Evaluation of optimal ground motion intensity measures of high-speed railway train running safety on bridges during earthquakes

Xiang Liu,Lizhong Jiang,Ping Xiang,Yulin Feng,Zhipeng Lai,Xiaoyun Sun 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.2

Due to the large number of railway bridges along China's high-speed railway (HSR) lines, which cover a wide area with many lines crossing the seismic zone, the possibility of a HSR train running over a bridge when an earthquake occurs is relatively high. Since the safety performance of the train will be threatened, it is necessary to study the safety of trains running over HSR bridges during earthquakes. However, ground motion (GM) is highly random and selecting the appropriate groundmotion intensity measures (IMs) for train running safety analysis is not trivial. To deal this problem, a model of a coupled trainbridge system under seismic excitation was established and 104 GM samples were selected to evaluate the correlation between 16 different IMs and train running safety over HSR bridges during earthquakes. The results show that spectral velocity (SvT1) and displacement (SdT1) at the fundamental period of the structure have good correlation with train running safety for mediumand long-period HSR bridges, and velocity spectrum intensity (VSI) and Housner intensity (HI) have good correlation for a wide range of structural periods. Overall, VSI and HI are the optimal IMs for safety analysis of trains running over HSR bridges during earthquakes. Finally, based on VSI and HI, the IM thresholds of an HSR bridge at different speed were analyzed.

Stability of positive steady-state solutions in a delayed Lotka-Volterra diffusion system

Xiang-Ping Yan,Cun-Hua Zhang 대한수학회 2012 대한수학회지 Vol.49 No.4

This paper considers the stability of positive steady-state so-lutions bifurcating from the trivial solution in a delayed Lotka-Volterra two-species predator-prey diffusion system with a discrete delay and sub-ject to the homogeneous Dirichlet boundary conditions on a general boun-ded open spatial domain with smooth boundary. The existence, unique-ness and asymptotic expressions of small positive steady-sate solutions bifurcating from the trivial solution are given by using the implicit func-tion theorem. By regarding the time delay as the bifurcation parameter and analyzing in detail the eigenvalue problems of system at the positive steady-state solutions, the asymptotic stability of bifurcating steady-state solutions is studied. It is demonstrated that the bifurcating steady-state solutions are asymptotically stable when the delay is less than a certain critical value and is unstable when the delay is greater than this critical value and the system under consideration can undergo a Hopf bifurcation at the bifurcating steady-state solutions when the delay crosses through a sequence of critical values.

A combined spline chirplet transform and local maximum synchrosqueezing technique for structural instantaneous frequency identification

Ping-Ping Yuan,Zhou-Jie Zhao,Ya Liu,Zhong-Xiang Shen 국제구조공학회 2024 Smart Structures and Systems, An International Jou Vol.33 No.3

Spline chirplet transform and local maximum synchrosqueezing are introduced to present a novel structural instantaneous frequency (IF) identification method named local maximum synchrosqueezing spline chirplet transform (LMSSSCT). Namely spline chirplet transform (SCT), a transform is firstly introduced based on classic chirplet transform and spline interpolated kernel function. Applying SCT in association with local maximum synchrosqueezing, the LMSSSCT is then proposed. The index of accuracy and Rényi entropy show that LMSSSCT outperforms the other time-frequency analysis (TFA) methods in processing analytical signals, especially in the presence of noise. Numerical examples of a Duffing nonlinear system with single degree of freedom and a two-layer shear frame structure with time-varying stiffness are used to verify the effectiveness of structural IF identification. Moreover, a nonlinear supported beam structure test is conducted and the LMSSSCT is utilized for structural IF identification. Numerical simulation and experimental results demonstrate that the presented LMSSSCT can effectively identify the IFs of nonlinear structures and time-varying structures with good accuracy and stability.

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.

Dynamic analysis of deployable structures using independent displacement modes based on Moore-Penrose generalized inverse matrix

Ping Xiang,Minger Wu,Rui Q. Zhou 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.6

Deployable structures have gained more and more applications in space and civil structures, while it takes a large amount of computational resources to analyze this kind of multibody systems using common analysis methods. This paper presents a new approach for dynamic analysis of multibody systems consisting of both rigid bars and arbitrarily shaped rigid bodies. The bars and rigid bodies are connected through their nodes by ideal pin joints, which are usually fundamental components of deployable structures. Utilizing the Moore-Penrose generalized inverse matrix, equations of motion and constraint equations of the bars and rigid bodies are formulated with nodal Cartesian coordinates as unknowns. Based on the constraint equations, the nodal displacements are expressed as linear combination of the independent modes of the rigid body displacements, i.e., the null space orthogonal basis of the constraint matrix. The proposed method has less unknowns and a simple formulation compared with common multibody dynamic methods. An analysis program for the proposed method is developed, and its validity and efficiency are investigated by analyses of several representative numerical examples, where good accuracy and efficiency are demonstrated through comparison with commercial software package ADAMS.

Structural instantaneous frequency extraction based on improved multi-synchrosqueezing generalized S-transform

Ping-Ping Yuan,Xue-Li Cheng,Hang-Hang Wang,Jian Zhang,Zhong-Xiang Shen,Wei-Xin Ren 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.5

A new method is proposed to improve the accuracy of structural instantaneous frequency (IF) extraction. The proposed method combines a new form of improved generalized S-transform (IGST) and a multi-synchrosqueezing operation. The parameters selection of the window function in IGST is derived through the concentration measure (CM) principle. Then, the multi-synchrosqueezing algorithm is employed to improve energy aggregation of time-frequency analysis (TFA). To verify the effectiveness and accuracy of the proposed improved multi-synchrosqueezing generalized S-transform (IMSSGST), a frequency-modulated multi-component signal is investigated. For structural IF extraction, a two-story shear frame and a threestory steel frame structure are introduced. Furthermore, the IF identification of a seven-story RC shear wall structure is conducted to verified the practicability in actual engineering. Numerical simulation and experimental results show that the proposed method can effectively improve the energy aggregation of TFA and effectively improve the accuracy of IF identification.

Molecular Characterization of Cold-Inducible β-Galactosidase from Arthrobacter sp. ON14 Isolated from Antarctica

( Xiang Xiao ),( Feng Ping Wang ),( Xu Ke ),( Xi Xiang Tang ),( Ying Bao Gai ),( Muhammad Aamer Mehmood ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.3

A psychrotrophic bacterium, Arthrobacter sp. ON14, isolated from Antarctica, was shown to exhibit a high β-galactosidase activity at a low temperature. A genomic library of ON14 was constructed and screened for β-galactosidase genes on functional plates containing 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-gal) as the substrate. Two different β-galactosidase genes, named as galA, galB, were found in ON14. Computational analyses of the genes revealed that the encoded protein GalA belongs to family 2 of glycosyl hydrolysases and is a cold-active protein, whereas GalB belongs to family 42 of glycosyl hydrolysases and is a mesophilic protein. Reverse transcription analyses revealed that the expression of galA is highly induced at a low temperature (4℃) and repressed at a high temperature (28℃) when lactose is used as the sole carbon source. Conversely, the expression of galB is inhibited at a low temperature and induced at a high temperature. The purified GalA showed its peak activity at 15℃ and pH 8. The mineral ions Na+, K+, Mg2+, and Mn2+ were identified as enzyme activators, whereas Ca2+ had no influence on the enzyme activity. An enzyme stability assay revealed that the activity of GalA is significantly decreased when it is incubated at 45℃ for 2 h, and all its activity is lost when it is incubated at 50℃.

Spatial Path Following Control of an Autonomous Underactuated Airship

Wei-Xiang Zhou,Chang Xiao,Ping-Fang Zhou,Deng-Ping Duan 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.7

This paper studies the spatial path following control of an autonomous underactuated airship in the presence of model uncertainties and external disturbances. Firstly, the nonlinear dynamics model, kinematics modeland path following error dynamics model are given. And the control objective is formulated. Then, an adaptivebackstepping sliding mode controller is designed. Besides, to overcome the disadvantage of dependence on theaccurate vehicle model, a nonlinear disturbance observer (NDOB) is adopted to estimate the attack and sideslip angular velocities. In addition, when backstepping technique is uesd, the complex analytic computation of commandderivative is required to be known. To handle this problem, a sliding mode differentiator is implemented to generatethe command derivatives. Finally, the closed loop stability for the system is proved using Lyapunov stability theory. Numerical simulations are given to demonstrate the effectiveness of the proposed method.

A taxonomic revision of the genus Mesa Saussure, 1892 from China, with a key to the Oriental species (Hymenoptera: Tiphiidae: Myzininae)

Liao Xiang-Ping,Chen Bin,Li Ting-Jing 한국응용곤충학회 2021 Journal of Asia-Pacific Entomology Vol.24 No.4

In this study, a total of eight fossorial aculeate wasps of the tiphiid genus Mesa Saussure, 1892 from China are revised, including two new species, viz., Mesa hongchibaensis sp. nov., and Mesa glaber sp. nov.. The following species Mesa dimidiata (Guérin-Méneville, 1837) and Mesa nursei (Turner, 1909) are newly recorded from China. The male specimen of Mesa formosensis Tsuneki (1986) is firstly found. In addition, an updated key to the Ori ental species of the genus is provided.

STABILITY OF POSITIVE STEADY-STATE SOLUTIONS IN A DELAYED LOTKA-VOLTERRA DIFFUSION SYSTEM

Yan, Xiang-Ping,Zhang, Cun-Hua Korean Mathematical Society 2012 대한수학회지 Vol.49 No.4

This paper considers the stability of positive steady-state solutions bifurcating from the trivial solution in a delayed Lotka-Volterra two-species predator-prey diffusion system with a discrete delay and subject to the homogeneous Dirichlet boundary conditions on a general bounded open spatial domain with smooth boundary. The existence, uniqueness and asymptotic expressions of small positive steady-sate solutions bifurcating from the trivial solution are given by using the implicit function theorem. By regarding the time delay as the bifurcation parameter and analyzing in detail the eigenvalue problems of system at the positive steady-state solutions, the asymptotic stability of bifurcating steady-state solutions is studied. It is demonstrated that the bifurcating steady-state solutions are asymptotically stable when the delay is less than a certain critical value and is unstable when the delay is greater than this critical value and the system under consideration can undergo a Hopf bifurcation at the bifurcating steady-state solutions when the delay crosses through a sequence of critical values.