Advanced Materials Research Vols. 168-170

Abstract: A kind of lightweight aggregate (LWA) has been successfully developed in Taiwan, which was made by expanding under heat fine sediments dredged from the Shihmen Reservoir. In this study the performances of concrete made from the aforementioned LWA were tested and compared with those of the companion normal weight concrete (NC). The test results show that the so produced lightweight concrete (LWAC) exhibited a comparable time-dependent properties (i.e., compressive strength, elastic modulus, drying shrinkage, and creep) as compared with those of the companion NC. Based on the results, it can be concluded that the use of prewetted LWAs and the incorporation of pozzolan materials can effectively control the drying shrinkage of LWAC. The specific creep of the LC mixture was obviously higher than that of the NC mixture at the same curing time.

Abstract: Through the in situ experiment of the ground-source heat pump (abbreviated as “GSHP”) system in Nanning Guangxi, this article has observed the temperature variation rules of the rock layers, by the temperature sensors buried in different depths and different locations from the Heat Exchanger. In addition, this article has also tried to explore the thermal environment of the rocks by analyzing the heat transfer of the soil layers acted under the thermal load in Southwest China regions where the ground water is abundant.

Abstract: Liangshui Tunnel of Lanzhou-Chongqing railway and Tianpingshan Tunnel of Guiyang-Guangzhou railway are the background work. Combining the construction process mechanics of soft rock, uniaxial compressive test, Brazilian test and direct shear test under different material proportion are carried out. After comparing and analyzing the basic physical and mechanical parameters of original rock and model materials, the similar materials for soft rock tunnel are attained. The effect of component proportion on material properties is analyzed. These results provide reliable material guarantee for model test of construction process mechanics in soft rock tunnels.

Abstract: Under the experimental condition,the crystal phases of mold fluxes contained cuspidine, wollastonite and melilite. The addition of TiO2 could stimulate Perovskite to be precipitated in mold fluxes whilst the growth of cuspidine and wollastonite were inhibited. At 1300°C mold fluxes existed mainly in glass phase, with few melilite phases existed in several sections while after TiO2 was added, perovskite was precipitated and melilite was dissolved.

Abstract: The numerical analysis of finite element coupling infinite element is recently used to simulate the effects of unbounded foundation of stresses and displacements. In this thesis, the finite element analysis is adopted to simulate the piles and the near soil; between the pile and the soil a joint element is designed to imitate the relative settlement while the infinite element is used to imitate the distant soil. elastic analysis way for concret elements and infinite elements are used, K-G model and E-U model for near soil.Calculation results show that using Goodman contact element to simulate the interaction of pile and soil has the advantage of flexibility;and the graphic formula of the calculation curves of nonlinear model and K-G model accords with that of the measure curve while the elastic calculation curve is far from the measure curve;the skin friction and pile-tip resistance pressure of the corner pile is the largest, the side pile less, and the center pile the least.The analysis of one example shows that the analytical model adopted in the thesis is reasonable, the results are both reasonable and accurate.

Abstract: In this paper, in-field ambient vibration testing of a highway bridge in South Korea under traffic loadings has been conducted to update its finite element model for future predictive analysis and diagnosis purpose. The research results presented in this paper are outcomes from an international REU (Research Experience for Undergraduates) program in smart structures funded by US-NSF (National Science Foundation) and hosted abroad by the Korean Advanced Institute of Science and Technology (KAIST). The monitoring, modeling, and model updating of civil infrastructures are vital in maintaining new design and maintenance standards. Using the frequency domain decomposition (FDD), experimental modal properties of the structure were found and, after a finite element model was created and updated based on the modal properties. From the results, it has been concluded that (a) the FDD method successfully identified the modal characteristics of the structure from ambient vibration, (b) that model updating improved the accuracy of the finite element model, (c) Representing the structural supports as springs in the FEM improved the results from the ideally supported model.

Abstract: The selection of constructive materials and structure inside long highway tunnel was studied aiming at the relatively closed internal structure of long highway tunnel combined with its environmental factors such as noise,illumination,temperature and humidity. This paper put forward the selection principle of materials and structure on pavement and wall inside highway tunnel, and confirmed suitable reflecting materials of pavement and noise-reducing materials of wall. Furthermore, the thesis designed materials and structure of pavement and wall in noise-reduction optimization. The research has an important instructional function on improving driving environment and noise-reduction effect and promoting the construction of resource-conserving and environment-friendly society and realizing sustainable development.

Abstract: By comprehensively analyzing the main factors affecting vertical ultimate bearing capacity of single pile, a prediction model of Support Vector Machine (SVM), which discusses the nonlinear relationship between vertical ultimate bearing capacity of single pile and influencing factors and analyzes the parameters on the performance of the model through sample knowledge learning, is established in this paper. The research results indicate that, SVM model, which is compared with BP neural networks model, possesses simple structure, flexible adaptability, high precision and powerful generalization ability, and can accurately reflect the actual mechanical characteristics of pile, therefore, SVM is an effective method for predicting vertical ultimate bearing capacity of single pile.

Abstract: The principle of total potential energy with least value in elastic system dynamics is established ,based on the principle of total potential energy with stationary value in elastic system dynamics which is drawn from the principle of virtual work and the principle of d’Alembert. It is sufficiency and necessary conditions for the real displacement of the equilibrium system of statics corresponding to dynamics system that total potential energy is the least value in elastic system dynamics.The testify of the principle provide a new method to establish differential equations in elastic system dynamics. Especially for complex system, The method is effective.

Abstract: It has been carried out the test and research to the stainless steel plate laser welding welded seam, by two-dimensional, three-dimensional appearance observation and tensile methods. Its result is: The YAG laser welding, is welding speed, frequency, pulse width and so on technological parameter influences to be big. In the power limit, raising the power or reducing welding speed; or increasing the frequency, or increasing the pulse width in critical value range, it be possible to increasing joints strength, however, when the pulse width surpasses critical value range its joints strength instead fall. In this study, the parameter that the appearance and the quality are all good of welded seam for welds speed 60mm/min, frequency 10Hz, pulse width 3ms, defocusing amount -1mm, the tensile strength of joints may reach 390MPa. The joints that the performance is good, its keyhole's microscopic appearance is also more complete good, but the joints that the macroscopic appearance is good, it has fine mechanical properties certain by no means. The three-dimensional observation of keyhole appearance is relatively feasible to be appraisal laser welding welded seam newest method，it is worthy discussing and carrying out.