Examination of electrical conductors following a fire

Electrical arcing under fire conditions is examined in this paper. It explains why arcs are started under fire conditions, while they are difficult to start under normal conditions.     

Are the energy efficient rates (RVRs) approximate in different climatic locations for the same building with the same reform?

This paper studies the annual heating and cooling energy consumption and the variation law with the tools of characteristic temperature method (CTM) when making the same energy-saving measures on the same building under 43 different climate conditions. It can be found that for the same building, under different climate conditions, the maximal difference in annual energy consumption is up to more than 70 times and after improving building envelope, annual heating and cooling energy reductions are greatly different under various weather conditions, which illustrates that building energy consumption and its reduction is completely dependent on climate conditions; and the energy-saving potentiality and economic value with the same measures are quite different under various climatic conditions. Nevertheless, annual energy efficient rates of cooling are approximate (33.9–39.8%) for the same building with the same energy efficient measures in 43 climate conditions with quite different climatic conditions, and those of heating are also approximate (between 16.2% and 19.5%). This paper proves again the common rule that climate conditions determine energy consumption while energy efficient rates depend on the energy efficient measures.     

Effect of pH on the physico-mechanical properties of marble

The physico-mechanical properties of rocks are important parameters in the planning and design of mining and civil constructional works. These properties are adversely affected by acidic and alkaline environments. In the present study, marble rock specimens were tested in the laboratory after treatment with different pH solutions for 15 h. The physico-mechanical properties of the marble were determined in both acidic and alkaline conditions. The study revealed that the strength properties are higher at pH 7 and lower in acidic and alkaline conditions. The strength reduction in acidic conditions is greater than that in the alkaline conditions.      

Normalized Relationships for Depth of Embedment of Sheet Pile Walls and Soldier Pile Walls in Cohesionless Soils

Normalized, non-dimensional relationships for calculating the depths of embedment of sheet pile walls and soldier pile walls embedded in cohesionless soils are presented. Rankine theory for lateral earth pressures in active and passive conditions are used in the analyses. Relationships are presented for cantilever walls and walls propped at crest. The proposed relationships can be used in dry soil conditions and as well as in saturated soil conditions with steady state seepage. The embedment depth relationships are presented in terms of non-dimensional parameters and can be used for a variety of soil conditions, dimensions and spacing of the walls, and depths of excavation. The presented relationships are simple, easy to use, and do not require tedious calculations.     

TBM tunnelling under adverse geological conditions: An overview

The adverse geological conditions frequently encountered during TBM tunnelling present great challenges, and may trigger potential hazards if no precaution and treatment measures are taken. Comprehensive studies on adverse conditions are essential and critical to successful TBM tunnelling. In this overview paper, attempts are made to define the adverse geological conditions for TBM tunnelling. A simple classification and the influencing factors related to the adverse geological conditions are presented for better understanding of the topic. The main problems involved and the corresponding mitigation measures for TBM tunnelling under adverse geological conditions are discussed. Finally, further research needs for better coping with these problems are emphasized.     

Getting it done: Critical success factors for project managers in virtual work settings

What conditions do project managers perceive as the most important to get the work done when working in fully dispersed settings? Rather than focusing on problems that managers experience when working in dispersed settings, our study highlights the conditions that are important for successful task accomplishment. We applied a Means-End-Chain (MEC) method to investigate the links between task accomplishment and relevant conditions that are attributes, benefits and values among a sample of experienced project managers (N = 30). Our results show that important conditions for successful project execution in a dispersed setting include rules of communication and its clarity; project management style and goal-setting; and managers' competences and trust in a team. In addition to these internal conditions, project managers also stress the importance of both corporate and technology support. These four conditions are all perceived as vital for task accomplishment in global dispersed projects.     

微生物絮凝剂

综述了微生物絮凝剂的产生和培养条件,同时讨论了微生物絮凝剂的絮凝反应条件,反应机理和在废水处理中的应用,提供了今后的研究方向。     

Effect of pore water pressure on tunnel support during static and seismic loading

The support of underground structures must be designed to withstand static overburden loads as well as seismic loads. New analytical solutions for a deep tunnel in a saturated poroelastic ground have been obtained for static and seismic loading. The static solution accounts for drainage and no-drainage conditions at the ground–liner interface. Linear elasticity of the liner and ground, and plane strain conditions at any cross-section of the tunnel are assumed. For tunnels in which ground stresses and pore pressures are applied far from the tunnel center, the drainage conditions at the ground–liner interface do not affect the stresses in the liner. The analytical solution shows that the stresses in the liner are exactly the same whether there is drainage or not at the ground–liner interface. Hence, if the drainage conditions in the tunnel are changed from full drainage to no-drainage or vice versa the stresses in the liner are not affected. However, the stresses and displacements in the ground change significantly from drainage to no-drainage conditions. For seismic loading a new analytical formulation is presented which provides the complete solution for the ground and the liner system for both dry and saturated ground conditions. The formulation is based on quasi-static seismic loading and elastic ground response; for a saturated ground, undrained conditions are assumed which indicate that the excess pore pressures generated during the seismic event do not dissipate. The results show that the racking deformations of a liner in dry or saturated ground are highly dependent on the flexibility of the liner.     

系杆拱桥吊杆索力测试研究

系杆拱桥的吊杆比较短,吊杆索力受两端约束条件影响比较大,采用振动频率法分析了吊杆在两端铰接、两端固结和等效铰接等3种约束条件下,其实测索力与设计值之间的差异.测试结果表明,将吊杆两端简化为等效铰接,综合考虑了吊杆抗弯刚度和两端约束条件的影响,根据吊杆振动频率与索力之间的关系,计算吊杆索力精度比较高,满足工程要求.     

A new test apparatus for the study of geotextiles behaviour as filters in unsteady flow conditions: relevance and use

In many applications, geotextiles are subjected to cyclic hydraulic loads, for example, when used as revetment filters. A new test apparatus has been developed to investigate the influence of a cyclic component in the hydraulic gradient and the effect of boundary conditions. The boundary conditions to be considered in such applications of geotextiles are mainly the normal effective stress and the type of contact, which can be more or less continuous. The test apparatus presented in the paper is capable of reproducing these conditions while imposing a cyclic gradient. A set of tests have been performed using the apparatus in cyclic flow conditions perpendicular to the filtering interface: typical test results are also presented in the paper.     

横观各向同性层状场地的动力边界条件

 采用横观各向同性层状弹性体模拟场地土, 对该场地底部采用了三种不同的边界: 固定边界、阻尼边界及半空边界。推导了这三种边界条件的公式, 并且给出了它们进入离散化后的Rayleigh 波与Love 波的代数特征方程方法。然后, 计算了场地在三种边界条件下对垂直及水平简谐集中荷载的位移响应, 并与理论解进行了比较, 指出了它们的适用范围。     

Temperature prediction for contour-insulated concrete-filled CHS subjected to fire using large time Green’s function solutions

An accurate numerical approach is developed in this paper for thermal analysis of contour-insulated concrete-filled circular hollow sections subjected to fire, based on analytical solutions of transient diffusion equations in radial coordinate system obtained using the Green’s function approach. The steel layer is conveniently treated as a thin film with lumped heat capacitance, i.e. the temperature distribution inside the steel section is assumed to be uniform. Perfect contact conditions are assumed at both of the insulation-steel and the steel-concrete interfaces. Solutions of the heat equations are represented by large time series expansions obtained from homogeneous boundary conditions using the eigenfunction approach. The time-varying boundary conditions, i.e. the fire conditions are incorporated in terms of Stieltjes integral by means of Duhamel’s theorem. Numerical models are developed using temporal discretization, while no spatial discretization is required since spatial variables are analytically tractable. The proposed numerical scheme is not restricted to any specific fire conditions, and can be used in conjunction with parametric fire as proposed in the Eurocode.     

Market strategies and core capabilities in the building industry

The objective of this study is to show that the core competence approach has validity when applied to construction. The focus is on the analysis of the fit between market strategies of firms in the building industry and their core capabilities. Certain strategies require specific core capabilities and key external and internal conditions supporting these capabilities. The resource-based approach focuses on the conditions in a firm, the internal capabilities, and supports a core capability that is demanded. The network literature will be related to external conditions that support a core capability of a firm active in a certain market. In a multiple case study, firms are analysed that are involved in different stages of the building process. The case studies demonstrate firms with consistent patterns of market strategies, core capabilities, and supporting internal and external conditions. The specific core capability of the firm under investigation determines the types of external and internal conditions that are critical.     

Risks in subcontracting: Subcontract conditions

The use of non-standard, contractor-prepared subcontract conditions is widespread in the Australian construction industry. Many conditions in such subcontracts are harsh and are viewed by Australian subcontractors as the most critical risk for which they make risk allowances in the bid price.     

甘肃临泽县地质灾害类型及特征

甘肃省张掖市临泽县是河西走廊地质灾害最为发育的县区之一。通过实地测量、调查评价和综合研究等手段,在概述县域自然地理条件及地质背景的基础上,县域内已有的地质灾害共30处,其中泥石流沟29条主要集中分布于祁连山和合黎山山前与走廊平原的过渡带,尤其是北部合黎山山前连片分布;崩塌1处为斜坡坡度65°的独山子崩塌。从地形条件、物质条件、降雨条件以及人类日益工程建设活动等方面研究表明,较大的沟床纵坡降比和流域面积、丰富的松散固体物质和短时间聚集的充足水源(多是有暴雨形成)是形成区内泥石流的基本条件。崩塌(不稳定斜坡)于公路沿线的人工开挖坡度大于60°的边坡地带。临泽县地质灾害具有不均匀性、突发性、周期性。该研究为县域地质灾害防灾减灾提供科学依据。     

成层地基非线性波动问题人工边界与波动输入研究

建立了考虑非线性效应的无限成层地基波动模拟的时域人工边界条件及相应的波动输入方法。首先，推导了线性阻尼介质中的一维人工边界公式，进而推广得到近似的二维人工边界方程：然后，通过等效线性化处理，获得了近似考虑远场成层地基非线性效应的人工边界：最后，建立了相应的波动输入方法。数值算例表明，所给出的人工边界与波动输入方法具有良好的精度，可以方便地应用于成层地基非线性波动问题的研究。     

A model to study the effects of different control strategies on space humidity during part-load conditions

Many air conditioning systems have small moisture removal capacities and are not equipped to maintain space humidity under part-load conditions particularly during hot and humid periods. They are able to provide desired temperature control but humidity. The primary objective of this work is to identify control strategies that can be used to prevent significant indoor humidity degradation during part-load conditions. These control strategies are chilled water flow control, bypass air control, variable air volume control, run-around coil control and low face velocity/high coolant velocity control. Coil simulations have been employed to study the part-load performance of these control strategies. The coil model compares favourably with experimental data to within ±6.5%. Simulation examples are conducted for each control strategy under varying part-load conditions. Results from the coil model have indicated that some strategies are more effective than others in sustaining acceptable indoor humidity under part-load conditions. For instance, chilled water control strategy has been observed to produce highest indoor humidity throughout the range of conditions studied while variable air volume system provides highly effective dehumidification performance of the cooling coil. In addition, higher ventilation rates have been observed to increase the space humidity during part-load conditions.     

A Computing Approach Using Probabilistic Neural Networks for Instantaneous Appraisal of Rear-End Crash Risk

Abstract:   Computing and information technology has significantly increased the capabilities to collect, store, and analyze freeway traffic surveillance data. The most common forms of such data are collected using the underground loop detectors. In the recent past the potential of using these data for identification of crash-prone conditions has been explored. In the present work, application of probabilistic neural networks (PNN) is explored to identify conditions prone to rear-end crashes on the freeway. PNN is a neural network implementation of the well-documented Bayesian classifier. In this research the rear-end crashes observed on the Interstate-4 corridor in Orlando FL are divided into two groups based on the average traffic speeds observed around the crash location prior to the crash occurrence. Using decision tree-based classification it was observed that although these two groups of crashes have comparable frequencies, traffic conditions belonging to one of the groups (characterized by a low-speed traffic regime) are comparatively rare on the freeways. Hence, if those conditions are encountered on the freeway in real time, then conditions may be considered prone to rear-end crashes. As conditions belonging to the other group of rear-end crashes (characterized by a medium-to-high speed regime) are more commonly observed on the freeway, PNN-based classification models are developed for this group. The rear-end crashes along with a sample of randomly selected noncrash cases were used to calibrate the classifiers. The output layer of the PNN models was modified to provide a measure of crash risk, instead of the binary classification based on an arbitrary threshold. A desirable threshold on this output may be established to separate crash-prone conditions from "normal" freeway traffic.     

Application of modified complementary reservoir approach in analysis of water distribution networks under pressure-deficient conditions

Hydraulic simulation models which simulate water distribution systems in different operating conditions are essential tools to evaluate network reliability. Simulation models found in most commercial software are not effectively capable of analyzing demand nodes under critical conditions such as fire-fighting demand or network pipe breakage. In the current study, a combination of hydraulic model and complementary reservoir solution (CRS) method is used for solving network's problems in critical conditions for both series-looped networks and a part of water network in Ilam city (Iran). Obtained results show that CRS provide more than actual need on the demand node for some reservoir total pressure heads. Thus, two modified versions of CRS method are proposed to deal with failures of CRS in such cases. Obtained results demonstrate improved efficiency in the combined model for analyzing networks in abnormal conditions.