• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1392-1400
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• 1996

The need of companies shorten the design-to-manufacturing process for new products with improved quality in cost effective manner places increasing demends on engineers to simulate the performance characteristics of a design before it is built of a prototype is developed. For theses demands CAE(Computer-Aided Engineering) offers engineers not only giving confidence of their design but also eliminating potential errors due totesting prototypes in small numbers. This paper present the method to predict the fatigue life using dynamics simulation and FEA(Finite Element Analysis) for construciton equipment in the computer before building prototype. The dynamicsimulatio is to get the load-time history corresponding to the maneuvering and driving of the construction equipment. The FEA is to build a model of the structure and then analyse to define the local stress response to applied loadings using linear static analysis.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.639-644
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• 2007

The accurate peak response estimation of a seismically excited structure with frictional damping system(FDS) is very difficult since the structure with FDS shows nonlinear behavior dependent on the structural period, loading characteristics, and relative magnitude between the frictional force and the excitation load. Previous studies have estimated that by replacing a nonlinear system with an equivalent linear one or by employing the response spectrum obtained based on nonlinear time history and statistical analysis. In the case that on earthquake load is defined with probabilistic characteristics, the corresponding response of the structure with FDS has probabilistic distribution. In this study, nonlinear time history analyses were performed for the structure with FDS subjected to artificial earthquake loads generated using Kanai-Tajimi filter. An equation for the probability density function (PDF) of the displacement response is proposed by adapting the PDF of the normal distribution. Finally, coefficients of the proposed PDF is obtained by regression analysis of the statistical distribution of the time history responses. Finally, the correlation between PDFs and statistical response distribution is presented.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.159-168
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• 1999

In seismic analysis, there are two main ways - uniform load method and dynamic analysis, dynamic analysis can be divided into response spectrum analysis and time history analysis. In case of which get the complexion of the vibration with 3-axis of coordinate direction in each mode of free vibration mode happened owing to complication of the shape, 3-dimensional dynamic analysis is recommended to perform as multi-mode spectral analysis in standard specification for highway bridge. The purpose of this study is to understand the dynamic behavior by performing multi-mode seismic analysis according to responses analysis and time history anal)'sis in using record of earthquake. In accordance with the criterion of seismic design as defined in standard specification for highway bridge by using modified records of the El Centre and Coyote Lake earthquake, response spectrum was constructed by using the tripartite logarithmic plot. The 3-span continuous space truss bridge was selected as model of numerical analysis. As the result performed time history analysis and analysis of response spectrum for the model of numerical analysis, the result of time history analysis was slightly larger than that of response spectrum analysis. This coincide with the tendency of the result came from the analysis when using a jagged response spectrum analysis, This coincide with the tendency of the result came from the analysis when using a jagged response spectrum for a single excitation. In the Process of performing these two analysis. response spectrum analysis is more effective than time history analysis in saving times in analyzing data.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.118-123
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• 2001

Most structures of automobile are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic farces for the evaluations of fatigue life and stress concentration exactly. It is rarely obtained the accurate load history of specified positions because of the errors such as modeling, measurement, and etc. In the beginning of design, exact load data are actually necessary for the fatigue strength and life analysis to minimize the cost and time of designing. In this paper, the procedure of practical dynamic load determination is developed by the combination of the principal stresses of F.E. analysis and experiment. Inverse problem and least square pseudo inverse matrix are adopted to obtain an inverse matrix of analyzed stresses matrix. Pseudo-Practical dynamic load was calculated for Lab. Test of sub-structure. GUI program(PLODAS) was developed for whole of above procedure. This proposed method could be extended to any geometric shape of structure.

• Wind and Structures
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• v.17 no.2
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• pp.227-244
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• 2013

Non-stationary extreme winds such as thunderstorm downbursts are responsible for many structural damages. This research presents a time domain approach for estimating along-wind load effects on tall buildings using multiple wind speed time history samples, which are simulated from evolutionary power spectra density (EPSD) functions of non-stationary wind fluctuations using the method developed by the authors' earlier research. The influence of transient wind loads on various responses including time-varying mean, root-mean-square value and peak factor is also studied. Furthermore, a simplified model is proposed to describe the non-stationary wind fluctuation as a uniformly modulated process with a modulation function following the time-varying mean. Finally, the probabilistic extreme response and peak factor are quantified based on the up-crossing theory of non-stationary process. As compared to the time domain response analysis using limited samples of wind record, usually one sample, the analysis using multiple samples presented in this study will provide more statistical information of responses. The time domain simulation also facilitates consideration of nonlinearities of structural and wind load characteristics over previous frequency domain analysis.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.43-49
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• 2012

In the design of high speed railway bridges is important a impact factor as a tool of assessing the dynamic capacitys of bridges. However, the impact factor(or dynamic amplification factor, DAF) of high speed railway bridges may essentially be changeable because the dynamic response is affected by the long train length(380 m), number of axles and high speed velocity(300 km/h)(Korea Train eXpress: KTX). Therefore, on this study will be examined the dynamic capacity and stability of the typical PSC Box Girder of high speed railway bridge. At first, the static/dynamic analysis is performed considering the axle load line of KTX based upon existing references. Additionally, the KTX moving load is transformed into the dynamic time series load for conducting various parameter studies like axle length, analytical time increment, velocity of KTX. The time history analysis is repeatedly performed to get maximum dynamic responce by varying axle load length, analytical time increment, velocity of KTX. The study shows that dynamic analysis has resonable results with optimal axle load length(0.6 m) and time increment(0.01 sec.) and maximum DAF and dynamic resonance happens at 270 km/h velocity of KTX.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.211-219
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• 2010

The design concept of high speed railway bridges is applied to a method for increasing the stiffness of existing bridge structures considering the impact factor by a static load. Generally, the process of structural design would be relied upon an advanced foreign technology. However, the dynamic amplification factor (DAF) and dynamic capacity assessment of high speed railway bridges may be conducted essentially a detailed estimation because the resonance phenomenon is affected by the long length (380 m) and high speed (300 km/h) moving of a high speed railway (Korea Train eXpress: KTX). Therefore, this study will be examined the dynamic capacity of the typical PSC Box Girder high speed railway bridge efficiently, and offered the basic information for the reasonable structural design. For this, the static analysis is conducted considering the load line diagram of KTX based upon existing references. In addition, the KTX moving load is transformed into the time series load considering various analytical variables. The time history analysis is assessed reasonable using the transformed time series load. At that time, analytical variables for calculating the time series load are considered loading node distance, time increment and KTX velocity variation etc. The dynamic capacity of the PSC Box Girder high speed railway bridge is examined based upon the FE analysis result systematically. The structural safety is assessed quantitatively in accordance with the related regulation of the inside and outside of the country.

• Earthquakes and Structures
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• v.15 no.2
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• pp.123-132
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• 2018

In this paper the strain energy density (SED) model is used to analyze the seismic behavior of suspen-domes and a new criterion is established for judging the seismic failure based on a characteristic point in the SED model. Firstly, a nonlinear time-history response analysis was carried out using the finite-element package ANSYS for typical suspen-domes subjected to different ground motions. The seismic responses including nodal displacements, ratios of yielding members, strain energy density and structural maximum deformation energy were extracted corresponding to the increasing peak ground acceleration (A). Secondly, the SED sum ($I_d$) was calculated which revealed that the $I_d-A$ curve exhibited a relatively large change (called a characteristic point) at a certain value of A with a very small load increment after the structures entered the elastic-plastic state. Thirdly, a SED criterion is proposed to judge the seismic failure load based on the characteristic point. Subsequently, the case study verifies the characteristic point and the proposed SED criterion. Finally, this paper describes the unity and application of the SED criterion. The SED method may open a new way for structural appraisal and the SED criterion might give a unified criterion for predicting the failure loads of various structures subjected to dynamic loads.

• Earthquakes and Structures
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• v.6 no.4
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• pp.437-455
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• 2014

Some conventional lateral load patterns for pushover analysis, and proposing a new accurate pattern was investigated in present research. The new proposed load pattern has load distribution according weight and stiffness variation in height and mode shape of structure. The assessment of pushover application with mentioned pattern in X type braced steel frames and steel moment resisting frames, with stiffness and mass variation in height, was studied completely and the obtained results were compared with nonlinear dynamic analysis method (including time history analysis). The methods were compared from standpoints of some basic parameters such as displacement, drift and shape of lateral load pattern. It is concluded that proposed load pattern results are closer to nonlinear dynamic analysis (NDA) compared to other pushover load patterns especially in tall and medium-rise buildings having different stiffness and mass during the height.

• Structural Engineering and Mechanics
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• v.20 no.6
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• pp.673-693
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• 2005

A general step-by-step simulation for the time-dependent analysis of segmentally-erected prestressed concrete box-girder bridges is presented. A three dimensional finite-element model for the balanced-cantilever construction of segmental bridges, including effects of the load history, material nonlinearity, creep, shrinkage, and aging of concrete and the relaxation of prestressing steel was developed using ABAQUS software. The models included three-dimensional shell elements to model the box-girder walls and Rebar elements representing the prestressing tendons. The step-by-step procedure allows simulating the construction stages, effects of time-dependent deformations of materials and changes in the structural system of the bridges. The structural responses during construction and throughout the service life were traced. A comparison of the developed computer simulation with available experimental results was conducted and good agreement was found. Deflection of the bridge deck, changes in stresses and strains and the redistribution of internal forces were calculated for different examples of bridges, built by the balanced-cantilever method, over thirty-year duration. Significant time-dependent effects on the bridge deflections and redistribution of internal forces and stresses were observed. The ultimate load carrying capacities of the bridges and the behavior before collapse were also determined. It was observed that the ultimate load carrying capacity of such bridges decreases with time as a result of time-dependent effects.