Applied Mechanics and Materials Vol. 684

Abstract: Three grading types of asphalt mixture are designed and respectively placed in intermediate course of asphalt concrete pavement with a typical semi-rigid base layer, the pavement structure model is established by the application of finite element software, the tensile stress at the bottom of intermediate course is analyzed under the wheel pressure of 1.5MPa, the finite element calculation results are led to the fatigue analysis software nSoft, the fatigue analysis results of intermediate course materials are obtained. The results show that the design gradation AC-20 mixture has excellent fatigue resistance in the pavement structure layer.

Abstract: FRP strength technique can increase the lateral strength of masonry walls, but the effect of the presence of pre-damage in the walls before retrofitted has not been studied. In this study, the experimental results from two half-scale RC-brick masonry walls with opening retrofitted with BFRP composite strips are presented. One wall was initially damaged in shear loading up to its maximum strength, and then repaired with BFRP sheets; another one was directly strengthened with BFRP sheets in the same strengthening configuration. All the walls were subjected to cyclic in-plane shear loading up to failure. Compared to the strengthened walls, the repaired masonry wall has almost the same failure mode and FRP strain rule, and slightly lower lateral strength and deformation capacity as well as energy dissipation capacity.

Abstract: Wind-induced vibration can affect the safety of power transmission tower. Vibration suppression of the high-rise tower is of concern in engineering. Vibration of the tower is mostly the first-order bending modal and this vibration can be suppressed by the tuned mass damper (TMD). This paper developed a TMD vibration damping device using eddy current damper constituted by magnetic steel installed in the vibration mass and fixed copper plate. It is characterized by simple structure and easy installation, and is suitable for wind-induced damage prevention of transmission tower. Focusing on a quadruple-circuit on the same steel tube tower, a vibration reduction test on a real-scale tower conducted. The result shows that the damping ratio of the tower after installed with the TMD device will increase about 3%. The actual test result verifies the effectiveness of the eddy current TMD device.

Abstract: In general it is difficult to obtain the results directly during process of structural reliability designing because of the complexity of the structure. It can calculate the structure reliability and failure probability effectively according to the combination of finite element method and theory of reliability. This paper introduces a method of structure reliability based on finite element method, summarizes a common method which has an important engineering application value to calculate the reliability such as using Monte-Carlo method to calculate reliability analysis combining with finite element method, recommends a common used software to reliability design and shows the process of using the software to reliability analysis.

Abstract: The sound barrier is one of the effective and economical engineering facilities to control the urban traffic noise. The characteristics of urban traffic noise are analyzed both in time-domain and frequency-domain. Then the noise reduction theory of sound barrier is introduced in detail. The determination of the influence factors in insertion loss is researched emphatically. The main procedure of the acoustics design of sound barrier is also systematically studied. According to the main design process of the acoustics design of sound barrier, simulation confirmation is conducted by acoustics software to confirm the noise reduction performance of the barrier.

Abstract: The paper proposes a design method for the layered and ring-shaped acoustic cloaking based on BM. According to the theory of PM cloaking, physical parameters of the ring-shaped acoustic cloaking are given by theoretical design. Further, based on the features of microstructure of BM, the relationship between the parameters of each layer of microstructure of BM and the analytic expression of the physical parameters of acoustic cloaking made of BM is determined, and the design methods for microstructure of layered and ring-shaped acoustic cloaking are discussed, namely, radial equidistant layered design and radial non-equidistant layered design (i.e. equal sectorial angle layered design). At last, according to the radial non-equidistant layered design parameters of the ring-shaped acoustic cloaking, the microstructure model of the layered and ring-shaped acoustic cloaking is designed. The results of the study can serve as theoretical basis for actual production and application of acoustic cloaking.

Abstract: Deformation of helical buckling appears on tubing string under axial compressive loads, and it may even make the tubing string fail when the loads are excessively large. To make clear stress distribution and variation of helical buckling tubing string, the formulas of equivalent stresses inside and outside of the tubing string are deduced based on the spring theory and the fourth strength theory. From the analysis, we can see that the equivalent VonMises stress increase with the clearance of tubing string and casing, and the increase are 22.44 percent and 45.9 percent respectively for inside and outside stress with clearance increase form 29.1mm to 39.69mm. The proposed method used for the helical buckling tubing string makes up the insufficient of traditional tubular mechanics effectively.

Abstract: Pipeline security is very important in oil and gas transportation. Traditional technology such as negative pressure wave detection, acoustic detection doesn’t match the need of pre-alarm. A fiber-optic distributed vibration sensor (FDVS) is proposed and investigated. It is found that the FDVS has the advantages of long sensing distance, high spatial resolution, high sensitivity, high reliability, etc. According to calculating the time delay of the two MZIs , the vibration can be located.

Abstract: Study of the traffic noise has important role in the improvement of urban living environment. The source of the noise of road vehicle and the spectral features of urban traffic noise are analysed in the paper. Through the investigation and monitoring on two typical roads, the distribution law of traffic noise along both sides of the road is analysed and a theoretical basis for the control of traffic noise is provided.

Abstract: Single-chip AT89C2051 as the main-control component of the device, we designed a digital thermometer from the aspects of hardware, it with the aid of temperature sensor DS18B20, the device used single bus technology to detect the ambient temperature (analogue) is converted into digital quantity, it was accepted, processed, judged by single-chip microcomputerand then control and display. The temperature measured range in - 30 °C to + 120 °C, the accuracy class + 0.5 °C, four LED Nixie tube as display mode.