Vibration, Structural Engineering and Measurement II

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Authors: Xiao Juan Quan, Kai Shi, Yi Bo Yan
Abstract: With the economy developing rapidly, China has entered the era of high-speed railway, but at the same time, the negative impact of high-speed railway is increasing obviously. The paper analyzes the induced environmental vibration problems due to the high-speed railway, the specific response in the power of the shield tunnel under the train loads, the tunnel structure and the surrounding strata, When the local layer is saturated sand, by calculating the pore water pressure and the layer stress, determining whether it can cause sand liquefaction phenomenon or not, judging the damage extent of tunnel structure, especially it may influences the normal operation of the train. The vertical displacement of the tunnel structure due to the dynamic train load may have impact on the normal operation of the train, where some preventive measures should be taken, such as concrete grouting reinforcement method. In this paper the non-reinforcement case is compared to the reinforcing ones, and different reinforcement ring thickness is studied in order to determine a reasonable thickness of the reinforcement. The main contents include the following work: (1)Response analysis by using the FLAC3D software to simulate the shield tunnel under the dynamic train loads which are the main cause of the displacement of the segment and surrounding strata. The simulation study mainly includes analysis of the changes of pore water pressure and stress. (2) Since train load can produce the vertical displacement, prevention and controlling measures should be taken, which mainly use grouting reinforcement.
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Authors: Wen Jun Luo, Xiao Yan Lei, Song Liang Lian, Lin Ya Liu
Abstract: A hybrid method combining FE and SEA was recently presented for predicting the steady-state response of vibro-acoustic systems. The new method is presented for the analysis of complex dynamic systems which is based on partitioning the system degrees of freedom into a ‘‘global’’ set and a ‘‘local’’ set. The global equations of motion are formulated and solved by using the finite element method (FEM).The local equations of motion are formulated and solved by using statistical energy analysis (SEA). The power input from the global degrees of freedom. This paper deduces the theory for the beam element , and Train-Ballastless Track-Bridge System provides an application, and it showed that the method yields very good results .
387
Authors: Hai Ming Liu, Xia Xin Tao, Xin Zheng, Fu Tong Wang
Abstract: The mechanism of local amplifying on attenuation of ground vibration from urban rail traffic is deal with by Zheng et al (2011). The vertical vibrations on ground points of a model with single soil layer overlaid on elastic half-space is calculated with transfer matrix method in frequency domain. The results show that the amplification could be simulated well by the calculation, and the location and degree of the amplification are governed by the ratio between shear modulus of the the overburden layer and the half space , the thickness and damping ratio of soil layers. It is further pointed out in this paper that the most significant factor is the impedance ratio at the buried velocity interface. Then the mechanics is explained as the meeting of the directly arriving surface wave and the reflected and refracted waves from the interface.
392
Authors: Yi Song Zou, Quan Hui Chang, Wei Peng
Abstract: In the cable-stayed bridge damage identification index based on the dynamic characteristics, it is the key and premises for cable-stayed bridge damage identification using dynamic index, how to extract the modal of structure exactly through optimal placement of sensors. This article uses simulated annealing, In line with the modal assurance criterion, extract mechanical analysis data of Zhangzhen cable-stayed bridge ANSYS finite element model and obtain optimized acceleration sensor layout scheme of main beam. Based on this optimization scheme we carry out a dynamic characteristics test on Zhangzhen cable-stayed bridge. Through the comparison between observation results and calculation results, we find they are very closely. To verify that the simulated annealing algorithm based on modal assurance criterion used in cable-stayed bridge acceleration sensors optimized is effective, viable, and correct.
396
Authors: Jing Li, Nan Zhang
Abstract: Based on the combination of finite element software ANSYS and acoustics software LMS Virtual.Lab Acoustics, this paper makes an analysis of the Vibration and sound radiation of the viaduct of urban rail transit. First of all, transient dynamic analysis of three-dimensional model of box girder was made in ANSYS, with train passing bridge simulated as a moving load or a moving mass-spring system. Then vibration displacement response obtained is taken as boundary condition of outer sound field, which can achieve accurate acoustic response in Virtual.Lab Acoustics. According to comparing the results of the two different models, we can draw that the noise pressure with the moving mass-spring system is higher than the other, and the noise pressure range is from 70 to 95 in decibels. Using the transient boundary element module of LMS Virtual.Lab Acoustics can solve engineering problems in time domain, with simulating the vibration properly.
401
Authors: Xiao Zhou Liu, Song Liang Lian, Hong Liang Wei
Abstract: 3D FEM models of ladder track and rail-bearing platform track on metro viaduct were established to analyze the vibration reduction characteristics of ladder track structure. Based on track irregularities measured by track inspection car, time-history vertical accelerations of rail, sleeper, flange and beam bottom were solved to contrast the dynamic characteristics of the two track structure. Results show that the vibration level of rail and sleeper are higher on ladder track than on rail-bearing platform track, and the vibration reducing effect of ladder track for flange and beam bottom mainly embodies in frequency range of 1~40Hz in which average vibration reduction values on flange and beam bottom are 28dB and 22dB, with maximum values 40dB and 33dB. The results can provide reference for design of ladder track as well as its application in metro line.
406
Authors: He Nian Zhang, Qi Yun Sun, Guang Jun Sun
Abstract: The environment vibration induced by urban rail transit becomes one of the severe environmental hazards and attracted great attention for researcher at home and abroad. Firstly,on the basis of track irregularity theory, an exciting force function of vibration source induced by ground line train is established. Then, the exciting force acts on the three-dimensional models of rail bearing structure and soil propagation path by utilizing the finite element software. The surrounding environment vibration response caused by train operation is simulated and the numerical results are compared and verified by the field measurement data. Furthermore, the parameter effects of train speed and properties of site soil on environment vibration are studied. The researches show that the numerical simulation in the paper can truly reflect the actual environment vibration caused by urban rail transit with ground line.
411
Authors: Yi Gang Wang, Yang Yang, Jia Shun Yang, Zhi Gang Yang
Abstract: This study is focused on the locomotive of high speed train. First, wind tunnel test is used to verify the credibility of numerical results. Then, in order to compare the difference of aerodynamic noise generated by different size locomotive, dimensionally similar models of 1/8th, 1/12th and 1/15th scale are studied by using numerical simulation, including stationary aerodynamic characteristics, fluctuation characteristics of unsteady flow, noise source distribution on surface and far-field noise spectral characteristics. Based on the result of pressure fluctuation, it is noted that the difference between 1/15th and 1/8th scale model is larger in individual parts, including the separation zone in the roof and the edge of window. In addition, according to the far-field noise calculation, the result of 1/12th scale model is better than 1/15th scale model. From the results mentioned above, 1/15th or much smaller scale model should not be used in wind tunnel test as possible.
417
Authors: Xue Ying Xu, Guo Hua Han, Zha Gen Ma
Abstract: As cars become quieter the sound quality of components becomes more critical in the customer perception of car quality. Considering that middle frequency noise plays an important roll for internal noise, the noise signals in the range from200Hz to 500Hz are specially emphasized. Then the acoustic evaluation parameters, such as Sound Pressure Level, Acceleration have been evaluated. Judged from experiences and measuring results, an abnormal noise comes from engine mounts, through the use of dynamic vibration absorber on engine mounts, Vibration on engine mounts and Sound Pressure Level in interior vehicle were greatly improved. At the same time, subjective evaluation also indicated that there was no complaint any more in passenger compartment. Dynamic vibration absorber can properly solve the abnormal noise.
423
Authors: Cun Yuan Mu, Cong Min Gao, Zhen Ge
Abstract: This paper analyzes the gearing noise of a reinforcing bar straightening cutting machine, according to the test of the machine around six positions under the background noise of 49dB(A). The test result shows highest noise is in the position 4 and position 6. The noise is arrived at 1026 dB(A). By frequency spectrum analysis before noise reduction and after noise reduction, Identify the source of main noise, points out relative elements gears 26/54, and presents some methods to decrease the noise: the methods of gear correction, improving the vibration resistance of mechanism, reducing noise in the view of process and control noise transmission. The best methods is gear correction and the test improves that it can reduce noise 0.5-2 dB(A). It can be a reference to the designers and manufactures.
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