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A novel finite element formulation for static bending analysis of functionally graded porous sandwich

Van Chinh NGUYEN; Trung Thanh TRAN; Trung NGUYEN-THOI; Quoc-Hoa PHAM

《结构与土木工程前沿(英文)》 2022年 第16卷 第12期   页码 1599-1620 doi: 10.1007/s11709-022-0891-4

摘要: This article aims to propose a finite element formulation based on Quasi-3D theory for the static bending analysis of functionally graded porous (FGP) sandwich plates. The FGP sandwich plates consist of three layers including the bottom skin of homogeneous metal, the top skin of fully ceramic and the FGP core layer with uneven porosity distribution. A quadrilateral (Q4) element with nine degrees of freedom (DOFs) per node is derived and employed in analyzing the static bending response of the plate under uniform and/or sinusoidally distributed loads. The accuracy of the present finite element formulation is verified by comparing the obtained numerical results with the published results in the literature. Then, some numerical examples are performed to examine the effects of the parameters including power-law index k and porosity coefficient ξ on the static bending response of rectangular FGP sandwich plates. In addition, a problem with a complicated L-shape model is conducted to illustrate the superiority of the proposed finite element method.

关键词: sandwich plates     functionally graded porous     static bending     Quasi-3D theory     Q4 element    

Static and dynamic analysis of functionally graded fluid-infiltrated porous skew and elliptical nanoplates

《结构与土木工程前沿(英文)》 2023年 第17卷 第3期   页码 477-502 doi: 10.1007/s11709-023-0918-5

摘要: The analysis of static bending and free and forced vibration responses of functionally graded fluid-infiltrated porous (FGFP) skew and elliptical nanoplates placed on Pasternak’s two-parameter elastic foundation is performed for the first time using isogeometric analysis (IGA) based on the non-uniform rational B-splines (NURBSs) basis function. Three types of porosity distributions affect the mechanical characteristics of materials: symmetric distribution, upper asymmetric distribution, and lower asymmetric distribution. The stress–strain relationship for Biot porous materials was determined using the elastic theory. The general equations of motion of the nanoplates were established using the four-unknown shear deformation plate theory in conjunction with the nonlocal elastic theory and Hamilton’s principle. A computer program that uses IGA to determine the static bending and free and forced vibration of a nanoplate was developed on MATLAB software platform. The accuracy of the computational program was validated via numerical comparison with confidence assertions. This set of programs presents the influence of the following parameters on the static bending and free and forced vibrations of nanoplates: porosity distribution law, porosity coefficient and geometrical parameters, elastic foundation, deviation angle, nonlocal coefficient, different boundary conditions, and Skempton coefficients. The numerical findings demonstrated the uniqueness of the FGFP plate’s behavior when the porosities are saturated with liquid compared with the case without liquid. The findings of this study have significant implications for engineers involved in the design and fabrication of the aforementioned type of structures. Furthermore, this can form the basis for future research on the mechanical responses of the structures.

关键词: static bending     free and forced vibrations     nonlocal theory     isogeometric analysis     fluid-infiltrated porous nanoplates    

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

《结构与土木工程前沿(英文)》 2023年 第17卷 第3期   页码 411-428 doi: 10.1007/s11709-023-0928-3

摘要: In this study, ultrahigh-performance fiber-reinforced concrete (UHPFRC) used in a type B70 concrete sleeper is investigated experimentally and parametrically. The main parameters investigated are the steel fiber volume fractions (0%, 0.5%, 1%, and 1.5%). Under European standards, 35 UHPFRC sleepers are subjected to static bending tests at the center and rail seat sections, and the screw on the fastening system is pulled out. The first cracking load, failure load, failure mode, crack propagation, load–deflection curve, load–crack width, and failure load from these tests are measured and compared with those of a control sleeper manufactured using normal concrete C50. The accuracy of the parametric study is verified experimentally. Subsequently, the results of the study are applied to UHPFRC sleepers with different concrete volumes to investigate the effects of the properties of UHPFRC on their performance. Experimental and parametric study results show that the behavior of UHPFRC sleepers improves significantly when the amount of steel fiber in the mix is increased. Sleepers manufactured using UHPFRC with a steel fiber volume fraction of 1% and a concrete volume less than 25% that of standard sleeper B70 can be used under the same loads and requirements, which contributes positively to the cost and surrounding environment.

关键词: pre-stressed concrete sleeper     ultrahigh performance fiber-reinforced concrete     pull-out test     static bending test     steel fiber     aspect ratio     volume fraction    

A new meshless approach for bending analysis of thin plates with arbitrary shapes and boundary conditions

《结构与土木工程前沿(英文)》 2022年 第16卷 第1期   页码 75-85 doi: 10.1007/s11709-021-0798-5

摘要: An efficient and meshfree approach is proposed for the bending analysis of thin plates. The approach is based on the choice of a set of interior points, for each of which a basis function can be defined. Plate deflection is then approximated as the linear combination of those basis functions. Unlike traditional meshless methods, present basis functions are defined in the whole domain and satisfy the governing differential equation for plate. Therefore, no domain integration is needed, while the unknown coefficients of deflection expression could be determined through boundary conditions by using a collocation point method. Both efficiency and accuracy of the approach are shown through numerical results of plates with arbitrary shapes and boundary conditions under various loads.

关键词: plate     bending     meshless method     collocation    

Improved prediction of pile bending moment and deflection due to adjacent braced excavation

《结构与土木工程前沿(英文)》 doi: 10.1007/s11709-023-0961-2

摘要: Deep excavations in dense urban areas have caused damage to nearby existing structures in numerous past construction cases. Proper assessment is crucial in the initial design stages. This study develops equations to predict the existing pile bending moment and deflection produced by adjacent braced excavations. Influential parameters (i.e., the excavation geometry, diaphragm wall thickness, pile geometry, strength and small-strain stiffness of the soil, and soft clay thickness) were considered and employed in the developed equations. It is practically unfeasible to obtain measurement data; hence, artificial data for the bending moment and deflection of existing piles were produced from well-calibrated numerical analyses of hypothetical cases, using the three-dimensional finite element method. The developed equations were established through a multiple linear regression analysis of the artificial data, using the transformation technique. In addition, the three-dimensional nature of the excavation work was characterized by considering the excavation corner effect, using the plane strain ratio parameter. The estimation results of the developed equations can provide satisfactory pile bending moment and deflection data and are more accurate than those found in previous studies.

关键词: pile responses     excavation     prediction     deflection     bending moments    

Damage detection in beam-like structures using static shear energy redistribution

《结构与土木工程前沿(英文)》 2022年 第16卷 第12期   页码 1552-1564 doi: 10.1007/s11709-022-0903-4

摘要: In this study, a static shear energy algorithm is presented for the damage assessment of beam-like structures. According to the energy release principle, the strain energy of a damaged element suddenly changes when structural damage occurs. Therefore, the change in the static shear energy is employed to determine the damage locations in beam-like structures. The static shear energy is derived from the spectral factorization of the elementary stiffness matrix and structural deflection variation. The advantage of using shear energy as opposed to total energy is that only a few deflection data points of the beam structure are required during the process of damage identification. Another advantage of the proposed approach is that damage detection can be performed without establishing a structural finite-element model in advance. The proposed technique is first validated using a numerical example with single, multiple, and adjacent damage scenarios. A channel steel beam and rectangular concrete beam are employed as experimental cases to further verify the proposed approach. The results of the simulation and experiment examples indicate that the proposed algorithm provides a simple and effective method for defect localization in beam-like structures.

关键词: damage detection     beam structure     strain energy     static displacement variation     energy damage index    

growth behavior of a 170 mm diameter stainless steel straight pipe subjected to combined torsion and bending

《结构与土木工程前沿(英文)》 2021年 第15卷 第4期   页码 905-913 doi: 10.1007/s11709-021-0683-2

摘要: In a nuclear powerplant, the rotary equipment, such as a pump directly fitted with hanger in the piping system, experiences torsional and bending loads. Higher crack growth rate occurs because of this torsional load in addition to the bending load. Hence, it is necessary to study the fatigue behavior of piping components under the influence of combined torsional and bending load. In this study, experimental fatigue life evaluation was conducted on a notched stainless steel SA312 Type 304LN straight pipe having an outer diameter of 170 mm. The experimental crack depth was measured using alternating current potential drop technique. The fatigue life of the stainless steel straight pipe was predicted using experiments, Delale and Erdogan method, and area-averaged root mean square–stress intensity factor approach at the deepest and surface points of the notch. Afterward, the fatigue crack growth and crack pattern were discussed. As a result, fatigue crack growth predicted using analytical methods are in good agreement with experimental results.

关键词: fatigue life     Delale and Erdogan method     RMS–SIF approach     stainless steel     torsion and bending load     fatigue crack growth    

A novel structural modification to eliminate the early coupling between bending and torsional mode shapes

Nazim Abdul NARIMAN

《结构与土木工程前沿(英文)》 2017年 第11卷 第2期   页码 131-142 doi: 10.1007/s11709-016-0376-4

摘要: In this paper, a novel structural modification approach has been adopted to eliminate the early coupling between the bending and torsional mode shapes of vibrations for a cable stayed bridge model generated using ABAQUS software. Two lateral steel beams are added to the middle span of the structure. Frequency analysis is dedicated to obtain the natural frequencies of the first eight mode shapes of vibrations before and after the structural modification approach. Numerical simulations of wind excitations are conducted for the 3D model of the cable stayed bridge with duration of 30 s supporting on real data of a strong wind from the literature. Both vertical and torsional displacements are calculated at the mid span of the deck to analyze both the bending and the torsional stiffness of the system before and after the structural modification. The results of the frequency analysis after applying lateral steel beams declared a safer structure against vertical and torsional vibrations and rarely expected flutter wind speed. Furthermore, the coupling between the vertical and torsional mode shapes has been removed to larger natural frequencies magnitudes with a high factor of safety. The novel structural approach manifested great efficiency in increasing vertical and torsional stiffness of the structure.

关键词: aeroelastic instability     structural damping     flutter wind speed     bending stiffness     torsional stiffness    

Static balancing of planar articulated robots

Giuseppe QUAGLIA,Zhe YIN

《机械工程前沿(英文)》 2015年 第10卷 第4期   页码 326-343 doi: 10.1007/s11465-015-0355-9

摘要:

Static balancing for a manipulator’s weight is necessary in terms of energy saving and performance improvement. This paper proposes a method to design balancing devices for articulated robots in industry, based on robotic dynamics. Full design details for the balancing system using springs are presented from two aspects: One is the optimization for the position of the balancing system; the other is the design of the spring parameters. As examples, two feasible balancing devices are proposed, based on different robotic structures: The first solution consists of linkages and springs; the other consists of pulleys, cross mechanisms and (hydro-) pneumatic springs. Then the two solutions are compared. Pneumatic, hydro-pneumatic and mechanical springs are discussed and their parameters are decided according to the requirements of torque compensation. Numerical results show that with the proper design using the methodology presented in this paper, an articulated robot can be statically balanced perfectly in all configurations. This paper therefore provides a design method of the balancing system for other similar structures.

关键词: robotics     static balancing     pneumatic spring     mechanical spring     torque compensation    

Analytical algorithms of compressive bending capacity of bolted circumferential joint in metro shield

《结构与土木工程前沿(英文)》   页码 901-914 doi: 10.1007/s11709-023-0915-8

摘要: The integrity and bearing capacity of segment joints in shield tunnels are associated closely with the mechanical properties of the joints. This study focuses on the mechanical characteristics and mechanism of a bolted circumferential joint during the entire bearing process. Simplified analytical algorithms for four stress stages are established to describe the bearing behaviors of the joint under a compressive bending load. A height adjustment coefficient, α, for the outer concrete compression zone is introduced into a simplified analytical model. Factors affecting α are determined, and the degree of influence of these factors is investigated via orthogonal numerical simulations. The numerical results show that α can be specified as approximately 0.2 for most metro shield tunnels in China. Subsequently, a case study is performed to verify the rationality of the simplified theoretical analysis for the segment joint via numerical simulations and experiments. Using the proposed simplified analytical algorithms, a parametric investigation is conducted to discuss the factors affecting the ultimate compressive bending capacity of the joint. The method for optimizing the joint flexural stiffness is clarified. The results of this study can provide a theoretical basis for optimizing the design and prediciting the damage of bolted segment joints in shield tunnels.

关键词: shield tunnel     segment joint     joint structural model     failure mechanism    

A simplified method for investigating the bending behavior of piles supporting embankments on soft ground

《结构与土木工程前沿(英文)》   页码 1021-1032 doi: 10.1007/s11709-023-0952-3

摘要: In recent years, concrete and reinforced concrete piles have been widely used to stabilize soft ground under embankments. Previous research has shown that bending failure, particularly during rapid filling on soft ground, is the critical failure mode for pile-supported embankments. Here, we propose an efficient two-stage method that combines a test-verified soil deformation mechanism and Poulos’ solution for pile–soil interaction to investigate the bending behavior of piles supporting embankments on soft ground. The results reveal that there are three possible bending failure scenarios for such piles: at the interface between the soft and firm ground layers, at mid-depths of the fan zone, and at the boundary of the soil deformation mechanism. The location of the bending failure depends on the position and relative stiffness of the given pile. Furthermore, the effect of embedding a pile into a firm ground layer on the bending behavior was investigated. When the embedded length of a pile exceeded a critical value, the bending moment at the interface between the soft and firm ground layers reached a limiting value. In addition, floating piles that are not embedded exhibit an overturning pattern of movement in the soft ground layer, and a potential failure is located in the upper part of these piles.

关键词: bending behavior     pile     embankment     soil−structure interaction     failure mode    

Erratum to: Bending and vibration of a discontinuous beam with a curvic coupling under different axial

《机械工程前沿(英文)》 2022年 第17卷 第2期 doi: 10.1007/s11465-022-0709-z

微分和表观静摩擦系数的表式

王渭源

《中国工程科学》 2001年 第3卷 第8期   页码 29-32

摘要:

当前,工程师和科学家都对微牛和纳牛量级载荷静摩擦系数(以下简称微牛纳牛静摩擦系数)很感兴趣。但文献中至今没有详细讨论过微牛纳牛静摩擦系数与载荷的关系,而且发表的实验结果都不相互讨论。从微分静摩擦系数的定义出发,导出几种典型模型下微分静摩擦系数和表观静摩擦系数的表式,并据此广泛讨论这些文献中的实验结果。

关键词: 微分静摩擦系数     微牛纳牛静摩擦系数     表观静摩擦系数     宏观静摩擦系数    

Distribution of background equivalent static wind load on high-rise buildings

Jianguo ZHANG , Ming GU ,

《结构与土木工程前沿(英文)》 2009年 第3卷 第3期   页码 241-248 doi: 10.1007/s11709-009-0036-z

摘要: In this paper, the along-wind and cross-wind fluctuating load distributions along the height of high-rise buildings and their correlations are obtained through simultaneous pressure measurements in a wind tunnel. Some typical methods proposed in some relative literatures, i.e., load-response correlation (LRC), and quasi-mean load (QML) and gust load envelope (GLE) methods, are verified in terms of their accuracy in describing the background equivalent static wind load distribution on high-rise buildings. Based on the results, formulae of the distribution of background equivalent static load on high-rise buildings with typical shapes are put forward. It is shown that these formulae are of high accuracy and practical use.

关键词: high-rise buildings     along-wind     cross-wind     background equivalent static wind load     close formulae    

Parameter prediction in laser bending of aluminum alloy sheet

WANG Xuyue, XU Weixing, CHEN Hua, WANG Jinsong

《机械工程前沿(英文)》 2008年 第3卷 第3期   页码 293-298 doi: 10.1007/s11465-008-0046-x

摘要: Based on the basic platform of BP neural networks, a BP network model is established to predict the bending angle in the laser bending process of an aluminum alloy sheet (1–2 mm in thickness) and to optimize laser bending parameters for bending control. The sample experimental data is used to train the BP network. The nonlinear regularities of sample data are fitted through the trained BP network; the predicted results include laser bending angles and parameters. Experimental results indicate that the prediction allowance is controlled less than 5%–8% and can provide a theoretical and experimental basis for industry purpose.

关键词: control     industry purpose     nonlinear     network     aluminum    

标题 作者 时间 类型 操作

A novel finite element formulation for static bending analysis of functionally graded porous sandwich

Van Chinh NGUYEN; Trung Thanh TRAN; Trung NGUYEN-THOI; Quoc-Hoa PHAM

期刊论文

Static and dynamic analysis of functionally graded fluid-infiltrated porous skew and elliptical nanoplates

期刊论文

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

期刊论文

A new meshless approach for bending analysis of thin plates with arbitrary shapes and boundary conditions

期刊论文

Improved prediction of pile bending moment and deflection due to adjacent braced excavation

期刊论文

Damage detection in beam-like structures using static shear energy redistribution

期刊论文

growth behavior of a 170 mm diameter stainless steel straight pipe subjected to combined torsion and bending

期刊论文

A novel structural modification to eliminate the early coupling between bending and torsional mode shapes

Nazim Abdul NARIMAN

期刊论文

Static balancing of planar articulated robots

Giuseppe QUAGLIA,Zhe YIN

期刊论文

Analytical algorithms of compressive bending capacity of bolted circumferential joint in metro shield

期刊论文

A simplified method for investigating the bending behavior of piles supporting embankments on soft ground

期刊论文

Erratum to: Bending and vibration of a discontinuous beam with a curvic coupling under different axial

期刊论文

微分和表观静摩擦系数的表式

王渭源

期刊论文

Distribution of background equivalent static wind load on high-rise buildings

Jianguo ZHANG , Ming GU ,

期刊论文

Parameter prediction in laser bending of aluminum alloy sheet

WANG Xuyue, XU Weixing, CHEN Hua, WANG Jinsong

期刊论文