A study on the temperature profile of bifurcation tunnel fire under natural ventilation

This study simulated a series of bifurcation tunnel fire scenarios using the numerical code to investigate the temperature profile of bifurcation tunnel fire under natural ventilation. The bifurcation tunnel fire scenarios considered three bifurcation angles (30°, 45°, and 60°) and six heat release rates (HRRs) (5, 10, 15, 20, 25, and 30 MW). According to the simulation results, the temperature profile with various HRRs and bifurcation angles was described. Furthermore, the effects of bifurcation angles and HRRs on the maximum temperature under the bifurcation tunnel ceiling and the temperature decay along the longitudinal direction of the branch were investigated. According to the theoretical analysis, two prediction models were proposed. These models can predict a bifurcation tunnel fire’s maximum temperature and longitudinal temperature decay in the branch. The results of this study could be valuable for modelling a bifurcation tunnel fire and benefit the fire engineering design of bifurcation tunnels.

A computer-based simulation and evaluation: Applying an automatic sprinkler system for extinguishing scooter fires in arcade areas

In Taiwan, arcade buildings function as areas for parking scooters, spaces for markets, and walkways for pedestrians. In recent decades, arcade fires have caused many cases of serious casualties due to the likely direction of fire that spreads from the first floor up, which hinders the evacuation routes. The majority of fire prevention research has focused on confined spaces or rooms instead of arcade areas. Specifically, the controlling of fire spreads that are caused by scooters in arcade areas has been rarely discussed. The variables of spaces, Response Time Index, and sprinkler activation temperatures are modeled in five fire scenarios with the Fire Dynamics Simulator software to simulate the real arcade fires in this paper. The results show that (1) setting an automatic sprinkler system can effectively suppress the arcade fires, (2) the quick response sprinkler RTI≦50 is the most effective type, and the result is similar to RTI=25, and (3) the sprinkler settings with either 2.3 meters or 2.6 meters do not have significant effects on heat release rates.

FDS simulation of smoke backlayering in emergency lay-by of a road tunnel with longitudinal ventilation

This paper investigates smoke movement and its stratification in a lay-by of a 900 m long road tunnel by computer simulation using Fire Dynamics Simulator. The lay-by is located upstream of the fire in its vicinity. The influence of lay-by geometry on smoke spread is evaluated by comparison with a fictional tunnel without lay-by. Several fire scenarios with various tunnel slopes and heat release rates of fire in the tunnels without and with the lay-by are considered. The most significant breaking of smoke stratification and decrease of visibility in the area of the lay-by can be observed in the case of zero slope tunnel for more intensive fires with significant length of backlayering. Several other features of smoke spread in the lay-by are analysed as well. The parallel calculations were performed on a high-performance computer cluster.

Pre-incident planning of fires in underground hard rock mines: old and new risks

Fires in underground mines may pose a challenge to fire and rescue personnel where the complex environment and multiple influences of a fire are poorly considered during pre-incident planning. A better knowledge of pre-incident planning in underground mines would improve the safety of personnel. This study on pre-incident planning in underground mines applied data from experiments, inventories and design fire studies. A number of questions were considered related to information sources, fire modelling, capturing complexity and using fire scenarios. When performing fire modelling, empirical models could be used to complement other modelling tools. The study found that for modelling of spatially extensive mine sections, the use of ventilation network-based mine fire simulations could be a better option. Using an analytical toolbox, an iterative testing of plans and an ongoing planning process, the pre-planning challenges for a mine can be mitigated. The purpose of this study was to examine existing pre-incident planning and propose information sources, tools and specific actions for future plans.

Investigation on the Effect of Platform Height on Smoke Characteristics of Fire Scenarios for Subway Stations

In this study, three full-scale experiments and a series of numerical simulations were conducted to investigate the influence of subway platform height and atrium ceiling height of subway stations on smoke control by mechanical exhausting systems. The smoke temperature variation with time, maximum temperature distribution, and smoke stratification were discussed. Results showed that the atrium had capacity to store smoke, especially at the early stage of smoke spread. However, the efficiency of smoke extraction did not increase simply with the rise in platform height and atrium ceiling height, and favorable smoke exhaust velocity was crucial for smoke elimination. The optimal smoke exhaust velocity was studied by numerical simulation and it was found that the area of smoke diffusion in subway stations with a higher platform was significantly smaller under the optimal smoke exhaust velocity. In addition, a prediction model of optimal smoke exhaust velocity with subway platform height was proposed. This study could provide on-site data and smoke spread characteristics for smoke control design, operation, and, significantly, guide safety evacuation of the exhaust system of subway stations.

A risk-based approach for structural assessment against fire considering escalation and passive fire protection (PFP) optimization

PurposeAccidental loadings such as fire constitute a great majority of potential and actual fatalities in both onshore and offshore installations. In order to prevent human loss and for a safe design of an asset, the risk of fire loading needs to be quantified, in terms of both probability/frequency and consequence aspects. In this paper the authors propose a novel risk-based approach for the assessment against accidental fire loading.Design/methodology/approachIn a conventional passive fire protection (PFP) analysis using ductility level analysis (DLA), fire loads are deterministically applied to a structure whose response is then analyzed. The initial PFP scheme is developed based on the analysis and then optimized. This approach is sometimes misinterpreted as a “risk-based” approach; however, it does not take into account the frequency aspect of the risk assessment. In a risk-based PFP analysis using DLA, fire scenarios are developed in a particular target zone. Then DLA is performed to determine the structural consequence. If personnel safety is of interest, the consequence of the structure is then linked to individual risk (IR) to determine fatalities. The amount of PFP to be applied on the structure is fully based on the risk that is produced by the fire scenarios in target zones.FindingsA new perspective on safe design of onshore/offshore structures for accidental loadings is outlined to estimate the associated risk to potential targets such as personnel as well as asset. The proposed assessment methodology will contribute toward identifying the mitigation measures and safety-critical procedures and equipment and toward a safer design.Originality/valueThis paper presents a new perspective in a safer design of onshore and offshore structures for a fire accidental loading based on risk calculation. Risk is defined as a combination of the frequency and consequence. An event frequency analysis is carried out to determine how often one should expect the event to occur. A consequence analysis is carried out to determine the severity levels of the event. In a risk-based consequence analysis, the severity levels are fully determined based on the risk associated with the event. The proposed novel risk-based assessment methodology against accidental fire loading contributes toward fully understanding the risk from an impact to personnel and to asset perspectives and leads toward safer and optimal design.