• Computers and Concrete
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• v.19 no.1
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• pp.7-17
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• 2017

In Chinese Design Codes, for super high-rise buildings with complex structural distribution, which are regarded as code-exceeding buildings, elasto-plastic time history analysis is needed to validate the requirement of "no collapse under rare earthquake". In this paper, a 117-story super high-rise building is discussed. It has a height of 597 m and a height-width ratio of 9.5, which have both exceeded the limitations stipulated by the Chinese Design Codes. Mega columns adopted in this structure have cross section area of about $45m^2$ at the bottom, which is infrequent in practical projects. NosaCAD and Perform-3D, both widely used in nonlinear analyses, were chosen in this study, with which two model were established and analyzed, respectively. Elasto-plastic time history analysis was conducted to look into its seismic behavior, emphasizing on the stress state and deformation abilities under intensive seismic excitation.From the comparisons on the results under rare earthquake obtained from NosaCAD and Perform-3D, the overall responses such as roof displacement, inter story drift, base shear and damage pattern of the whole structure from each software show agreement to an extent. Besides, the deformation of the structure is below the limitation of the Chinese Codes, the time sequence and distribution of damages on core tubes are reasonable, and can dissipate certain inputted energy, which indicates that the structure can meet the requirement of "no collapse under rare earthquake".

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1085-1092
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• 2005

The OHT(Over Head Transportation) Vehicle transports heavy products quickly and repeatedly at the industrial workplace. The belt in the OHT vehicle is used to support the weight of the OHT Cage. The fatigue of the belt is caused by the dynamic load during the operation time. Since the fatigue fracture of the belt affects the safety at the workplace, the correct prediction of the dynamic load is necessary to calculate the fatigue life of the belt on the design step. In this paper a computer aided analysis method is proposed for the belt in the early design stage using dynamic analysis, stress analysis, belt tensile test, belt fatigue test and fatigue lift prediction method. From the dynamic load time histories and the stress of the belt FE model, a dynamic stress time history is produced. Using linear damage law and cycle counting method, fatigue life cycle is calculated. The method developed in this paper is used to reduce the time and cost for designing the OHT belt in different environment and condition.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.260-267
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• 2001

In this study straightforward design procedure for unbond brace hysteretic dampers is developed. The required amount of equivalent damping to satisfy given performance acceptance criteria is obtained conveniently based on the capacity spectrum method without carrying out time-consuming nonlinear dynamic time history analysis. Then the size of the unbend braces is determined from the required equivalent damping. Parametric study is performed for the design variables such as natural period, yield strength, the stiffness after the first yield, yield stress of the unbond brace.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.114-121
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• 2004

Recently, the finite element absolute nodal coordinate formulation (ANCF) was developed for the large deformation analysis of flexible bodies in multi-body dynamics. This formulation is based on the finite element procedures and the general continuum mechanics theory to represent the elastic forces. In this paper, a computation method of dynamic stress in flexible multi-body dynamics using absolute nodal coordinate formulation is proposed. Numerical examples, based on an Euler-Bernoulli beam theory, are shown to verify the efficiency of the proposed method. This method can be applied for predicting the fatigue life of a mechanical system. Moreover, this study demonstrates that structural and multi-body dynamic models can be unified in one numerical system.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.557-562
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• 2003

The responses of the floor system of a railway bridge are investigated for fatigue life prediction of damaged members using fracture mechanics approach. Numerical analysis of the structure is performed in order to see the influence of track-structure interaction and continuity of the truss connection on the response of the bridge members. Fatigue crack growth analysis is carried through equivalent stress obtained from time-history analysis. The results of time-history analysis agree with measured responses. The fatigue propagation life increases as the curvature in the coped stringer increases.

• Structural Engineering and Mechanics
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• v.19 no.3
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• pp.347-359
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• 2005

This paper attempts to develop the analytical model of estimating the fatigue damage using a linear elastic fracture mechanics method. The stress history on a welding member, when a truck passed over a bridge, was defined as a block loading and the crack closure theory was used. These theories explain the influence of a load on a structure. This study undertook an analysis of the stress range frequency considering both dead load stress and crack opening stress. A probability method applied to stress range frequency distribution and the probability distribution parameters of it was obtained by Maximum likelihood Method and Determinant. Monte Carlo Simulation which generates a probability variants (stress range) output failure block loadings. The probability distribution of failure block loadings was acquired by Maximum likelihood Method and Determinant. This can calculate the fatigue reliability preventing the fatigue failure of a welding member. The failure block loading divided by the average daily truck traffic is a predictive remaining life by a day. Fatigue reliability analysis was carried out for the welding member of the bottom flange of a cross beam and the vertical stiffener of a steel box bridge by the proposed model. Results showed that the primary factor effecting failure time was crack opening stress. It was important to decide the crack opening stress for using the proposed model. Also according to the 50% reliability and 90%, 99.9% failure times were indicated.

• Journal of East-West Nursing Research
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• v.16 no.1
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• pp.61-69
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• 2010

Purpose: The aim of this study was to identify the correlation among job stress, drinking, and smoking of local government staff. Methods: The participants of this study were 205 government staffs working in a local government office. The data were collected by self-report using questionnaires from March 2 to April 30, 2009. The data were analyzed using t-test, Chisquare test, ANOVA, and Man-Whitney test. Results: Physical stress was the highest in job stress components. Majority of the participants (96%) had drinking experiences more than once per month. 25.4% of respondents reported they drank more than 10 glasses each time. Smoking was habitual in 36.6% of the subjects and 28% of subjects had participation in a smoking cessation program. Respondents who reported high job stress had a longer history of smoking. Conclusions: Job stress was highly associated with drinking and smoking. Stress control programs and smoking and alcohol cessation/moderation programs could be beneficial for the health of government staffs.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.272-280
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• 2003

A definite shut-in pressure in hydraulic fracturing techniques is needed for obtaining the correct information on the in-situ stress regimes in rock masses. The relation between the behaviour of hydraulically induced fractures and the condition of remote stress is considered to be major reasons of an ambiguous shut-in pressure in hydraulic fracturing pressure-time history curves. This paper describes the results of a series of numerical analyses carried out using UDEC(Universal Distinct Element Code, Itasca), which is based on the discrete element method, to compare several methods for determining the shut-in pressure during hydraulic fracturing. The fully coupling of hydraulic and mechanical analysis was applied, and the effects of four different discontinuity geometries in numerical modelling have been investigated for this purpose. The effects of different remote stress regimes and different physical properties on hydraulic fracture propagation have been also analyzed. Several methods for obtaining shut-in pressure from the ambiguous shut-in curves have been applied to all the numerical models. The graphical intersection methods, such as (P vs. t) method, (P vs. log(t)) method, (log(P) vs. log(t)) method, give smaller values of the shut-in pressure than the statistical method, (dP/dt vs. P). Care should be taken in selecting a method for shut-in pressure, because there can be existed a stress anomaly around the wellbore and fracturing from the wellbore by a constant flow rate may have a more complicate mechanism.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.114-119
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• 2004

Endbeam is an important structural member of freight bogie for the support of service loading. In general, more than 25 years' durability is necessary. However, endbeam occur fatigue fracture in dynamic stress concentration location because comparatively strength and stiffness are low. Therefore, structure analysis is performed to evaluate structural problem of endbeam and local strain range as durability analysis. The number of cycles is extracted concerning the bogie in operation by measurement dynamic stress time history on critical part which is crack initiation in actual fact. At this time rainflow cycle counting is used to consider change of stress for operating condition. Based on the fatigue life curves and the stress analysis, the fatigue life of the endbeam is predicted and compared with the experimentally determined fatigue life, resulting in a fairly good correlation.

• Earthquakes and Structures
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• v.10 no.5
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• pp.1089-1109
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• 2016

Modified two-surface model (M2SM) is one of the steel elasto-plastic hysteretic constitutive models that consider both analysis accuracy and efficiency. However, when M2SM is used for complex strain history, sometimes the results are irrational due to the limitation of stress-strain path judgment. In this paper, the defect of M2SM was re-modified by improving the judgment of stress-strain paths. The accuracy and applicability of the improved method were verified on both material and structural level. Based on this improvement, the nonlinear time-history analysis was carried out for a deck-through steel arch bridge with a 200 m-long span under the ground motions of Chi-Chi earthquake and Niigata earthquake. In the analysis, we compared the results obtained by hysteretic constitutive models of improved two-surface model (I2SM) presented in this paper, M2SM and the bilinear kinematic hardening model (BKHM). Results show that, although the analysis precision of displacement response of different steel hysteretic models differs little from each other, the stress-strain responses of the structure are affected by steel hysteretic models apparently. The difference between the stress-strain responses obtained by I2SM and M2SM cannot be neglected. In significantly damaged areas, BKHM gives smaller stress result and obviously different strain response compared with I2SM and M2SM, and tends to overestimate the effect of hysteretic energy dissipation. Moreover, at some position with severe damage, BKHM may underestimate the size of seismic damaged areas. Different steel hysteretic models also have influences on structural damage evaluation results based on deformation behavior and low cycle fatigue, and may lead to completely different judgment of failure, especially in severely damaged areas.