• Title/Summary/Keyword: Finite Element Approach (FEA)

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Finite element analysis based fatigue life evaluation approach for railway bridges: a study in Indian scenario

  • Ajmal, P.C. Hisham;Mohammed, Althaf
    • Structural Monitoring and Maintenance
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    • v.5 no.4
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    • pp.429-443
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    • 2018
  • Fatigue is a principal failure mode for steel structures, and it is still less understood than any other modes of failure. Fatigue life estimation of metal bridges is a major issue for making cost effective decisions on the rehabilitation or replacement of existing infrastructure. The fatigue design procedures given by the standard codes are either empirical or based on nominal stress approach. Since the fatigue life estimation through field measurements is difficult and costly, more researches are needed to develop promising techniques in the fatigue analysis of bridges through Finite Element Analysis (FEA). This paper aims to develop a methodology for the Fatigue life estimation of railway steel bridge using FEA. The guidelines of IIW-1823-07 were used in the development of the methodology. The Finite Element (FE) package ANSYS and the programming software MATLAB were used to implement this methodology on an Indian Railway Standard (IRS) welded plate girder bridge. The results obtained were compared with results from published literature and found satisfactory.

Modelling of recycled aggregate concrete-filled steel tube (RACFST) beam-columns subjected to cyclic loading

  • Yang, You-Fu
    • Steel and Composite Structures
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    • v.18 no.1
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    • pp.213-233
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    • 2015
  • A nonlinear finite element analysis (FEA) model is presented for simulating the behaviour of recycled aggregate concrete-filled steel tube (RACFST) beam-columns subjected to constant axial compressive load and cyclically increasing flexural loading. The FEA model was developed based on ABAQUS software package and a displacement-based approach was used. The proposed engineering stress versus engineering strain relationship of core concrete with the effect of recycled coarse aggregate (RCA) replacement ratio was adopted in the FEA model. The predicted results of the FEA model were compared with the experimental results of several RACFST as well as the corresponding concrete-filled steel tube (CFST) beam-columns under cyclic loading reported in the literature. The comparison results indicated that the proposed FEA model was capable of predicting the load versus deformation relationship, lateral bearing capacity and failure pattern of RACFST beam-columns with an acceptable accuracy. A parametric study was further carried out to investigate the effect of typical parameters on the mechanism of RACFST beam-columns subjected to cyclic loading.

Optimal Design for the Thermal Deformation of Disk Brake by Using Design of Experiments and Finite Element Analysis (실험계획법과 유한요소해석에 의한 디스크 브레이크의 열변형 최적설계)

  • Lee, Tae-Hui;Lee, Gwang-Gi;Jeong, Sang-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.12
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    • pp.1960-1965
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    • 2001
  • In the practical design, it is important to extract the design space information of a complex system in order to optimize the design because the design contains huge amount of design conflicts in general. In this research FEA (finite element analysis) has been successfully implemented and integrated with a statistical approach such as DOE (design of experiments) based RSM (response surface model) to optimize the thermal deformation of an automotive disk brake. The DOE is used for exploring the engineer's design space and for building the RSM in order to facilitate the effective solution of multi-objective optimization problems. The RSM is utilized as an efficient means to rapidly model the trade-off among many conflicting goals existed in the FEA applications. To reduce the computational burden associated with the FEA, the second-order regression models are generated to derive the objective functions and constraints. In this approach, the multiple objective functions and constraints represented by RSM are solved using the sequential quadratic programming to archive the optimal design of disk brake.

Design Optimization Process for Electromagnetic Vibration Energy Harvesters Using Finite Element Analysis (유한요소 해석을 이용한 전자기형 진동 에너지 하베스터의 최적설계 프로세스)

  • Lee, Hanmin;Kim, Young-Cheol;Lim, Jaewon;Park, Seong-Whan;Seo, Jongho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.10
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    • pp.809-816
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    • 2014
  • This paper presents a systematic optimization process for designing an electromagnetic vibration energy harvester using FEA(finite element analysis) to improve computational accuracy and efficiency. A static FEA is used in the optimization process where trend analysis in a short period of time is rather important than precise computation, while a dynamic FEA is used in the verification step for the final result where precise computation is more important. An electromechanical transduction factor can be calculated efficiently by using an approach to use the radial component of magnetic flux density directly instead of an approach to compute the flux density gradient. The proposed optimization process was verified through a case study where simulation and experiment results were compared.

2D Analysis Approach Method of a Small BLDC Motor Having Permanent Magnet Overhang Structure (영구자석 오버행 구조를 가진 소형 BLDC 모터의 2차원 해석 접근 방법)

  • Kim, Hoe-Cheon;Jung, Tae-Uk
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.26 no.7
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    • pp.39-44
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    • 2012
  • This paper deals with the characteristic analysis of small power brushless DC (BLDC) motor considering the rotor magnet overhang flux. In the driving characteristics analysis using 2D FEA (Finite Element Analysis), the rotor magnet overhang effect can't be considered and it should be neglected. To consider rotor magnet overhang effect, 3D FEA should be required. But 3D FEA requires very long calculation time even though the high specification computer is used. In this paper, the 3D electromagnetic model of BLDC motor is approximated as the 2D electromagnetic model considering overhang effect. In this paper, the concept of overhang coefficient is applied, and the coefficient according to load torque variance is deduced.

Can finite element and closed-form solutions for laterally loaded piles be identical?

  • Sawant, Vishwas A.;Shukla, Sanjay Kumar
    • Structural Engineering and Mechanics
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    • v.43 no.2
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    • pp.239-251
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    • 2012
  • The analysis of laterally loaded piles is generally carried out by idealizing the soil mass as Winkler springs, which is a crude approximation; however this approach gives reasonable results for many practical applications. For more precise analysis, the three- dimensional finite element analysis (FEA) is one of the best alternatives. The FEA uses the modulus of elasticity $E_s$ of soil, which can be determined in the laboratory by conducting suitable laboratory tests on undisturbed soil samples. Because of the different concepts and idealizations in these two approaches, the results are expected to vary significantly. In order to investigate this fact in detail, three-dimensional finite element analyses were carried out using different combinations of soil and pile characteristics. The FE results related to the pile deflections are compared with the closed-form solutions in which the modulus of subgrade reaction $k_s$ is evaluated using the well-known $k_s-E_s$ relationship. In view of the observed discrepancy between the FE results and the closed-form solutions, an improved relationship between the modulus of subgrade reaction and the elastic constants is proposed, so that the solutions from the closed-form equations and the FEA can be closer to each other.

Prediction of Crack Growth Lives of an Aged Korean Coast Guard Patrol Ship based on Extended Finite Element Method(XFEM) J-Integral (확장 유한 요소법(XFEM) J-적분을 이용한 노후 순시선의 균열 성장 수명 예측)

  • Kim, Chang-Sik;Li, Chun Bao;Kim, Young Hun;Choung, Joonmo
    • Journal of the Society of Naval Architects of Korea
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    • v.54 no.4
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    • pp.335-343
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    • 2017
  • The Newman-Raju formula and contour integral-based finite element analyses(FEAs) have been widely used to assess crack growth rates and residual lives at crack locations in ships or offshore structures, but the Newman-Raju formula is known to be less accurate for the complicated weld details and the conventional FEA-based contour integral approach needs concentrated efforts to construct FEA models. Recently, an extended finite element method(XFEM) has been proposed to reduce those modeling efforts with reliable accuracy. Stress intensity factors(SIFs) from the approaches such as the Newman-Raju formula, conventional FEA-based J-integral, and XFEM-based J-integral were compared for an infinitely long plate with a propagating elliptic crack. It was concluded that the XFEM approach was far reliable in terms of prediction ability of SIFs. Assuming a 25 year-aged coast guard patrol ship had the prescribed cracks at the bracket toes attached to longitudinal stiffeners in way of deck and bottom, SIFs were derived based on the three approaches. To obtain axial tension loads acting on the longitudinal stiffeners, long term hull girder bending moments were assumed to obey Weibull distribution of which two parameters were decided from a reference (DNV, 2014). For the complicated weld details, it was concluded that the XFEM approach could cost-effectively and accurately estimate the crack growth rates and residual lives of ship structures.

Evaluation of Seismic Response of Masonry Walls Strengthened with Steel-bar Truss Systems by Non-linear Finite Element Analysis (비선형 유한요소 해석에 의한 강봉 트러스 시스템으로 보강된 조적벽체의 내진거동 평가)

  • Hwang, Seung-Hyeon;Yang, Keun-Hyeok;Kim, Sang-Hee;Lim, Jin-Sun;Im, Chae-Rim
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.4
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    • pp.20-27
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    • 2021
  • The present study presents a nonlinear finite element analysis (FEA) approach using the general program of Abaqus to evaluate the seismic response of unreinforced masonry walls strengthened with the steel bar truss system developed in the previous investigation. For finite element models of masonry walls, the concrete damaged plasticity (CDP) and meso-scale methods were considered on the basis of the stress-strain relationships under compression and tension and shear friction-slip relationship of masonry prisms proposed by Yang et al. in order to formulate the interface characteristics between brick elements and mortars. The predictions obtained from the FEA approach were compared with test results under different design parameters; as a result, a good agreement could be observed with respect to the crack propagation, failure mode, rocking strength, peak strength, and lateral load-displacement relationship of masonry walls. Thus, it can be stated that the proposed FEA approach shows a good potential for designing the seismic strengthening of masonry walls.

Assessment of non-prismatic beams having symmetrical parabolic haunches with constant haunch length ratio of 0.5

  • Yuksel, S. Bahadir
    • Structural Engineering and Mechanics
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    • v.42 no.6
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    • pp.849-866
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    • 2012
  • Single span historic bridges often contain non-prismatic members identified with a varying depth along their span lengths. Commonly, the symmetric parabolic height variations having the constant haunch length ratio of 0.5 have been selected to lower the stresses at the high bending moment points and to maintain the deflections within the acceptable limits. Due to their non-prismatic geometrical configuration, their assessment, particularly the computation of fixed-end horizontal forces (FEFs) and fixed-end moments (FEMs) becomes a complex problem. Therefore, this study aimed to investigate the behavior of non-prismatic beams with symmetrical parabolic haunches (NBSPH) having the constant haunch length ratio of 0.5 using finite element analyses (FEA). FEFs and FEMs due to vertical loadings as well as the stiffness coefficients and the carry-over factors were computed through a comprehensive parametric study using FEA. It was demonstrated that the conventional methods using frame elements can lead to significant errors, and the deviations can reach to unacceptable levels for these types of structures. Despite the robustness of FEA, the generation of FEFs and FEMs using the nodal outputs of the detailed finite element mesh still remains an intricate task. Therefore, this study advances to propose effective formulas and dimensionless estimation coefficients to predict the FEFs, FEMs, stiffness coefficients and carry-over factors with reasonable accuracy for the analysis and re-evaluation of the NBSPH. Using the proposed approach, the fixed-end reactions due to vertical loads, and also the stiffness coefficients and the carry-over factors of the NBSPH can be determined without necessitating the detailed FEA.

Structure Optimization FEA Code Development Under Frequency Constraints by Using Feasible Direction Optimization Method (유용방향법 최적화 알고리즘을 사용한 고유진동수에 대한 구조 최적설계 FEA 모듈 개발)

  • Cho, Hee Keun
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.22 no.1
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    • pp.63-69
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    • 2013
  • In order to find the optimum design of structures that have characteristic natural frequency range, a numerical optimization method to solving eigenvalue problems is a widely used approach. However in the most cases, it is difficult to decide the accurate thickness and shape of structures that have allowable natural frequency in design constraints. Parallel analysis algorithm involving the feasible direction optimization method and Rayleigh-Ritz eigenvalue solving method is developed. The method is implemented by using finite element method. It calculates the optimal thickness and the thickness ratio of individual elements of the 2-D plane element through a parallel algorithm method which satisfy the design constraint of natural frequency. As a result this method of optimization for natural frequency by using finite element method can determine the optimal size or its ratio of geometrically complicated shape and large scale structure.