Experimental study of the thermal behaviour of radiant floors

This study focuses on the experimental analysis of the thermal behaviour of radiant floor heating in an industrial building and the authors conclude that in order to reduce costs and increase user comfort, optimum values of concrete conductivity and embedded depth of the heating element need to be selected.     

相变材料固-液相变点热导率的测试研究

基于移动的相界面曲线与两相热物理性质的关系,提出了通过测定相界面的移动速率来确定相变材料固—液相变温度点热导率等多个热物性参数的方法。对于熔点较低的物质的热导率可用相变导热反问题的近似分析解求得,对于熔点较高的物质可用数值计算与实验相结合的方法测定,并设计了相应的测试装置。用金属材料对此方法进行了检定,测试所得的结果与文献数据较吻合,表明该方法可用于金属及合金相变条件下热传导的研究以及相变温度附近固、液相热导率的测试。     

On the hydraulic behavior of unsaturated nonwoven geotextiles

Geotextiles have been widely used in soil structures for separation, filtration, reinforcing, and drainage. They are often used to provide reinforcement and drainage for retaining walls and embankments. It has been reported, however, that geotextiles may not drain water as effectively as was initially expected. In this study, published data on the hydraulic properties of unsaturated geotextiles are compiled and analyzed in order to highlight the hydraulic characteristics of unsaturated geotextiles.

The application of the van Genuchten equations originally developed for the water characteristic curve and the hydraulic conductivity curve of unsaturated soil to unsaturated geotextiles is then examined and discussed. Finally, the drainage from a one-dimensional sand column having a horizontal geotextile layer was analyzed using the finite element method and the van Genuchten equations to assess the utility of this procedure for further study of unsaturated/saturated water flow within the soil–geotextile system.     

On the thermo-mechanical properties of unsaturated soils

The establishment of energy balance equation is necessary to study the thermo-mechanical properties of unsaturated soils.To solve this equation,the determination of two fundamental parameters as volumetric specific parameter and thermal conductivity coefficient is essential.In this paper,the effective thermal conductivity coefficient of dry soil grain is analyzed for soils with different compositions,and the thermo-mechanical properties of porous media with water and gas are studied by considering the soil water retention curve（SWRC）.Different methods,i.e.volumetric average method,self-consistent method,Hashin-Strikman method,are employed to calculate thermal conductivity coefficients,and a new method is proposed to determine the thermo-mechanical parameters.Comparison of the results obtained by different methods shows that the proposed method is in a good agreement with the experimental results and is suitable for describing the main properties of the thermo-mechanical behaviors of soils.The relationship between the SWRC and the seepage curve is further studied by the natural proportional rule.The characteristics of the SWRC,its differential coefficient and the seepage curve,are investigated by considering the physico-mechanical mechanism;the limit scopes of the indices of the SWRC and the seepage curve are also given.     

Seismic behaviour of concrete-filled steel tubular frame to RC shear wall high-rise mixed structures

Composite frames consisting of concrete-filled steel tubular (CFST) columns and steel beam are being used more and more popularly in building structures. In China, the composite frame structures are often mixed with reinforced concrete shear walls to form a high-rise building system. However, there was seldom information on the seismic performance of this kind of mixed construction. Shaking table tests on two building models with 30 storeys consisting of composite frames and RC shear walls were thus presented in this paper. CFST columns with circular and square sections were used in the composite frames respectively. Three kinds of real earthquake records, including Taft (EW), El Centro (NS) and Tianjin waves with peak accelerations of 0.2g, 0.4g, 0.6g, and 0.8g, were applied respectively to simulate different levels of earthquakes in the tests. It was found that the composite frames cooperated well with the core RC shear wall structure under earthquakes, and the two building models exhibited excellent seismic performance.     

The behaviour of masonry walls subjected to fire: Modelling and parametrical studies in the case of hollow burnt-clay bricks

A thermo-mechanical model is adopted in order to investigate the fire behaviour of clay masonry walls. In this analysis, conductive, convective and radiative thermal transfers are considered together with local energy consumption due to phase changes. These latter are essentially initiated by both the vaporisation of adsorbed water and the chemical transformation of clay under rising temperatures. Therefore, experimental tests at both the material scale and the brick scale are performed in order to identify the parameters that characterise the thermo-hygral behaviour of clay. For this purpose, numerical simulations are carried out on the experimentally tested hollow bricks in order to determine by back analysis these material parameters. The thermal model being validated, the thermo-mechanical behaviour of a masonry wall subjected to fire, is thereafter investigated by adopting a full three-dimensional finite-element analysis. Numerical simulations results are compared to the experimentally measured ones in terms of both temperature and out-of plane displacement fields. In this analysis, it is shown that a non-linear elastic behaviour for bricks and mortar with temperature-dependent mechanical parameters is sufficient to retrieve the overall behaviour of thin masonry walls. Finally, a parametric study provides the influence of each material parameter on the fire behaviour of the partition walls.     

Measured and predicted performance of prefabricated vertical drains (PVDs) with and without vacuum preloading

This paper presents the effectiveness of vacuum preloading in accelerating the consolidation of PVD improved soft Bangkok clay by comparing with the corresponding results without vacuum preloading. Laboratory tests were conducted using a large scale consolidometer having diameter of 300 mm and height of 500 mm with reconstituted specimens installed with prefabricated vertical drains (PVD) with and without vacuum preloading. In addition, field data were collected from Second Bangkok International Airport (SBIA) site improved by PVD with and without vacuum pressures. Analyses were carried out to compare the compressibility parameters (C_h and k_h/k_s) by back-calculation of laboratory and field settlements using Hansbo (1979) method. From the laboratory tests, the horizontal coefficient of consolidation (C_h) values from reconstituted specimens were 1.08 and 1.87 m²/yr for PVD without and with vacuum pressure, respectively and the k_h/k_s values were 2.7 for PVD only and 2.5 for vacuum-PVD. After the improvement, the water contents of the soft clay were reduced, thereby, increasing its undrained shear strengths. Similarly, the field data analysis based on the back-calculated results showed that the k_h/k_s were 7.2 and 6.6 for PVD without and with vacuum, respectively. The C_h values increased slightly from 2.17 m²/yr for PVD only to 3.51 m²/yr for vacuum-PVD. The time to reach 90% degree of consolidation for soils with vacuum-PVD was one-third shorter than that for soils with PVD only because of higher C_h values. Thus, the addition of vacuum pressure leads to increase horizontal coefficient of consolidation which shortened the time of preloading. The PVDCON software was found to be useful to predict the settlements of the PVD improved ground with and without vacuum preloading.     

Effect of vertical stress rest period on deformation behaviour of unbound granular materials: Experimental and numerical investigations

Repeated load triaxial test is used to assess the deformation behaviour of unbound granular materials (UGMs) in flexible road pavements. Repeated load pulse characteristics (i.e. shape, loading period and rest period) are the stress configurations used in the experimental set-up to simulate the passing axle loads. Some researchers and standard testing protocols suggest a rest period of varying durations after a loading phase. A thorough review of existing literature and practises has revealed that there is no agreement about the effect of the rest period of vertical stress pulse on the deformation behaviour of the UGMs. Therefore, the main objective of this study is to investigate the effect of repeated stress rest period on the deformation behaviour of UGMs experimentally. Experiments are conducted, both with and without rest period, using basalt and granite crushed rocks from Victoria, Australia. Furthermore, in order to gain insight into the effect of the rest period, finite element modelling is also developed. Both the experimental and modelling results show that the rest period has a noticeable effect on both resilient and permanent deformation behaviours of UGMs. It is, therefore, recommended to take extra precautions while adopting a particular standard testing protocol and to supplement the results by additional tests with different loading configurations.     

Experimental investigation of the effect of carbon nanotubes and carbon fibres on the behaviour of plain cement composite beams

In this article, the behaviour of reinforced cement composite beams with multi-walled carbon nanotubes (MWCNTs) and carbon fibres (CFs) is investigated. The percentage of CFs was fixed at 0.25 wt% of cement, while the percentage of MWCNTs was varied from 0.25, 0.5, 0.75, 1 wt% of cement. Dispersion of both MWCNTs and CFs was carried out using ultrasonic energy. Composite beams were tested under flexure in order to evaluate their mechanical properties such as flexural strength, toughness and ductility. These results were then compared with the results of plain cement control beams. The present work also investigates the optimum percentage of fibres that gives the best results both in terms of enhanced properties and economy.     

Generalised beam theory to analyse the buckling behaviour of circular cylindrical shells and tubes

A formulation of generalised beam theory (GBT) developed to analyse the elastic buckling behaviour of circular hollow section (CHS) members (cylinders and tubes) is presented in this paper. The main concepts involved in the available GBT are adapted to account for the specific aspects related to cross-section geometry. Taking into consideration the kinematic relations used in the theory of thin shells, the variation of the strain energy is evaluated and the terms are physically interpreted, i.e., they are associated with the geometric properties of the CHS. Besides the set of shell-type deformation modes, the formulation also includes axisymmetric and torsion deformation modes. In order to illustrate the application and capabilities of the formulated GBT, the local and global buckling behaviour of CHS members subjected to (i) compression (columns), (ii) bending (beams), (iii) compression and bending (beam-columns) and (iv) torsion (shafts), is analysed. Moreover, the GBT results are compared with estimates obtained by means of shell finite element analyses and are thoroughly discussed.     

超浅埋和不良地质隧道进洞方案

以金鸡岭隧道工程为例,结合工程地质情况,具体阐述了超浅埋、不良地质隧道进洞方案,详细介绍了施工时的前期准备工作,洞口段的处理及开挖施工,并提出了施工组织管理方法,最后进行了经验总结,以期指导实践。     

盐度对浒苔渗沥液和城市污水联合处理效果影响

盐度是浒苔渗沥液和生活污水联合处理的主要限制因素.试验中采用SBR生物处理工艺对浒苔渗沥液和生活污水进行联合处理,并考察了浒苔渗沥液与生活污水混合比例对处理效果的影响.随着浒苔渗沥液投加比例的增加,盐度含量递增,结果表明：①当盐度低于3.2 g/L时,COD处理效果未受显著影响,当盐度高于3.2 g/L时,COD处理效...     

Numerical analysis of thermal process in the near field around vertical disposal of high-level radioactive waste简

For deep geological disposal of high-level radioactive waste (HLW) in granite, the temperature on the HLW canisters is commonly designed to be lower than 100 °C. This criterion dictates the dimension of the repository. Based on the concept of HLW disposal in vertical boreholes, thermal process in the near field (host rock and buffer) surrounding HLW canisters has been simulated by using different methods. The results are drawn as follows: (a) the initial heat power of HLW canisters is the most important and sensitive parameter for evolution of temperature field; (b) the thermal properties and variations of the host rock, the engineered buffer, and possible gaps between canister and buffer and host rock are the additional key factors governing the heat transformation; (c) the gaps width and the filling by water or air determine the temperature offsets between them.     

On the behaviour and adaptation of office occupants

During the warm summer of 2006 a comprehensive longitudinal field survey of the adaptive actions of occupants, their thermal satisfaction and the coincident environmental conditions was conducted in eight Swiss office buildings. We have applied logistic regression techniques to these results to predict the probability of occupants’ actions to adapt both personal (clothing, activity and drinking) and environmental (windows, doors, fans and blinds) characteristics. We have also identified, for each type of control action exercised, the increases in temperature at which thermal sensation votes are reported. These “empirical adaptive increments” have also been defined for combinations of control action. In this paper we present the field survey methodology as well as the results relating to the above, which we discuss along with scope for further related work.     

Enablers and barriers of the multi-user virtual environment for exploratory creativity in architectural design collaboration

Pioneering psychology and co-design research has highlighted the potential that multi-user virtual environment (MUVE) may help architects’ exploratory creativity that is a recursive search to discover an optimal match of novel and appropriate solutions. However, it has been not reported hitherto in what ways MUVE helps or obstructs architects’ exploratory creativity in individual and collaborative modes of collaboration. To investigate this issue, we compared MUVE and sketching media in face-to-face and remote collaboration modes, involving 22 pairs of architecture major students. Based on interview and video-observation, we discovered that (1) in MUVE, anthropomorphic avatars, which other media do not have, enabled individual and collaborative explorations to discover unexpected affordances of new solutions, with evaluation on physical properties and layouts of solutions. In addition, (2) co-presence with collaborator’s avatars enabled inspiration on new ways of problem-solving and puzzle-making through shared design processes and events, with co-evaluation on social aspects of design solutions. (3) Co-presence in a shared environment also allowed mutual co-exploration that promotes emerging creative solutions, with co-modification on design errors. As barriers of MUVE, (4) avatar’s immersion caused inconvenient perception to explore large-scaled environments and track collaborators’ different experiences, but the barriers were not reported in remote collaboration.     

张弦拱结构的结构分析与其静力性能研究

对张弦拱结构的受力件能与分析方法进行了系统的研究.根据张弦拱结构的自平衡特点,建它索与拱的变形协调方程,给出了张弦拱结构的平衡微分方程,并设定位移甬数,用伽辽金法进行求解,以求得张弦拱结构的内力与位移.这一连续化理论计算方法与非线性有限元分析方法、模型试验结果都进行了分析比较,证明本理论方法计算方便、直观精确,可用于张弦拱结构的分析与计算.根据理论公式,对张弦拱结构的静力性能进行了讨论,包括结构的线性性能、拱的弯曲刚度贡献、结构挠度与支座的水平位移、预应力过程等方面,对张弦拱结构的研究与设计有较好的指导意义.     

超前地质预报在长大隧道中的应用

结合南疆吐库二线铁路喀拉塔格隧道的施工实际,介绍了超前地质预报在长大隧道中的应用,实践表明,超前地质预报对保证施工进度以及最大限度节省投资都起到重要的作用,通过超前地质预报杜绝了不安全事故的发生,实现了社会效益和经济效益的最大化。     

玄武岩纤维增强混凝土静、动力性能试验研究

对纤维体积含量分别为0、0．1％、0．2％、0．3％的幺武岩纤维增强混凝上进行试验,研究了玄武岩纤维体积掺量对混凝土抗压强度、劈裂抗拉强度的影响,并利用φ100mm的SHPB装置进行了冲击压缩试验,得到了不同应变率下的全过程应力-应变曲线。试验结果表明：混凝土材料具有应变速率敏感性,随着应变率的增加,混凝土的峰值应力增加,发现玄武岩纤维的体积掺量为0．1％时,具有最好的力学性能。     

Strength and compressibility behaviors of expansive soil treated with coffee husk ash

Various factors can affect the durability of roads, such as the strength of sub-grade, the quality of the sub-base and base course, the environments and properties of the soil used. Particularly, roads built on expansive soil are susceptible to early damage due to the swelling and shrinkage characteristics of this kind of soil under changing moisture conditions. The most common technique used to improve the properties of problematic soil is stabilization with additives. Using waste materials to improve the properties of expansive soil is a recent trend in soil stabilization. This study deals with the treatment of expansive soil with coffee husk ash (CHA). Coffee husk is a by-product of coffee production, and CHA is the resulting ash after burning it. In this study, the bearing capacity and compressibility characteristics of expansive soil (specifically black cotton (BC) soil) stabilized with varying percentages of CHA (5%, 10%, 15%, and 20%) are investigated. Then, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) were used to analyze the influence of CHA on surface morphology and chemical composition of the studied soil. The results showed that the soil treated with CHA is generally improved in terms of strength. Addition of 20% CHA increases the bearing capacity of the soil by three-fold. In addition, the morphological studies of the soil samples treated with 10% and 15% CHA indicated the formation of hydrated particles and cementitious compounds as a result of the reaction between the soil and CHA. This indicates the potential usage of CHA as a stabilization agent and subsequently, it can address the disposal and environmental concerns related to coffee husk.     

关于沥青混合料配合比设计与压实度标准的探讨

文章就沥青混凝土路面施工中混合料配合比设计与优化提出注意事项．同时对沥青混凝土路面压实度标准进行了探讨。