• Journal of the Korean Geotechnical Society
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• v.35 no.7
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• pp.29-39
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• 2019

Load distributive compression anchors distribute the compressive stress in the grout and increase the pull-out capacity of the anchor by using multiple anchor bodies. In this anchor type, the spacing between the anchor bodies has a large influence on the stress in the grout. However, there are few researches about the spacing and there are no design standards. Therefore, the effect of the anchor body spacing on the grout stress was analyzed by performing finite element analyses. First, the applicability of the numerical modeling was verified by comparing with field test results of a compression anchor. Then, the parametric study was performed varying soil type, anchor body spacing, and load magnitude. The analysis results showed that the maximum compressive stress in the grout increased at the narrower spacing and the tensile stress developed at the wider spacing. Therefore, the optimum spacing was defined as the spacing, which prevents the superposition of compressive stresses and minimize the tensile stress. Finally, the optimum spacing was proposed according to the soil type and the load magnitude.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.2
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• pp.1-10
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• 1989

In this paper, dynamic response of a truss bridge due to constantly moving train loads is analysed. Dynamic response of the bridge is found by the mode superposition method with the solution of the eigenvalue problem by Householder transformation and QL algorithm. To prove the validity of the analysis procedure, the response due to a very slowly moving load is compared with the result from the static analysis program, and the dynamic response is also compared with the result from the direct integration method. Based upon this, the variation of dynamic amplification factors is investigated by changing the train types and speeds, and the result is compared with the code specified impact factor. From this study, it was known that the dynamic amplification factor is not quite different by train types in low speeds but in high speeds it is, and in the case of electric car and U. I. C. loads the factor could exceed the code specified impact factor depending upon the speed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.743-751
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• 2000

Because welding residual stress is formidable result in electric resistance spot welding process, and it detrimentally affect to fatigue crack initiation and growth at nugget edge of spot welded la p joints, it should be considered in fatigue analysis. Thus, accurate prediction of residual stress is very important. In this study, nonlinear finite element analysis on welding residual stress generated in process of the spot welding was conducted, and their results were compared with experimental data measured by X-ray diffraction method. By using their results, the maximum principal stress considered welding residual stress at nugget edge of the spot welded lap joint subjected to tension-shear load was calculated by superposition method. And, the $\Delta$P- $N_f$ relations obtained through fatigue, tests on the IB-type spot welded lap joints was systematically rearranged with the maximum principal stress considered welding residual stress. From the results, it was found th2at fatigue strength of the IB-type spot welded lap joints could be systematically and more reasonably rearranged by the maximum principal stress($\sigma$1max-res considered welding residual stress at nugget edge of the spot welding point.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.253-261
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• 2014

In this paper, vibration analysis of power differential gear train for 2.5MW wind turbine system is analyzed. which system is composed of two planetary gear set, one helical gear set and main shaft that connected by flange. Planetary gear set, helical gear set, main shaft are modeled in MASTA program and housing, torque arm, carrier, flange components are modeling by finite element method. Each models are combined by component mode superposition. To analysis of natural vibration characteristic about 2.5MW wind turbine gear train was performed and check about critical speed with wind load, mass unbalance, angle misalignment excitation frequency.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.535-541
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• 1997

It is proper that the load distribution and the actual stress of members is analyzed by field measurement in estimating to the behavior of truss railway bridges, but those procedures are very difficult. So, the studies for the deduction of the stress, using the indirect data which are able to get from the research and investigation without field measurement, are needed. In this study, to investigate quantitically the variation of the stress of members, the stresses are obtained from the simulation which is considered the the reduction of the section area and the stiffness due to the corrosion and the degree of the stress ratio and the distribution is calculated. As the results, the stress of truss members is almost lineary increased to the decreasing of the area and the lower chord is greatly affected. And the increasing of the stress is predicted by the superposition to the results of the amount of that in each members.

• Elastomers and Composites
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• v.48 no.2
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• pp.156-160
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• 2013

A study on compressive creep behavior of ACM rubber for automotive engine gasket was performed using TMA thermal analysis. From the results of isothermal measurements with constant load of 1 N at several different temperatures of 160, 180, 200, and $220^{\circ}C$, compressive creep data at the given temperatures were obtained, and therefrom, shift factor ($a_T$) and master curve at reference temperature of $160^{\circ}C$ were obtained using time-temperature superposition principle (TTSP). $C_1$ and $C_2$ of WLF (Williams-Landel-Ferry) equation were calculated through the WLF plot as -1.107 and 11.571, respectively. From this, life time of ACM rubber at $120^{\circ}C$ was predicted as about 24,000 hrs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.3
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• pp.87-94
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• 2007

A structural dynamic analysis can be divided into a time domain analysis and a frequency domain analysis. The time domain analysis makes use of a direct integration method or a mode superposition method and the frequency domain analysis applies a DFT method. Generally the DFT method is more effective method in case of calculating response of periodic excitation. But in case of transient excitation exact solution can not be acquired. So, by modifying the response or increasing the period accuracy of solution can be enhanced. Accordingly this study analyzed dynamic responses of structures under aperiodic moving load in time domain and frequence domain. Consequently it is concluded that exact solution would be get enough using DFT method by increasing the duration of free vibration or modifying the dynamic response.

• Structural Engineering and Mechanics
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• v.52 no.3
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• pp.485-505
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• 2014

This study aimed to develop an approach to accurately predict the wind models and wind effects of large wind turbines. The wind-induced vibration characteristics of a 5 MW tower-blade coupled wind turbine system have been investigated in this paper. First, the blade-tower integration model was established, which included blades, nacelle, tower and the base of the wind turbine system. The harmonic superposition method and modified blade element momentum theory were then applied to simulate the fluctuating wind field for the rotor blades and tower. Finally, wind-induced responses and equivalent static wind loads (ESWL) of the system were studied based on the modified consistent coupling method, which took into account coupling effects of resonant modes, cross terms of resonant and background responses. Furthermore, useful suggestions were proposed to instruct the wind resistance design of large wind turbines. Based on obtained results, it is shown from the obtained results that wind-induced responses and ESWL were characterized with complicated modal responses, multi-mode coupling effects, and multiple equivalent objectives. Compared with the background component, the resonant component made more contribution to wind-induced responses and equivalent static wind loads at the middle-upper part of the tower and blades, and cross terms between background and resonant components affected the total fluctuation responses, while the background responses were similar with the resonant responses at the bottom of tower.

• Land and Housing Review
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• v.1 no.1
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• pp.43-50
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• 2010

In this study, the influences of steel dampers on the behavior of RC frames were investigated using the experimental approach to suggest the installation methods of steel dampers using K-barces. The performances of RC frames with dampers can be evaluated by superposition the load-displacement curves of RC frames and steel dampers with regard to the influences of K-braces. Three specimens are tested to investigate the cyclic behavior of RC frames with dampers. The performances of RC frames with dampers with respect to strength, rigidity, and hysteretic performance are examined. It was found that test results demonstrates the effect of seismic retrofit on RC frames with steel dampers(D-RCF-KBSF, D-RCF-KBSP) compared with RC frames(N-RCF). An approximate design curves may not be good agreement with those of the tests, it is conservative enough so that you can design of RC frames with steel damper with regard to the influences of K-braces.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1077-1085
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• 2016

Linear roller bearing (LRB) is an important mechanical element that is widely used in precise positioning systems that are subjected to large loads. This paper presents a new model for estimating the displacement of an LRB subjected to external forces. For this purpose, assuming that the linear motion block (LM block) is rigid, the equilibrium conditions for the LRB were obtained by solving the equilibrium equations of the rollers and the rigid LM block using the iterative Newton-Raphson method. The contact loads between the rollers and raceways were determined considering the profiled rollers. Then, the structural deformations of the LM block, subjected to the contact loads from the rigid LM block model, were computed using a finite element model for the LM block. The displacements of the LRB were then determined by superposition of the rigid LM block displacements on the induced displacements due to the structural deformations of the LM block. The proposed method was verified through comparison with a program by the bearing manufacturer.