. However, empirical studies of different gas types and leakage scenarios are required.

This study presents a comprehensive comparison of image quality between synchrotron-based and laboratory-based nano-computed tomography (nano-CT) systems, using a standardized 3D test phantom composed of monodisperse silica spheres. A round-robin approach was employed across multiple international facilities to benchmark performance across various imaging modalities and setups, including absorption and phase contrast techniques. Image quality was quantitatively assessed using three-dimensional signal-to-noise ratio (SNR3D), detection effectiveness (DE3D) and modulation transfer function (MTF3D) metrics. The results reveal that, while synchrotron-based nano-CT consistently delivers superior spatial resolution and shorter scan times, laboratory-based systems demonstrate competitive image quality at the cost of extended acquisition durations. Beyond the experimental comparison, the main contribution of this work is a standardized, open-source analysis framework that quantifies nano-CT image quality using SNR3D, DE3D and MTF3D of a specific phantom. This combination of metrics provides a reproducible basis for cross-platform benchmarking of synchrotron and laboratory nano-CT implementations and can be readily applied to future instruments.

The thermal spray industry identified the need for repeatable and reproducible feedstock powder characterization methods, especially particle size distribution (PSD), for cost effective manufacturing of thermal barrier coatings. The PSD measurement by a laser light scattering method was identified as the technique most widely used in the industry. This technique offers high resolution, rapid measurements and ease of use. A round robin study by nine laboratories using different models of a commercial light scattering instrument has been completed as the first step towards the development of a Standard Reference Material (SRM) for the calibration of light scattering instrument. Other measurement techniques were also employed for additional comparison. The PSD measurements employing light scattering techniques evidenced some method dependence, despite the use of identical sample preparation procedures. The round robin results will serve as reference values for the development of the SRM.

FDS (Fire Dynamics Simulator) is the open-source software developed by NIST of USA. Pyrolysis is considerd to solve the one-dimensional heat conductivity equation in three directions respectively. FDS is applied widely for building fires, tunnel fires and so on. Since combustion analysis is significant for proactive measures, we have acquired enough skill to use for science programs. We have executed fire spread simulations of small plastic gears with a diameter of 30 mm and 10 mm in thickness in a closed duct to evaluate the capability of FDS as a development tool. In this report, we have investigated the combustion characteristics of an upper gear for the distance between two gears and aperture ratio of upper surface of the duct. We prepared an analytical model with 2.5 mm mesh size to compare time variation of temperature with the experimental results. Our numerical calculations correlated well with our experimental results. In addition, the time variation of concentration of a fuel gas showed a physically reasonable behavior. For the small distance between gears, the fuel gas generated from an under gear mainly plays an important role in ignition of the upper gear. We understand the effect of temperature and fuel concentration generaterd by the under gear. FDS Ver. 6 is applicable to solid combustion phenomena for 10 mm size plastics.

The effective notch stress approach for the fatigue strength assessment of welded structures as included in the Fatigue Design Recommendations of the IIW requires the numerical analysis of the elastic notch stress in the weld toe and/or weld root which is fictitiously rounded with a radius of 1 mm. In order to establish guidelines for modelling the structure and evaluating the results, several numerical analyses have been performed in a round robin. This covers three welded details of different complexity where either the weld toe or the weld root is the potential crack location. The first example is a cruciform joint with non-load carrying fillet welds in one load case and load carrying in the other. The second is a complex T-joint of rectangular hollow section (RHS) members which was also subject of the so-called SAE-FDE weld challenge to predict fatigue life. The third is the fillet-welded end connection of a RHS joint being prone to fatigue failure at the weld root with non-fused root faces. The results are compared with each other and conclusions are drawn with regard to appropriate modelling and to the scatter of results to be expected.

Fire accidents can cause severe damage to aircraft and jeopardize passenger safety. Current research on civil aviation safety generally focuses on guaranteeing continued operational safety and airworthiness, typically treating fire as a potential hazard or risk factor. In addition, fire prevention design in civil aviation is generally based on pessimistic assumptions that components have lost their intended functions in fire scenarios, leading to redundant or inadequate fire prevention design. Therefore, this paper proposes a probabilistic assessment methodology for structural failure severity of aero‐engine components in fire scenarios based on cumulative failure frequency (CFF). The proposed methodology first considers all possible combinations of fire scenarios that may occur in an aero‐engine by discretizing the probability distributions of the random variables associated with these scenarios. Subsequently, fire simulation using the fire dynamics simulator in conjunction with heat transfer analysis is carried out to determine the temperature distribution of structural elements. To enhance the computational efficiency of consequence analysis, a temperature approximation model based on the extreme learning machine is then introduced to reduce computational burden. Finally, structural failure severity is quantified by identifying the state of each structural element with the inclusion of the transition state and calculating the corresponding CFF. A case study is presented to demonstrate the applicability of the proposed methodology in identifying critical structural elements in fire scenarios, thereby validating its practicality and effectiveness.

With the rapid development of architectural technology, long-span structures have been widely used due to their vast interior space and beautiful architectural composition. Due to the characteristics and high costs of coating materials on large steel structures, fire resistance designs for these kinds of structures have become more and more important. This paper presents comprehensive case analyses of the fire performance of single-layer cylindrical reticulated shells. Nonuniform fire temperature fields of single-layer cylindrical reticulated shells in different fire scenarios were generated using a Fire Dynamics Simulator (FDS). The influences of different parameters on the air temperature field during a fire in a reticulated shell structure were analyzed. A Finite Element (FE) model was developed using the FE software ABAQUS to model the structural behavior of single-layer cylindrical reticulated shells in different fire scenarios. The effects of various parameters on the responses of single-layer cylindrical reticulated shells during a fire were investigated. Using the results from the performance-based analysis in this research, we propose some recommendations for fire resistance designs for single-layer cylindrical reticulated shells.

Automaattiset sprinklerilaitteistot ovat tehokas keino pienentää rakennuspaloihin liit­tyviä riskejä. Ympäristöministeriön uusi asetus rakennusten paloturvallisuudesta on avannut uu­sia mahdollisuuksia sisällyttää sprinklereiden vaikutus rakennussuunnitteluun. Useissa kohteissa on voitu osoittaa, että esimerkiksi teräsosien palosuojauksen määrää voidaan vähentää merkittävästi tai jopa jättää kokonaan pois, silloin kun sprinklerijärjestelmä toimii suunnitellulla tavalla. Toimintavarmat ja palonkestävät suunnitteluratkaisut edellyttävät, että sprinklereille käytetyt luotettavuustasot sekä oletettuun palonkehitykseen perustuvat suunnittelumenetelmät ovat kattavasti perusteltuja. Tämä artikkeli esittelee tutkimuksen, jolla pyrittiin määrittämään sprinklerilaitteistojen luotettavuustasoja tyypillisissä rakennuskohteissa sekä arvioimaan mahdollisia hyötyjä voidaan saavuttaa, jos sprinklerijärjestelmän luotettavuus otetaan huomioon teräsrakenteiden rakennesuunnitteluun.

Smoke extraction systems, either static with natural ventilation, or dynamic with mechanical ventilation are required to keep smoke layer at high levels in many tall atria. It is observed that a design fire with high heat release rate (HRR) is commonly used for designing natural vents, but a low HRR is used for mechanical ventilation system. This will not produce a sustainable environment. There are no internationally agreed on design guides to determine the HRR in the design fire for different extraction systems and scenarios. This issue will be studied using a Computational Fluid Dynamics (CFD)-based software, the Fire Dynamics Simulator (FDS) version 6.7.1. Simulations on natural smoke filling, static and dynamic smoke extractions were carried out in a big example atrium. CFD-FDS predictions were compared with previous full-scale burning tests. Results confirmed that static smoke extraction is a good option for big fires, and a dynamic system is best for small fires. A sustainable new hybrid design combining the advantages of static and dynamic systems is proposed, which could result in a lower smoke temperature and higher smoke layer interface height, indicating a better extraction design.

Adequate design methods and tools are vital to any construction project, especially when its complexity and value are high. Tunnels, road or railway, are a good example of such structures. This paper deals with the topic of computer modelling utilization in the design and evaluation of fire safety in tunnels. The capabilities of selected software - Fire dynamics simulator + Evac - are demonstrated on a practical example - Tunnel Lucivna in the Slovak Republic. In this example case, both fire and evacuation modelling is used in conjunction to assess the overall fire safety of the tunnel. The results show the effects of fire on the tunnel structure as well as the persons inside the tunnel trying to evacuate.

With the recent release of AASHTOWare Pavement ME Design software, there will be a greater emphasis on measuring the coefficient of thermal expansion (CTE) of concrete because of its significance on predicted distress and design life. The most widely used test method to measure the CTE of concrete is the AASHTO T 336 test method. Data are presented from an interlaboratory (round robin) study conducted by FHWA; this study included 20 CTE units and laboratories representing FHWA, state highway agencies, universities, commercial testing laboratories, and the concrete paving industry. As part of the study, each laboratory tested nine concrete specimens (three concrete mixtures 3 three specimens per mixture) that spanned the typical range of CTE values for concrete. On the basis of this interlaboratory study for the AASHTO T 336 test method, the within-laboratory single operator standard deviation was found to be 0.12 mstrain/°C and the between-laboratory standard deviation was found to be 0.28 mstrain/°C. Data from the study also showed that there was no statistically significant difference between custom-built CTE devices versus commercially available testing devices. This demonstrates the ruggedness of the current test method.

The Fire and Smoke Simulator (FSSIM) [1] Version 1.5 is a continuous time, physics-based simulation of the spread of fire and smoke inside a multi-level, multi-compartment geometry with complex ventilation. The model was developed to aid designers in analyzing the effect of changes in fire protection systems (both passive and active) and compartment layout on fire spread potential. It is also used to provide data on fire-related phenomena (e.g. temperature, smoke, activation of detection system, and effectiveness of active or passive fire protection) to support recoverability and vulnerability analyses. Extensive verification and validation exercises have been performed to demonstrate the applicability of FSSIM [2]. Additionally, a novel methodology to account for the known stratification effects of elevated fuel packages has been investigated in FSSIM. The current effort will examine the performance of FSSIM in simulating the 1986 Lawrence Livermore National Laboratory (LLNL) enclosure fire tests [3]. The performance of FSSIM will then be compared to other commonly used fire simulation tools, including the Consolidated Model of Fire and Smoke Transport (CFAST) [4], and the Fire Dynamics Simulator (FDS) [5]. This study is intended to demonstrate the relative level of accuracy that can be obtained from several fire models using simplistic methodologies such as those that may be employed in the design evaluation stage of fire hazard analysis. This effort supports the use of single zone models in the design and fire hazard analysis of highly complex buildings with multiple challenging design fire scenarios.

The prediction performance of design fire curves is numerically investigated for tunnel fire using the fire dynamics simulator (FDS). A large eddy simulation (LES) was adopted in the simulation of a previous 750 kW tunnel fire experiment. Based on the experimental heat release rate, t2-fire growth, quadratic and exponential design fire curves (DFCs) are mathematically constructed and adopted in the FDS simulation. The predictions of each DFCs are compared against the experimentally measured smoke temperature, smoke travel time, and carbon monoxide (CO) concentration. In addition, the prediction performance of the mixture fraction (MF) and mixing controlled fast chemistry (MCFC) combustion models, is compared. The simulation results of the MF and MCFC models are similar except for the CO concentration features. For the performance of the DFCs, t2-fire growth curve with the MF combustion model is the most effective combination, which demonstrated the most reasonable agreement with the experimental data.

Performance-based life-safety design depends on a comparison between the time required for escape (Required Safe Escape Time -RSET) and the time to loss of tenability (Available Safe Escape Time -ASET).Both include a number of stages, involving a variety of processes and requiring a range of input data.A problem for the design engineer is that while all stages need to be addressed to obtain a realistic outcome for the analysis, some aspects are reasonably well understood and quantified, while others are often oversimplified or ignored.For the RSET time line, most emphasis is usually placed upon the travel time component, representing the physical movement of occupants into and through the escape routes.However, the time required for occupants to engage in a range of behaviours before the travel phase (pre-movement time), often represents a greater component of the total escape time.Pre-movement time distributions are dependent upon key features such as occupancy type, warnings, occupant characteristics, building complexity and fire safety management strategy.It is proposed that a practical solution for the engineer is to apply pre-movement time distributions measured from monitored evacuations, fire incidents, or derived using behavioral models, and specified in terms of a number of "design behavioural scenarios" analogous to "design fire scenarios", classified according to the key features listed.A problem with the evaluation of travel time, is that most calculation methods assume no interaction between the occupants and the fire effluent.If occupants are exposed to irritant smoke, then movement speeds are likely to be reduced.A calculation method is proposed, relating predicted travel speed to smoke and irritant concentrations.The ASET time line ends when occupant incapacitation is predicted from exposure to fire effluent.This depends upon the time-concentration curves for the main toxic fire effluents, requiring inputs on smoke and toxic product yields under different fire conditions.Existing engineering calculations use only smoke density and/or carbon monoxide, with yields often treated as constants, usually for the well-ventilated fire case.A method is proposed, whereby yield data for major toxic effluent species can be obtained over a range of fire conditions, expressed in relation to the global equivalence ratio.Results are illustrated for carbon monoxide and hydrogen cyanide.

An integrated probabilistic risk assessment methodology is developed for the purpose of quantifying the life safety level of people present in buildings in the context of fire safety design. Multiple risk based concepts and tools have been developed in previous research to objectify performance based design methods for simple building types and layouts. However, these available models lack an integrated approach for challenging building designs and moreover they are not adequately coupled, most often resulting in a significant computational effort. Hence, there is a need for a pratical and efficient framework for dealing with complicated building layouts and different occupancy types. Therefore, a computationally efficient quantitative risk assessment method is developed that provides a framework by combining deterministic sub-models and probabilistic techniques to quantify the fire safety level by means of failure probabilities, individual and societal risk. The deterministic framework is supported by analytical and numerical models. The probabilistic framework is supported by response surface modelling, sampling techniques and limit state design. Following the theoretical description of the model, a case study of a five storey commercial shopping mall of 25,000 m² is elaborated and discussed as proof of concept. Multiple fire, building and occupant variables are implemented in the model. Three different fire safety designs are compared, resulting in quantified risks between 10-6 and 10-8. The case study proves the validity of the newly developed integrated methodology for this type of buildings and its benefits in fire safety engineering.