《Cement and Concrete Composites》2003,25(1):153-157

An experimental method based on laser triangulation was used to measure the 3-D profile of fracture surface of concrete. The projective-covering method was established to determine the fractal characteristics of fracture surface. Based on the experiment, the influence of composition of concrete on the fractal dimension, including water–binder ratio, maximum aggregate size and aggregate type, was investigated. The variation of fractal dimension with the material composition was also analysed to make further understanding of fracture mechanism of concrete.  相似文献   

    

《Cement and Concrete Composites》2001,23(4-5):381-387

The weak transition zone between new and old concrete controls many properties of repaired concrete. The transition zone between aggregates and cement pastes of normal concrete has been studied by a number of researchers. But to date, there is little information available about the interfacial zone between new and old concrete. In this paper, major properties of the transition zone between new and old concrete with different binders were studied by using both scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The bond strength was also investigated. The test results show that the binder is a vital factor, which affects the morphology (size and shape), mineralogy and the microstructure of the transition zone in repaired concrete.  相似文献   

    

《Cement and Concrete Composites》2001,23(2-3):299-311

When plaster is put in water, a network of needles is spontaneously formed. The morphology of the plaster microstructure have been studied in order to understand precisely its role with respect to its physical properties. Three microstructures of plaster were prepared from different hydration conditions, to obtain three crystal sizes at a given level of porosity. We propose a morphological characterization and modeling of the plaster microstructure by means of simple tools of mathematical morphology. From the use of a two parameters random model of microstructure, the Boolean model, contact properties between the microstructural units made of gypsum needles are estimated, and bounds of the elastic behavior of the plaster are compared to measurements.  相似文献   

    

《Engineering Fracture Mechanics》1986,24(1):103-110

The thick-shell line spring method combined with the complentary energy method has been applied to the analysis of load-displacement curves and crack opening angle (COA) for work-hardening plates with a surface crack. The growth of the surface crack has been simulated based upon the COA-criterion, and the condition of the leak before break (LBB) has been discussed for a surface-cracked plate subjected to tension. It has been found that the LBB condition highly depends on the original shape of the surface crack. Short and deep surface cracks satisfy the LBB condition, while flat and shallow cracks do not. Further, the results have been compared with the net section stress criterion.  相似文献   

    

《Automation in Construction》1999,8(4):503-510

The initiation of a renovation project usually involves a long process of contemplation under conditions of high uncertainty. Large organizations, that own many buildings and other facilities, can greatly benefit from a decision-support model, which can be transformed to a computerized semi-automatic tool. It will aid them develop and execute a reasonable and economical policy of rehabilitating, renovating, remodeling, or rebuilding their facilities. This paper presents a systematic four-module decision support model: (a) Preliminary survey of background conditions; (b) Evaluation and ranking of the facility's physical condition; (c) Generation of viable alternatives for rehabilitation, renovation, or reconstruction; and (d) Quantitative techno-economic comparison among the alternatives, and systematic presentation of recommendations. The paper concludes with a demonstrative example, concerning the renovation of a 25-year-old dining facility, that highlights both the practicality of the model and the benefits from utilizing it.  相似文献   

    

《International Journal of Project Management》1988,6(1):5-10

Project management is considered from the broader perspective of general management fundamentals. These act as the necessary foundation stones on which more specialized project management techniques can be based. Fundamentals such as proper accounting, budgeting, administration and quality assurance are described briefly, before some more specific concepts are advanced. The project team, the phasing of projects, planning the cost—time relationship and general management involvement are all discussed. Finally, a ‘plan for action’, for those wishing to implement project management, is suggested.  相似文献   

    

《Energy and Buildings》2004,36(5):415-422

The potential of controlling techniques for an electrochromic device is investigated in a systematic way, using both experimental and theoretical tools. Concerning the theoretical part a model was developed in the TRNSYS environment and validated against experimental data. These data were collected from experiments, which were carried out in a PASSYS test cell with a movable wall. Having established a good model performance several cases of window types (such as a 4 mm clear window and a low-e double glazing) and controlling strategies for the electrochromic device are simulated. Obtained results from the series of simulations were compared in terms of the heating and cooling loads of the test cell for each case. It was found that the development of a scheduled control strategy for the electrochromic glazing is better in terms of cooling loads. Finally, a more sophisticated control strategy was examined based on the adaptive fuzzy approach.  相似文献   

    

《Energy and Buildings》2004,36(12):1259-1263

Almost in all the major cities in Asian countries, residential buildings are characterized with high-rise and high density. Under this circumstance, achieving comfortable and healthy indoor environment with minimized energy consumption becomes a very challenging engineering and societal issue. While the wide use of air-conditioning helped to improve thermal comfort, health problems associated with poor indoor air qualities have appeared more frequently. The increased energy consumption is also a great concern in view of its impact on the energy economics of the region. Drawn from some of the onsite measurements and survey, and also the author’s personal observation, some of the key issues are discussed in this paper.  相似文献   

    

《Energy and Buildings》2004,36(12):1273-1280

This paper investigates a hybrid cooling system, utilizing wind-driven cross ventilation and radiational panel cooling in an office setting. The characteristics of the indoor environment are examined using computational fluid dynamics (CFD) simulation, which is coupled with a radiation heat transfer simulation, and HVAC control in which the PMV value for a human model in the center of the room is controlled to attain the target value. The system is devised with an energy-saving strategy, which utilizes stratified room air with a vertical temperature gradient. The cooled air settles down within the lower part of the room, while the hot and humid air passes through the upper region of the room, sweeping out the heat and contaminants generated indoors. This strategy is found to be quite energy-efficient in the intermediate seasons of spring and autumn in Japan. Even under hot and humid outdoor conditions, the hybrid system coupled with radiational cooling would bring significant energy savings are possible compared with a hybrid system coupled with underfloor air-conditioning.  相似文献   

    

《Energy and Buildings》2004,36(8):737-748

Past design analysis integration efforts have addressed the need to achieve seamless data integration between design and analysis software applications. These efforts have been dominated by an interoperability focus. Recently, it has been recognized that these solutions suffer from several limitations. For one, they assume a ‘perfect world’ in which all information is structured and all mappings between design and analysis representations exist on a generic level. Secondly, most interoperability solutions have a data focus, whereas true design analysis integration requires a “language” to express both analysis requests and the answers that are generated by experts responding to these requests. An intrinsic part of this language is the logic of the design analysis process. Hence, the integration effort requires a strong process rather than data focus. The Design Analysis Integration (DAI)-Initiative aims to steer towards new solutions for design analysis integration that may overcome the limitations of current data-centric interoperability approaches. This paper reports on the first phase of the development, which has produced a first-generation ‘workbench’ prototype for managing a process driven design analysis dialogue. The workbench is meant to enable a more robust use of existing building models such as IFC for the mapping to simulation tools. The paper presents the underlying theories, prototype development, and findings from the research and concludes with a discussion of future work, targeting extension and benchmarking of the current prototype.  相似文献