Advanced Materials Research Vols. 446-449

Abstract: The isolation system between the upper structure and the foundation could reduce the seismic response of the former. A system combined of sliding and lead rubber bearings (LRB) is more effective in seismic isolation than using the later alone. In this research, the seismic responses of a building which was set with LRB and a combined system (the proportions between the sliding and LRB were 1/6, 1/4 and 1/3) respectively were analyzed and compared to that of the building without base isolation system to investigate the effect of seismic isolation. The relationship between isolation coefficient and the proportion of bearings was studied. The results show that the combined system could reduce the seismic response of structure, and it is more effective in seismic isolation if the leading bearing is relatively more.

Abstract: The aim of the research is to determine the strain-temperature rate and investigate the apparent thermal expansion coefficient of three kinds of concrete (ATEC). The strain of concrete with the dimension of 100mm×100mm×100mm subject to freeze-thaw cycles and chloride salt attack were measured using an embedded strain gauge. The ATEC was calculated from the strain-temperature rate using linear regression. The results show that the absolute value of ATEC of specimen saturated by 3.5 wt. % chloride salt solution was reducing with the progress of freeze-thaw cycles. However, the ATEC of the dried specimen subject to heating and cooling is independent from water to cement ratio, and approximately maintains the same level during the whole heating and cooling cycle, and the ATEC of air-entrained specimen is constant within 20 cycles. Overall, deterioration of concrete matrix can be evaluated by apparent thermal expansion coefficient besides weight loss and dynamic elastic modulus.

Abstract: In the design of the asphalt pavement or asphalt overlay, consider about the viscoelastic fracture mechanics behavior of asphalt mixture is significant in researching the asphalt pavement craze or the extending behavior of reflective crack. This paper employs nonlinear finite element software ABAQUS to analysis about the viscoelastic of asphalt mixture in the basis of the vicoelastic breaking theory, analyze the Traffic dynamic loading different speeds, different grassroots modulus to contain crack pavement structure system of the displacement field and stress field of influence.The calculation results show that the curve of the stress intensity factor in the crack tip moves as the increase of the speed, but the maximum is virtually unchanged; and it is proportional to the grassroots modulus variations, that is the stress intensity factor increases as the increase of grassroots modulus. With the effect of partial load, the stress intensity factor is formed by KⅠ、KⅡ. It is mainly assumed by KⅡ when grassroots modulus is low, and as the grassroots modulus increases, the KⅠ is increases, But KⅡ changes little.

Abstract: Analysis the factors of mass concrete temperature crack. Combined with the Nan Yang Branch of CUCC cement clinker production line of the second phase of mass concrete construction, it proposed some measures about how to prevent the temperature stress crack of mass concrete due to hydration heat of cement generated temperature difference .By controlling the temperature of the concrete strictly, decreasing the temperature difference between inside and outside, preventing shrinkage joint, reducing the slump loss, delaying setting time, etc. To ensure from the construction maintaining process of mass concrete foundation floor, the tensile strength of concrete is always greater than the maximum temperature tensile stress to prevent temperature cracks appear ensure the quality of mass concrete construction.

Abstract: In order to research the effectiveness of passive control on transmission tower vibration control under seismic excitation, suspended mass pendulum (SMP) is carried out in this study. Based on the mechanism and equation of earthquake vibration control, earthquake induced vibration control for transmission tower model with suspended mass pendulums was performed by using numerical simulation. Using SAP2000 software, three-dimensional finite element model of a transmission tower is created, and seismic records are selected by different site soils. Typical time history curves and the maximum responses of displacement, axis force, shear force and moment of the transmission tower without and with suspended mass pendulums are obtained by numerical simulation analysis. The results show that the SMP is very effective in mitigating tower vibration, and the method can be a reference for practice engineering application.

Abstract: In order to determine the criterion for the threshold exceedance method, which is for wind environment evaluation, the relevant theory and wind tunnel experiment means were proposed herein. Maximum joint probability decision rule and empirical mode decomposition are employed to deal with the results of wind tunnel experiment, so that the criterion obtained would be more reliable. The effects of a gusty wind on human are also considered. The comparison of the present results and the other criteria is conducted. It indicates that the former is slightly stricter.

Abstract: Volumetric parameters of asphalt mixture are essential for a better understanding of the properties of an asphalt mixture. This is even more applicable for a dense-graded asphalt mixture, where volumetric parameters have a significant correlation with its pavement performance, especially against rutting and moisture. This paper deals with the choice of the representative volumetric parameter for dense-graded asphalt mixture. A total of 6 volumetric parameters were studied. Volumetric analysis showed that linear correlation existed between any two of volumetric parameters. The change of volumetric parameters was mainly caused by the variation of gradation. The test result indicated that volumetric parameters were sensitive to the variation of gradation. The finding also indicated with the variation of gradation, the change rate of is the largest. Based on the research above, was selected as the representative volumetric parameter for dense-graded asphalt mixture.

Abstract: The TBM cutter wear causes not only low performance of tunneling but also the additional cost of cutter discs and potential safety hazard in construction. Excessive cutter wear and replacement were observed in tunneling with a TBM through sandy cobble stratum in Chengdu metro Line 1. Comparison with other geological layer, the ground has leaded to more cutter wear. Moreover, the form of wear is great varieties which include flat wear, multi-flat wear, eccentric wear and cutter bearing breakage etc. Based on the statistical analysis, general rule can be found that the number of cutter wear or replacement increases along the outer radial direction of the cutterhead. This paper has adopted the engineering analog method and theoretical research to study the mechanism of cutter wear. There are three forces acting on the cutter, namely the normal force, the rolling force and the side force. Thereinto, the high shock the normal force and random side force are primary causes of cutter wear. Putting the engineering geology and field survey into consideration, the immediate causes could be as follows: ①There are more hard cobble stone with high quartz contents in the layer; ②When the cutter traversed from soft soil to hard rock, very high shock loads can be imposed on the cutter assembly; ③The roller cutters sometimes were blocked and resulted in flat wear because of muck cake in the centre part of the chamber. In a word, the main causes of cutter wear are geological condition. By analyzing the TBM performance, the soil conditioning should be highlighted for the pebbles with sand matrix layers. Soil conditioning not only improves the flow of muck, control of earth pressure, face stability, but also reduces cutter, cutterhead and screw conveyor wear. The results are to be applied to a tunneling project where such ground condition was encountered

Abstract: This review describes the author's research progress of dispersive-tube structure, summarizes the basic concepts of dispersive-tube structure, the mechanical characteristics of concrete tube, and the wind resistant behavior with the seismic performance. Examples of related studies have shown that, dispersive-tube structure have significant advantages in the structural performance and economic performance.

Abstract: Fatigue failure is the major cause of malignant accident of gantry crane. In this paper fatigue analysis of gantry crane is studied . Based on the result of FEM(Finite Element Method) and the ANN(Artificial Neural Network), nonlinear ralationship between fatigue damage and dynamic load is built. By the trained ANN, the corresponding fatigue damage is obtained when input random sampling load data, and then fatigue life is calcutated. The Example shows high efficient and accuracy of the present method.