• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.5
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• pp.35-45
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• 2001

Recently, the floor systems those require large open space may have low inherent damping due to the decline of the use of curtain walls. Furthermore, the use of the high strength materials has resulted in more flexible and longer spanning in floor systems. The long span structures such as shopping malls, offices and large assembly rooms may lead to significant dynamic response due to human activities. Excessive vibrations make the occupants uncomfortable and deteriorate the serviceability of buildings. It is now proved that footfall loading is the major source of floor vibrations. The common method of application of walking loads for the vibration analysis of structures subjected to walking loads is to inflict measured walking loads and periodic function at a node. But this method could not account for the moving effect of walking. In this study, natural frequency and damping ratio of example structure are evaluated by heel drop tests. And the application of equivalent walking loads is used for on efficient vibration analysis of the plate structures subjected to walking loads.

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.77-85
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• 2012

The membrane structure maintains stable form by giving initial tension to ductile membrane and increasing the stiffness of exterior that is much adopted in the large span spatial structure by making its thickness thin. This kind of membrane structure has characteristic that can express free-form curve, so the selection of structural form is very important. So, this paper proposes the expression of free-form surface based on NURBS basis function and the finite element method considering geometrical nonlinearity for the deduction of large deformation result. Also, for minimizing the approximation of the surface that is derived from the form-finding result, the interface method that change finite element mesh to NURBS is proposed. So, the optimum surface of free-form membrane is derived.

• Journal of Navigation and Port Research
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• v.31 no.5 s.121
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• pp.421-426
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• 2007

Recently, the defect maintenance period of the new construction structure was extended from 5 years to 10 years. And according to change of realization on the quality of construction and maintenance, a development of semi-permanent method of construction is required for maintenance of blind parts of underwater structure, such as bridge, dam, harbor, etc. In this study, we proposed a floating type sector dry caisson, which is effective to the maintenance of submerged large structures. These large structures were being maintained incompletely, partly due to unskilled divers and difficult working condition. Considering the easiness of access to the maintenance area and the cost for set up the working structure, especially for the case of structure slabs close to the sea surface and harrow pile span structures, we developed and introduced a sector dry caisson instead of the full caisson structure. By doing this, it is easy to move out the caisson rapidly in emergence case. Therefore, we expect that the floating sector caisson will contribute to reduce working time and improve the quality of underwater work in future days.

• Journal of Korean Association for Spatial Structures
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• v.2 no.4 s.6
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• pp.61-76
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• 2002

The structure system that is discreterized by continuous shells is usually used to make a large space structures and these structures show the collapse mechanisms that are captured at over the limit load, and snap-through and bifurcation are most well known of it. For the collapse mechanism, rise-span ratio, element stiffness and load mode are main factor, which it give an effect to unstable behavior. Moreover, resist force of structure can be reduced by initial condition and initial imperfection significantly. In order to investigate the instability of shell structures, the finite deformation theory can be applied and it becomes a nonlinear mathematics in which use equation of tangential stiffness incrementally. With an initial imperfection, using simple example and Flow Truss Dome, the buckling characteristics of space truss is main purpose of this paper, and unstable behavior is studied by proposed the numerical method. Also, by using MIDAS, this research work analyzes displacements and inner forces as the design load of model, and the ratio of buckling load of design load is investigated.

• Wind and Structures
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• v.36 no.2
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• pp.133-147
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• 2023

The random vibration of saddle membrane structures under wind load is studied theoretically and experimentally. First, the nonlinear random vibration differential equations of saddle membrane structures under wind loads are established based on von Karman's large deflection theory, thin shell theory and potential flow theory. The probabilistic density function (PDF) and its corresponding statistical parameters of the displacement response of membrane structure are obtained by using the diffusion process theory and the Fokker Planck Kolmogorov equation method (FPK) to solve the equation. Furthermore, a wind tunnel test is carried out to obtain the displacement time history data of the test model under wind load, and the statistical characteristics of the displacement time history of the prototype model are obtained by similarity theory and probability statistics method. Finally, the rationality of the theoretical model is verified by comparing the experimental model with the theoretical model. The results show that the theoretical model agrees with the experimental model, and the random vibration response can be effectively reduced by increasing the initial pretension force and the rise-span ratio within a certain range. The research methods can provide a theoretical reference for the random vibration of the membrane structure, and also be the foundation of structural reliability of membrane structure based on wind-induced response.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.227-231
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• 2008

There are many retractable roof structures in the world. Retractable roofs will be classified by various factors and user, for example span length, moving mechanism, opening system, roof material and utility in over 100 examples. Therefore I will present considerations in architectural planning and structural design.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.235-239
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• 2008

Cable systems are a construction of elements carrying only tension and no compression or bending in membrane structure. Tensile membrane structures are most often used as roofs as they can economically and attractively span large distances. But cable systems have weaknesses to vibration by earthquake, wind and vehicle loads. Damage detection of cable systems by using existing safety diagnosis is difficult to detect the characteristic change of overall structural action. If cable snaps are occurred to cable release and tear in tension structures, these are set up a vibration. So, we used piezo-electric materials, and The principle of operation of a piezoelectric sensor is that a physical dimension, transformed into a force, acts on two opposing faces of the sensing element. In this study, the development on test method of cable system is proposed and tested by tensile strength using piezo-electric materials.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.618-622
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• 2011

Specialized large-scale computational finite-element and molecular dynamic models have been used in order to understand and predict how dislocation density emission and contact stress field due to nanoindentation affect inelastic deformation evolution scales that span the molecular to the continuum level in ductile crystalline systems. Dislocation density distributions and local stress fields have been obtained for different crystalline slip-system and grain-boundary orientations. The interrelated effects of grain-boundary interfaces and orientations, dislocation density evolution and crystalline structure on indentation inelastic regions have been investigated.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.03a
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• pp.71-74
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• 1998

In recent years, advances in construction techniques and materials have given rese to flexible light-weight structures like high-rise buildings and long-span bridges. Because these structures extremely susceptible to environmental loads, such as earthquakes and strong winds, these random loadings usually produce large deflection and acceleration on these structures. Vibration control system of structures are becoming an integral part of the structural system of the next generation of tall building. The proposed control system is applied to single degree of structure with mass damping and compared with conventional PID and neural network PID control system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.335-338
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• 2010

구조물의 상태평가는 구조물 고유의 동특성을 분석함으로써 평가할 수 있다. 구조물은 태풍, 지진 및 기타 외적 환경 등에 의하여 손상이 발생하고 이러한 구조물의 손상은 강성의 변화로 이어져 구조물의 동특성에 변화를 일으킨다. 따라서 손상 발생 전후의 동적응답을 각각 계측한 후 구조물 식별(Structural System Idetification)을 통하여 고유진동수 및 모드형상을 추출하고 수학적인 기법을 사용하여 구조물을 구성하고 있는 개별 부재 혹은 부재 그룹의 강성을 비교함으로써 손상의 발생여부 및 손상정도를 추정할 수 있다. 본 연구에서는 지붕트러스 구조물에 대하여 손상평가를 수행하고 이를 검증할 수 있는 Mock-up 구조물을 설계 및 시공하였다.