• Structural Engineering and Mechanics
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• 제71권5호
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• pp.545-552
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• 2019

The analysis and design of complex structures like sandwich-panel elements are difficult; the use of finite element method for the analysis is complicated and time consuming when non-linear effects are considered. On the other hand, artificial neural network (ANN) models can capture the non-linear effects and its application requires lesser computational demand. Two ANN models were trained, tested and validated to compute the force for a given displacement of a sandwich-type roof element; 2555 force and element deformation pairs were used for training the ANN models. For the models trained without considering the damping effect, there were two values in the input layer: maximum displacement and current displacement, and for the model considering damping, displacement from the previous step was used as an additional input. Totally, 400 ANN models were trained. Results show that there is a good agreement between the experimental and simulated data, and the models showed a good performance with a mean square error value of 4548.85. Both the ANN models could simulate the inelastic behaviour, loss of rigidity, and evolution of permanent displacements. The models could also interpolate and extrapolate, which enables them to be used as an analysis and design tool for such complex elements.

• 대한공간정보학회지
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• 제11권2호
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• pp.53-59
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• 2003

오늘날 과학과 경제 성장의 급속한 발달로 인해 많은 시설들이 건설되어 왔으며, 그 중에서 구조물들은 기술의 발달 및 제한적 공간의 효율적 사용으로 인하여 대형화 및 고층화가 가속되고 있는 실정으로 인해, 많은 구조물의 안전성 문제가 대두되고 있다. 특히, 과거의 노후화된 구조물은 유지 관리에 많은 인력과 예산이 필요하며, 구조물의 안전 상태를 손쉽게 모니터링 할 수 있는 기법의 개발은 시급하다고 할 수 있다. 그러므로, 구조물의 유지 관리 시스템은 구조물을 보다 효율적으로 관리하여 구조물의 내구성과 안전성을 증가시키며, 구조물 거동 시스템은 효율적인 유지관리 차원을 위한 경제적, 기술적인 결정체라 할 수 있다. 따라서, 본 연구에서는 위성을 이용한 GPS 측량방법으로 보다 경제적이고 정확한 자료를 취득하고, 구조물의 안전 상태가 자동 모니터링 되는 구조물 거동 경보 시스템을 개발하였다. 이렇게 개발된 구조물 거동 시스템은 구조물 거동의 절대 변위를 측정하여 구조적 변형,손상 감지등을 지속적으로 모니터링 함으로써 신뢰성과 안전성을 증진시킬 수 있을 것으로 기대된다.

• Smart Structures and Systems
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• 제31권4호
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• pp.421-436
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• 2023

This paper presents a vibration displacement measurement and damage identification method for a space truss structure from its vibration videos. Features from Accelerated Segment Test (FAST) algorithm is combined with adaptive threshold strategy to detect the feature points of high quality within the Region of Interest (ROI), around each node of the truss structure. Then these points are tracked by Kanade-Lucas-Tomasi (KLT) algorithm along the video frame sequences to obtain the vibration displacement time histories. For some cases with the image plane not parallel to the truss structural plane, the scale factors cannot be applied directly. Therefore, these videos are processed with homography transformation. After scale factor adaptation, tracking results are expressed in physical units and compared with ground truth data. The main operational frequencies and the corresponding mode shapes are identified by using Subspace Stochastic Identification (SSI) from the obtained vibration displacement responses and compared with ground truth data. Structural damages are quantified by elemental stiffness reductions. A Bayesian inference-based objective function is constructed based on natural frequencies to identify the damage by model updating. The Success-History based Adaptive Differential Evolution with Linear Population Size Reduction (L-SHADE) is applied to minimise the objective function by tuning the damage parameter of each element. The locations and severities of damage in each case are then identified. The accuracy and effectiveness are verified by comparison of the identified results with the ground truth data.

• Geomechanics and Engineering
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• 제9권3호
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• pp.275-286
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• 2015

A new method is presented to recover missing deformation data of lateral walls of foundation pit when the monitoring is interrupted; the method is called Dynamic Mathematical Model - Parameter Interpolation. The deformation of lateral walls of foundation pit is mainly affected by the type of supporting structure and the situation of constraints, therefore, this paper mainly studies the two different kinds of variation law of deep horizontal displacement when the lateral walls are constrained or not, proposes two dynamic curve models of normal distribution type and logarithmic type, deals with model parameters by interpolating and obtains the parameters of missing data, then missing monitoring data could be Figured out by these parameters. Compared with the result from the common average method which is used to recover missing data, in the upper 2/3 of the inclinometer tube, the result by using this method is closer to the actual monitoring data, in the lower 1/3 part of the inclinometer tube, the result from the common average method is closer to the actual monitoring data.

• 한국정보통신학회논문지
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• 제20권3호
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• pp.639-646
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• 2016

본 연구에서는 특수한 상황(미끄러짐 발생 및 회전관성이 부하로 작용하는 경우)에서의 회전 엔코더 기반 측정방법의 단점을 극복하기 위하여 광 변위센서(ADNS-9500)를 사용한 비접촉식 변위 측정방법을 제안하였다. 정확한 변위 측정을 위해 데이터 수집 보드와 랩뷰를 활용하여 실험적으로 광 변위센서의 성능을 분석하였으며, 반복실험을 통해 실험조건(측정방향, 속도, 가속도, 높이, 표면 재질)에 따른 광 변위센서의 성능특성을 파악하였다. 성능실험 결과, 광 변위센서를 사용하여 정확하게 평면운동을 측정하기 위해서는 광 변위센서와 지면(대상 물체의 표면)과의 높이를 2.4 mm-3.2 mm로 일정하게 유지시켜야 하며, 각각의 축 방향, 속도, 표면 재질을 고려하여 민감도를 수정하여 변위 계산식에 적용해야 하는 것을 확인하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.846-853
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• 2006

In this study, quantitative sensitivity analysis on rockfill material influencing the dam crest displacement of Concrete-Faced Rockfill Dam(CFRD) was carried out. The purpose of this study is to indicate the most important input parameter and to show the quantitative variation of displacement at the crest of CFR type dam with this input parameter. The rockfill material properties for parametric study were obtained from the results of large scale triaxial tests on 34 rockfill materials in the 22 different sites. From the statistical analysis on these data, some statistical characteristics of rockfill material properties such as property range, distribution characteristics, and correlation between the properties were investigated. based on these characteristics, 27 property combinations were constituted by Latin Hypercube sampling method. Dam crest displacements after construction, impounding, and earthquake loading were evaluated by static and dynamic numerical analysis on each combination. From the sensitivity analysis, it was found that the crest displacement of CFR type dam was absolutely affected by the shear modulus of rockfill material and the effect of friction angle of it was negligible. This relative difference of sensitivity was more outstanding in case of crest settlement than in case of crest horizontal displacement. Also, it was found that the settlement and horizontal displacement of dam crest logarithmically decreased as the shear modulus increased and the difference between the maximum value and the minimum vale amounted to about 9.5 times in case of settlement and about 10 times in case of horizontal displacement.

• 보존과학회지
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• 제22권
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• pp.31-42
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• 2008

석조문화재는 설계 도면이 소실된 경우가 많으며 정확한 형태정보가 없어 보존과 원형복원에 큰 어려움이 있다. 최근에 정밀실측과 같이 수치정보를 구축하는 연구가 활발히 진행되고 있지만, 대부분 2차원적으로서 활용도에 한계가 있다. 이를 보완하는 새로운 기법으로 3차원 영상 스캐닝 시스템이 도입되고 있다. 이 연구에서는 대원사다층 석탑을 대상으로 3D 스캐닝을 통하여 3차원 영상분석과 자료를 구축하고 실측도를 작성하였으며, 이를 바탕으로 수평 및 수직 변위를 평가하였다. 부재별 수치를 측정한 결과, 각 방면에서 서로 다른 수치를 보이고 있으며 상하 및 좌우변위가 나타났다. 수평적 상하변위는 좌면과 우면에서 탑신의 상부로 갈수록 컸으며, 수직적 좌우변위는 8층 옥개석이 북서쪽으로 치우쳐 있는 것으로 확인되었다. 이와 같은 변위측정과 평가는 석조문화재의 특성상 불균등한 표면과 프로그램 및 연구자에 따라 약간의 오차는 발생할 수 있다. 앞으로 다양한 실측과 안정성 평가연구가 진행된다면 석조문화재의 원형보존과 훼손상태 파악에 대한 정확한 자료를 제시할 수 있을 것이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.719-722
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• 2002

Cylindrical cam mechanisms are used commonly in many automatic machinery. But the cylindrical cam is very difficult to design and manufacture the shape. The motion analysis of the cylindrical cam can check the accuracy between designed data and manufactured data of the cam shape and can reproduce without the cam design data. The motion analysis of the cylindrical cam consists of displacement analysis, velocity analysis and acceleration analysis. This paper performs the motion analysis of a cylindrical cam with translating follower by using a relative velocity method and a central difference method. The displacement is calculated by using the central difference method and the velocity is calculated by the relative velocity method. The relative velocity method is defined by the relative motion between follower and cam at a center of a follower roller. The central difference method is derived in the 3 dimensional space.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1102-1107
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• 2004

High-speed railway bridges subject to effect of statical loads by temperature change as well as dynamic loads by interaction between vehicle load which run specially fast and behavior of bridges, If suitable longitudinal expansion by temperature change of bridge does not happened, it can cause unhealthy condition for the parts of bridges as well as can generate addition stress to bridges, For these reason, Analysis and Estimation of data about behavior of bridges occupies important factor in that estimate the remaining life of bridges and select the maintenance, repair and retrofit. In this paper, Analysis for the long-term behavior of bridges using Longitudinal displacement and Temperature data that is actuality measured data to the bridges of Seoul-Busan high speed railroad test section has been made.

• 제어로봇시스템학회논문지
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• 제10권11호
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• pp.1012-1016
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• 2004

In the present paper, equivalent beam and equivalent bimorph beam models for IPMC(ionic Polymer-Metal Composite) actuators are described. Physical properties of an IPMC, such as Young's modulus and electro-mechanical coupling coefficient. are determined from the rule of mixture, bimorph beam equations, and measured force-displacement data of a cantilevered IPMC actuator. By using a beam equation with estimated physical properties, actuation displacements of a cantilevered IPMC actuator was calculated and a good agreement between the computed tip displacements and the measured data was observed. Finite element analysis(FEA) combined with the estimated physical properties was used to reproduce the force-displacement relationship of an IPMC actuator. Results from the FEA agreed well with the measure data. The proposed models might be used for modeling of IPMC actuators with complicated shapes and boundary conditions.