• Title/Summary/Keyword: Finite element (FE) modeling

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Numerical simulation of an external prestressing technique for prestressed concrete end block

  • Murthy, A. Rama Chandra;Ganapathi, S. Chitra;Saibabu, S.;Lakshmanan, N.;Jayaraman, R.;Senthil, R.
    • Structural Engineering and Mechanics
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    • v.33 no.5
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    • pp.605-619
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    • 2009
  • This paper presents the details of finite element (FE) modeling and analysis of an external prestressing technique to strengthen a prestressed concrete (PSC) end block. Various methods of external prestressing techniques have been discussed. In the proposed technique, transfer of external force is in shear mode on the end block creating a complex stress distribution. The proposed technique is useful when the ends of the PSC girders are not accessible. Finite element modeling issues have been outlined. Brief description about material nonlinearity including key aspects in modeling inelastic behaviour has been provided. Finite element (FE) modeling including material, loading has been explained in depth. FE analysis for linear and nonlinear static analysis has been conducted for varying external loadings. Various responses such as out-of-plane deformation and slip have been computed and compared with the corresponding experimental observations. From the study, it has been observed that the computed slope and slip of the steel bracket under external loading is in good agreement with the corresponding experimental observations.

FEA of the blast loading effect on ships hull

  • Hamdoon, Muhsin;Zamani, Nader;Das, Sreekanta
    • Ocean Systems Engineering
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    • v.1 no.3
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    • pp.223-239
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    • 2011
  • In combat operations, naval ships may be subjected to considerable air blast and underwater shock loads capable of causing severe structural damage. As the experimental study imposes great monetary and time cost, the numerical solution may provide a valuable alternative. This study emphasises on numerical analysis for optimization of stiffened and unstiffened plate's structural response subjected to air blast load. Linear and non linear finite element (FE) modeling and analysis was carried out and compared with existing experimental results. The obtained results reveal a good agreement between numerical and experimental observations. The presented FE models can eliminate confusion regarding parameters selection and FE operations processing, using commercial software available currently.

Stress-Pore Pressure Coupled Finite Element Modeling of NATM Tunneling (NATM 터널의 응력-간극수압 연계 유한요소모델링)

  • Yoo, Chung-Sik;Kim, Sun-Bin
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.189-198
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    • 2006
  • This paper concerns the finite element (FE) modeling approach for NATM tunneling in water bearing ground within the framework of stress-pore pressure coupled analysis. Fundamental interaction mechanism of ground and groundwater lowering was first examined and a number of influencing factors on the results of coupled FE analysis were identified. A parametric study was then conducted on the influencing factors such as soil-water characteristics, location of hydraulic boundary conditions, the way of modeling drainage flow, among others. The results indicate that the soil-water characteristics plays the most important role in the tunneling-induced settlement characteristics. Based on the results, modeling guidelines were suggested for stress-pore prssure coupled finite element modeling of NATM tunneling.

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Simulation and experimental analysis of active vibration control of smart beams under harmonic excitation

  • Malgaca, L.;Karagulle, H.
    • Smart Structures and Systems
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    • v.5 no.1
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    • pp.55-68
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    • 2009
  • In the present study, active control of a smart beam under forced vibration is analyzed. The aluminum smart beam is composed of two piezoelectric patches and strain gauge. One of the piezoelectric patches is used as controlling actuator while the other piezoelectric patch is used as vibration generating shaker. The smart beam is harmonically excited by the piezoelectric shaker at its fundamental frequency. The strain gauge is utilized to sense the vibration level. Active vibration reduction under harmonic excitation is achieved using both strain and displacement feedback control. Control actions, the finite element (FE) modeling and analyses are directly carried out by using ANSYS parametric design language (APDL). Experimental applications are performed with LabVIEW. Dynamic behavior at the tip of the beam is evaluated for the uncontrolled and controlled responses. The simulation and experimental results are compared. Good agreement is observed between simulation and experimental results under harmonic excitation.

Use of UHPC slab for continuous composite steel-concrete girders

  • Sharif, Alfarabi M.;Assi, Nizar A.;Al-Osta, Mohammed A.
    • Steel and Composite Structures
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    • v.34 no.3
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    • pp.321-332
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    • 2020
  • The loss of composite action at the hogging moment zone for a continuous composite girder reduces the girder stiffness and strength. This paper presents an experimental investigation of the use of an ultra-high performance concrete (UHPC) slab at the hogging moment zone and a normal concrete (NC) slab at the sagging moment zone. The testing was conducted to verify the level of loading at which composite action is maintained at the hogging moment zone. Four two-span continuous composite girders were tested. The thickness of the UHPC varied between a half and a full depth of slab. The degree of shear connection at the hogging moment zone varied between full and partial. The experimental results confirmed the effectiveness of the UHPC slab to enhance the girder stiffness and maintain the composite action at the hogging moment zone at a load level much higher than the upper service load limit. To a lesser degree enhanced performance was also noted for the smaller thickness of the UHPC slab and partial shear connection at the hogging moment zone. Plastic analysis was conducted to evaluate the ultimate capacity of the girder which yielded a conservative estimation. Finite element (FE) modeling evaluated the girder performance numerically and yielded satisfactory results. The results indicated that composite action at the hogging moment zone is maintained for the degree of shear connection taken as 50% of the full composite action and use of UHPC as half depth of slab thickness.

Stress-Pore Pressure Coupled Finite Element Modeling of NATM Tunneling (NATM 터널의 응력-간극수압 연계 유한요소모델링)

  • Yoo, Chung-Sik;Kim, Sun-Bin
    • Journal of the Korean Geotechnical Society
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    • v.22 no.10
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    • pp.5-20
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    • 2006
  • This paper concerns the finite element (FE) modeling approach for NATM tunneling in water bearing ground within the framework of stress-pore pressure coupled analysis. Fundamental interaction mechanism of ground and groundwater lowering was first examined and a number of influencing factors on the results of coupled FE analysis were identified. A parametric study was then conducted on the influencing factors such as soil-water characteristics, location of hydraulic boundary conditions, the way of modeling drainage flow, among others. The results indicate that the soil-water characteristics play the most important role in the tunneling-induced settlement characteristics. Based on the results, modeling guidelines were suggested for stress-pore pressure coupled finite element modeling of NATM tunneling.

3D Semi-elliptical Interfacial Crack Front Stress Fields in Welded Joints (용접부 3차원 반타원 계면균열선단에서의 응력장)

  • 최호승;이형일;송원근
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.4
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    • pp.649-659
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    • 2002
  • For a variety of elastic-plastic stress fields of plane strain specimens, many research works verified the validity of J-T approach. To generalize the validity of J-T method, however, further investigations are needed for more practical 3D structures than the idealized geometries as plane strain specimens. In this work, selecting two main types of structures such as plate and straight pipe, we perform 3D finite element(FE) modeling, and accompanying elastic, elastic-plastic FE analyses. We then study the validity of J-T application to 3D structures, and present some useful informations for the design or assessment of pipe welds by comparing the stress fields from the detailed 3D FE analyses to those predicted with J-T two parameters.

Enthalpy - based homogenization procedure for composite piezoelectric modules with integrated electrodes

  • Kranz, Burkhard;Benjeddou, Ayech;Drossel, Welf-Guntram
    • Smart Structures and Systems
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    • v.12 no.5
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    • pp.579-594
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    • 2013
  • A new enthalpy - based procedure for the homogenization of the electromechanical material parameters of composite piezoelectric modules with integrated electrodes is presented. It is based on a finite element (FE) modeling of the latter's representative volume element (RVE). In contrast to most previously published homogenization approaches that are based on averaged quantities, the presented method uses a direct evaluation of the electromechanical enthalpy. Hence, for the linear orthotropic piezoelectric composite behavior full set of elastic, piezoelectric, and dielectric material parameters, 17 load cases (LC) are used where each load case leads directly to one material parameter. This gives the possibility to elaborate a very strict and easy to program processing. In conjunction with the 17 LC, the enthalpy - based homogenization is particularly suitable for laminated composite piezoelectric modules with integrated electrodes. In this case, the electric load has to be given at the electrodes rather than at the RVE FE model boundaries. The proposed procedure is validated through its comparison to literature available results on a classical 1-3 piezoelectric micro fiber (longitudinally polarized) reinforced composite and a $d_{15}$ shear piezoelectric macro-fiber (transversely polarized) composite module.

Low-cycle fatigue in steel H-piles of integral bridges; a comparative study of experimental testing and finite element simulation

  • Karalar, Memduh;Dicleli, Murat
    • Steel and Composite Structures
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    • v.34 no.1
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    • pp.35-51
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    • 2020
  • Integral abutment bridges (IABs) are those bridges without expansion joints. A single row of steel H-piles (SHPs) is commonly used at the thin and stub abutments of IABs to form a flexible support system at the bridge ends to accommodate thermal-induced displacement of the bridge. Consequently, as the IAB expands and contracts due to temperature variations, the SHPs supporting the abutments are subjected to cyclic lateral (longitudinal) displacements, which may eventually lead to low-cycle fatigue (LCF) failure of the piles. In this paper, the potential of using finite element (FE) modeling techniques to estimate the LCF life of SHPs commonly used in IABs is investigated. For this purpose, first, experimental tests are conducted on several SHP specimens to determine their LCF life under thermal-induced cyclic flexural strains. In the experimental tests, the specimens are subjected to longitudinal displacements (or flexural strain cycles) with various amplitudes in the absence and presence of a typical axial load. Next, nonlinear FE models of the tested SHP specimens are developed using the computer program ANSYS to investigate the possibility of using such numerical models to predict the LCF life of SHPs commonly used in IABs. The comparison of FE analysis results with the experimental test results revealed that the FE analysis results are in close agreement with the experimental test results. Thus, FE modeling techniques similar to that used in this research study may be used to predict the LCF life of SHP commonly used in IABs.

J-T Characterization of Stress Fields Along 3D Semi-Elliptical Interfacial Crack Front (J-T에 의한 3차원 반타원 계면균열선단 응력장의 기술)

  • Choi, Ho-Seung;Lee, Hyung-Yil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.7
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    • pp.1250-1261
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    • 2002
  • Many research works have validated the J-T approach to elastic-plastic crack-tip stress fields in a variety of plane strain specimens. To generalize the validity of J-T method, further investigations are however needed for more practical 3D structures than the idealized plane strain specimens. In this work, we perform 3D finite element (FE) modeling of welded plate and straight pipe, and accompanying elastic, elastic-plastic FE analyses. Manual 3D modeling is almost prohibitive, since the models contain semi-elliptical interfacial cracks which require singular elements. To overcome this kind of barrier, we develop a program generating the meshes for semi-elliptical interfacial cracks. We then compare the detailed 3D FE stress fields to those predicted with J-T two parameters. Thereby we extend the validity of J-T application to 3D structures and infer some useful informations for the design or assessment of pipe welds.