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- 저자 : Yuntai Zhang (검색결과 4 건)
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Critical coupling span number in high-speed railway simply supported beam bridge
Yuntai Zhang,Lizhong Jiang,Wang-Bao Zhou,Yulin Feng,Xiang Liu,Zhipeng Lai 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.1
In long-distance railways, some particular spans of high-speed railway simply supported beam bridges (HSRSBs) are commonly selected as the target structure. The target structure is the part of interest for the study and intended to be analyzed. Due to longitudinal constraints of the track system, the target structure is tightly coupled with other spans within certain range, and is affected by the coupled spans under longitudinal earthquake condition. A massive amount of time-consuming computation is required to determine the coupling span number using current finite element models. In an effort to overcome this challenge, an equivalent method for the longitudinal constraints of the track system is proposed, which greatly reduces the complexity of finite element model while retaining calculation precision. The coupling span number was determined by seismic analyses of a large number of cases using equivalent finite element models. Moreover, the influence of pier height and bottom pier stiffness on coupling span number was studied. Based on the relationship between the equivalent boundary sensitivity critical point and coupling span number, a method to quickly obtain coupling span number of the target structure in arbitrary HSRSB was constructed.
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Yulin Feng,Lizhong Jiang,Wangbao Zhou,Yuntai Zhang,Xiang Liu 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.5
To study the vibration characteristics of a high-speed railway continuous girder bridge-track coupling system (HSRCBT), a coupling vibration analysis model of an m-span continuous girder bridge-subgrade-track system with n-span approach bridge was established. The model was based on the energy and its variational method, where both the interlaminar slip and shear deformation effects were considered. In addition, the free vibration equations and natural boundary conditions of the HSRCBT were derived. Further, according to the coordination principle of deformation and mechanics, an analytical method for calculating the natural vibration frequencies of the HSRCBT was obtained. Three typical bridge-subgrade-track coupling systems of high-speed railway were taken and the results of finite element analysis were compared to those of the analytical method. The errors between the simulation results and calculated values of the analytical method were less than 3%, thus verifying the analytical method proposed in this paper. Finally, the analytical method was used to investigate the influence of the number of the approach bridge spans and the interlaminar stiffness on the natural vibration characteristics of the HSRCBT based on the degree of sensitivity. The results suggest the approach bridges have a critical number of spans and in general, the precision requirements of the analysis could be met by using 6-span approach bridges. The interlaminar vertical compressive stiffness has very little influence on the low-order natural vibration frequency of HSRCBT, but does have a significant influence on higher-order natural vibration frequency. As the interlaminar vertical compressive stiffness increases, the degree of sensitivity to interlaminar stiffness of each of the HSRCBT natural vibration characteristics decrease and gradually approach zero.
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Zhipeng Lai,Lizhong Jiang,Xiang Liu,Yuntai Zhang,Tuo Zhou 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.4
A high-speed railway (HSR) bridge may undergo long-term deformation due to the degradation of material stiffness, or foundation settlement during its service cycle. In this study, an analytical model is set up to evaluate the influence of this longterm vertical bridge deformation on the track geometry. By analyzing the structural characteristics of the HSR track-bridge system, the energy variational principle is applied to build the energy functionals for major components of the track-bridge system. By further taking into account the interlayer’s force balancing requirements, the mapping relationship between the deformation of the track and the one of the bridge is established. In order to consider the different behaviors of the interlayers in compression and tension, an iterative method is introduced to update the mapping relationship. As for the validation of the proposed mapping model, a finite element model is created to compare the numerical results with the analytical results, which show a good agreement. Thereafter, the effects of the interlayer’s different properties of tension and compression on the mapping deformations are further evaluated and discussed.
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A stochastic finite element method for dynamic analysis of bridge structures under moving loads
Xiang Liu,Lizhong Jiang,Ping Xiang,Zhipeng Lai,Yuntai Zhang,Lili Liu 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.1
In structural engineering, the material properties of the structures such as elastic modulus, shear modulus, density, and size may not be deterministic and may vary at different locations. The dynamic response analysis of such structures may need to consider these properties as stochastic. This paper introduces a stochastic finite element method (SFEM) approach to analyze moving loads problems. Firstly, Karhunen-Loéve expansion (KLE) is applied for expressing the stochastic field of material properties. Then the mathematical expression of the random field is substituted into the finite element model to formulate the corresponding random matrix. Finally, the statistical moment of the dynamic response is calculated by the point estimation method (PEM). The accuracy and efficiency of the dynamic response obtained from the KLE-PEM are demonstrated by the example of a moving load passing through a simply supported Euler-Bernoulli beam, in which the material properties (including elastic modulus and density) are considered as random fields. The results from the KLE-PEM are compared with those from the Monte Carlo simulation. The results demonstrate that the proposed method of KLE-PEM has high accuracy and efficiency. By using the proposed SFEM, the random vertical deflection of a high-speed railway (HSR) bridge is analyzed by considering the random fields of material properties under the moving load of a train.
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