Search | Engineering

订阅投稿

首页工程期刊工程焦点工程成就工程前沿关于我们 English

资源类型

期刊论文 333

会议视频 9

年份

2023 24

2022 41

2021 37

2020 40

2019 14

2018 14

2017 13

2016 18

2015 22

2014 16

2013 12

2012 18

2011 15

2010 10

2009 7

2008 8

2007 8

2006 3

2005 4

2004 2

展开︾

关键词

环境 5

农业科学 4

横沙东滩 3

人工神经网络 2

土壤 2

基质吸力 2

微波遥感 2

抗生素 2

膨胀土 2

重金属 2

风化砂 2

Cas12a 1

DX桩 1

Lagrangian松弛 1

McCormick包络 1

SWAT模型 1

上海港 1

中断模型；k-可靠性；对偶；线性规划松弛；互补松弛型 1

互花米草 1

展开︾

检索范围：

排序：展示方式：

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

HTML PDF 收藏

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

HTML PDF 收藏

Seismic effects on reinforcement load and lateral deformation of geosynthetic-reinforced soil walls

《结构与土木工程前沿（英文）》 2021年第15卷第4期页码 1001-1015 doi: 10.1007/s11709-021-0734-8

摘要： Current design methods for the internal stability of geosynthetic-reinforced soil (GRS) walls postulate seismic forces as inertial forces, leading to pseudo-static analyses based on active earth pressure theory, which yields unconservative reinforcement loads required for seismic stability. Most seismic analyses are limited to the determination of maximum reinforcement strength. This study aimed to calculate the distribution of the reinforcement load and connection strength required for each layer of the seismic GRS wall. Using the top-down procedure involves all of the possible failure surfaces for the seismic analyses of the GRS wall and then obtains the reinforcement load distribution for the limit state. The distributions are used to determine the required connection strength and to approximately assess the facing lateral deformation. For sufficient pullout resistance to be provided by each reinforcement, the maximum required tensile resistance is identical to the results based on the Mononobe–Okabe method. However, short reinforcement results in greater tensile resistances in the mid and lower layers as evinced by compound failure frequently occurring in GRS walls during an earthquake. Parametric studies involving backfill friction angle, reinforcement length, vertical seismic acceleration, and secondary reinforcement are conducted to investigate seismic impacts on the stability and lateral deformation of GRS walls.

关键词： geosynthetics reinforced soil retaining walls seismic performance

HTML PDF 收藏

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

HTML PDF 收藏

Finding buckling points for nonlinear structures by dynamic relaxation scheme

Mohammad REZAIEE-PAJAND, Hossein ESTIRI

《结构与土木工程前沿（英文）》 2020年第14卷第1期页码 23-61 doi: 10.1007/s11709-019-0549-z

摘要： Dynamic Relaxation Method (DRM) is an explicit approach for solving the simultaneous systems of equations. In this tactic, the fictitious mass and damping are added to the static governing equations, and an artificial dynamic system is constructed. By using DRM for nonlinear analysis, the structural static equilibrium path is obtained. This outcome is extremely valuable, since it leads to the behavior of structures. Among the finding related to the structural static path are the critical and buckling points for nonlinear structures. In this paper, a new way for calculating the load factor is proposed by setting the external work zero. Mixing the dynamic relaxation scheme with external work technique has not been formulated so far. In all incremental-iterative methods, the load factor increment sign should be determinated by extra calculations. This sign leads to increase or decrease of the load increment. It is worth emphasizing that sign of the load factor increment changes at the load limit points. Therefore, the sign determinations are required in the common work control methods. These disadvantages are eliminated in the proposed algorithm. In fact, the suggested load factor depends only on the Dynamic Relaxation (DR) fictitious parameters. Besides, all DR calculations are performed via vector operation. Moreover, the load factor is calculated only by one formula, and it has the same relation in the all solution processes. In contrast to the arc length techniques, which requires the sign determined, the proposed scheme does not need any sign finding. It is shown that author’s technique is quicker than the other dynamic relaxation strategies. To prove the capability and efficiency of the presented scheme, several numerical tests are performed. The results indicate that the suggested approach can trace the complex structural static paths, even in the snap-back and snap-through parts.

关键词： load factor external work dynamic relaxation static equilibrium path large displacement

HTML PDF 收藏

Nonlinear analysis of cable structures using the dynamic relaxation method

Mohammad REZAIEE-PAJAND, Mohammad MOHAMMADI-KHATAMI

《结构与土木工程前沿（英文）》 2021年第15卷第1期页码 253-274 doi: 10.1007/s11709-020-0639-y

摘要： The analysis of cable structures is one of the most challenging problems for civil and mechanical engineers. Because they have highly nonlinear behavior, it is difficult to find solutions to these problems. Thus far, different assumptions and methods have been proposed to solve such structures. The dynamic relaxation method (DRM) is an explicit procedure for analyzing these types of structures. To utilize this scheme, investigators have suggested various stiffness matrices for a cable element. In this study, the efficiency and suitability of six well-known proposed matrices are assessed using the DRM. To achieve this goal, 16 numerical examples and two criteria, namely, the number of iterations and the analysis time, are employed. Based on a comprehensive comparison, the methods are ranked according to the two criteria. The numerical findings clearly reveal the best techniques. Moreover, a variety of benchmark problems are suggested by the authors for future studies of cable structures.

关键词： nonlinear analysis cable structure stiffness matrix dynamic relaxation method

HTML PDF 收藏

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

HTML PDF 收藏

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

HTML PDF 收藏

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

HTML PDF 收藏

A fast and accurate dynamic relaxation scheme

Mohammad REZAIEE-PAJAND, Mohammad MOHAMMADI-KHATAMI

《结构与土木工程前沿（英文）》 2019年第13卷第1期页码 176-189 doi: 10.1007/s11709-018-0486-2

摘要： Dynamic relaxation method (DRM) is one of the suitable numerical procedures for nonlinear structural analysis. Adding the fictitious inertia and damping forces to the static equation, and turning it to the dynamic system, are the basis of this technique. Proper selection of the DRM artificial factors leads to the better convergence rate and efficient solutions. This study aims to increase the numerical stability, and to decrease the analysis time. To fulfil this objective, the reduction rate of analysis error for consecutive iterations is minimized. Based on this formulation, a new time step is found for the viscous dynamic relaxation. After combining this novel relationship with the other DRM factors, various geometrical nonlinear structures, such as, trusses, frames and shells are analyzed. The obtained results verify the efficiency of authors’ scheme.

关键词： viscous dynamic relaxation time step displacement error geometric nonlinear analysis

HTML PDF 收藏

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

HTML PDF 收藏

The stress relaxation of cement clinkers under high temperature

Xiufang WANG,Yiwang BAO,Xiaogen LIU,Yan QIU

《机械工程前沿（英文）》 2015年第10卷第4期页码 413-417 doi: 10.1007/s11465-015-0357-7

摘要：

The energy consumption of crushing is directly affected by the mechanical properties of cement materials. This research provides a theoretical proof for the mechanism of the stress relaxation of cement clinkers under high temperature. Compression stress relaxation under various high temperatures is discussed using a specially developed load cell, which can measure stress and displacement under high temperatures inside an autoclave. The cell shows that stress relaxation dramatically increases and that the remaining stress rapidly decreases with an increase in temperature. Mechanical experiments are conducted under various temperatures during the cooling process to study the changes in the grinding resistance of the cement clinker with temperature. The effects of high temperature on the load-displacement curve, compressive strength, and elastic modulus of cement clinkers are systematically studied. Results show that the hardening phenomenon of the clinker becomes apparent with a decrease in temperature and that post-peak behaviors manifest characteristics of the transformation from plasticity to brittleness. The elastic modulus and compressive strength of cement clinkers increase with a decrease in temperature. The elastic modulus increases greatly when the temperature is lower than 1000 °C. The compressive strength of clinkers increases by 73.4% when the temperature drops from 1100 to 800 °C.

关键词： stress relaxation high temperature cement clinker compression elastic modulus

HTML PDF 收藏

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

HTML PDF 收藏

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

HTML PDF 收藏

Numerical investigation of the ultimate lateral resistance of piles in soft clay

Konstantinos P. TZIVAKOS,Michael J. KAVVADAS

《结构与土木工程前沿（英文）》 2014年第8卷第2期页码 194-200 doi: 10.1007/s11709-014-0251-0

摘要： The paper presents a numerical study on the undrained lateral response of a single, free-head, reinforced concrete pile in soft clays. Soil conditions simulating normally consolidated clays are examined—undrained shear strength increasing with depth—and the pile-soil interaction under static lateral loading is analyzed. The nonlinear ? curves proposed in literature for soft clays are imported into a beam-on-nonlinear-Winkler-foundation simulation in order to predict the pile head lateral load—displacement curve and the distribution of the horizontal displacement and bending moment along the pile. The striking differences among these methods require further investigation via 3D finite element analyses. The determination of the ultimate soil resistance from the results of the finite element analyses aims at providing the estimation of a range of values for the ultimate soil resistance coefficient with depth and the comparison of the derived values to the corresponding ones proposed by existing methodologies.

关键词： laterally loaded pile soft clay p?y curves finite element method (FEM)