• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.3
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• pp.373-384
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• 2000

To assess the safety of nonlinear steel frame structures subjected to short duration dynamic loadings, especially seismic loading, a nonlinear time domain reliability analysis procedure is proposed in the context of the stochastic finite element concept. In the proposed algorithm, the finite element formulation is combined with concepts of the response surface method, the first order reliability method, and the iterative linear interpolation scheme. This leads to the stochastic finite element concept. Actual earthquake loading time-histories are used to excite structures, enabling a realistic representation of the loading conditions. The assumed stress-based finite element formulation is used to increase its efficiency. The algorithm also has the potential to evaluate the risk associated with any linear or nonlinear structure that can be represented by a finite element algorithm subjected to seismic loading or any short duration dynamic loading. The algorithm is explained with help of an example and verified using the Monte Carlo simulation technique.

• Journal of computational fluids engineering
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• v.19 no.4
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• pp.29-36
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• 2014

A computational study of a thermal striping in the upper plenum of PGSFR(Prototype Generation-IV Sodium-cooled Fast Reactor) being developed at the KAERI(Korea Atomic Energy Research Institute) is presented. The LES(Large Eddy Simulation) approach is employed for the simulation of thermal striping in the upper plenum of the PGSFR. The LES is performed using the WALE (Wall-Adapting Local Eddy-viscosity) model. More than 19.7 million unstructured elements are generated in upper plenum region of the PGSFR using the CFX-Mesh commercial code. The time-averaged velocity components and temperature field in the complicated upper plenum of the PGSFR are presented. The time history of temperature fluctuation at the eight locations of solid walls of UIS(Upper Internal Structure) and IHX(Intermediate Heat eXchanger) are additionally stored. It has been confirmed that the most vulnerable regions to thermal striping are the first plate of UIS. From the temporal variation of temperature at the solid walls, it was possible to find the locations where the thermal stress is large and need to assess whether the solid structures can endure the thermal stress during the reactor life time.

• Journal of Energy Engineering
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• v.8 no.4
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• pp.605-611
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• 1999

Conventional methods for assessing remaining life of critical high temperature components in fossil power plants rely on nondestructive inspection practices and accompanying life analysis based on fracture mechanics By using these conventional methods. It has been difficult to perform uninterrupted in-service inspection for life prediction. Thus, efforts have been made for developing on-line remaining life monitoring systems employing information on the shape of structures, operating variables and material properties. In thus study, a software for on-line life monitoring system which performs real-time life evaluation of a high temperature system headers was developed. The software is capable of evaluating creep and fatigue life usage from the real-time stress data calculated by using temperatures/stress transfer Green functions derived in advance for the specific headers. The major benefits of the developed software life in determining future operating schedule, inspection interval, and replacement plan by monitoring real-time life usage based on prior operating history.

• Tunnel and Underground Space
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• v.21 no.2
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• pp.128-137
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• 2011

The shut-in pressure calculated in common hydrofracturing test for vertical borehole equals generally to the minimum horizontal principal stress, so it should be considered as an essential parameter for determining the in-situ stress regime around the rock mass. It shows usually an ambiguous value in pressure-time history curves, however, because of the relationship between the behavior of hydraulic fractures and the condition of remote stress regime. In this study, a series of numerical analyses have been carried out to compare several methods for determining the shut-in pressure during hydrofracturing. The hydraulic-mechanical coupling has been applied to numerical analysis for simulating the fracture propagation by hydraulic pressure, and the different discontinuity geometry has been considered in numerical models to examine the effect of numerical element shape on fracture propagation pattern. From the numerical simulations with the four different discontinuity geometries, it was revealed that the shut-in pressure obtained from graphical methods rather than statistical method was relatively small. Consequently a care should be taken in selecting a method for determining the shut-in pressure when a stress anomaly around borehole and a fracture propagation with complicate mechanism are considered.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6627-6640
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• 2015

This study was performed to determine the complaint rates of musculoskeletal symptoms and its association with related factors among manufacturing workers. The self-administered questionnaires were given to 856 male with 50 or less employees in manufacturing industries. As a results, complaint rates of work-related musculoskeletal symptoms of the body sites was 61.2% for shoulders, 55.4% for low back, 55.3% for neck, 38.6%, for legs/feet, 32.2% for hands/wrists/fingers and 26.9% for arms/elbows. In logistic regression analysis of significant factors related with musculoskeletal symptoms of body sites, neck was related with marital status, subjective health status, smoking, drinking coffee and occupational stress, shoulders was related with job tenure, shift work, visiting out-patient department and occupational stress, arms/elbows was related with sleeping time, experience of sick absence and occupational stress, hands/wrists/fingers was related with age, smoking, drinking coffee, working hour, job position, job tenure, visiting out-patient department and occupational stress, low back was related with educational level, BMI, sleeping time, job position, job tenure, visiting out-patient department and occupational stress and legs/feet was related with marital status, job position, job tenure, history of hospitalization and occupational stress.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.325-330
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• 2011

RCP(Reactor coolant pump) must be designed to preserve it's functions on normal or abnormal environments and seismic event same as operating basis earthquake(OBE) and safe shutdown earthquake(SSE). Generally, there are static and dynamic analytical method which can be applied by a floor response spectrum or time history analysis for the seismic qualification. Initially, It was accomplished a detailed structural FE-model for finite element analysis on the bases of 3-dimensional solid model which was made by the RCP drawing. As the result of dynamic characteristic using the detailed FE-model, it's shown about 12Hz natural frequency of 1st bending mode shape and maximum displacement has 11mm with the structural bending by single-point response spectrum(SPRS) method at all elevation. But maximum displacement has 7.6mm by multi-point response spectrum(MPRS) method which was applied to the three floor response spectrum at each elevation. Therefore, On a large heighten structures as RCP, The application by SPRS method causes to be more conservative results. Finally, A simpled equivalent beam model which was developed by use of iteration of detailed FE-model is shown the result more similar with those of natural frequencies and SPRS analysis. And maximum equivalent stress and displacement of the simpled beam has verified with 180MPa and 7.1mm each at 15sec as results by SSE time history method.

• Computational Structural Engineering
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• v.8 no.3
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• pp.113-122
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• 1995

The purpose of this study is to evaluate performance and safety of structures designed according to current seismic code or provisions (e.g., Uniform Building Code(UBC), NEHRP provisions, etc.) during lifetime of structures. The performance is represented in terns of reliability in this paper. To perform reliability analyses, a large number of time history response analyses for a given structure are usually required. In this study, to perform reliability analyses ground motions are generated based on nonstationary random process and structures are designed based on UBC. In this paper, responses of structures under a given earthquake is evaluated using dynamic nonlinear time history analyses and also an equivalent nonlinear system (ENS) with response scaling factors. The ENS system is described in the companion paper. Therefore, this paper evaluates the seismic performance of structures and also verify the accuracy of ENS.

• Structural Engineering and Mechanics
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• v.20 no.2
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• pp.173-189
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• 2005

The paper presents a finite element model for studying timber-concrete composite beams under long-term loading. Both deformability of connection system and rheological behaviour of concrete, timber and connection are fully considered. The creep of component materials and the influence of moisture content on the creep of timber and connection, the so-called "mechano-sorptive" effect, are evaluated by means of accurate linear models. The solution is obtained by applying an effective step-by-step procedure in time, which does not require storing the whole stress history in some points in order to account for the creep behaviour. Hence the proposed method is suitable for analyses of composite beams subjected to complex loading and thermo-hygrometric histories. The possibility to accurately predict the long-term response is then shown by comparing numerical and experimental results for different tests.

• Clinical and Experimental Pediatrics
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• v.48 no.6
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• pp.575-579
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• 2005

Urinary incontinence is the most common urinary symptom in children and causes considerable anxiety in children and parents. In most cases, there is no underlying organic pathology and the longterm prognosis is excellent. Despite these reassuring facts, children with wetting problems can be a challenge for primary pediatrician. This is probably because the problem is poorly understood, there is no readily identifiable medical pathology, and because treatment is usually time consuming and arduous. There is a great demand for treatment because wetting is an unpleasant symptom that can cause a stress and anxiety in the family. There may also be other coexisting problems such as urinary tract infection, constipation, soiling, and behavioral or emotional difficulties. Despite the frequency and vexing nature of voiding dysfunction, physicians may not always obtain a careful history to identify and to treat children properly with this condition. This article addresses the comprehensive diagnostic and therapeutic approach to such children.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1210-1215
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• 2002

The spent fuel handling tool is used to handle the refuel bundle and treated by hoist rope on the bridge crane. The new developed handling tool of NPP(Nuclear Power Plant) should be conformed the structural stability under earthquake condition. In this study, the stress and seismic analysis of the handling tool are performed by finite element method. Using the Floor Response Spectrum(FRS) obtained through the time history analysis, the modal and seismic analysis under Operating Basis Earthquake(OBE) and Safe Shutdown Earthquake(SSE) load conditions are carried out. Total 4 cases of different locations of the trolly and the hook are investigated. With the spring-damper element, the tension analysis of hoist rope is conducted. The stability of handling tool under earthquake load condition is conformed with regulatory guide.