• Proceedings of the Computational Structural Engineering Institute Conference
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.84-91
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• 2001

In this study, the adaptive analysis procedure of crack propagation based on the element-free Galerkin(EFG) method is presented. The adaptivity analysis in quasi-static crack propagation is achieved by adding and/or removing the node along the background integration cell that are refined or recovered according to the estimated error. These errors are obtained basically by calculating the difference between the values of the projected stresses and original EFG stresses. To evaluate the performance of proposed adaptive procedure, the crack propagation behavior is investigated for several examples. The results of these examples show the efficiency and accuracy of proposed scheme in crack propagation analysis.

• Journal of the Korean Society of Safety
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• 제12권2호
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• pp.70-79
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• 1997

This paper presents a study on the fuzzy linguistic variable based approach for safety assessment of human body in ELF electromagnetic field considering power system states. To cope with the demand in modern industry, the power system becomes larger in scale, higher in voltage. The advent of high voltage system has increased the relative importance of field effects. The analysis of ELF electromagnetic field based on Quasi-Static Method is introduced while the power system is included to model the expected and/or unexpected uncertainty caused by the load fluctuation and parameter changes. In order to analyze the power system, Monte Carlo simulation method and contingency analysis method are adopted in normal state and alert state, respectively. In the safety assessment of human body, the approach based on fuzzy linguistic variable is employed to overcome the shortcomings resulting from a crisp set concept. The suggested scheme is applied to a sample system(modified IEEE 14 bus system) to validate the usefulness.

• Journal of the Korean Society for Precision Engineering
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• 제19권9호
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• pp.34-40
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• 2002

Machining accuracy is affected by quasi-static errors of machining center. Since machine errors have a direct influence upon both the surface finish and geometric shape of the finished workpiece, it is very important to measure the machine errors and to compensate these errors. The laser measurement method for identifying geometric errors of machine tool has the disadvantages such as high cost, long calibration time and usage of volumetric error synthesis model. Accordingly, this paper deals with analysis of the geometric errors of a machine tool using ball bar test without using complicated error synthesis model. Statistical analysis method was adopted in this paper for deriving geometric errors using hemispherical helix ball bar test. As a result of experiment, geometric errors of the vertical machining center are compensated by 88%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.188-193
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• 2013

The large mass method for dynamic analysis of statically determinate beams subjected to in-phase support motions is justified by showing that the equation of motion of the beams under consideration is equivalent to that of large mass model of the beam when an appropriate large mass ratio is employed. The accuracy of the stress responses based on the beam large mass method is investigated through careful numerical tests. The numerical results are compared to analytic solutions and the comparison shows that the large mass method yields not only the time history of motion but also the distributions of bending moment and shear force accurately.

• Journal of the Korean Society of Safety
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• 제31권4호
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• pp.64-74
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• 2016

Recently, the seismic stability evaluation of concrete gravity dams is raised due to the failure of dams occurred by the Izmit, Turkey and JiJi, Taiwan earthquake in 1999. Dams failure may incur loss of life and properties around the dam as well as damage to dam structure itself. Recently, there has been growing much concerns about "earthquake - resistance" or "seismic safety" of existing concrete gravity dams designed before current seismic design provisions were implemented. This research develops three evaluation levels for seismic stability of concrete gravity dams on the basis of the evaluation method of seismic stability of concrete gravity dams in U.S.A., Japan, Canada, and etc. Level 1 is a preliminary evaluation which is for purpose of screening. Level 2 is a pseudo-static evaluation on the basis of the seismic intensity method. And level 3 is a detail evaluation by the dynamic analysis. Evaluation results on existing concrete gravity dams on operation showed good seismic performance under designed artificial earthquake(KHC earthquake).

• Steel and Composite Structures
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• 제26권5호
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• pp.549-556
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• 2018

Progressive building collapse occurs when failure of a structural component leads to the failure and collapse of surrounding members, possibly promoting additional failure. Global system collapse will occur if the damaged system is unable to reach a new static equilibrium configuration. The most common type of primary failure which led to the progressive collapse phenomenon, is the sudden removal of a column by various factors. In this study, a method is proposed to prevent progressive collapse phenomena in structures subjected to removal of a single column. A vierendeel peripheral frame at roof level is used to redistribute the removed column's load on other columns of the structure. For analysis, quasi-static approach is used which considers various load combinations. This method, while economically affordable is easily applicable (also for new structures as well as for existing structures and without causing damage to their architectural requirements). Special emphasis is focused on the evolution of vertical displacements of column removal point. Even though additional stresses and displacements are experienced by removal of a structural load bearing column, the proposed method considerably reduces the displacement at the mentioned point and prevents the collapse of the structural frame.

• Smart Structures and Systems
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• 제11권4호
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• pp.331-348
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• 2013

Effective monitoring, reliable data analysis, and rational data interpretations are challenges for engineers who are specialized in bridge health monitoring. This paper demonstrates how to use the Global Positioning System (GPS) and accelerometer data to accurately extract static and quasi-static displacements of the bridge induced by ambient effects. To eliminate the disadvantages of the two separate units, based on the characteristics of the bias terms derived from the GPS and accelerometer respectively, a wavelet based multi-step filtering method by combining the merits of the continuous wavelet transform (CWT) with the discrete stationary wavelet transform (SWT) is proposed so as to address the GPS deformation monitoring application more efficiently. The field measurements are carried out on an existing suspension bridge under the normal operation without any traffic interference. Experimental results showed that the frequencies and absolute displacements of the bridge can be accurate extracted by the proposed method. The integration of GPS and accelerometer can be used as a reliable tool to characterize the dynamic behavior of large structures such as suspension bridges undergoing environmental loads.

• Structural Engineering and Mechanics
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• 제4권6호
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• pp.655-678
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• 1996

The paper reports on alternative hybrid/mixed formulations being developed by the Structural Analysis Research Group of Institute Superior T$\acute{e}$cnico. These formulations open the scope and increase the power of the finite element method by allowing different fields to be independently approximated, within certain consistency criteria, and by enhancing the use of a wide range of approximation functions. They have been applied to the analysis of 2-D problems, laminar structures and solids, using different constitutive relations, both in quasi-static and dynamic regimes. The fundamental properties of the formulations are identified and assessed and their performance is illustrated using simple, linear applications.

• Structural Engineering and Mechanics
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• 제59권5호
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• pp.921-932
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• 2016

This paper presents a theoretical analysis for determining the transverse deflection of simply supported battened beams subjected to a uniformly distributed transverse quasi-static load. The analysis considers not only the shear effect but also the discrete effect of battens on the transverse deflection of the battened beam. The analytical solution is obtained using the principle of minimum potential energy. Numerical validation of the present analytical solution is accomplished using finite element methods. The present analytical solution shows that the shear effect on the transverse deflection of battened beams increases with the cross-section area of the main member but decreases with the cross-section area of the batten. The longer the battened beam is, or the larger the moment of inertia of the main member is, the smaller the shear effect will be.

• Journal of Advanced Marine Engineering and Technology
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• 제27권2호
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• pp.289-298
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• 2003

Meshfree approximations exhibit significant Potential to solve partial differential equations. Meshfree methods have been successfully applied to various problems which the traditional finite element methods have difficulties to handle including the quasi-static and dynamic fracture, large deformation problems, contact problems, and strain localization problems. Reproducing Kernel Particle Method (RKPM) is used in this research fur to its built-in feature of multi-resolution. the sound mathematical foundation and good numerical performance. A formulation of RKPM is reviewed and numerical examples are given to verify the accuracy of the proposed meshfree method for largely deformed elasto-plastic material.