The seismic performance of lead-rubber bearings (LRBs) is significantly affected by both the axial force and loading rate they experience. Accurate assessment of LRBs’ seismic performance, therefore, requires realistic simulation of these forces and rates, as well as of the response of the isolated structure during seismic events. This study conducted a series of real-time hybrid simulations (RTHS) to evaluate the seismic behavior of LRBs in such conditions. The simulations focused on a two-span continuous bridge isolated by LRBs atop the central pier, exposed to horizontal and vertical ground motions. In the RTHS framework, the LRBs were physically tested in the laboratory, while the remainder of the bridge was numerically modeled. Findings from these simulations indicated that the vertical ground motion had a minimal effect on the lateral response of the bridge when isolated by LRBs.

Structures compromised by a seismic event may be susceptible to aftershocks or subsequent occurrences within a particular duration. Considering that the shape ratios of sections, such as column shape ratio (CSR) and wall shape ratio (WSR), significantly influence the behavior of reinforced concrete (RC) piloti structures, it is essential to determine the best appropriate methodology for these structures. The seismic evaluation of piloti structures was conducted to measure seismic performance based on section shape ratios and inter-story drift ratio (IDR) standards. The diverse machine-learning models were trained and evaluated using the dataset, and the optimal model was chosen based on the performance of each model. The optimal model was employed to predict seismic performance by adjusting section shape ratios and output parameters, and a recommended approach for section shape ratios was presented. The optimal section shape ratios for the CSR range from 1.0 to 1.5, while the WSR spans from 1.5 to 3.33, regardless of the inter-story drift ratios.

Performance-Based Seismic Design (PBSD) is an approach that evaluates how structures will perform under different levels of seismic activity. It focuses on ensuring that buildings not only withstand earthquakes but also meet specific performance objectives, such as minimizing damage or maintaining functionality after the event. Unlike traditional methods, PBSD allows for more tailored, cost-effective designs by considering varying degrees of acceptable damage based on the structure's importance and use. PBSD was introduced in Korea in 2016 to replace elastic design, which is inevitable to over-design to cope with all variables such as earthquakes and winds. When PBSD is applied to the structural design new building, One of the challenges of PBSD is the complexity involved in creating accurate inelastic analysis models. The process requires significant time and effort to analyze the results, as it involves detailed simulations of how structures will behave under seismic stress. Additionally, organizing and interpreting the analysis data to meet performance objectives can be labor-intensive and technically demanding. In order to solve this problem, a post-processor program was developed in this study. A post-processor was developed based on Excel program using Visual Basic for Applications(VBA). Because analysis outputs of Perform-3D, that is a commercial software for structural analysis and design, are very complicated, generation of tables and graphs for report is significant time and effort consuming task. When the developed post-processor is used to make the seismic design report, the required task time is significantly reduced.

The purpose of this study is to experimentally analyze the seismic performance of a vertical irregular beam-column specimen reinforced with RBS (Replaceable Steel Brace System), a steel brace system. To evaluate the seismic performance of RBS, three specimens were manufactured and subjected to cycle loading tests. The stiffness ratio of beam-upper column of the non-retrofitted specimen was 1.2, and those of the two retrofitted specimens were 1.2 and 0.84. The stiffness ratio of the beam-lower column of all specimens was 0.36. And the stiffness ratio were used for variable. As a result of the experiment, the specimen retrofitted with RBS showed improved maximum load, effective stiffness and energy dissipation capacity compared to the non-retrofitted specimen with the same beam-upper column stiffness ratio. The specimen with 0.84 beam-upper column stiffness ratio showed improved performance compared to the specimen with 1.2 stiffness ratio.

국내에서 지진 발생빈도가 증가함에 따라 다가구주택 필로티기둥의 내진보강이 필수적이다. FRP 패널은 경량성과 고강도를 갖춘 내진 보강재료 사용되고 있으나, 상대적으로 낮은 임계온도로 인해 화재에 취약하다. 따라서 FRP 패널로 보강된 RC 기둥의 내화 성능을 확보할 방안이 필요하다. 본 연구에서는 FRP 패널로 보강된 RC 기둥의 내화성능을 평가하기 위해, FRP 패널의 열적특성(비열, 열전도율, Weight loss)을 확인하는 소재시험을 진행하였다. 또한, FRP 패널로 보강된 RC 단주기둥에 뿜칠을 도포하고, 표준화재 1시간 동안의 온도거동을 분석하였다.

지진발생 시, 건물은 작게는 손상에서 크게는 붕괴까지 이어지므로 인명과 재산상의 피해가 생길 수 있다. 이러한 지진의 위험성에 대비하여 건물의 내진성능평가가 필요하다. 현재 내진성능평가 기법의 경우 개별 건물을 대상으로 하기에 많은 시간이 투자되어야 한다. 따라서, 지역규모의 건물들을 대상으로 하는 내진성능평가 기법의 개발이 필요한 실정이다. 본 연구는 RC 주거형 건물의 내진 성능을 평가하고 보강계획을 수립하기 위해 비선형 Shear Spring을 가진 단자유도모델을 구축하였다. 구조물의 비선형 응답을 모사 하기 위한 비선형 Shear Spring은 T-SR-μ를 매개변수로 정의된다. 해당모델에 100개의 PEER 지진을 적용하여, 최대층간변위비 응답 으로 건물의 내진성능을 평가하였다. 제안기법의 적용성을 확인하기 위하여 상세모델과 비교하였을 때, 두 모델 모두 건물의 내진성 능을 같은 수준으로 판단하였음을 확인하였다. 본 연구는 제안된 방식이 실제 건물의 내진성능을 예측할 수 있음을 보여주었다.

원자력 발전소에 설치되는 안전관련 기기의 손상은 심각한 사고로 이어질 수 있으므로 반듯이 지진안전성을 확보하여야 한 다. MCC, Switchgear, Inverter, Battery charger 등의 전기캐비닛은 대표적인 안전관련 기기이다. 대부분의 실험적 연구는 실험대 상기기의 크기와 실험장비의 성능한계 등으로 인하여 주요부품을 대상으로 하며, 실제 원자력발전소에 납품하는 전기캐비닛을 이용하 여 3축 동시가진에 의한 진동대 실험을 수행한 연구는 많지 않다. 따라서 실제기기를 대상으로 3축 진동대 실험을 통하여 내진성능과 한계상태를 직접적으로 평가하기 위한 연구가 필요하다. 이러한 한계상태평가의 주요 목적은 다양한 부품으로 구성된 캐비닛 단위 실 제기기의 임계 가속도 및 고장 모드를 조사하는 것이다. 본 논문에서는 3축 진동대 실험으로 한계상태 내진성능실험을 수행하여 원자 력발전소에 납품되는 것과 동일한 4종의 전기캐비닛들의 한계상태를 분석하였다.

High-rise buildings are equipped with TMD (Tuned Mass Damper), a vibration control device that ensure the stability and usability of the building. In this study, the seismic response control performance was evaluated by selecting the design variables of the TMD based on the installation location of the twisted irregular building. To this end, we selected analysis models of 60, 80, and 100 floors with a twist angle of 1 degree per floor, and performed time history analysis by applying historical seismic loads and resonant harmonic loads. The total mass ratio of TMDs was set to 1.0%, and the distributed installation locations of TMDs were selected through mode analysis. The analysis results showed that the top-floor displacement responses of all analysis models increased, but the maximum story drift ratio decreased. In order to secure the seismic response control performance by distributed installation of TMDs in twisted irregular buildings, it is judged that the mass ratio distribution of TMDs will act as a key variable.

Dynamic responses of nuclear power plant structure subjected to earthquake loads should be carefully investigated for safety. Because nuclear power plant structure are usually constructed by material of reinforced concrete, the aging deterioration of R.C. have no small effect on structural behavior of nuclear power plant structure. Therefore, aging deterioration of R.C. nuclear power plant structure should be considered for exact prediction of seismic responses of the structure. In this study, a machine learning model for seismic response prediction of nuclear power plant structure was developed by considering aging deterioration. The OPR-1000 was selected as an example structure for numerical simulation. The OPR-1000 was originally designated as the Korean Standard Nuclear Power Plant (KSNP), and was re-designated as the OPR-1000 in 2005 for foreign sales. 500 artificial ground motions were generated based on site characteristics of Korea. Elastic modulus, damping ratio, poisson’s ratio and density were selected to consider material property variation due to aging deterioration. Six machine learning algorithms such as, Decision Tree (DT), Random Forest (RF), Support Vector Machine (SVM), K-Nearest Neighbor (KNN), Artificial Neural Networks (ANN), eXtreme Gradient Boosting (XGBoost), were used t o construct seispic response prediction model. 13 intensity measures and 4 material properties were used input parameters of the training database. Performance evaluation was performed using metrics like root mean square error, mean square error, mean absolute error, and coefficient of determination. The optimization of hyperparameters was achieved through k-fold cross-validation and grid search techniques. The analysis results show that neural networks present good prediction performance considering aging deterioration.

Existing reinforced concrete (RC) building frames constructed before the seismic design was applied have seismically deficient structural details, and buildings with such structural details show brittle behavior that is destroyed early due to low shear performance. Various reinforcement systems, such as fiber-reinforced polymer (FRP) jacketing systems, are being studied to reinforce the seismically deficient RC frames. Due to the step-by-step modeling and interpretation process, existing seismic performance assessment and reinforcement design of buildings consume an enormous amount of workforce and time. Various machine learning (ML) models were developed using input and output datasets for seismic loads and reinforcement details built through the finite element (FE) model developed in previous studies to overcome these shortcomings. To assess the performance of the seismic performance prediction models developed in this study, the mean squared error (MSE), R-square (R2), and residual of each model were compared. Overall, the applied ML was found to rapidly and effectively predict the seismic performance of buildings according to changes in load and reinforcement details without overfitting. In addition, the best-fit model for each seismic performance class was selected by analyzing the performance by class of the ML models.

For low-rise piloti-type buildings that suffered significant damage in the Pohang earthquake, the seismic performance of those designed by codes issued before and after the earthquake has been recently revised. This study started with the expectation that many of the requirements presented in the current codes may be excessive, and among them, the spacing of column stirrup could be relaxed. In particular, the recently revised design code of concrete structures for buildings, KDS 41 20 00, suggests that the column stirrup spacing is 1/2 of the minimum cross-sectional size or 200 mm, which is strengthened compared to KBC 2016, but relaxed than the current KDS, 41 17 00, which is 1/4 of the minimum size or 150 mm. As a result of the study, it was found that the target performance level was sufficiently satisfied by following the current standards and that it could be satisfied even if the relaxed spacing was followed. Therefore, the strict column stirrup spacing of KDS 41 17 00 could be relaxed if a wall other than core walls is recommended in the current guideline for the structural design of piloti-type buildings.

Phayathonzu temple in Myanmar was made of masonry bricks, and so it was vulnerable to lateral load such as earthquake. Especially, it has many difficulties in structural modeling and dynamic analysis because the discontinuous characteristics of masonry structure should be considered. So, it is necessary to provide the seismic performance evaluation technology through the inelastic dynamic modeling and analysis under earthquake loads for the safety security of masonry brick temple. Therefore, this study analyzes the seismic behavior characteristics and evaluates the seismic performance for the 479 structure with many cracks and deformations. Through the evaluation results, we found out the structural weak parts on earthquake loads.

Earthquakes of magnitude 3.0 or greater occur in Korea about 10 times on average yearly, and the number of earthquakes occurring in Korea is increasing. As many earthquakes have recently occurred, interest in the safety of nuclear power plants has increased. Nuclear power plants are equipped with many cabinet-type control facilities to regulate safety facilities, and function maintenance is required during an earthquake. The seismic performance of the cabinet is divided into structural and functional performances. Structural performance can be secured during the design procedure. Functional performance depends on the vibration performance of the component. Therefore, it is necessary to confirm the seismic performance of the components. Generally, seismic performance is confirmed through seismic simulation tests. When checking seismic performance through seismic simulation tests, it is difficult to determine the effect of frequency and maximum acceleration on an element. In this paper, shaking table tests were performed using various frequencies and various maximum accelerations. The seismic performance characteristics of the functions of electrical equipment components were confirmed through tests.

The purpose of this study is to experimentally analyze the seismic performance of beam-column specimens with vertical irregular, which were reinforced with RHS (Replaceable steel haunch system). a steel haunch system. To evaluate the seismic performance of the RHS, three specimens were manufactured and subjected to cycle loading tests. Retrofitted specimens have different beam-upper column stiffness ratio as a variable. The stiffness ratio of beam-upper column were considered to be 1.2 and 0.84. As a result of the test, the specimen reinforced with RHS showed improved maximum load and effective stiffness, and energy dissipation capacity compared to the non-retrofitted specimen with same beam-upper column stiffness ratio. The specimen with 0.84 beam-upper column stiffness ratio showed improved performance than the specimen with 12.

본 연구에서는 수소 자원의 활용도가 높아짐에 따라 수소 저장 용기의 내진 성능을 평가하기 위해 수소 저장 시설을 방문하여 현장 조사를 수행하였다. 외관 조사 중, 수조 저장 용기의 지지부에서 부식이 진행됨을 확인하였고, 이에 대한 대책안 으로 내부식성 재료인 CFRP로 대체하여 성능을 평가, 검증하였다. 이를 위해 현장 조사 결과를 바탕으로 상용 유한요소해석 프 로그램인 ABAQUS를 사용하였으며, 해석 결과 CFRP로 제작된 수소 저장 용기의 지지부는 강재 대비 약 12배 이상 뛰어난 성 능을 보였다. Hashin Damage Criteria를 기반으로 CFRP 지지부의 안전성 검토를 수행한 결과 최대 손상 지수가 0.065로 확인되 었다. 기초부 콘크리트의 경우, 쪼갬 및 휨 인장 응력에 대한 안전성을 검토하였으며, 허용 강도 대비 7~36%의 안전도를 보였 다. 이를 근거로 CFRP를 수소 저장 용기의 지지부에 적용하는 것은 합리적이며, 뛰어난 경제성을 보인다. 다만, 이러한 결과는 수치 해석에 의하므로 실규모 지진동 모사 시험을 통해 해석 모델의 신뢰성을 보충할 필요가 있다.

This paper describes the seismic performance evaluation of reinforced concrete bridge columns under constant and varying axial forces. For this purpose, nine identical circular reinforced concrete columns were designed seismically by KIBSE (2021) and KCI (2021). A comparison of lateral forces with theoretical strength shows that the safety factor for columns under varying axial forces is less marginal than those under constant axial forces. In addition, columns under varying axial forces exhibit significant fluctuations in the hysteretic response due to continuously varying axial forces. This is particularly prominent when many varying axial force cycles within a specific lateral loading cycle increase. Moreover, the displacement ductility of columns under varying axial forces does not meet the code-specified required ductility in the range of varying axial forces. All varying axial forces affect columns' strength, stiffness, and displacement ductility. Therefore, axial force variation needs to be considered in the lateral strength evaluation of reinforced concrete bridge columns.

The ductility of the system based on the capacity of each structural member constituting the seismic force-resisting system is a significant factor determining the structure’s seismic performance. This study aims to provide a procedure to supplement the current seismic design criteria to secure the system’s ductility and improve the seismic performance of the steel ordinary moment frames. For the study, a nonlinear analysis was performed on the 9- and 15-story model buildings, and the formation of collapse mechanisms and damage distribution for dynamic loads were analyzed. As a result of analyzing the nonlinear response and damage distribution of the steel ordinary moment frame, local collapse due to the concentration of structural damage was observed in the case where the influence of the higher mode was dominant. In this study, a procedure to improve the seismic performance and avoid inferior dynamic response was proposed by limiting the strength ratio of the column. The proposed procedure effectively improved the seismic performance of steel ordinary moment frames by reducing the probability of local collapse.

Recently, the occurrence frequency of earthquake has increased in Korea, and the interests for seismic reinforcement of existing school buildings have been raised. To this end, the seismic performance evaluations for school buildings that did not accomplish the seismic design are required. In particular, this study checks the eigenvalue analysis, pushover curves, maximum base shears, performance points and story drift ratios, and then analyzes the seismic performance characteristics according to bracing configuration of steel frame system reinforcement. Also, this study presents the practical field application methods through the comparison of analysis results for the seismic performance characteristics.

This study aims to assess the seismic performance of retrofitted reinforced concrete columns using a Replaceable Steel Brace (RSB) system, subjected to combined axial, lateral, and torsional loadings. Through experimental testing, one non-retrofitted concrete column specimen and two retrofitted specimens with variable sliding slot lengths were subjected to eccentric lateral loads to simulate realistic seismic loading. The retrofitted specimens with RSBs exhibited enhanced resistance against shear cracking, effective torsional resistance, and demonstrated the feasibility of easy replacement. The RSB system substantially improved seismic performance, achieving approximately 1.7 times higher load capacity and 3.5 times greater energy dissipation compared to non-retrofitted column, thus validating its efficacy under combined loading conditions.

The purpose of this study is to experimentally analyze the seismic performance of column with RSB (Replaceable Steel Brace), a steel brace system with slot length as a variable. To evaluate the seismic performance of the RSB, three specimens were manufactured and subjected to cyclic loading tests. The length of the sliding slots were considered to be 5 mm and 10mm to enable the brace to resist the load from the initiation of flexural crack and shear crack. As a result of the test, the specimen reinforced with the RSB showed improved maximun load and effective stiffness, and energy dissipation capacity compared to the non-reinforced specimens. The specimens with 5mm sliding slot showed little difference in test result compared to the specimen with a 10mm sliding slot, indicating that the length of sliding slot has little influence on the effectiveness of RSB.