Parametric study of urban fire spread using an urban fire simulation model with fire department suppression

Although urban conflagrations are rare now, the threat still exists in two situations—following an earthquake and when a wildland fire reaches an urban area. In this paper, we first extend a previously developed urban fire simulation model to include fire department suppression, making it a complete, integrated ignition-spread-suppression model that can now better estimate urban fire risk and help understand the effectiveness of fire department efforts. We then apply this Urban Fire Simulation model (UFS2) to a case study area in California and conduct a parametric study to examine the key factors that influence fire spread and the interactions among them. The results suggest that urban fire spread is highly variable and under the right combination of unlucky but possible circumstances—many ignitions, high wind speeds, and limited water availability—the losses can be very high, much higher than observed in recent earthquakes. In addition to the three factors mentioned, the locations of the ignitions (relative to wind direction and fire breaks), number of engines, and engine arrival times are shown to be important. Strong interactions are evident between wind speed and number of ignitions, and between water availability and number of engines.     

人员疏散模拟中几何数据创建方法和实现

围绕火灾情况下建筑物内人员安全疏散的数值模拟，讨论了几何数据创建过程中的一些思路和方法。通过建立图形操作界面，利用菜单、按键、鼠标和图形的即时显示，能够方便实现疏散计算所需的建筑几何数据的准备，提高工作效率，对疏散模拟计算起到重要作用。     

形状敏度及水平集在结构优化中的运用

建立了水平集方法和结构优化问题模型,对形状敏度进行了分析,导出了演化水平集方程所需要的速度场,并结合工程实例,证明了其有效性,以推广基于敏度分析的水平集方法在结构优化中的应用。     

建筑消防监督现状分析与改进途径

针对建筑消防监督存在的审查不全面、消防设备不完整、责任制度不健全等问题,分析了这些问题的产生原因,指出建筑消防人员要调整工作思路,健全建筑工程消防监督法规,从而使建筑工程消防监督审核工作更加适应社会和经济的发展。     

建筑防火设计方法的思想回归与创新

从建筑防火设计方法与思想的历史演变角度入手，分析了古代朴素的防火设计方法，以及近代以指令性条文构筑的建筑防火设计规范化设计方法体系。从古代个案的设计实践到近代对历史的火灾经验教训的总结，着重探讨了随着城市的现代化发展和建筑工程技术的进步，大型、复杂的建筑迅速增多而产生的以现代火灾科学技术为基础的性能化防火设计方法。     

PC变截面空心板桥缺陷建模方法研究

根据对某大桥现状及国内外研究现状的广泛了解,对各种病害机理进行了总结和分析,对PC变截面空心板缺陷建模方法作了研究,以便在今后的设计、施工、养护过程中能找出控制裂缝的有效办法。     

基于炭化速度的梁柱木构件防火设计方法研究

由于缺乏对木结构火灾性能的系统研究,现行国家标准《木结构设计规范》(GB 50005-2003)(2005版)和《建筑设计防火规范》(GB 50016-2014)仅对木结构构件的耐火极限进行了相关规定,没有涉及木材的燃烧机理、炭化速度以及木构件耐火极限的计算方法,限制了木结构向多层和大跨方向的发展。本文较系统地研究了我国工程常用树种的燃烧性能和炭化速度,得到了木材炭化速度计算式,提出了与试验结果吻合的木构件基于炭化速度的防火设计方法,为相关标准的制修订提供依据,为木结构在我国的推广应用提供支撑。     

消防职业技能训练操法的探索与实践

消防控制室操作人员应急处置能力是火灾情况下直接影响自动消防设施发挥作用的关键因素,也是当前消防职业技能训练的一个难点问题.编制消防职业技能训练操法,提出提高训练质量的对策,为我国消防职业技能操法科学施训提供了思路、方法和途径.     

电导率线性变化高密度电法有限元正演模拟

本文从点电流源的边值问题出发,推导了相应的变分问题,采用矩形网格剖分、双线性插值的有限元法,给出了完整的电导率线性变化的高密度电法正演算法,进而编制了相应的正演程序。利用该程序对一个水平层状的地电模型进行计算,将有限元解与解析解对比分析,验证了该算法的正确性和有效性;然后以电导率线性变化的层状模型、对称高阻体、对称低阻体典型模型进行正演计算,得到了相应的视电阻率断面图,结果表明其模拟效果良好。     

Principles and applications of probability-based inverse modeling method for finding indoor airborne contaminant sources

Building indoor air quality (IAQ) has received growing attentions lately because of the extended time people spend indoors and the increasing reports of health problems related to poor indoor environments. Recent alarms to potential terrorist attacks with airborne chemical and biological agents (CBA) have further highlighted the research needs on building vulnerability and protection. To maintain a healthful and safe indoor environment, it is crucial to identify contaminant source locations, strengths, and release histories. Accurate and prompt identification of contaminant sources can ensure that the contaminant sources can be quickly removed and contaminated spaces can be effectively isolated and cleaned. This paper introduces a probability concept based prediction method—the adjoint probability method-that can track potential indoor airborne contaminant sources with limited sensor outputs. The paper describes the principles of the method and presents the general modeling algorithm and procedure that can be implemented with current computational fluid dynamics (CFD) or multi-zone airflow models. The study demonstrates the application of the method for identifying airborne pollutant source locations in two realistic indoor environments with few sensor measurement outputs. The numerical simulations verify the feasibility and accuracy of the method for indoor pollutant tracking applications, which forms a good foundation for developing an intelligent and integrated indoor environment management system that can promptly respond to indoor pollution episodes with effective detection, analysis, and control.     

地下工程施工模型数字与数值一体化自动建模方法

借助数字模型能最大程度地表达实际物体,考虑地下工程施工过程的特点,将地质模型与构筑物模型和数值模型相结合,提出一种新的地下工程施工过程有限元建模方法--CDIM模型转化法.其核心思想是将三维数字模型经过特定方式转化为符合有限元网格要求的数值计算模型.具体转化过程:①根据计算范围对数字模型进行区域切割;②从切割模型提取控...     

A geometrically and locally adaptive remeshing method for finite difference modeling of mining-induced surface subsidence

Surface subsidence induced by underground mining is a typical serious geohazard.Numerical approaches such as the discrete element method(DEM)and finite difference method(FDM)have been widely used to model and analyze mining-induced surface subsidence.However,the DEM is typically computationally expensive,and is not capable of analyzing large-scale problems,while the mesh distortion may occur in the FDM modeling of largely deformed surface subsidence.To address the above problems,this paper presents a geometrically and locally adaptive remeshing method for the FDM modeling of largely deformed surface subsidence induced by underground mining.The essential ideas behind the proposed method are as follows:(i)Geometrical features of elements(i.e.the mesh quality),rather than the calculation errors,are employed as the indicator for determining whether to conduct the remeshing;and(ii)Distorted meshes with multiple attributes,rather than those with only a single attribute,are locally regenerated.In the proposed method,the distorted meshes are first adaptively determined based on the mesh quality,and then removed from the original mesh model.The tetrahedral mesh in the distorted area is first regenerated,and then the physical field variables of old mesh are transferred to the new mesh.The numerical calculation process recovers when finishing the regeneration and transformation.To verify the effectiveness of the proposed method,the surface deformation of the Yanqianshan iron mine,Liaoning Province,China,is numerically investigated by utilizing the proposed method,and compared with the numerical results of the DEM modeling.Moreover,the proposed method is applied to predicting the surface subsidence in Anjialing No.1 Underground Mine,Shanxi Province,China.     

Hierarchical modeling method and dynamic characteristics of cutter head driving system in tunneling boring machine

Traditional modeling method is difficult to establish the fully coupled model of the cutter head driving system in tunneling boring machine (TBM) owing to the structural complexity. In this paper, a generalized hierarchical modeling method is proposed to establish the entirely dynamic model of the TBM cutter head driving system. The components are equivalent to beam element with the same mass and stiffness characteristics, and the nonlinear coupling factors such as time-varying mesh stiffness, transmission error and gear backlash of both the multiple pinions driving and planetary gearbox are considered. The overall dynamic equation is formed by assembling the unit matrixes of basic finite elements according to the coupling relationships. Based on the proposed model, the vibration modes of driving system are classified into axial modes, rotational modes and lateral modes with distinct characteristics. The effects of coupling parameters on the natural frequency of driving system are investigated as well. The dynamic model is also simulated to analyze the dynamic response of driving system under two load conditions, cyclic external loads and simulated external loads. The main response frequency components and the effect of damping coefficients on vibration amplitudes are investigated. The proposed modeling method can be generalized to other complex driving system, and the obtained results provide data support for the dynamic design of driving system in TBM.     

Comparison of shallow tunneling method with pile and rib method for construction of subway station in soft ground

In the present study, a comparison between the new shallow tunneling method (STM) and the traditional pile and rib method (PRM) was conducted to excavate and construct subway stations in the geological conditions of Tehran. First, by selecting Station Z6 located in the Tehran Subway Line 6 as a case study, the construction process was analyzed by PRM. The maximum ground settlement of 29.84 mm obtained from this method was related to the station axis, and it was within the allowable settlement limit of 30 mm. The acceptable agreement between the results of numerical modeling and instrumentation data indicated the confirmation and accuracy of the excavation and construction process of Station Z6 by PRM. In the next stage, based on the numerical model validated by instrumentation data, the value of the ground surface settlement was investigated during the station excavation and construction by STM. The results obtained from STM showed a significant reduction in the ground surface settlement compared to PRM. The maximum settlement obtained from STM was 6.09 mm as related to the front of the excavation face. Also, the sensitivity analysis results denoted that in addition to controlling the surface settlement by STM, it is possible to optimize some critical geometric parameters of the support system during the station excavation and construction.     

Three‐dimensional computer‐aided finite element method retrofitting modeling and non‐destructive testing techniques for the assessment of actual existing high‐rise fire‐damaged reinforced concrete building

Concrete is generally fire resistant. A fire in a concrete structure rarely results in a serious damage as to require substantial demolition. But, loss of the utility of a building could result in serious financial consequences for the owner, which calls for immediate reinstatement. To work out proper and efficient repair strategy, however, would require a thorough investigation of the effect of fire on the structural properties of the concrete and steel; the significance which any permanent change in material characteristics may have on the future structural performance of the member; the feasibility of repairs to compensate of any unacceptable reduction in structural performance, durability, and so on; and the influence which fire exposure of individual member may have on the performance of the entire structure. These all said tasks are dependent on the complete analysis of the fire‐damaged building. Without it, no repair works estimation, extent of repair and kind of repair can be carried out for the fire‐damaged buildings. Therefore, the impeccable analysis and design is of utmost importance for repair of such buildings after preliminary investigation of the extent of fire damages to the concrete structural members. This forms the basis of this research study, which aims at detailed analysis and design of the actual existing high‐rise fire‐damaged buildings for fire retrofitting and assessment of fire damages by non‐destructive techniques. Fire damages in buildings due to explosion, accidents or by some other reasons cause severe structural damages. The structural integrity of existing buildings is now a burning issue. Analytical, theoretical and design‐cum‐construction techniques are constantly being reviewed by government agencies and engineering consultants. Therefore, researchers are delving into this matter to find the best retrofitting techniques for fire‐damaged buildings. This paper is an outcome of such detailed research studies. It covers the actual case study of existing buildings, review of existing knowledge for fire damages and their mitigation and protective design technologies, and analytical and computational techniques, which have limited research data. In this study, Extended 3D Analysis of Building Systems (ETABS) is used as software for fire retrofitting analysis, and UBC‐97 is used as a code for the fire analysis and design. The ETABS building model is verified by manual calculations as well. Copyright © 2011 John Wiley & Sons, Ltd.     

Stability analysis and optimization of excavation method of double-arch tunnel with an extra-large span based on numerical investigation

The Xiamen Haicang double-arch tunnel has a maximum span of 45.73 m and a minimum burial depth of 5.8 m. A larger deformation or collapse of the tunnel is readily encountered during tunnel excavation. It is therefore necessary to select a construction approach that is suitable for double-arch tunnel projects with an extra-large span. In this study, three construction methods for double-arch tunnels with extra-large spans were numerically simulated. Subsequently, the deformation behavior and stress characteristics of the surrounding rock were obtained and compared. The results showed that the double-side-drift method with temporary vertical support achieves better adaptability in the construction of such tunnels, which can be observed from both the numerical results and in situ monitoring data. In addition, the improved temporary support plays a critical role in controlling the surrounding rock deformation. In addition, the disturbance resulting from the excavation of adjacent drifts was obvious, particularly the disturbance of the surrounding rock caused by the excavation of the middle drift. The present findings can serve as the initial guidelines for the construction of ultra-shallowly buried double-arch tunnels with extra-large spans.