Applied Mechanics and Materials Vols. 584-586

Abstract: Aging mechanism of dam concrete under the action of freeze-thaw damage was analyzed by testing macro and micro performance. The results show that compressive, splitting tensile and flexural strengths reached 58.4%, 61.3% and 57.8% of the initial values after 150 cycles. Strength is the most sensitive indicator of freeze-thaw damage, followed by weight loss rate, relative dynamic elastic modulus and ultrasonic velocity. After freeze-thaw damage, concrete structure becomes loose, porous amount gradually increased and pore size especially over 25nm expanded. Microcracks not only exist in the hydration products, but also destroy the bubbles structure in air entrained concrete, which is the main cause of freeze-thaw damage.

Abstract: A significant number of crowd accidents have occurred in sport venues in the past as well as recently. Statistics of crowd disasters were discussed and the results of time and location are 1509 deaths and 10642 injuries, incidence of crowd accidents in grandstand areas is up to 54%. Serious security risks still exist, and we should pay more attention to sports building safety. Different stages of accidents include crowd gathering, trigger factors, accident happened and rescue failure. Finally, crowd disaster risk in sport venues was identified. This paper aims to lay a foundation to improve comprehensive disaster prevention system in stadium.

Abstract: In order to better study the wear state of vital parts of the large scale equipment, and overcoming the disadvantage of small sample of vital parts, we use the least squares support vector machine (LS_SVM) algorithm to predict the wear state of vital parts. Using of quantum particle swarm optimization (QPSO) to optimize parameters least squares support vector machine, and achieved good results. Compared those with the method that use of curve fitting to predict the data development trend, show that this method is superior to the curve fitting method, and has good application value.

Abstract: Several conventional steady-state measuring methods of material coefficient of thermal conductivity was systemically compared and discussed. The limitations and shortcomings of the infinite flat layer method, the infinitely long cylinder method and the concentric spherical shell layer method were pointed out. A new method for measuring the material coefficient of thermal conductivity, standard sample method, was proposed. The measure principle, the preparation of standard sample, the measure process and the obtainment of the result were presented. The advantages and applicability of the standard sample method to measure coefficient of thermal conductivity were evaluated.

Abstract: The apparent quality of the concrete is its side performance and affects the aesthetic effect of the building. However, the apparent quality is closely relevant to the strength and the durability of the concrete. The experimental results show that some measures, such as optimizing the ratio of mixing and making use of the defoamers, can improve the apparent quality of the self-compacting concrete.

Abstract: To meet the requirements of a large-scale soil moisture monitoring system, this dissertation developed a new type of capacitive soil moisture sensor based on the detection and amplification of the singal peak-to-peak value named PA-1 sensor. PA-1 sensor was calibrated and evaluated under static laboratory conditions. A new type of soil moisture sensor named PA-1 is developed, which is based on the relationship between soil moisture and soil relative permittivity. Circuit design, operating features and exterior design of the sensor are introduced. PA-1 is calibrated in solution samples using the standard calibration method. Calibration experiment results show that PA-1 has a very linear measurement curve. The performance of PA-1 is studied and compared to the widely used Decagon Company’s EC-5 capacitive soil moisture sensor. Experiment results show that PA-1 has advantages of high sensitivity, low temperature drift, strong tolerance to electromagnetic interference and low power consumption. Keywords: sensor, Precision Agriculture, low temperature drift, low power consumption.

Abstract: The right project delivery system is critical to the success of a project. A factors index system is important to choose a right project delivery system. Based on features and business properties of a project,a factors index system is established including the project, the performance of project, project parties and external environment. After using the two methods of index selectionfrequency number statistic and correlation analysis method, 19 factors in the said 4 levels are finally selected to form the factors index system, which can be a reference for selecting the project delivery system.

Abstract: In this paper, four bidding enterprises participated in the tendering of municipal engineering construction are evaluated in the bidding process, tendering process and bid evaluation of a large museum by applying the fuzzy comprehensive evaluation method and referring to features of municipal engineering construction projects, so as to select the best bidder. With this method, there will be few subjective factors influencing the decision makers during the bid evaluation process, which can reflect the strength of each bidder objectively and accurately, and improve the bid evaluation method in comprehensiveness and rationality.

Abstract: With the development of economy, project contract has now become global. However, there’re always different kinds of risks. Among all, the combination of environmental risks,strategic risks and executive risks may pose huge challenges to the project management. This article is mainly focus on the current development and risks of the international project contract, and provides solutions to the unnecessary lost caused by the differences of culture, politics, nature and laws between China and foreign countries during the project cooperation.

Abstract: A multidimensional approach ABC - XYZ, etc. has been used successfully in a number of areas, including logistics, retail, pharmaceuticals. In this paper, this approach is considered for the evaluation of diverse construction projects.