• Computers and Concrete
• /
• v.31 no.5
• /
• pp.405-417
• /
• 2023

The submerged floating tunnel (SFT) is tethered by mooring lines anchored to the seabed, therefore, the structural integrity of the anchor should be sensitively managed. Despite their importance, reaction forces cannot be simply measured by attaching sensors or load cells because of the structural and environmental characteristics of the submerged structure. Therefore, we propose an effective method for estimating the reaction forces at the seabed anchor of a submerged floating tunnel using a structural pattern model. First, a structural pattern model is established to use the correlation between tunnel motion and anchor reactions via a deep learning algorithm. Once the pattern model is established, it is directly used to estimate the reaction forces by inputting the tunnel motion data, which can be directly measured inside the tunnel. Because the sequential characteristics of responses in the time domain should be considered, the long short-term memory (LSTM) algorithm is mainly used to recognize structural behavioral patterns. Using hydrodynamics-based simulations, big data on the structural behavior of the SFT under various waves were generated, and the prepared datasets were used to validate the proposed method. The simulation-based validation results clearly show that the proposed method can precisely estimate time-series reactions using only acceleration data. In addition to real-time structural health monitoring, the proposed method can be useful for forensics when an unexpected accident or failure is related to the seabed anchors of the SFT.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.10a
• /
• pp.254-260
• /
• 1995

본 연구에서는 제어 알고리듬 적용면에서 가속도 계측이 보다 용이한 점을 고려하여 가속도가 포함된 가속도-속도-변위 되먹임 제어 알고리듬을 개발하고, 이를 유압식 능동 질량구동장치에 적용하여 능동제어시스템의 성능을 실증적으로 검토한다. 이 때 능동제어시스템의 구성요소들의 동특성을 시스템 모델링에 포함하여 제어력을 산정함으로써 시간 지연의 영향을 효과적으로 보상하는 방안을 제시한다.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1997.04a
• /
• pp.144-151
• /
• 1997

구조물로부터 측정된 가속도 시간이력을 이용하여 구조손상을 찾아내고 평가하는 기법을 제시하였다. 구조계의 손상을 찾아내는 알고리즘의 주요한 수단으로써 parametric system identification 방법을 사용하였고 매개변수화된 구조물의 최적 매개변수를 추정하기 위해 구속된 비선형 최적화기법을 사용하였다. 손상된 부재를 분리하기 위한 방법으로서 적합적 매개변수 모음법을 적용하였고 손상의 정도를 통계적으로 평가하기 위하여 측정된 가속도 시간이력에 time window 기법을 적용하였다. 가속도 이력 측정에 있어서의 불충분성과 측정오차를 고려하여 알고리즘을 개발하였고, 조화진동하중으로 구조물을 가진하여 구조 손상을 진단하는 수치모의 실험을 실시하였다.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2005.05a
• /
• pp.87-92
• /
• 2005

The ground-motion (GM) attenuation relations available in Korea has required the validation process for large earthquakes since most of them were developed based on small earthquake database, The Fukuoka earthquake (M=7.0) that occurred near the Korean Peninsula provides invaluable data to indirectly evaluate the attenuation characteristics of the strong GM in Korea. The GM levels (PGA, SA) obtained from the KIK-net downhole stations near the epicenter (R<100km) are reasonably predicted by the GM attenuation relation developed by KEPRI in 2003 for the Kori NPP site, the result of which validates the use of KEPRI GM attenuation relation for predicting GM induced by future large earthquakes. Also, the comparison between the Osaki spectra and response spectra of KIK-net downhole data reveals that the amplitude levels of Osaki spectra are higher than the spectra from KIK-net stations which are believed to be installed at the seismic basement.

• Journal of the Korean Geophysical Society
• /
• v.8 no.3
• /
• pp.109-113
• /
• 2005

The ground-motion (GM) attenuation relations available in Korea has required the validation process for large earthquakes since most of them were developed based on small earthquake database. The Fukuoka earthquake (M=7.0) that occurred near the Korean Peninsula provides invaluable data to indirectly evaluate the attenuation characteristics of the strong GM in Korea. The GM levels (PGA, SA) obtained from the KIK-net downhole stations near the epicenter (R<100km) are reasonably predicted by the GM attenuation relation developed by KEPRI in 2003 for the Kori NPP site, the result of which validates the use of KEPRI GM attenuation relation for predicting GM induced by future large earthquakes. Also, the comparison between the Osaki spectra and response spectra of KIK-net downhole data reveals that the amplitude levels of Osaki spectra are higher than the spectra from KIK-net stations which are believed to be installed at the seismic basement.

• Smart Structures and Systems
• /
• v.6 no.9
• /
• pp.1057-1077
• /
• 2010

An early detection of structural damages is critical for the decision making of repair and replacement maintenance in order to guarantee a specified structural reliability. Consequently, the structural damage detection, based on vibration data measured from the structural health monitoring (SHM) system, has received considerable attention recently. The traditional time-domain analysis techniques, such as the least square estimation (LSE) method and the extended Kalman filter (EKF) approach, require that all the external excitations (inputs) be available, which may not be the case for some SHM systems. Recently, these two approaches have been extended to cover the general case where some of the external excitations (inputs) are not measured, referred to as the adaptive LSE with unknown inputs (ALSE-UI) and the adaptive EKF with unknown inputs (AEKF-UI). Also, new analysis methods, referred to as the adaptive sequential non-linear least-square estimation with unknown inputs and unknown outputs (ASNLSE-UI-UO) and the adaptive quadratic sum-squares error with unknown inputs (AQSSE-UI), have been proposed for the damage tracking of structures when some of the acceleration responses are not measured and the external excitations are not available. In this paper, these newly proposed analysis methods will be compared in terms of accuracy, convergence and efficiency, for damage identification of structures based on experimental data obtained through a series of laboratory tests using a scaled 3-story building model with white noise excitations. The capability of the ALSE-UI, AEKF-UI, ASNLSE-UI-UO and AQSSE-UI approaches in tracking the structural damages will be demonstrated and compared.

• Smart Structures and Systems
• /
• v.24 no.5
• /
• pp.631-639
• /
• 2019

Finite element analysis is one of the important methods to study the structural performance. Due to the simplification, discretization and error of structural parameters, numerical model errors always exist. Besides, structural characteristics may also change because of material aging, structural damage, etc., making the initial finite element model cannot simulate the operational response of the structure accurately. Based on Bayesian methods, the initial model can be updated to obtain a more accurate numerical model. This paper presents the work on the field test, modal identification and model updating of a Chinese reinforced concrete pagoda. Based on the ambient vibration test, the acceleration response of the structure under operational environment was collected. The first six translational modes of the structure were identified by the enhanced frequency domain decomposition method. The initial finite element model of the pagoda was established, and the elastic modulus of columns, beams and slabs were selected as model parameters to be updated. Assuming the error between the measured mode and the calculated one follows a Gaussian distribution, the posterior probability density function (PDF) of the parameter to be updated is obtained and the uncertainty is quantitatively evaluated based on the Bayesian statistical theory and the Metropolis-Hastings algorithm, and then the optimal values of model parameters can be obtained. The results show that the difference between the calculated frequency of the finite element model and the measured one is reduced, and the modal correlation of the mode shape is improved. The updated numerical model can be used to evaluate the safety of the structure as a benchmark model for structural health monitoring (SHM).

• Composites Research
• /
• v.22 no.5
• /
• pp.1-7
• /
• 2009

The vehicle structure of Automated People Mover(APM) made of aluminum honeycomb sandwich with WR580INF4000 glass-fabric epoxy laminate facesheets was evaluated by structural test and finite element analysis. The test of the vehicle structure was conducted according to JIS E 7105. The structural integrity of vehicle structure was evaluated by stress, deflection and natural frequency obtained from dial-gauge and acceleration sensor. And the proposed finite element models were compared with the results of structural test. The results of finite element analysis showed good agreement with those of structural test. Also, in order to improve the stiffness of vehicle structure, the modified underframe model with reinforced side sill was proposed in design stage. The composite vehicle structures with modified underframe model had the improved structural stiffness about 44%.

• Structural Engineering and Mechanics
• /
• v.22 no.3
• /
• pp.293-310
• /
• 2006

In seismic prone areas it is possible to meet very different objects (equipment components, on shelf artefacts, simple architectural elements) that can be modelled as a rigid body rocking on a rigid foundation. The interest in their behaviour can have different reasons: seismological, in order to estimate the ground motion intensity, or more strictly mechanical, in order to limit the response severity and to avoid overturning. The behaviour of many rigid bodies subjected to twenty wide ranging acceleration recordings is studied here. The response of the blocks is described using kinematic and energy parameters. A condition under which a so called scale effect is tangible is highlighted. The capacity of the signals to produce overturning is compared to different ground motion parameters, and a good correlation with the Peak Ground Velocity is unveiled.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2005.04a
• /
• pp.688-695
• /
• 2005

The aim of this study is to develop a procedure to estimate the wind loads from the accelerations of a tall building structure. The wind loads may be directly calculated using the inverse analysis or simply integrating the wind pressures of the overall structure. But, these methods are too expensive and impossible to implement in some cases. In this study, a simple method is proposed to estimate the wind loads using the Kalman filter. This method is very stable compared to the direct integration of the acceleration to get the velocity or displacement. The proposed method is verified thorough numerical analysis, and results show that the proposed method is robust and estimates the wind loads accurately.