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Experimental and theoretical investigations of the lateral vibrations of an unbalanced Jeffcott rotor

Ali ALSALEH, Hamid M. SEDIGHI, Hassen M. OUAKAD

《结构与土木工程前沿（英文）》 2020年 第14卷 第4期   页码 1024-1032 doi: 10.1007/s11709-020-0647-y

摘要： The current work experimentally explores and then theoretically examines the lateral vibrations of an unbalanced Jeffcott rotor-system working at several unbalance conditions. To this end, three conditions of eccentric masses are considered by using a Bently Nevada RK-4 rotor kit. Measurements of the steady-state as well as the startup data at rigid and flexible rotor states are captured by conducting a setup that mimics the vibration monitoring industrial practices. The linear governing equation of the considered rotor is extracted by adopting the Lagrange method on the basis of rigid rotor assumptions to theoretically predict the lateral vibrations. The dynamic features of the rotor system such as the linearized bearing induced stiffness are exclusively acquired from startup data. It is demonstrated that, with an error of less than 5%, the proposed two-degrees-of-freedom model can predict the flexural vibrations at rigid condition. While at flexible condition, it fails to accurately predict the dynamic response. In contrast to the other works where nonlinear mathematical models with some complexities are proposed to mathematically model the real systems, the present study illustrates the applicability of employing simple models to predict the dynamic response of a real rotor-system with an acceptable accuracy.

关键词： rotor-dynamics     Jeffcott rotor     lateral vibrations     Lagrange method     system-equivalent stiffness     sleeve bearings     oil film induced stiffness    

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Deformation control criterion of shield tunnel under lateral relaxation of soft soil

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 780-795 doi: 10.1007/s11709-023-0944-3

摘要： Metro shield tunnels under the lateral relaxation of soil (LRS) are susceptible to significant lateral deformations, which jeopardizes the structural safety and waterproofing. However, deformation control standards for such situations have not been clearly defined. Therefore, based on a specific case, a model test is conducted to realize the LRS of a shield tunnel in a sandy stratum to reveal its effect on segment liners. Subsequently, a deformation control criterion is established. The LRS is simulated by linearly reducing the loads applied to the lateral sides of the segment structure. During lateral unloading, the lateral earth pressure coefficient on the segment decreases almost exponentially, and the structural deformation is characterized by horizontal expansion at the arch haunches and vertical shrinkage at the arch vault and arch bottom. Based on the mechanical pattern of the segment structure and the acoustic emission, the deformation response of a segment can be classified into three stages: elastic and quasi-elastic, damage, and rapid deformation development. For a shield tunnel with a diameter of approximately 6 m and under the lateral relaxation of sandy soil, when the ellipticity of the segment is less than 2.71%, reinforcement measures are not required. However, the segment deformation must be controlled when the ellipticity is 2.71% to 3.12%; in this regard, an ellipticity of 3% can be used as a benchmark in similar engineering projects.

关键词： shield tunnel     lateral relaxation of soil     deformation control criterion of segment structure     model test    

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Torsional vibrations of a cylindrical foundation embedded in a saturated poroelastic half-space

Dazhi WU,Lu YU

《结构与土木工程前沿（英文）》 2015年 第9卷 第2期   页码 194-202 doi: 10.1007/s11709-015-0292-z

摘要： Considering the interactions between an embedded foundation and saturated soil, the torsional vibrations of a cylindrical foundation embedded in a saturated poroelastic medium are analyzed in this paper. Both a rigid foundation and an elastic foundation are considered. Assuming both the side surface and the bottom surface of the foundation are perfectly bonded to soil, the reaction torques that the side soil and bottom soil acting on the foundation can be gained from basic dynamic equations of the poroelastic medium. According to the dynamic equilibrium equations of a foundation under harmonic torque, the torsional vibrations of an embedded cylindrical foundation are presented. Besides, the angular amplitude of the foundation, the equivalent stiffness and damping coefficients of the soil are expressed explicitly. Selected examples are presented to investigate the influence of relevant parameters on the torsional vibrations.

关键词： embedded foundation     saturated soil     rigid foundation     elastic foundation     torsional vibration    

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Association of gene variants with juvenile amyotrophic lateral sclerosis

《医学前沿（英文）》 doi: 10.1007/s11684-023-1005-y

摘要： Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive degeneration of motor neurons, and it demonstrates high clinical heterogeneity and complex genetic architecture. A variation within TRMT2B (c.1356G>T; p.K452N) was identified to be associated with ALS in a family comprising two patients with juvenile ALS (JALS). Two missense variations and one splicing variation were identified in 10 patients with ALS in a cohort with 910 patients with ALS, and three more variants were identified in a public ALS database including 3317 patients with ALS. A decreased number of mitochondria, swollen mitochondria, lower expression of ND1, decreased mitochondrial complex I activities, lower mitochondrial aerobic respiration, and a high level of ROS were observed functionally in patient-originated lymphoblastoid cell lines and TRMT2B interfering HEK293 cells. Further, TRMT2B variations overexpression cells also displayed decreased ND1. In conclusion, a novel JALS-associated gene called TRMT2B was identified, thus broadening the clinical and genetic spectrum of ALS.

关键词： TRMT2B     amyotrophic lateral sclerosis     mitochondrial complex I     tRNA methylation     reactive oxygen species    

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Model testing of tripod caisson foundations in silty clay subjected to eccentric lateral loads

《结构与土木工程前沿（英文）》 2023年 第17卷 第3期   页码 467-476 doi: 10.1007/s11709-023-0933-6

摘要： In this study, model tests were conducted to investigate the bearing capacities of tripod caisson foundations subjected to eccentric lateral loads in silty clay. Lateral load–rotation curves of five eccentric-shaped tripod suction foundations were plotted to analyze the bearing capacities at different loading angles. It was observed that the loading angle significantly influenced the bearing capacity of the foundations, particularly for eccentric tripod caisson foundations. Compared with eccentric tripod caisson foundations, the traditional tripod foundation has a relatively high ultimate lateral capacity at the omnidirectional loading angle. By analyzing the displacement of the caissons, a formula for the rotational center of the tripod caisson foundation subjected to an eccentric lateral load was derived. The depth of the rotation center was 0.68–0.92 times the height of the caisson when the bearing capacity reached the limit. Under the undrained condition, suction was generated under the lid of the “up-lift” caisson, which helps resist lateral forces from the wind and waves.

关键词： tripod caisson foundation     silty clay     eccentric lateral capacity     model tests    

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Environmental problems of vibrations induced by railway traffic

XIA He, CAO Yanmei, De Roeck Guido, Degrande Geert

《结构与土木工程前沿（英文）》 2007年 第1卷 第2期   页码 142-152 doi: 10.1007/s11709-007-0015-1

摘要： In this paper, a general review is made on the problems of vibrations of the ground and nearby buildings induced by railway traffic, and on the researches on this subject in theoretical analyses, numerical simulations, and field experiments. The characteristics of ground vibrations induced by railway traffic and their propagation, from the aspects of duration, intensity distribution, vehicle load and speed, are summarized. The vibration influences on the daily life of people, the operation of high-tech devices and the safety of buildings, and the vibration properties of subsoil and buildings adjacent to the underground, ground and elevated railway systems are introduced.

关键词： underground     vibration     numerical     subsoil     propagation    

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Increased expression of coronin-1a in amyotrophic lateral sclerosis: a potential diagnostic biomarker

《医学前沿（英文）》 2022年 第16卷 第5期   页码 723-735 doi: 10.1007/s11684-021-0905-y

摘要： Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease. At present, no definite ALS biomarkers are available. In this study, exosomes from the plasma of patients with ALS and healthy controls were extracted, and differentially expressed exosomal proteins were compared. Among them, the expression of exosomal coronin-1a (CORO1A) was 5.3-fold higher than that in the controls. CORO1A increased with disease progression at a certain proportion in the plasma of patients with ALS and in the spinal cord of ALS mice. CORO1A was also overexpressed in NSC-34 motor neuron-like cells, and apoptosis, oxidative stress, and autophagic protein expression were evaluated. CORO1A overexpression resulted in increased apoptosis and oxidative stress, overactivated autophagy, and hindered the formation of autolysosomes. Moreover, CORO1A activated Ca2+-dependent phosphatase calcineurin, thereby blocking the fusion of autophagosomes and lysosomes. The inhibition of calcineurin activation by cyclosporin A reversed the damaged autolysosomes. In conclusion, the role of CORO1A in ALS pathogenesis was discovered, potentially affecting the disease onset and progression by blocking autophagic flux. Therefore, CORO1A might be a potential biomarker and therapeutic target for ALS.

关键词： amyotrophic lateral sclerosis     coronin-1a     autophagy     pathogenesis    

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Running train induced vibrations and noises of elevated railway structures and their influences on environment

He XIA, Fei GAO, Xuan WU, Nan ZHANG, Guido DE ROECK, Geert DEGRANDE

《结构与土木工程前沿（英文）》 2009年 第3卷 第1期   页码 9-17 doi: 10.1007/s11709-009-0010-9

摘要： The vibrations and noises of elevated railway structures have been cause for concern due to their effects on the environment and the people living near elevated lines. In this paper, the main structural features of some new elevated bridges and station hall were introduced. The generation mechanism of vibrations and noise of elevated structures induced by trains were investigated. The noise induced by different types of elevated bridges, their influences on the environment and the theoretical method for the analysis of structure borne noise was analyzed. Finally, several field measurements on train induced noises at the platforms of elevated subway stations and bridges were presented.

关键词： railway     elevated structure     bridge     station     vibration     noise     environment    

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efficiency optimization and Sobol’s sensitivity indices of MTMDs design parameters for buffeting and flutter vibrations

Nazim Abdul NARIMAN

《结构与土木工程前沿（英文）》 2017年 第11卷 第1期   页码 66-89 doi: 10.1007/s11709-016-0356-8

摘要： This paper studies optimization of three design parameters (mass ratio, frequency ratio and damping ratio) of multiple tuned mass dampers MTMDs that are applied in a cable stayed bridge excited by a strong wind using minimax optimization technique. ABAQUS finite element program is utilized to run numerical simulations with the support of MATLAB codes and Fast Fourier Transform FFT technique. The optimum values of these three parameters are validated with two benchmarks from the literature, first with Wang and coauthors and then with Lin and coauthors. The validation procedure detected a good agreement between the results. Box-Behnken experimental method is dedicated to formulate the surrogate models to represent the control efficiency of the vertical and torsional vibrations. Sobol’s sensitivity indices are calculated for the design parameters in addition to their interaction orders. The optimization results revealed better performance of the MTMDs in controlling the vertical and the torsional vibrations for higher mode shapes. Furthermore, the calculated rational effects of each design parameter facilitate to increase the control efficiency of the MTMDs in conjunction with the support of the surrogate models.

关键词： MTMDs     power spectral density     fast Fourier transform     minimax optimization technique     Sobol’s sensitivity indices     Box-Behnken method    

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Optimum lateral extent of soil domain for dynamic SSI analysis of RC framed buildings on pile foundations

Nishant SHARMA, Kaustubh DASGUPTA, Arindam DEY

《结构与土木工程前沿（英文）》 2020年 第14卷 第1期   页码 62-81 doi: 10.1007/s11709-019-0570-2

摘要： This article describes a novel approach for deciding optimal horizontal extent of soil domain to be used for finite element based numerical dynamic soil structure interaction (SSI) studies. SSI model for a 12 storied building frame, supported on pile foundation-soil system, is developed in the finite element based software framework, OpenSEES. Three different structure-foundation configurations are analyzed under different ground motion characteristics. Lateral extent of soil domain, along with the soil properties, were varied exhaustively for a particular structural configuration. Based on the reduction in the variation of acceleration response at different locations in the SSI system (quantified by normalized root mean square error, ), the optimum lateral extent of the soil domain is prescribed for various structural widths, soil types and peak ground acceleration levels of ground motion. Compared to the past studies, error estimation analysis shows that the relationships prescribed in the present study are credible and more inclusive of the various factors that influence SSI. These relationships can be readily applied for deciding upon the lateral extent of the soil domain for conducting precise SSI analysis with reduced computational time.

关键词： soil structure interaction     optimum lateral extent of soil domain length     multi-storyed framed building     pile foundation     OpenSEES     L-K boundaries     dynamic analysis    

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Response of basement wall in tall buildings foundation under lateral loading

Irfan JAMIL; Irshad AHMAD; Aqeel Ur REHMAN; Aqib AHMED; Ameer HAMZA; Wali ULLAH

《结构与土木工程前沿（英文）》 2022年 第16卷 第11期   页码 1415-1423 doi: 10.1007/s11709-022-0885-2

摘要： With increasing population and limitation of availability of land, tall buildings supported on piled raft foundations are increasingly used in the modern world. To increase the ratio of floor area to height, and to fulfill storage and parking facilities requirements, these tall buildings usually have more than one basement level. Conventionally, during the foundation design, engineers have not considered the basement wall contribution to resisting lateral load induced by earthquake or wind and this can result in an uneconomical construction of foundations. In this research work, an experimental study was performed on small-scale models, in order to study basement wall contribution, and the raft contribution including for piled raft foundations, to resisting lateral load. Three configurations of piles in 2 × 2, 2 × 3, and 3 × 3 patterns were tested as a pile group, piled raft and piled raft with a basement wall. Results show that when a basement wall is present, the lateral displacement decreases and the demand on each pile decreases. The piled raft design can become more economical for tall buildings if the basement’s walls are taken into account.

关键词： basement wall     lateral load     displacement     piled raft    

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Evaluation of liquefaction-induced lateral displacement using Bayesian belief networks

Mahmood AHMAD, Xiao-Wei TANG, Jiang-Nan QIU, Feezan AHMAD

《结构与土木工程前沿（英文）》 2021年 第15卷 第1期   页码 80-98 doi: 10.1007/s11709-021-0682-3

摘要： Liquefaction-induced lateral displacement is responsible for considerable damage to engineered structures during major earthquakes. Therefore, an accurate estimation of lateral displacement in liquefaction-prone regions is an essential task for geotechnical experts for sustainable development. This paper presents a novel probabilistic framework for evaluating liquefaction-induced lateral displacement using the Bayesian belief network (BBN) approach based on an interpretive structural modeling technique. The BBN models are trained and tested using a wide-range case-history records database. The two BBN models are proposed to predict lateral displacements for free-face and sloping ground conditions. The predictive performance results of the proposed BBN models are compared with those of frequently used multiple linear regression and genetic programming models. The results reveal that the BBN models are able to learn complex relationships between lateral displacement and its influencing factors as cause–effect relationships, with reasonable precision. This study also presents a sensitivity analysis to evaluate the impacts of input factors on the lateral displacement.

关键词： Bayesian belief network     seismically induced soil liquefaction     interpretive structural modeling     lateral displacement    

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Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent

Xiaoliang MENG, Ledong ZHU, Zhenshan GUO

《结构与土木工程前沿（英文）》 2011年 第5卷 第4期   页码 510-517 doi: 10.1007/s11709-011-0129-3

摘要： By examining the two neighboring Haihe Bridges with semi- and full-closed bridge decks, the aerodynamic interference between the two decks on the vortex-induced vibration (VIV) and the corresponding aerodynamic mitigation measures are investigated via a series of wind tunnel tests with a spring-suspended sectional model aided with computational fluid dynamics (CFD) method. The results show that the VIV responses of both bridges can be significantly affected by the aerodynamic interference and that the extent of the influence varies with the shapes of the windward and leeward decks. The VIV amplitudes of the windward bridge are often fairly close to those of the single bridge. However, those of the leeward bridge are magnified substantially by aerodynamic interference if the same structural and aerodynamic configurations are adopted for the two bridges. Otherwise, the VIV responses are not significantly increased and may even be reduced by the aerodynamic interference if different configurations are employed for the two bridges. Furthermore, an effective combined measure of adding wind barriers and sharpening the wind fairing noses of the two box decks is presented for mitigating both the vertical and torsional VIV responses of the windward and leeward bridges.

关键词： separated parallel decks     vortex-induced vibration     aerodynamic interference     aerodynamic mitigation measure     semi-closed box deck     full-closed box deck    

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Vehicle-bridge coupled vibrations in different types of cable stayed bridges

Lingbo WANG,Peiwen JIANG,Zhentao HUI,Yinping MA,Kai LIU,Xin KANG

《结构与土木工程前沿（英文）》 2016年 第10卷 第1期   页码 81-92 doi: 10.1007/s11709-015-0306-x

摘要： Numerical analyses of the coupled vibrations of vehicle-bridge system and the effects of different types of cable stayed bridges on the coupled vibration responses have been presented in this paper using ANSYS. The bridge model and vehicle model were independently built which have no internal relationship in the ANSYS. The vehicle-bridge coupled vibration relationship was obtained by using the APDL program which subsequently imposed on the vehicle and bridge models during the numerical analysis. The proposed model was validated through a field measurements and literature data. The judging method, possibility, and criterion of the vehicle-bridge resonance (coupled vibrations) of cable stayed bridges (both the floating system and half floating system) under traffic flows were presented. The results indicated that the interval time between vehicles is the main influence factor on the resonance excitation frequency under the condition of equally spaced traffic flows. Compared to other types of cable stayed bridges, the floating bridge system has relatively high possibility to cause vehicle-bridge resonance.

关键词： vehicle-bridge coupled vibration     cable stayed bridge     resonances of vehicle-bridge system    

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Lateral displacement of soft ground under vacuum pressure and surcharge load

Chin-Yee ONG, Jin-Chun CHAI

《结构与土木工程前沿（英文）》 2011年 第5卷 第2期   页码 239-248 doi: 10.1007/s11709-011-0110-1

摘要： Surcharge load (e.g. embankment fill) will induce settlement and outward lateral displacement, while vacuum pressure will induce settlement and inward lateral displacement of a ground. Ideally, combination of surcharge load and vacuum pressure can reduce or minimize the lateral displacement. Laboratory large scale model (length: 1.50 m, width: ~0.62 m, height: 0.85 m) tests and finite element analyses (FEA) were conducted to investigate the main influencing factors on lateral displacement of a soft clayey ground under the combination of vacuum pressure and surcharge load. For the conditions investigated, the results indicate that the outward lateral displacement increases with the increase of the ratio of surcharge load to vacuum pressure ( ) and the loading rate of the surcharge load ( ). Also, it is shown that for a given and condition, lateral displacement reduces with the increase of the initial undrained shear strength ( ) of the ground. To predict the lateral displacement of a ground under the combination of surcharge load and vacuum pressure, the loading conditions in terms of and , and value of the ground have to be considered.

关键词： vacuum consolidation     lateral displacement     PVD     finite element analysis     surcharge load    

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标题 作者 时间 类型 操作

Experimental and theoretical investigations of the lateral vibrations of an unbalanced Jeffcott rotor

Ali ALSALEH, Hamid M. SEDIGHI, Hassen M. OUAKAD

期刊论文

Deformation control criterion of shield tunnel under lateral relaxation of soft soil

期刊论文

Torsional vibrations of a cylindrical foundation embedded in a saturated poroelastic half-space

Dazhi WU,Lu YU

期刊论文

Association of gene variants with juvenile amyotrophic lateral sclerosis

期刊论文

Model testing of tripod caisson foundations in silty clay subjected to eccentric lateral loads

期刊论文

Environmental problems of vibrations induced by railway traffic

XIA He, CAO Yanmei, De Roeck Guido, Degrande Geert

期刊论文

Increased expression of coronin-1a in amyotrophic lateral sclerosis: a potential diagnostic biomarker

期刊论文

Running train induced vibrations and noises of elevated railway structures and their influences on environment

He XIA, Fei GAO, Xuan WU, Nan ZHANG, Guido DE ROECK, Geert DEGRANDE

期刊论文

efficiency optimization and Sobol’s sensitivity indices of MTMDs design parameters for buffeting and flutter vibrations

Nazim Abdul NARIMAN

期刊论文

Optimum lateral extent of soil domain for dynamic SSI analysis of RC framed buildings on pile foundations

Nishant SHARMA, Kaustubh DASGUPTA, Arindam DEY

期刊论文

Response of basement wall in tall buildings foundation under lateral loading

Irfan JAMIL; Irshad AHMAD; Aqeel Ur REHMAN; Aqib AHMED; Ameer HAMZA; Wali ULLAH

期刊论文

Evaluation of liquefaction-induced lateral displacement using Bayesian belief networks

Mahmood AHMAD, Xiao-Wei TANG, Jiang-Nan QIU, Feezan AHMAD

期刊论文

Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent

Xiaoliang MENG, Ledong ZHU, Zhenshan GUO

期刊论文

Vehicle-bridge coupled vibrations in different types of cable stayed bridges

Lingbo WANG,Peiwen JIANG,Zhentao HUI,Yinping MA,Kai LIU,Xin KANG

期刊论文

Lateral displacement of soft ground under vacuum pressure and surcharge load

Chin-Yee ONG, Jin-Chun CHAI

期刊论文