• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.401-411
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• 2001

This paper deals with the vibration analysis of the rectangular plates which are subjected to uniform in-plane stresses and supported on In-homogeneous Pasternak foundation. Two parametric foundation which Winkler foundation parameter and shear foundation parameter considered, is called by the Pasternak foundation. The values of Winkler foundation parameter of central and border zone of plate are chosen as k₁and k₂respectively, and the value of shear foundation is chosen as constant about all zone of plate. After composing global flexural stiffeness matrix, geometrical stiffeness matrix, mass matrix, and the stiffeness matrix of the Pasternak foundation, eigenvalue problems which are composed of these matrices are solved. The result shows that the shear foundation parameter must not be ignore when considering the stiffeness of foundation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.166-172
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• 2016

This paper deals with the seismic qualification of the reflective metal insulation for thermal shielding that is installed on the outer surfaces of the main equipment of the primary coolant system of a nuclear power plant. A small-scale model of the reactor pressure vessel, which has equivalent dynamic characteristics, was designed to be tested in domestic seismic testing facilities in the future. In this study, seismic analysis of the small-scale model installed with metal insulation was performed using equivalent static analysis and response spectrum analysis. The required Response Spectrum for main equipment of the primary coolant system of APR-1400 plant were considered to establish the enveloping response spectrum, which was applied to the seismic analysis model. The results from two seismic analysis methods were compared to show the structural adequacy of the metal insulator design against a safe shutdown earthquake. This study will form the basis for the seismic testing to support the seismic qualification of the reflective metal insulator.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1265-1271
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• 2011

In this study, the safety of a rack structure was evaluated through seismic analysis considering fluid-structure interactions using a finite-element model. The rack structure was immersed under water, so it was influenced by the water. The fluid-structure interaction can be specified in terms of the hydrodynamic effect, which is defined as the added mass per unit length. Modal analysis and seismic analysis using the Floor Response Spectrum (FRS) were carried out under Operating Basis Earthquake (OBE) and Safe Shutdown Earthquake (SSE) conditions. The analytical maximum displacements of the rack structure were 0.29 and 0.36 mm under OBE and SSE conditions, respectively. The maximum stresses were 17.9 MPa under OBE conditions and 19.6 MPa under SSE conditions; these results corresponded to 23 % and 14% of the yield strength of the applied material, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.81-86
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• 2016

The valves used to control or shut off the flow through a pipeline can be divided into many different types, including gate valves, globe valves, and check valves. Globe valves, in particular, have excellent properties, and because they can easily control the flow under high-pressure conditions, they are generally used in LNG ship and steam pipelines. In this paper, a method for changing the shape of a seat was suggested to solve the valve leakage problem from a structural perspective. In addition, the stress distribution and directional deformation were compared for each model. The suggested models were thus validated, and the optimized seat structure, which includes a self-supporting capability for decreasing the amount of leakage, was determined.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.103-112
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• 2005

This study examines the stability of Sungsu bridge which was issued nine years ago because of its collapse accident and now is on the progress of extension work in each construction stage by construction monitoring system. From this study, the measured value in each construction stage of anchorage truss and suspended truss shows the agreement with the analytical values up to 60~110 percents, and the elements' stresses emanating from the pre-loading stage, are also similar to the analytical value. Regarding these results, it is expected that each member has enough stiffness and the construction condition is satisfactory. In addition, it is expected that the transverse members and sway bracing bolts integrate completely the existing truss and new attached truss as a one body from the result of the vibration test to find out the integration rates.

• Geotechnical Engineering
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• v.11 no.1
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• pp.101-112
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• 1995

Deformational characteristics of soils, often expressed in terms of shear modulus and material damping ratios, are important parameters in the design of soil-structure systems subjected to cyclic and dynamic loadings. In this paper, deformational characteristics of dry sand at small to intermediate strains were investigated using resonant column/torsional shear(RC 175) apparatus. Both resonant column(dynamic) and torsional shear (cyclic) tests were performed in a sequential series on the same specimen. With the modification of motion monitoring system, the elastic zone, where the stress strain relationship is independent of loading cycles and strain amplitude, was veri tied and hysteretic damping was found even in this zone. At strains above cyclic threshold, shear modulus increases and damping ratio decreases with increasing number of loading cycles. Moduli and damping ratios of dry sand are independent of loading frequency and values obtained from pseudostatic torsional shear tests are Identical with the values from the dynamic resonant column test, provided the effect of number of loading cycles is considered in the conlparison. Therefore, deformational characteristics determined by RC/TS tests may be applied in both dynamic and static analyses of soil-structure systems.

• Journal of Practical Engineering Education
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• v.13 no.2
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• pp.327-332
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• 2021

Materials used for education include SM20C, Al6061, and acrylic. SM20C materials are used a lot in certification tests and functional competitions as carbon steel, but they are also used in industrial sites. Al6061 is said to be a material that produces a lot of tools because it has lower hardness than carbon steel and is highly flexible. When practical guidance is given to students using acrylic materials, it is a material that causes vibration and tool damage due to excessive cutting. In this process, we examine how impact on the 5-axis equipment 2NC head can affect precision control. The weakest part of a five-axis equipment is the head that controls the AC axis. In the event of precision and cumulative tolerances in this area, the precision of all products is reduced. Thus, a key part of the 2NC head, the spindle housing was carried out using Al7075 T6 (U.S. Alcoasa) material and the entire body using FCD450 (spherical graphite cast iron). In the vibration and cutting process acting on these two materials, the analysis was carried out to determine the value of applying the force as a finite element analysis under extreme conditions. We hope that using these analytical data will help students see and understand the structure of 5-axis machining rather than 5-axis cutting.

• Journal of Korean Society of Steel Construction
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• v.25 no.3
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• pp.307-320
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• 2013

This paper proposes a new hybrid support structure by the driven piles which removes disadvantages of the existing type of support structure for offshore wind turbines. The hybrid type of support structure is combined with concrete cone and steel shaft, and is supported not only by gravity type foundations but also by driven piles. For three dimensional analysis of the huge and thick concrete structure, a solid-shell element that is capable of exact modeling and node interpolations of stresses is developed. By applying wave theory of stream function and solid-shell element in XSEA simulation software for fixed offshore wind turbines, a quasi-static analysis and natural frequency analysis of proposed support structure are performed with the environmental condition on Southwest Coast in Korea. In the result, lateral displacement is not exceed allowable displacement and a superiority of dynamic behavior of new hybrid support structure is validated by natural frequency analysis. Consequently, the hybrid support structure presented in this study has a structural stability enough to be applied on real-site condition in Korea. The optimized structures based on the preliminary design concept resulted in an efficient structure, which reasonably reduces fabrication costs.

• Journal of the Korea Convergence Society
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• v.5 no.2
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• pp.13-18
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• 2014

In this study, two models due to the configuration of ripper at excavator are investigated by structural and fatigue analyses. The maximum stress and deformation are happened at the axis connected with the body of working device and the direct working part respectively. Model 1 is thought to have more structural durability than model 2. Fatigue life or damage in case of 'SAE bracket history' whose load change is most severest among non-uniform fatigue loads is shown to become most unstable. But life or damage in case of 'Sample history' whose load change is slowest among non-uniform fatigue loads is shown to become most stable. These study results can be effectively utilized with the design of ripper at excavator by anticipating and investigating prevention and durability against its fatigue damage.

• Journal of the Korea Convergence Society
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• v.4 no.2
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• pp.21-27
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• 2013

Spot welding is automation of assembly process, without increasing the vehicle weight and economy, there is a fuel economy improvement of motor vehicles and to widely used in the automotive industry. But By irregular load from the road surface while at the vehicle is running, stress concentration occurs in the weld point, fatigue failure occurs frequently. Considering change of stiffness is the essential fatigue life of the evaluation spot weld. In this paper, by performing a linear static analysis was to understand the vulnerable part. Acquire to the fatigue properties of the spot weld, take the load history of the three levels in the time domain, was performed by setting as a condition of quasi-static fatigue analysis. and Fatigue life prediction method of the spot weld was by applying the method according to the fatigue damage accumulation and the conventional method was compared analyzed with the results shown.