Fire Technology最新文献

Fire incidents in automated vehicle parking (AVP) structures are rare, yet the impact of such incidents on the structural integrity of these systems is crucial for design considerations. Although sprinklers are recognized for their effective fire suppression in various settings, the effectiveness of sprinkler systems in AVP structures fire incidents and their contribution to the post fire conditions of these structures has received scant attention. Consequently, this study performed a comprehensive numerical evaluation of fire performance within these structures, with a primary focus on the evaluation of sprinkler systems. Three distinct fire location scenarios were employed to assess the performance of the sprinkler systems and post fire conditions of the structure. The evaluation process starts with simulation of each scenario using the Fire Dynamics Simulator (FDS). Subsequently, the FDS results were transferred to OpenSees to perform thermo-mechanical analyses. The post-fire conditions of the structure were then evaluated based on structural responses obtained from OpenSees and based on performance-based assessment (PBA) criteria. The findings indicated that the employed sprinkler configuration effectively reduced the vertical progression of fire. Notably, when the fire ignited in proximity to the facade, the sprinkler system had a lower performance compared to the other scenarios. This finding suggests the need for adopting advanced suppression system configurations that are specifically designed to reduce fire risks in these facade-proximate areas. Furthermore, these observations highlight the potential value of considering the use of non-combustible materials in facade design to improve fire safety. The outcome of this study provides insights for enhancing the fire safety measures in car parks with steel structures. Such enhancements are crucial for establishing a robust fire safety framework in these environments.

Subway trains cannot stop immediately to extinguish fires and evacuate passengers if a fire accident occurs. The piston wind generated by train movement coupled with longitudinal ventilation, makes the process of high-temperature smoke spreading upstream and downstream of the fire source more complex and unpredictable. The evacuation process of personnel is affected by high-temperature smoke in tunnels, it is worthwhile to investigate personnel evacuation in interval tunnels under longitudinal ventilation during a train fire. This paper uses a three-dimensional compressible (N - S) equation and a fully buoyant corrected Renormalization-group (RNG) (k - varepsilon) turbulence model to build a fire smoke spread model. Additionally, a cellular automaton model is employed to construct a simulation model for the evacuation of personnel in interval tunnels. We used the models to investigate the influence of longitudinal ventilation speed on smoke spread and the evacuation behavior characteristics of personnel under a moving subway train with fire. Results show that smoke spreads downstream of the fire source, and the temperature of smoke in tunnels decreases as longitudinal ventilation speed increases. A prediction model between longitudinal ventilation and the peak value of smoke temperatures in tunnels was modified based on Li's prediction model. Meanwhile, the total evacuation time decreases as the longitudinal ventilation speed increases. A theoretical prediction model between the peak value of smoke temperatures and total evacuation time is developed. The model parameters are determined using a nonlinear fitting method. The influence of longitudinal ventilation on the average flow rate and arrival time at the exit upstream of the fire source is less. However, it has a significant effect downstream of the fire source. As the longitudinal ventilation speed increases, the average flow rate at the exit downstream of the fire source increases, leading to a decrease in total evacuation time. A notable consideration is that the elderly or minors are significantly affected by smoke in the late stages of evacuation process, leading to an increase in total evacuation time.

This study analyzes socio-economic demographics (including Geomatic conzoom® segmented demographic variables) as well as building and property registration information as risk factors in relation to the prevalence of residential building fires within 100 m × 100 m cells. The logistic regression model achieved a receiver operating curve (ROC) of 0.74 and a precision-recall curve of 0.12 on the testing dataset. The model identifies 19 significant variables related to the risk of residential fire. The top 5 highest performing variables in our model and their odds ratios are the following: number of people (OR 1.25), Multi/family residence-building type (OR 1.20), number of buildings (OR 1.18), conzoom® Type C—Country/Rural Communities (OR 0.85), construction year (OR 0.87). These results indicate that socio-economic factors play a large role in influencing fire vulnerability within residential areas and can help prioritize resource allocation to reduce fire vulnerability in the identified risk factor groups.

The failure of steel connections can lead to the progressive collapse of the entire structure. Accurate modelling of steel connections at elevated temperature allows structural fire engineers to design steel structures that may deal with the severity of a fire. The prEN 1993-1-14 proposes numerical design calculation for the static design check of steel connections. This paper presents a component-based finite element model (CBFEM) to design the T-stubs at elevated temperatures. The generated model is verified and validated against the results from the analytical model and experimental study. The resistance, failure modes and the load-deformation curves are used to validate and verify the CBFEM models for steel connection design at elevated temperatures. The results stated that the CBFEM is a practical design tool to model bolted connections at elevated temperatures and it is possible to apply the recommended 5% plastic limit strain by EN 1993-1-5 for fire design of bolted connections.

Underground pipelines of different burial depths are extensively utilized in the transportation industry for the conveyance of combustible gases. Failure of these pipelines could result in a jet fire in a pit (JFP), potentially endangering nearby pipes, structures, and individuals. The objective of this study is to analyze the flame geometry and temperature distribution of a JFP. A facility, comprising a jet fire apparatus and a rectangular pit, was constructed to experimentally simulate JFPs across three distinct burial depths and nineteen nozzle exit velocities. The JFP can manifest as an impinging jet flame (IJF), a transitional jet flame (TJF) or a jet flame ejected from the pit top (JFEPT), depending on the burial depth and nozzle exit velocity. An increase in burial depth reduces the critical velocities that differentiate these three flame patterns. Empirical correlations for the flame length and width of JFPs are developed, considering different burial depths, exit velocities, and pit dimensions. Additionally, two correlations available in the literature are validated for predicting the temperature distribution of TJF and JFEPT, respectively. These findings can inform the safety design of pipeline burial depths, considering the behavior of JFPs.

Previous research has identified sociodemographic inequalities in fire prevention measures. This study examined whether sociodemographic differences persist in the Swedish population concerning fire prevention measures and particularly whether there remains an inverted u-curve related to age in protection habits. Additionally, it investigated whether fire protection practices are influenced by the level of societal protection. The research utilised survey data and register data from The Swedish Civil Contingencies Agency and Statistics Sweden. A latent class analysis was conducted, dividing respondents into four latent classes, followed by two binomial regression analyses. The study revealed three key findings regarding fire protection measures. First, certain demographic groups, namely the young, women, single and childfree households, low-income and low-education individuals, immigrants, and urban residents, are disproportionately lacking optimal fire safety measures. Second, although a safety maturity curve is still observed, older adults in Sweden today are considerably more protected compared to 15–20 years ago, indicating that safety practices employed during middle age continue into old age. Third, a trend is observed where individuals living in areas with more efficient professional rescue services tend to have lower levels of personal fire protection, suggesting a rational choice based on the perceived level of societal protection.

A novel mathematical model for the critical ventilation velocity to prevent smoke backlayering in tunnels is presented, addressing limitations of prior approaches. The basis of the model is a rigorous characterisation of the physical processes by the characteristic quantities. Empirical parameters within the new model are determined, to align with results from both full-size and small-scale tunnel experiments. Data from numerical simulations (CFD, Computational Fluid Dynamics), validated by known test data, are then used to estimate the effects of tunnel slope and other parameters on the critical velocity. The model is seen to approximate the critical velocity well, following all trends identified by test data and CFD parameter studies. The empirically calibrated equation permits prediction of the critical velocity beyond the narrow range of tunnel geometries where known results already give an answer. The resulting equation has practical application for tunnel design.