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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    

Lateral-torsional buckling capacity assessment of web opening steel girders by artificial neural networks

Yasser SHARIFI,Sajjad TOHIDI

《结构与土木工程前沿(英文)》 2014年 第8卷 第2期   页码 167-177 doi: 10.1007/s11709-014-0236-z

摘要: Bridge girders exposed to aggressive environmental conditions are subject to time-variant changes in resistance. There is therefore a need for evaluation procedures that produce accurate predictions of the load-carrying capacity and reliability of bridge structures to allow rational decisions to be made about repair, rehabilitation and expected life-cycle costs. This study deals with the stability of damaged steel I-beams with web opening subjected to bending loads. A three-dimensional (3D) finite element (FE) model using ABAQUS for the elastic flexural torsional analysis of I-beams has been used to assess the effect of web opening on the lateral buckling moment capacity. Artificial neural network (ANN) approach has been also employed to derive empirical formulae for predicting the lateral-torsional buckling moment capacity of deteriorated steel I-beams with different sizes of rectangular web opening using obtained FE results. It is found out that the proposed formulae can accurately predict residual lateral buckling capacities of doubly-symmetric steel I-beams with rectangular web opening. Hence, the results of this study can be used for better prediction of buckling life of web opening of steel beams by practice engineers.

关键词: steel I-beams     lateral-torsional buckling     finite element (FE) method     artificial neural network (ANN) approach    

Experimental research on self-stressing and self-compacting concrete filled steel tube columns subjected to eccentric

Chengkui HUANG, Zuoqing SHANG, Peng ZHANG,

《结构与土木工程前沿(英文)》 2009年 第3卷 第4期   页码 455-461 doi: 10.1007/s11709-009-0058-6

摘要: A total of fifteen self-stressing and self-compacting concrete (SSC) filled steel tube columns and three common self-compacting concrete filled steel tube (CFST) columns are tested under eccentric compression load to analyze the effect of initial self-stress on the compression behavior of CFSTs. The results show that the elastic working range of the columns is lengthened because of initial self-stress and it slightly decreases with the increase of load eccentricity ratio and slenderness ratio. Because of the initial self-stress, the concrete core is always under compression in three directions, so the compactness is enhanced and the ultimate bearing capacity obviously increases; but the initial self-stress hardly affects the failure mode of the columns.

关键词: increase     capacity     failure     CFSTs     CFST    

Lateral shear performance of sheathed post-and-beam wooden structures with small panels

《结构与土木工程前沿(英文)》   页码 1117-1131 doi: 10.1007/s11709-023-0939-0

摘要: Sheathed post-and-beam wooden structures are distinct from light-wood structures. They allow for using sheathing panels that are smaller (0.91 m × 1.82 m) than standard-sized panels (1.22 m × 2.44 m or 2.44 m × 2.44 m). Evidence indicates that nail spacing and panel thickness determine the lateral capacity of the wood frame shear walls. To verify the lateral shear performance of wood frame shear walls with smaller panels, we subjected 13 shear walls, measuring 0.91 m in width and 2.925 m in height, to a low-cycle cyclic loading test with three kinds of nail spacing and three panel thicknesses. A nonlinear numerical simulation analysis of the wall was conducted using ABAQUS finite element (FE) software, where a custom nonlinear spring element was used to simulate the sheathing-frame connection. The results indicate that the hysteretic performance of the walls was mainly determined by the hysteretic performance of the sheathing-frame connection. When same nail specifications were adopted, the stiffness and bearing capacity of the walls were inversely related to the nail spacing and directly related to the panel thickness. The shear wall remained in the elastic stage when the drift was 1/250 rad and ductility coefficients were all greater than 2.5, which satisfied the deformation requirements of residential structures. Based on the test and FE analysis results, the shear strength of the post-and-beam wooden structures with sheathed walls was determined.

关键词: post-and-beam wooden structures with sheathed walls     low reversed cyclic loading     bearing capacity     stiffness     numerical simulation    

Influence of steel corrosion on axial and eccentric compression behavior of coral aggregate concrete

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1415-1425 doi: 10.1007/s11709-021-0786-9

摘要: To study the behavior of coral aggregate concrete (CAC) column under axial and eccentric compression, the compression behavior of CAC column with different types of steel and initial eccentricity (ei) were tested, and the deformation behavior and ultimate bearing capacity (Nu) were studied. The results showed that as the ei increases, the Nu of CAC column decreases nonlinearly. Besides, the steel corrosion in CAC column is severe, which reduces the steel section and steel strength, and decreases the Nu of CAC column. The durability of CAC structures can be improved by using new organic coated steel. Considering the influence of steel corrosion and interfacial bond deterioration, the calculation models of Nu under axial and eccentric compression were presented.

关键词: coral aggregate concrete column     axial compression     eccentric compression     steel corrosion     calculation model    

Stress-strain relationship of recycled self-compacting concrete filled steel tubular column subjected to eccentric

Feng YU, Cheng QIN, Shilong WANG, Junjie JIANG, Yuan FANG

《结构与土木工程前沿(英文)》 2020年 第14卷 第3期   页码 760-772 doi: 10.1007/s11709-020-0618-3

摘要: As a typical compression member, the concrete-filled steel tube has been widely used in civil engineering structures. However, little research on recycled self-compacting concrete filled circular steel tubular (RSCCFCST) columns subjected to eccentric load was reported. In this study, 21 specimens were designed and experimental studies on the stress-strain relationship of were carried out to study the mechanical behaviors. Recycled coarse aggregate replacement ratio, concrete strength grade, length to diameter ratio and eccentric distance of specimens were considered as the main experimental parameters to carry out eccentric compression tests. The corresponding stress-strain relationship curves were used to analyze the influence of concerned parameters on eccentric load-bearing capacity of RSCCFCST columns. The experimental results show that the strain of the eccentric compression stress-strain curves increase with the increase of recycled coarse aggregate replacement ratio and concrete strength grade. With increase of eccentric distance, the ductility of specimens increases while the bearing capacity decreases. Moreover, a phenomenological model of RSCCFCST columns is proposed, which exhibits versatile ability to capture the process during loading. The present study is expected to further understanding the behaviors and to provide guidance of RSCCFCST columns in design and engineering applications.

关键词: concrete filled circular steel tubular columns     recycled self-compacting concrete     eccentric compression     recycled coarse aggregate replacement ratio     stress-strain relationship    

Variable eccentric distance-based tool path generation for orthogonal turn-milling

Fangyu PENG,Wei WANG,Rong YAN,Xianyin DUAN,Bin LI

《机械工程前沿(英文)》 2015年 第10卷 第4期   页码 352-366 doi: 10.1007/s11465-015-0361-y

摘要:

This study proposes an algorithm for maximizing strip width in orthogonal turn-milling based on variable eccentric distance. The machining error model is first established based on the local cutting profile at the contact line. The influencing factors of the strip width are then investigated to analyze their features and determine an optimizing strategy. The optimized model for maximum machining strip width is formulated by adopting a variable eccentric distance. Hausdorff distance and Fréchet distance are introduced in this study to implement the constraint function of the machining error in the optimized model. The computing procedure is subsequently provided. Simulations and experiments have been conducted to verify the effectiveness of the proposed algorithm.

关键词: orthogonal turn-milling     variable eccentric distance     local cutting profile     machining strip-width maximization    

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    

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    

Behaviors of recycled aggregate concrete-filled steel tubular columns under eccentric loadings

Vivian W. Y. TAM, Jianzhuang XIAO, Sheng LIU, Zixuan CHEN

《结构与土木工程前沿(英文)》 2019年 第13卷 第3期   页码 628-639 doi: 10.1007/s11709-018-0501-7

摘要: The paper investigates the behaviors of recycled aggregate concrete-filled steel tubular (RACFST) columns under eccentric loadings with the incorporation of expansive agents. A total of 16 RACFST columns were tested in this study. The main parameters varied in this study are recycled coarse aggregate replacement percentages (0%, 30%, 50%, 70%, and 100%), expansive agent dosages (0%, 8%, and 15%) and an eccentric distance of compressive load from the center of the column (0 and 40 mm). Experimental results showed that the ultimate stresses of RACFST columns decreased with increasing recycled coarse aggregate replacement percentages but appropriate expansive agent dosages can reduce the decrement; the incorporation of expansive agent decreased the ultimate stresses of RACFST columns but an appropriate dosage can increase the deformation ability. The recycled coarse aggregate replacement percentages have limited influence on the ultimate stresses of the RACFST columns and has more effect than that of the normal aggregate concrete-filled steel tubular columns.

关键词: concrete filled steel tubes     recycled aggregate concrete     columns     expansive agent     eccentric load    

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    

Displacement and force analyses of piles in the pile-caisson composite structure under eccentric inclined

《结构与土木工程前沿(英文)》 doi: 10.1007/s11709-023-0957-y

摘要: A novel anchorage for long-span suspension bridges, called pile-caisson composite structures, was recently proposed by the authors in an attempt to reduce the construction period and costs. This study aims to investigate the displacement and force behavior of piles in a pile-caisson composite structure under eccentric inclined loading considering different stratum features. To this end, both 1g model tests and three-dimensional numerical simulations were performed. Two groups of 1g model tests were used to validate the finite-element (FE) method. Parametric studies were then performed to investigate the effects of groundwater level, burial depth of the pile-caisson composite structure, and distribution of soil layers on the performance of the pile-caisson composite structure. The numerical analyses indicated that the influence of the groundwater level on the stability of the caisson was much greater than that of the piles. In addition, increasing the burial depth of the pile-caisson composite structure can assist in reducing the displacements and improving the stability of the pile-caisson composite structure. In addition, the distribution of soil layers can significantly affect the stability of the pile-caisson composite structure, especially the soil layer around the caisson.

关键词: composite structure     piles     foundation     suspension bridge     1g model test     finite-element analysis    

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    

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    

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    

标题 作者 时间 类型 操作

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

期刊论文

Lateral-torsional buckling capacity assessment of web opening steel girders by artificial neural networks

Yasser SHARIFI,Sajjad TOHIDI

期刊论文

Experimental research on self-stressing and self-compacting concrete filled steel tube columns subjected to eccentric

Chengkui HUANG, Zuoqing SHANG, Peng ZHANG,

期刊论文

Lateral shear performance of sheathed post-and-beam wooden structures with small panels

期刊论文

Influence of steel corrosion on axial and eccentric compression behavior of coral aggregate concrete

期刊论文

Stress-strain relationship of recycled self-compacting concrete filled steel tubular column subjected to eccentric

Feng YU, Cheng QIN, Shilong WANG, Junjie JIANG, Yuan FANG

期刊论文

Variable eccentric distance-based tool path generation for orthogonal turn-milling

Fangyu PENG,Wei WANG,Rong YAN,Xianyin DUAN,Bin LI

期刊论文

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

期刊论文

Association of gene variants with juvenile amyotrophic lateral sclerosis

期刊论文

Behaviors of recycled aggregate concrete-filled steel tubular columns under eccentric loadings

Vivian W. Y. TAM, Jianzhuang XIAO, Sheng LIU, Zixuan CHEN

期刊论文

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

期刊论文

Displacement and force analyses of piles in the pile-caisson composite structure under eccentric inclined

期刊论文

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

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