• Steel and Composite Structures
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• 제38권3호
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• pp.271-280
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• 2021

In this study, the fatigue property of U rib-to-crossbeam connections in orthotropic steel bridge (OSB) crossbeams under heavy traffic vehicle load was investigated considering the effects of in-plane shear stress. The applicability of an improved structural stress (ISS) method was validated for the fatigue behavior analysis of nonwelded arc-shaped cutout regions in multiaxial stress states. Various types of fatigue testing specimens were compared for investigating the equivalent structural stress, fatigue crack initiation positions, and failure modes with the unified standards. Furthermore, the implications of OSB crossbeams and specified loading cases are discussed with respect to the improved method. The ISS method is proven to be applicable for analyzing the fatigue property of nonwelded arc-shaped cutout regions in OSB crossbeams. The used method is essential for gaining a reliable prediction of the most likely failure modes under a specific heavy traffic vehicle load. The evaluated results using the used method are proven to be accurate with a slighter standard deviation. We obtained the trend of equivalent structural stress in arc-shaped cutout regions and validated the crack initiation positions and propagation directions by comparing them with the fatigue testing results. The implications of crossbeam spans on fatigue property are less significant than the effects of crossbeams.

• 한국기계가공학회지
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• 제17권3호
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• pp.109-119
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• 2018

The purpose of this study is to evaluate the structural safety of the front-end loader for the 90 kW class of agricultural tractors in impact test conditions. Deformation and stress on the loader under the impact test conditions are analyzed using the commercial finite element analysis software ANSYS. In previous research dealing with the initial design of the loader, the maximum stress occurred in the mount and exceeded the yield strength of the material. In this paper, an improved design of the mount of the loader was proposed to reduce the stress concentration in the initial design. The safety of the improved design was verified by performing rigid-body dynamics analysis, transient structural analysis, and static structural analysis under three impact test conditions: a drop and catch test, a corner pull test, a corner push test. It was found that the local stress concentration in the mount that appeared in the initial design was greatly reduced in the improved design, and that the maximum stresses occurred in the three impact test conditions are smaller than the yield strength. It is expected that the design improvement of the mount proposed in this study and the method of analysis may be effectively used to enhance structural safety in the development of new model front loaders in the future.

• Structural Engineering and Mechanics
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• 제66권5호
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• pp.649-663
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• 2018

The scaled boundary finite element method is extended to evaluate the dynamic stress intensity factors and T-stress with a numerical procedure based on the improved continued-fraction. The improved continued-fraction approach for the dynamic stiffness matrix is introduced to represent the inertial effect at high frequencies, which leads to numerically better conditioned matrices. After separating the singular stress term from other high order terms, the internal displacements can be obtained by numerical integration and no mesh refinement is needed around the crack tip. The condition numbers of coefficient matrix of the improved method are much smaller than that of the original method, which shows that the improved algorithm can obtain well-conditioned coefficient matrices, and the efficiency of the solution process and its stability can be significantly improved. Several numerical examples are presented to demonstrate the increased robustness and efficiency of the proposed method in both homogeneous and bimaterial crack problems.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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• pp.406-413
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• 1998

The distinct element method is improved to consider the charateristics of stress wave propagation in media involving the discontinuous faces. The distinct element method has many advantages to analyse the characteristics of the reflection, refraction and deflection of the waves in nonhomogeneous media. The double-suing connection system is adopted instead of the single-spring connection system because the distinct element cannot be used for analysing the contact behavior between the different materials by only one contact spring. For the verification of the improved code, the results of the numerical analysis are compared with that of the photoelastic experiments which are one or two dimensional wave propagation problem of the nonhomogeneous media including the different accoustic impendence material or voids. It is shown that the characteristics of the stress wave propagation in nonhomogeneous media can be simulated appropriately using the improved distinct element method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.69-76
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• 2002

In this paper, several improved Element-Free Galerkin (EFG) methods containing singular expression in their approximation functions are compared one another through a patch test with near-tip field. Intrinsic enrichments that expand the basis function partially and fully with known near-tip displacement field and a local enrichment using auxiliary supports based on the partition of unity concept are examined by evaluating a relative stress norm error and the stress intensity factor. Some numerical examinations graphically show that how the size of compact support, dilation parameter and the diffraction parameter can affect the accuracy of the improved EFG methods in the error and the stress intensity factor.

• Structural Engineering and Mechanics
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• 제13권5호
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• pp.491-504
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• 2002

Recently we formulated a 2D hybrid stress element from the 3D Hellinger-Reissner principle for the analysis of thick bodies that are symmetric to the thickness direction. Polynomials have typically been used for all the displacement and stress fields. Although the element predicted the dominant stress and all displacement fields accurately, its prediction of the out-of-plane shear stresses was affected by the very high order terms used in the polynomials. This paper describes an improved formulation of the 2D element using Fourier series expansion for the out-of-plane displacement and stress fields. Numerical results illustrate that its predictions have markedly improved.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.868-880
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• 2020

One of the main concerns in the structural integrity of offshore pipelines is mechanical damage from external loads. Pipelines are exposed to fatigue failure in welded joints due to geometric discontinuity. In addition, fatigue loads such as currents, waves, and platform motions may cause significant plastic deformation and fracture or leakage within a relatively low-cycle regime. The 2007 ASME Div. 2 Code adopts the master S―N curve for the fatigue evaluation of welded joints based on the mesh-insensitive structural stress. An extension to the master S―N curve was introduced to evaluate the low-cycle fatigue strength. This structural strain method uses the tensile properties of the material. However, the monotonic tensile properties have limitations in describing the material behavior above the elastic range because most engineering materials exhibit hardening or softening behavior under cyclic loads. The goal of this study is to extend the cyclic stress-strain behavior to the structural strain method. To this end, structural strain-based procedure was established while considering the cyclic stress-strain behavior and compared to the structural strain method with monotonic tensile properties. Finally, the improved prediction method was validated using fatigue test data from full-scale girth-welded pipes.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1990년도 봄 학술발표회 논문집
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• pp.53-58
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• 1990

This study was intended to provide efficient algorithms for high quality postprocess on the basis of microcomputers with limited capacity and functionality. Improved methods of postprocessing including stress contouring, internal force diagraming, and displacement animation, were proposed and implemented into a new finite element system. Visualization of three-dimensional structural behaviors was treated with special emphasis.

• 한국지반환경공학회 논문집
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• 제15권1호
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• pp.25-34
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• 2014

본 연구의 목적은 개량체 구조형상변화에 따른 복합지반에서의 역학 및 침하특성을 분석하는 것에 있다. 본 연구의 실험은 원형토조에 강도 및 치환율별로 격자형 개량체를 만들어 복합지반을 조성한 후 응력을 재하하는 방식으로 총 9 케이스를 수행하였다. 또한 심도별 응력분포 및 응력분담비 등을 분석하기 위해 유한요소해석을 실내 모형실험과 동일조건으로 모델링하여 해석하였다. 연구결과, 격자형 개량체로 구성된 복합지반은 원형 개량체에 비해 저치환율을 제외한 중간 및 고치환율에서 응력분담비가 증가하며 그 결과, 침하량은 감소하는 경향을 보였다. 본 연구는 구조형상 변화에 따른 형상효과비 및 침하저감계수 제시를 통해 부족한 복합지반의 개량체 구조형상에 대한 연구 참고자료 및 향후 추가 연구에 도움이 될 것으로 판단된다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.42-49
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• 2001

In this paper the efficient finite element for stress analysis of plane stress/strain problems is proposed. This element is achieved by adding the bubble-mode function to 8-node element. The stiffness matrix of the element is calculated by using modified numerical integration order to avoid spurious zero energy mode. In order to demonstrate the performance of this element numerical tests for various verification problems are carried out. The results of numerical tests show accuracy and reliability of the element presented in this paper.