• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.2
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• pp.123-131
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• 1994

Experimental studies were conducted to make clear the soil moisture environment under the condition of paddy-upland rotational fields by investigating water-table depths and soil moisture contents during growing season of crops in two kinds of soil. The following results were obtained. 1.Although water-table depths fluctuated with the amount of rainfall in the experimental field, it seemed that the variation of vater4able depths in the paddy-upland rotational, field was strongly affected by the condition of locations on paddy fields. 2.It is recognized that the concept of sum of excess water depth(SEWxx) and sum of excess water day(SEDxx) can be used to represent the soil moisture stress index due to the fluctuation of water-table depths. 3.The results of this study clearly indicate that drainage in paddy-upland rotational field to maintain an optimum soil moisture content must be made by introducing the concept of block drainage which needs both subsurface drainage and intercept drainage around a field. 4.Soil moisture contents were affected by both the amount of rainfall and water-table depths, however, the moisture content for top soil showed higher correlation with the amount of rainfall while that for subsoil with water-table depths.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.1
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• pp.1-6
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• 2017

This paper presents development of the nine-node co-rotational(CR) planar element applicable for elastoplastic and contact analysis. The CR formulation is one of the efficient geometrically nonlinear formulations. It is based on the assumptions of small strain and large displacement. Further, it is extended to both elastoplastic analysis and contact analysis in this paper. For accurate plastic analysis, nine-node quadrilateral element, which can provide accurate stress prediction, is chosen. Bi-linear hardening rule based on Newton- Raphson return-mapping is employed. Also, Lagrange multiplier is used in order for constraints regarding the contact analysis. The present development is validated via the time transient problems. The present results are compared with those obtained by the other existing software.

• Advances in nano research
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• v.6 no.1
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• pp.39-55
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• 2018

Forced vibration analysis of a cracked functionally graded microbeam is investigated by using modified couple stress theory with damping effect. Mechanical properties of the functionally graded beam change vary along the thickness direction. The crack is modelled with a rotational spring. The Kelvin-Voigt model is considered in the damping effect. In solution of the dynamic problem, finite element method is used within Timoshenko beam theory in the time domain. Influences of the geometry and material parameters on forced vibration responses of cracked functionally graded microbeams are presented.

• Proceedings of the Safety Management and Science Conference
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• 2004.05a
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• pp.211-220
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• 2004

The vertical impact crusher is the machine which could produce artifical sand similar to natural aggregates in the site of guarry and pits. FEM was used to analyse the stress and strength of the machine at high rotational speed. The test specimen was made from the same material as the shaft and tension tests were conducted. The Shaft under extreme conditions was analysed to determine maximum stress level and its location from the results. The maximum level of stress and its location could be predicted.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.143-147
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• 1992

Description of the behavior of the R.C structural members fixed on massive concrete is not normally generalization of recognized configuration for regular R.C. design guidanes. This can be due to the complexity of evaluation of internal resistancy and deflection changes of the members subjected to the various external forces. On the base of axially loaded member fixed on footing, however, the estimation of deflection changes due to flexural force shear force and rotational force is to be carried out in ways of specifying the bond characteristics of axial bars embedded in massive concrete. This work is to quantify adhesion of steel-concrete, initial concrete cracking stress near bar rib, maximum bond stress and residual stress in concrete respectively. In addition to quantification of them for particulate behavior, the suggestions of multi-linear bond stress-slip diagram made in carrying out finite element analyses for adhesion failure, examining concrete cracking status and reviewing existing experimental data lead to alternatively constructed relationship between bond stress and slip for a axial bars embedded massive concrete.

• Journal of Wind Energy
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• v.14 no.3
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• pp.109-119
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• 2023

A structural safety evaluation was conducted for the stabbing system for the pre-piling jacket substructure currently being developed in South Korea, considering pile construction errors due to its lateral movement that may occur during construction in the ocean. Based on (1) the maximum stress generated by the stabbing system, (2) the maximum rotational displacement of the guide cone, and (3) the maximum stress generated by the horizontal hydraulic pressure cylinder, the structural safety of the stabbing system was examined under the initial loading condition and three possible load combinations during its construction. In order to evaluate the structural safety of the stabbing system, a concept of stress safety factor (= Yield stress / Max. Von-Mises stress) was used. It was found that the stabbing system considered in this study has a sufficient margin of safety.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.221-232
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• 1998

This study presents a fatigue line with a plastic rotational angle to a great extent of plastic strain of Low-Cycle-Fatigue period, such as earthquake, etc. This fatigue line with a plastic rotational angle is measured and analysed more simply in practice rather than Woehler's fatigue line which is developed in stress variation of the structure. It shows that the slope of fatigue line with a plastic rotational angle is equal to that with plastic strain through the experiments by proving the correlation that the plastic strain ratio is directly proportional to the plastic rotational angle in plastic hinge. The theory is induced by Manson and Coffin strain fatigue line, and the experiments are tested by ECCS. The location of the plastic hinge is achieved and accurate plastic strain ratio is calculated through FEM.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.245-248
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• 1997

Excessive stress on the bone-stem interface may cause local micromotion that could produce midthigh pain, interface bone resorption and prevent bony ingrowth. It is important for clinician and prosthetic designer to develop an understanding of the load transfer mechanism, its associated stress pattern and its relationships with the particular mechanical characteristics of the femoral stem designs. Finite element method (FEM) is preeminently suited to provide information in this respect. The authors developed 3-dimensional numerical finite element models implanted with the straight stem which is composed of total 1170 elements of 8 nodes and with the curved stem which is composed of total 885 elements of 8 node, and analysed the relative micromotions between the straight stem and the curved stem in immediate postoperative stage of an uncemented total hip replacement in load simulating the single leg stance. The results showed that the rotational displacement was occupied over 90% of total micromotion in both types of stem and was peak at the proximal medial portion of the stem, but markedly less distally. The curved stem was more stable especially in terms of rotational stability. It is recommended that surgeons do not allow the patient weight bearing until bony ingrowth was achieved. In the future more attention should be drawn to increase initial rotational stability of the two types of femoral stem to prevent loosening from excessive micromotion.

• Structural Engineering and Mechanics
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• v.60 no.5
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• pp.903-921
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• 2016

To study the effect of looseness on mechanical behavior of dovetail mortise-tenon joints, five dovetail mortise-tenon joints, including one intact joint and four loose joints, were fabricated and tested under cycle lateral loadings, and non-linear finite element models using the software ABAQUS were also developed. The effects of looseness on stress distribution, rotational stiffness and bearing capacity of joints were studied based on the analysis of test and simulation results. The results indicate that the hysteretic loops are anti-Z-shaped and present typical characteristics of pinching and slippage, the envelop curves of joints are classified as following two stages: elastic and strengthening stage. The peak stress, rotational stiffness and bearing capacity of joints were reduced due to looseness. The moment-rotation theoretical model of intact joint was simplified in terms of the relation of construction dimensions for buildings, and the moment-rotation theoretical model considering the effect of looseness was proposed and validated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.109-110
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• 2018

Preloading Strut applied during installation of the wall jack, but additionally serves to minimize the displacement of soil pressure acting upon dissolution due to the difficulty. In this study, we developed an index of support for the release of stress to facilitate the dismantling of the strut uninstall. The refractive support the axial force acting on the strut are supportable, is refracted at minimum load, disassembly should be easy. In order to find the optimal shape and structural stability of the refractive support We have performed the numerical analysis and performance test to determine the final model. We carried out model tests and UTM test in order to understand the refractive performance and durability of the refractive support for optimal model. Results of the test UTM is refracted all shot 5 times within a target hit number, it was found that there is no problem of the refractive performance. Further, the results of model experiments, it was found that to ensure sufficient durability more than the performance target value of the pin joint support structure.