scholarly journals Research on Flashover Prediction Method of Large-Space Timber Structures in a Fire

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5515
Author(s):  
Yongwang Zhang ◽  
Lu Wang
Keyword(s):  
Prediction Method ◽  
Critical Conditions ◽  
Maximum Temperature ◽  
Timber Structures ◽  
Fire Dynamics ◽  
Large Space ◽  
Time Model ◽  
Control Factors ◽  
Fire Safety Design ◽  
Temperature Time

Due to the flammability of materials and the vastness of space, flashover fires of large-space timber structures pose a huge threat to lives as well as the structures themselves. Therefore, it is necessary to study the critical conditions, control factors and prediction methods of flashover fires. To address this issue, hundreds of design conditions were simulated by Fire Dynamics Simulator (FDS) with variations in space size, the heat release rate (HRR) of fire source and fire growth type. A temperature–time model of the maximum temperature of the smoke layer near the ceiling (Tmax) was established, and the critical condition that uses this model to predict the occurrence of flashover was determined. Furthermore, a mathematical formula was established that can accurately predict the flashover induction time when the Tmax exceeds 400 °C. This research can provide a reference for the performance-based fire safety design of large-space timber structures.

scholarly journals Risk Analysis and Control Factors Based on Excavation of a Large Underground Subway Station under Construction

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1629
Author(s):  
Zhien Zhang ◽  
Mingli Huang ◽  
Baohua Wu
Keyword(s):  
Large Scale ◽  
Complex Structure ◽  
Subway Station ◽  
Multidimensional Space ◽  
Large Space ◽  
Control Factors ◽  
Underground Subway Station ◽  
Subway Stations ◽  
Under Construction ◽  
And Control

Considering the convenience of pedestrian transfer, reasonable structural stress and beautiful shape design, most subway stations adopt symmetrical design. At present, the new subway station is developing in the direction of a multidimensional space, as well as a large scale, and complex structure. Tunnel construction also presents unpredictability, coupling amplification and high risks. For example, a subway extension project involves construction, which would affect the normal use of the subway or damage its structure. Based on excavation of the largest underground subway station under construction in China, the Erligou station extension project (line 16 of Beijing Metro), and using theoretical analysis, numerical simulation, monitoring data, and other research methods, this paper quantitatively analyzes the risk of a large space station’s construction process on the adjacent existing station structure and track, as well as highlights key, high-risk sub-projects, or construction steps, combined with specific engineering measures to ensure safety during construction of a new station. The general rules concerning large space subway station construction are further summarized to provide reference for similar projects.

Relationship between heating/cooling period and changing temperature conditions in the urban areas of Hungary

2020 ◽  
Author(s):  
Csenge Dian ◽  
Attila Talamon ◽  
Rita Pongrácz ◽  
Judit Bartholy
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Energy Consumption ◽  
Extreme Values ◽  
Building Design ◽  
Temperature Time Series ◽  
Maximum Temperature ◽  
Design Parameters ◽  
Daily Average ◽  
Temperature Time

<p>Climate change, extreme weather conditions, and local scale urban heat island (UHI) effect altogether have substantial impacts on people’s health and comfort. The urban population spends most of its time in buildings, therefore, it is important to examine the relationship between weather/climate conditions and indoor environment. The role of buildings is complex in this context. On the one hand UHI effect is mostly created by buildings and artificial surfaces. On the other hand they account for about 40% of energy consumption on European average. Since environmental protection requires increased energy efficiency, the ultimate goal from this perspective is to achieve nearly zero-energy buildings. When estimating energy consumption, daily average temperatures are taken into account. The design parameters (e.g. for heating systems) are determined using temperature-based criteria. However, due to climate change, these critical values are likely to change as well. Therefore, it is important to examine the temperature time series affecting the energy consumption of buildings. For the analysis focusing on the Carpathian region within central/eastern Europe, we used the daily average, minimum and maximum temperature time series of five Hungarian cities (i.e. Budapest, Debrecen, Szeged, Pécs and Szombathely). The main aim of this study is to investigate the effect of changing daily average temperatures and the rising extreme values on building design parameters, especially heating and cooling periods (including the length and average temperatures of such periods).</p>

scholarly journals Prediction of fire loading on the structures using computational fluid dynamics

2020 ◽  
Vol 313 ◽  
pp. 00033
Author(s):  
Romana Erdelyiová ◽  
Lucia Figuli ◽  
Matúš Ivančo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Structure Design ◽  
Gas Temperature ◽  
Fire Load ◽  
Fire Dynamics ◽  
Large Space ◽  
Space Objects ◽  
Fire Loading ◽  
A Performance

The development of a fire in a large-space fire section differs significantly from the development in a small fire section. In large-space objects, to design structures under the fire load often proceeds through a performance-based approach. Advanced methods can be used in all parts of the design in predicting of the scatter of temperature field, in calculating of the heat transfer to the structure and in assessing of the mechanical behaviour of the structure or its part under the fire load. The prediction of the gas temperature in the fire compartment is crucial for the structure design. The paper is focused on selection of different fire scenarios in the large-space building. The aim is to provide background for structural design in a fire using a performance-based design. The problem is solved by using FDS (Fire Dynamics Simulator) software based on the CFD (Computational Fluid Dynamics) method.

scholarly journals Modified Fire Simulation Curve of Cabin Temperatures in Postcrash Fires for Fire Safety Engineering

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Qingsong Zhang ◽  
Naiwen Jiang ◽  
Hanpeng Qi ◽  
Xingna Luo
Keyword(s):  
Fire Safety ◽  
Safety Management ◽  
Influence Factors ◽  
Safety Engineering ◽  
Fire Simulation ◽  
Fire Dynamics ◽  
Aircraft Cabins ◽  
Fire Safety Engineering ◽  
Fire Safety Design ◽  
Scale Test

The fire simulation curve this paper presents is based on a curve which is proposed by Barnett in 2002. The curve is used to study the temperature change in a fire scenario in the interior of a rectangular compartment. However, it is not applicable to use in some long, limited spaces with arc boundaries, such as aircraft cabins. Some improvements and simplifications are made to the curve to solve this problem. A numerical simulation is conducted via the modified curve in a B737 fuselage during a postcrash fire. The result is compared with a fire dynamics simulator (FDS) simulation and a full-scale test undertaken by the National Aeronautics and Space Administration (NASA). The practicability and accuracy of the modified curve is proved through the relevant analysis and the main relative error analysis. The time to flashover is also predicted by the curve and the FDS simulation, respectively. Several parameters are chosen as influence factors to study their effect on the time to flashover in order to delay the occurrence of the flashover. This study may provide a technical support for the cabin fire safety design, safety management, and fire safety engineering.

scholarly journals Monitoring observed changes in warm-days extremes over Turkey

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Mohsen Abbasnia 1 ◽  
Hüseyin Toros2
Keyword(s):  
High Elevation ◽  
Maximum Temperature ◽  
Daily Maximum Temperature ◽  
Annual Number ◽  
Daily Maximum ◽  
Atmospheric Humidity ◽  
Eastern Area ◽  
Increased Risk ◽  
The Mean ◽  
Temperature Time

This study aimed to analyze warm-days changes extracted from daily maximum temperature time-series of 71 stations in Turkey during 1961–2016. First, the trend analysis of warm-days events indicated that the annual count of warm-days occurrences has been significance rising by a rate of 1.4 days per decade over more than 90 percent of the studied stations. Thus, there are consistent patterns in daily warming throughout the study area. The spatial maps showed that the lowest frequency in the minimum annual number of warm-days occurred in western areas by a total number of 21 days and its highest occurred in the eastern area by a total number of 35 days. Moreover, the highest frequency in the mean and minimum annual count of warm-days observed in the northwestern lowlands and their frequency has decreased toward the eastern mountainous. Also, the highest range of differences between the annual count of maximum and minimum values has happened in the eastern regions which are characterized by high elevation and the lower existence of atmospheric humidity. Therefore, a higher moisture content of the atmosphere in lowland coastal stations favors severe warm-days and the increased risk of human health.

scholarly journals Climate reference stations in Germany: Status, parallel measurements and homogeneity of temperature time series

2016 ◽  
Vol 13 ◽  
pp. 163-171 ◽  
Author(s):  
Frank Kaspar ◽  
Lisa Hannak ◽  
Klaus-Jürgen Schreiber
Keyword(s):  
Time Series ◽  
Seasonal Cycle ◽  
Type A ◽  
Temperature Time Series ◽  
Current Status ◽  
Maximum Temperature ◽  
Specific Task ◽  
New Instrumentation ◽  
Temperature Time ◽  
Parallel Measurements

Abstract. Germany's national meteorological service (Deutscher Wetterdienst, DWD) operates a network of so-called "climate reference stations". These stations fulfill several tasks: At these locations observations have already been performed since several decades. Observations will continuously be performed at the traditional observing times, so that the existing time series are consistently prolonged. Currently, one specific task is the performance of parallel measurements in order to allow the comparison of manual and automatic observations. These parallel measurements will be continued at a subset of these stations until at least 2018. Later, all stations will be operated as automatic stations but will also be used for the comparison of subsequent sensor technologies. New instrumentation will be operated in parallel to the previously used sensor types over sufficiently long periods to allow an assessment of the effect of such changes. Here, we present the current status and an analysis of parallel measurements of temperature at 2 m height. The analysis shows that the automation of stations did not cause an artificial increase in the series of daily mean temperature. Depending on the screen type, a bias with a seasonal cycle occurs for maximum temperature, with larger differences in summer. The effect can be avoided by optimizing the position of the sensor within the screen.

scholarly journals Fire behaviors along timber linings affixed to tunnel walls in mines

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0260655
Author(s):  
Ke Gao ◽  
Zimeng Liu ◽  
Changfa Tao ◽  
Zhiqiang Tang ◽  
Yisimayili Aiyiti ◽  
...  
Keyword(s):  
Cross Section ◽  
Flame Spread ◽  
Maximum Temperature ◽  
Spread Rate ◽  
Smoke Movement ◽  
Fire Dynamics ◽  
Flame Spreading ◽  
Wind Speeds ◽  
Flame Spread Rate ◽  
Tunnel Cross Section

Timber linings are applied as primary supports in the tunnel fault and fracture zones of mines. These linings are essential to prevent broken rock from falling during the occurrence of exogenous fires. In this study, experiments and numerical simulations were carried out using a fire dynamics simulator to investigate the flame-spread rate, flame characteristics, smoke movement, and spread process of timber-lining fires under different wind speeds of 0, 0.25, 0.5, and 0.75 m/s. It was found that cross-section flame spreading follows the three-stage sidewall-ceiling-sidewall pattern. Moreover, the average flame-spread rate increases along the vertical flame-spreading direction and decreases when the flame reaches the timber-lining corners. Moreover, the flame lengths underneath the timber-lining ceiling in the x-direction are longer than those in the y-direction. As the wind speed increases, the normalized flame lengths R(f) in the two directions decrease, and the maximum temperature underneath the ceiling decreases. In addition, the maximum temperature in the three tunnel sections of interest is first recorded in the tunnel cross-section in the initial fire stage. Higher wind speeds correspond to farther distances of the maximum-temperature points of the three timber-lining sections from the fire source.

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