• Geotechnical Engineering
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• v.5 no.1
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• pp.19-26
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• 1989

In this study, the finite element method for nonlinear problems is developed theroretically to see the design loads of foundation, when the circular plate resting on elasto-viscoplastic soil medium is loaded axisymmetrically. The paper shows that the plastic zone of soil medium is displayed at the near the edge of plate at the first place; when the plastic zone of soil medium is linked around central axis, the external load is termed by allowable load or design load, and then the contact pressure changes abruptly, in this case it is approved to be the risk of shear failure. The results of numerical analysis using the Mohr-Coulomb yield criterion, and experimental analysis for a appropriate safety factor are approximative, but numerical results are smaller than the value based on Terzaghi's theory.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.261-267
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• 2006

The required storage inventory is a very important decision variable which determines the storage capacity of a container terminal. Generally, the required storage inventory is dependent upon such factors as ship headway, allowable dwell time of containers, loading/unloading time per ship, and so on. Until now, the required storage inventory is estimated under the assumption that the factors are deterministic in several studies. However, this study proposes how to estimate a required storage inventory satisfying the required service level under the assumption that a containership's load size is probabilistic. Numerical experiments, which use a simulation show that the proposed method can estimate more adequately the maximum storage inventory than other methods under a probabilistic environment.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.223-231
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• 2007

Considering wind speed uncertainty, reliability analysis of the LNG unloading arm at Tongyoung Production Site was performed. Extreme distribution of wind speed was estimated from the data collected at the weather center and wind load was calculated using wind velocities and coefficients of wind pressure. The unloading arm was modeled with plate and solid elements. Contact elements were used to describe the interface between base of structure andground. Response surface for maximum effective stress was found for reliability analysis and then reliability functions was defined and used to determine exceeding probability of allowable and yield stresses. In addition, sensitivity analysis was also performed to estimate the effect of possible material deterioration in the future.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.627-635
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• 2020

In this study, the optimal support span determination of pipeline system was carried out in consideration of the effects of seismic loads. The theoretical support and structural analysis were used to determine the optimal support span of piping system according to pipe diameter using theoretical and structural deflection criteria. The reliability of the analysis results was secured by comparing the structural and theoretical results. In particular, the optimum support span of piping system was obtained by considering the effects of seismic load, and the optimal support span of pipe diameter and piping system tended to be proportional to each other. When considering the effects of earthquakes on different pipe diameters(300~2,500mm), the span length is reduced by up to 48% at the allowable stress criterion, and the pipe span length is reduced by up to 5.9% at the deflection criterion. It can be seen that the effect of the seismic load on the determination of the piping span length has a greater effect on the stress than the displacement.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.2
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• pp.79-86
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• 2014

This paper describes an integrity evaluation method for emergency diesel generator(EDG) and rotor part of EDG. EDG is a very important equipment in the nuclear power plant(NPP). EDG supplies electricity to the safety-related equipments for the safety shut down of NPP in an emergency situation of earthquake. The safety of the rotor part of EDG is also important during seismic impact from earthquake. The finite element modelling of the EDG including rotor part was constructed. The modal analysis of EDG was firstly performed. The first natural frequency was calculated and revealed higher than the cutoff frequency of seismic spectrum. Then the stress analysis was done to compare with the allowable stress. The safety of the rotor part was investigated by the finite element analysis of the rotor and journal bearing interaction to find film thickness and critical speed. The seismic load was applied to rotor part in a manner that the load was a weighted static load. Analysis results showed that the maximum stress was within the range of allowable stress and the film thickness is larger than the permissible minimum thickness, and the critical speed was out of the operating speed. Hence, the structural and dynamic integrity of EDG could be confirmed by the numerical analysis method used in this paper. However, dynamic analysis of a rotating rotor and supporting bearing with the seismic impact needs to be investigated in a more rigorous method since the seismic load to the rotating part complicates the behavior of rotating system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.44-54
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• 2018

Stress and fatigue of the distributor, an equipment of the high-pressure evaporator for the HRSG, were evaluated according to ASME Boiler & Pressure Vessel Code Section VIII Division 2. First, from the results of the piping system analysis model, reaction forces of the tubes connected to the distributor were derived and used as the nozzle load applied to the detailed analysis model of the distributor afterward. Next, the detailed model to analyze the distributor was constructed, the distributor being statically analyzed for the design condition with the steam pressure and the nozzle load. As a result, the maximum stress occurred at the bore of the horizontal nozzle, and the primary membrane stress at the shell and nozzle was found to be less than the allowable. Next, for the transient operating conditions given for the distributor, thermal analysis was performed and the structural analysis was carried out with the steam pressure, nozzle load, and thermal load. Under the transient conditions, the maximum stress occurred at the vertical downcomer nozzle, and of which fatigue life was evaluated. As a result, the cumulative usage factor was less than the allowable and hence the distributor was found to be safe from fatigue failure.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.293-304
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• 2018

This paper described a results of field test based on plate bearing test of the restoration material, which was developed to restore the ground cavity due to sewerage damage. The analysis of bearing capacity characteristics on the restoration materials was performed by experimental results. The results showed that the load bearing capacity in the maximum stress condition of the foundation ground is about 66%-70%, when the expansion mat is embedded at the bottom of 0.1 m and 0.2 m from the ground surface. However, The load bearing capacity of expansion mat according to embedded depth was not large. The load bearing capacity of concrete mats was about 82%-90% compared with that of ground surface, and it showed about 50% of the load bearing capacity compared with the expansion mat. As a result of analysis of allowable bearing capacity according to restoration materials, it was confirmed that the allowable bearing capacity of the expansion mat and the concrete was about 130%-150% and about 160% more than the foundation ground, respectively.

• Journal of the Korean Geotechnical Society
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• v.38 no.10
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• pp.61-74
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• 2022

Considering that the number of cases in which a structure foundation is located on weathered rock has been increasing recently, for adequate design bearing capacity of a foundation on weathered rock, allowable bearing capacities of such foundations in geotechnical investigation reports were studied. With reference to the study results, the allowable bearing capacity of a foundation on weathered rock was approximately 400-700 kN/m², with a large variation, and was considered a conservative value. Because the allowable bearing capacity of the foundation ground is an important index in determining the foundation type in the early design stage, it can have a significant influence on the construction cost and period according to the initial decision. Thus, in this study, six large-scale plate-bearing tests were conducted on weathered rock, and the bearing capacity and settlement characteristics were analyzed. According to the test results, the bearing capacities from the six tests exceeded 1,500 kN/m², and it shows that the results are similar with the one of bearing capacity formula by Pressuremeter tests when compared with the various bearing capacity formula. In addition, the elastic modulus determined by the inverse calculation of the load-settlement behavior from the large-scale plate-bearing tests was appropriate for applying the elastic modulus of the Pressuremeter tests. With consideration of the large-scale plate-bearing tests in this study and other results of plate-bearing tests on weathered rock in Korea, the allowable bearing capacity of weathered rock is evaluated to be over 1,000 kN/m². However, because the settlement of the foundation increases as the foundation size increases, the allowable bearing capacity should be restrained by the allowable settlement criteria of an upper structure. Therefore, in this study, the anticipated foundation settlements along the foundation size and the thickness of weathered rocks have been evaluated by numerical analysis, and the foundation size and ground conditions, with an allowable bearing capacity of over 1,000 kN/m², have been proposed as a table. These findings are considered useful in determining the foundation type in the early foundation design.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.299-306
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• 2002

The load frequency control(LFC) of power system is one of important subjects in view of system operation and control. That is, even though the rapid load disturbances are applied to the given power system, the stable and reliable power should be supplied to the users, converging unconditionally and rapidly the frequency deviations and the tie-line power flow ones of each area into allowable boundary limits. Nonetheless of such needs, if the internal parameter perturbation and the sudden load variation are given, the unstable phenomena of power systems can be often brought out because of the large frequency deviation and the unsuppressible power line one. So, an optimal modulation controller for UC of multi-area power system is designed by a recursive algorithm that determines the state weighting matrix Q of a linear quadratic performance criterion. The optimal modulation controller is based on optimal control and can obtain the exact dynamic response of the UC of multi-area power system in the time domain. The performances of the resultant optimal modulation control, that is, the steady-state deviations of frequency and tie-line power flow and the related dynamics, were investigated and analyzed in detail by being applied to the UC of multi-area power system in the perturbations of predetermined internal parameters. Through the simulation results tried variously in this paper for disturbance of stepwise load changes, the superiorities of the proposed optimal modulation controller in robustness and stability were proved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.235-241
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• 2014

As a fiber-optic cable is being unwound, it is protected by a tube that is designed to prevent unwinding problems such as tangling and unintentional cutting. In addition, a guide body is separated from the protective tube if a shear pin breaks when the maximum allowable load is exceeded. Therefore, it is important to analyze and predict the unwinding behavior of the protective tube, as well as the load on the shear pin, to enhance the likelihood of a successful operation when laying cables at extreme depths. In this study, the protective tube and the guide body are modeled with particles and are constrained with a constant-length constraint. The load on the shear pin was verified against experimental data, and the unwinding behavior was predicted from the load prediction results.