• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.34-41
• /
• 2020

In recent years, magnitude and frequency of earthquakes have increased in Korea. Damage to a bridge, which is one of the main infrastructures, can directly lead to considerable loss of human lives. Therefore, engineers need to evaluate the seismic fragility of the structure and prepare for the possible seismic damage. In particular, the number of aging bridges over 30 years of service increases, and thus the seismic analysis and fragility requires accounting for the aging and retrofit effects on the bridge. In this study, the nonlinear static and dynamic analyses were performed to evaluate the effects of the aging and FRP retrofit on a PSC bridge. The aging and FRP retrofit were applied to piers that dominate the response of the bridge during earthquakes. The maximum displacement of the bridge increased due to the aging of the pier but decreased when FRP retrofit applied to the aged pier. In addition, seismic fragility analysis was performed to evaluate the seismic behavior of the bridge combined with the seismic performance of the pier. Compared with the aged bridge, the FRP retrofit bridge showed a decrease in the seismic fragility in all levels of damage. The reduction of the seismic fragility in the FRP bridge was prominent as the value of PGA and level of damage increased.

• Smart Structures and Systems
• /
• v.16 no.6
• /
• pp.1133-1145
• /
• 2015

A new neural network (NN) predictive controller (NNPC) algorithm has been developed and tested in the computer simulation of active control of a nonlinear structure. In the present method an NN is used as a predictor. This NN has been trained to predict the future response of the structure to determine the control forces. These control forces are calculated by minimizing the difference between the predicted and desired responses via a numerical minimization algorithm. Since the NNPC is very time consuming and not suitable for real-time control, it is then used to train an NN controller. To consider the effectiveness of the controller on probability of damage, fragility curves are generated. The approach is validated by using simulated response of a 3 story nonlinear benchmark building excited by several historical earthquake records. The simulation results are then compared with a linear quadratic Gaussian (LQG) active controller. The results indicate that the proposed algorithm is completely effective in relative displacement reduction.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.1
• /
• pp.48-55
• /
• 2018

The purpose of the present study is to compare the reduction rate of natural frequency and the increase rate of damping parameter with structural damage in system. For this purpose, experiment and numerical simulation analysis are performed for the 2-span H-Beam with lower natural frequency and higher damping parameter from free vibration in structure. The response signal by impact load before and after damage is analyzed at 14 locations. The response signals for all locations are performed fast fourier transform to estimate the natural frequency reduction rate and wavelet transform to estimate the damping parameter increase rate. The time domain function corresponding to each scale(frequency) is separated from the response signal by wavelet parameter. The estimation of damping parameter increase rate using wavelet transform is more sensitive than the estimation of natural frequency reduction rate in structure.

• Nuclear Engineering and Technology
• /
• v.53 no.4
• /
• pp.1331-1344
• /
• 2021

This study is to evaluate the seismic capacity of the fire-damaged cabinet facility in a nuclear power plant (NPP). A prototype of an electrical cabinet is modeled using OpenSees for the numerical simulation. To capture the nonlinear behavior of the cabinet, the constitutive law of the material model under the fire environment is considered. The experimental record from the impact hammer test is extracted trough the frequency-domain decomposition (FDD) method, which is used to verify the effectiveness of the numerical model through modal assurance criteria (MAC). Assuming different temperatures, the nonlinear time history analysis is conducted using a set of fifty earthquakes and the seismic outputs are investigated by the fragility analysis. To get a threshold of intensity measure, the Monte Carlo Simulation (MCS) is adopted for uncertainty reduction purposes. Finally, a capacity estimation model has been proposed through the investigation, which will be helpful for the engineer or NPP operator to evaluate the fire-damaged cabinet strength under seismic excitation. This capacity model is presented in terms of the High Confidence of Low Probability of Failure (HCLPF) point. The results are validated by the proper judgment and can be used to analyze the influences of fire on the electrical cabinet.

• Structural Engineering and Mechanics
• /
• v.17 no.3_4
• /
• pp.527-537
• /
• 2004

Consequence-Based Engineering (CBE) is a new paradigm proposed by the Mid-America Earthquake Center (MAE) to guide evaluation and rehabilitation of building structures and networks in areas of low probability - high consequence earthquakes such as the central region of the U.S. The principal objective of CBE is to minimize consequences by prescribing appropriate intervention procedures for a broad range of structures and systems, in consultation with key decision makers. One possible intervention option for rehabilitating unreinforced masonry (URM) buildings, widely used for essential facilities in Mid-America, is passive energy dissipation (PED). After the CBE process is described, its application in the rehabilitation of vulnerable URM building construction in Mid-America is illustrated through the use of PED devices attached to flexible timber floor diaphragms. It is shown that PED's can be applied to URM buildings in situations where floor diaphragm flexibility can be controlled to reduce both out-of-plane and in-plane wall responses and damage. Reductions as high as 48% in roof displacement and acceleration can be achieved as demonstrated in studies reported below.

• Journal of Korea Multimedia Society
• /
• v.14 no.8
• /
• pp.1010-1019
• /
• 2011

This was a preliminary research for the goal of understanding between internal structure of Osteogenesis Imperfecta Murine (OIM) bone and its fragility. 54 hyperspectral bone data sets were captured by using JASCO 2000 Raman spectrometer at UMKC-CRISP (University of Missouri-Kansas City Center for Research on Interfacial Structure and Properties). Each data set consists of 1,091 data points from 9 OIM bones. The original captured hyperspectral data sets were noisy and base-lined ones. We removed the noise and corrected the base-lined data for the final efficient classification. High dimensional Raman hyperspectral data on OIM bones was reduced by Principal Components Analysis (PCA) and Linear Discriminant Analysis (LDA) and efficiently classified for the first time. We confirmed OIM bones could be classified such as strong, middle and weak one by using the coefficients of their PCA or LDA. Through experiment, we investigated the efficiency of classification on the reduced OIM bone data by the Bayesian classifier and K -Nearest Neighbor (K-NN) classifier. As the experimental result, the case of LDA reduction showed higher classification performance than that of PCA reduction in the two classifiers. K-NN classifier represented better classification rate, compared with Bayesian classifier. The classification performance of K-NN was about 92.6% in case of LDA.

• Journal of Dairy Science and Biotechnology
• /
• v.22 no.2
• /
• pp.143-150
• /
• 2004

The osteoporosis is a disease characterized by lower bone mineral content, deterioration of bone tissue and a reduction in the protein and mineral matrix of the bone. The bone becomes more porous leading to increased bone fragility and risk of fracture, particularly of the hip, spine and wrist. Osteoporosis can result in disfigurement, lowered self·esteem, reduction or loss of mobility, and decreased independence. Adequate calcium intake through milk and milk products in childhood and adolescence is a decisive marker for obtaining a maximum bone mass (peak adult bone mass) and f3r the prevention of osteoporosis. Calcium is one of the most critical nutrients associated with the osteoporosis. Dietary calcium is of great significance for healthy skeletal growth and development. The bone mineral content and bone mineral density of young adults is directly related to the calcium intake through milk and dairy products. Milk and milk products are the important sources of calcium as the richness and bioavailability of this nutrient is very high as compared to other food products. If enough calcium is not supplemented through diet, calcium from the bone will be depleted to maintain the blood plasma calcium level. The article focuses on the various issues related to osteoporosis manifestation and the role of dietary calcium especially calcium derived from dairy products.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.04a
• /
• pp.97-104
• /
• 2000

Evaluating a Review-Level Ground Motion is a key to efficiently perform Seismic Margin Assessment of nuclear power plants whose purpose is to determine a ground motion level for which a plant has high-confidence-of-a-low-probability of seismic-induced core damage and to identify any weaker-link components. In this study a method to obtain RLGMs is reviewed which is recommended by Electric Power Research Institute and implemented to be applied to Limerick site in eastern and central U. S as a case study. This method provides reasonable and site-specific RLGMs as minimum required plant HCLPF for SMA that meet a target mean seismic core-damage frequency based on seismic hazard results and generic values of uncertainty and randomness parameters of the core-damage fragility curves. In addition high-frequency RLGM is justifiably modified to reflect the increased seismic capacity of high-frequency components and spatial variation and incoherence of input ground motion on a basemat of large structures by establishing a method to obtain high0-frequency reduction factors according to EPRI guidelines.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.427-434
• /
• 2006

The stone pagoda on the Miruksa temple site has a high value as architectural history, because this stone pagoda is one of the oldest and grandest stone pagodas which remain in Korea today. However, this stone pagoda has remained only six stones of the northeastern part, becased this stone pagoda was collapsed at past. Therefore, it is important to know the original structure and form of this stone pagoda. Hypotheses about collapse cause of this stone pagoda are presented as four cases: collapse by earthquake, collapse by fragility of ground, collapse by durability reduction, and collapse by lightning, On the basis of these four collapse hypotheses in this study, we investigate collapse phenomenon through the structural analysis using discrete element method and evaluate collapse causes of this stone pagoda.

• Journal of Korean Association for Spatial Structures
• /
• v.20 no.4
• /
• pp.159-167
• /
• 2020

The resilience performance evaluation method of a structure can evaluate the ability to recover after an earthquake disaster, and this study deals with the consideration and introduction of the resilience performance evaluation method. The resilience evaluation method can be expressed as a quantified number by constructing a loss estimation model and a recovery evaluation model. The recovery evaluation model should consider downtime in addition to the repair time, and the loss estimation model should consider not only direct loss to structures and non-structures, but also indirect loss due to functional loss of the building. In addition, to build a loss estimation model, the structure should be simplified to perform an efficient analysis. Therefore, in this study, the equivalent terminal induction system proposed cantilever-type and rahmen-type SDOF, and it is evaluated somewhat conservatively compared to the example structure, and it is judged that there is a need to improve the hysteresis characteristics by applying the stiffness reduction factor of the SDOF model.