The 2024 Noto Peninsula Earthquake in Japan caused significant damage to wooden structures due to strong ground motion and widespread liquefaction. This study examines the damage patterns observed in wooden houses and analyzes the underlying structural vulnerabilities that contribute to these patterns. Key findings include standard failure modes such as foundation settlement, soft-story collapse, torsional deformation, and joint failure. The evolution of Japan’s seismic design standards has been reviewed, highlighting the importance of balanced wall distribution, reinforced connections, and lightweight roofing systems. Based on field investigations, this study systematically classifies the types of seismic damage in wood structures. It develops a qualitative performance curve that visually illustrates structural behavior in terms of inclination, seismic damage patterns, and repairability. Furthermore, a seismic damage taxonomy is proposed to infer the causes of damage through logical links between observed failure patterns and structural vulnerabilities. This research establishes a practical foundation for the seismic design and retrofit strategies of wood structures, ultimately contributing to the advancement of earthquake-resilient construction practices.

The concept of resilience has gained increasing attention amid growing urbanization and rising vulnerability to infrastructure. While various methodologies exist for evaluating the resilience of lifeline systems, few address the distinct structural features and failure modes of railway networks. This study refines existing approaches by incorporating characteristics unique to high-speed railways, with a focus on two key aspects. First, we define the structure of railway networks by identifying nodes and links, and deriving link-specific resilience criteria based on the fragility characteristics and recovery profiles of their structural components. Second, we utilize real data from the Korean railway system to quantify the performance degradation caused by component failures during seismic events. To assess the framework’s applicability, we use a simplified network and a more complex one integrating Korea’s Honam Line and Honam High-Speed Line. The framework effectively identifies critical scenarios and provides a valuable tool for decision-makers in assessing seismic risk and planning recovery for railway infrastructure.

Seismic design and risk assessment require input ground motions that accurately reflect both the seismic intensity associated with the target hazard level and the regional seismic characteristics of Korea. In this study, a scenario earthquake was defined through seismic hazard deaggregation. Due to the lack of recorded ground motions in Korea for this particular scenario, a finite fault was modeled. Seed ground motions related to the scenario earthquake were generated using the empirical Green’s function method, based on the 912 Gyeongju earthquake. During the spectral matching process, the convergence of the spectrum used for ground motion selection and the target Uniform Hazard Spectrum (UHS) was analyzed. This analysis led to the proposal of specific spectral conditions for selecting ground motions. The final set of input ground motions was then applied in time-history analyses of a nuclear power plant containment structure to assess its seismic response characteristics. The analysis results demonstrate that the proposed ground motion generation procedure applies to the development of ground motions in regions with moderate seismicity.

In the United States, seismic design standards are crucial in classifying buildings into Risk Categories I to IV. These categories are based on the buildings' occupancy type and the potential risk they pose to public safety, the protection of human life, and the socioeconomic consequences of structural collapse in the event of an earthquake. As the risk category increases, a higher seismic importance factor and more stringent drift limits are imposed on the respective building. This results in enhanced lateral strength and stiffness of the seismic force-resisting system. This study, which compares the seismic demands of special moment frame buildings assigned to high-risk categories, focusing on static system overstrength, ductility, and collapse risk, provides practical insights for structural engineers and architects. For this purpose, nonlinear static and dynamic analyses are performed to quantify the seismic demands of 18 steel frame buildings assigned to Risk Categories II, III, and IV. The findings indicate that buildings in Risk Category II do not meet the target collapse risk of 1% in 50 years, as specified in ASCE/SEI 7. For buildings in higher risk categories, the equivalent lateral force method for estimating seismic base shear is deemed more effective in ensuring adequate seismic performance.

펄스형 지진이 비펄스형 지진보다 구조물에 보다 큰 손상을 유발하는 것으로 알려져 있다. 펄스형 지진으로부터 속도펄스를 추출 하면 펄스주기를 평가할 수 있는데, 55개의 펄스형 지진기록을 선정하여 펄스 주기를 평가하고 펄스 주기에 따라서 세 그룹으로 구분 하였다. 펄스 주기를 달리하는 따른 세 개의 지진그룹에 대하여 가속도, 속도, 변위에 대한 평균 응답스펙트럼을 비교한 결과, 펄스 주 기와 펄스주기에 대응하는 주기영역에서의 응답스펙트럼은 밀접한 연관성이 있음을 알 수 있었다. 펄스형 지진의 펄스주기가 교량 의 지진취약도에 미치는 영향을 분석하기 위하여, 세 가지 지진그룹의 펄스주기와 유사한 고유주기를 가지는 세 가지 교량모델을 작 성하여 지진취약도 해석을 수행하였다. 교량의 고유 주기와 펄스형 지진의 펄스 주기가 서로 유사할수록, 교량의지진취약도가 증가 함을 알 수 있다. 즉, 두 주기 간의 유사성이 증가할수록, 교량의 비탄성 응답이 증가하며 이에 따른 구조적 손상이 크게 증가한다고 할 수 있다.

The 3T irregular shape structure is used for designing wind loads in high-rise buildings. Among them, the Tapered shape is a shape with a cross-section that changes throughout the entire floor. Recently, various advanced Tapered shapes have been applied, such as having a cross-section that varies only in part of the height or combining different shapes. In this study, an analysis model was selected by applying three types of Tapered part locations(Bottom, Middle, Top) and angles as design variables. Equivalent static seismic loads and historical earthquake records were applied to compare and analyze the seismic response of the Tapered models with regular-shaped models. As a result of the analysis, positioning the partial taper in the middle shows the lowest seismic response. Additionally, a larger taper angle decreased the story drift ratio, top-story displacement, shear wall shear force, and column bending moment, while increasing absolute acceleration and column axial force.

Our study develops a finite element analysis (FEA) model to evaluate the seismic performance of a two-story reinforced concrete (RC) school building and validates it through experiments. We developed a methodology that reflects failure modes from past experiments and validated it by comparing results at both the member (columns) and system (beam-column joints) levels. We created an FEA model for seismic-vulnerable RC moment frames using this methodology. This model incorporates bond-slip effects using three methods: Merged Nodes, Constrained Beam in Solid Penalty (CBISP), and Constrained Beam in Solid Friction (CBISF), which model the interaction between reinforcement and concrete. The approach provides a reliable tool for evaluating seismic performance and improves the accuracy of reinforced concrete frame evaluations.

Most reinforced concrete (RC) school buildings constructed in the 1980s have seismic vulnerabilities due to low transverse reinforcement ratios in columns and beam-column joints. In addition, the building structures designed for only gravity loads have the weak-columnstrong- beam (WCSB) system, resulting in low lateral resistance capacity. This study aims to investigate the lateral resistance capacities of a two-story, full-scale school building specimen through cyclic loading tests. Based on the experimental responses, load-displacement hysteresis behavior and story drift-strain relationship were mainly investigated by comparing the responses to code-defined story drift limits. The test specimen experienced stress concentration at the bottom of the first story columns and shear failure at the beam-column joints with strength degradation and bond failure observed at the life safety level specified in the code-defined drift limits for RC moment frames with seismic details. This indicates that the seismically vulnerable school building test specimen does not meet the minimum performance requirements under a 1,400-year return period earthquake, suggesting that seismic retrofitting is necessary.

A seismic intensity map, which describes ground motion distribution due to an earthquake, is crucial for disaster evaluation after the event. The ShakeMap system, developed and disseminated by the USGS, is widely used to generate intensity maps in many countries. The system utilizes a semi-variogram model to interpolate the measured intensities at seismic stations spatially. However, the default semi-variogram model embedded in ShakeMap is based on data from high seismic regions, which may not be suitable for the Korean Peninsula, categorized as a low-to-moderate seismic region. To address this discrepancy, this study aims to develop the region-specific semi-variogram model using local records and a region-specific ground motion model (GMM). To achieve this, we followed these steps: 1) collected records from significant earthquake events in South Korea, 2) calculated residuals between the observed intensities and predictions by the GMM, and 3) created semi-variogram models using weighted least squares regression to better fit short separation distances for PGA, PGV, SA0.2, and SA1.0. We compared the developed semi-variogram models with conventional models embedded in ShakeMap. Validation tests showed that the region-specific semi-variogram model reduced the mean squared error of intensity predictions by approximately 3.5% compared to the conventional model.

Reinforced concrete (RC) columns exhibit cyclic damage, such as strength degradation, under cyclic lateral loading, such as earthquakes. Considering the cyclic damage, the nonlinear load-deformation response of RC columns can be simulated using a lumped plasticity model. Based on an experimental database, this study calibrates lumped plasticity model parameters for 371 rectangular and 290 circular RC columns. The model parameters for adequate flexural rigidity, plastic rotation capacity, post-capping rotation capacity, moment strength, and cyclic strength degradation parameter are adjusted to match each experimentally observed load-deformation response. We have developed predictive equations that accurately relate the model parameters to the design characteristics of RC columns through regression analyses, providing a reliable tool for engineers and researchers. To demonstrate their application, the proposed and existing models numerically simulate the earthquake response of a bridge pier in a metropolitan railway bridge. The pier is subjected to several ground motions, increasing intensity until collapse occurs. The proposed lumped plasticity model showed about 41% less vulnerable to collapse.

본 논문에서는 진동대 실험 데이터를 활용하여 기존 지진취약도 곡선을 업데이트하기 위해 파티클 필터링(Particle Filtering, PF)의 적용 타당성을 분석하였다. PF는 비선형적이며, 비가우시안적인 문제를 다루는 데 적합하며, 기존 베이지안 업데이트 기법인 분산점 변환(Unscented Transformation, UT)과 마르코프 연쇄 몬테카를로(Markov Chain Monte Carlo, MCMC)에 비해 지진취약도 곡선 업데 이트 과정에서 더 높은 정확성과 안정성을 제공하였다. 연구 결과, PF는 HAZUS, HRC, 변형률 기반(Strain-based) 손상 상태에서 기존 기법보다 더 보수적인 지진취약도 곡선을 도출하였으며, 불확실성이 큰 상황에서도 안정적인 결과를 제공하였다. 특히, PF는 재추출 (Resampling) 과정을 통해 불확실성을 효과적으로 감소시켜 더 신뢰할 수 있는 지진취약도 평가 결과를 제공하였다. 본 연구는 PF가 지진공학 분야에서 지진취약도의 정확성과 안정성을 높이는 데 유용한 도구임을 시사한다.

Piloti-type buildings are widely constructed in urban areas of South Korea. Due to stiffness irregularities, piloti-type buildings are vulnerable to lateral loads such as earthquakes. Although seismic retrofitting is necessary for piloti-type buildings, many of these structures are privately owned, and the extensive number of buildings creates significant challenges in terms of cost and time for regional seismic performance evaluation. This study proposes a methodology for determining the seismic performance of multiple piloti-type buildings within a region by utilizing structural parameters. Information on piloti-type buildings is classified into public building data and exterior building data, which are integrated to define structural parameters for estimating the first natural period of the buildings. Linear regression analysis was performed to develop a regression equation correlating structural parameters with the natural period. Additionally, the natural period and structural parameters are used to perform another linear regression analysis to estimate the yield and ultimate points of the capacity curve. The capacity curves derived from the regression equations facilitate seismic performance evaluation based on structural parameters.

The primary purpose of this study is to develop system modules of school buildings and the seismic loss function of the system modules for regional loss assessment of school buildings. System modules of school buildings were developed through statistical analysis of school facilities in Korea. The structural system of school buildings with non-seismic details is defined as reinforced concrete with partially masonry walls (RCPM), and 27 system modules of RCPM were developed considering the number of stories, spans, and the age of the building. System modules were designed to assess the structural behavior by applying the shear spring model and the shear failure of the columns of the school building. Probabilistic seismic demand models for each component of system modules were derived through nonlinear dynamic analysis to determine the relationship between seismic intensity, drift ratio, and peak floor acceleration of system modules. The seismic loss function was defined as the total damage ratio, which is the ratio of replacement cost to repair cost to evaluate the seismic loss quantitatively. The system module-based seismic loss well predicted the observed data. It will be possible to help many stakeholders make risk-informed decisions for a region through the regional loss assessment of school buildings in Korea.

There are now many seismic observatory stations, excluding the acceleration monitoring network for infrastructures, of more than 300 operated by several public and governmental organizations across South Korea. The features of the site and properties of the stations were not investigated, and they have been assumed or guessed to estimate the site-specific seismic responses during the 2016 Gyeongju and 2017 Pohang earthquake events. For these reasons, various and intensive geotechnical and geophysical investigations have been conducted to quantify the site characteristics at 15 seismic stations selected in southeastern Korea. The VS profiles were, at first, obtained by performing only a downhole seismic test (DHT) at 7 stations, and were compared with those from a surface wave method. Then, the shear wave velocity (VS) profiles were deduced by combining three types of in situ seismic methods composed of a cross-hole seismic test, DHTs, and full-waveform sonic loggings at the 8 other stations, especially to complement the application limits of DHT and reduce the depth-dependent uncertainty in VS profile. The representative site characteristic profiles for each station regarding VS and VP with borehole stratigraphy and density were determined based on robust investigations. Various site parameters related to seismic responses at the seismic stations of interest were obtained for the site-specific geotechnical information, which would be useful to earthquake engineering practices.

This study presents a seismic fragility assessment methodology incorporating the cumulative damage effects of repeated seismic loading on structures. Conventional seismic fragility assessment methods typically focus on single earthquakes across multiple structures; however, seismic events often occur in sequences, with each event adding cumulative damage that can amplify the overall damage. Ignoring the effects of repeated earthquakes in fragility assessments may lead to underestimating seismic risk. This study proposes a simplified but efficient fragility assessment method that accounts for repeated earthquake effects using probabilistic combinations of each damage state. This procedure applied the capacity spectrum method to consider capacity degradation from displacement caused by prior earthquakes. Applying various earthquake scenarios, this study analyzes the effects of damage accumulation from earthquake occurrence sequences, structural behavior types, and seismic design levels on the fragility of structures under repeated earthquake events.

Being in a stable continental region (SCR) with a limited history of instrumentation, South Korea has not collected sufficient instrumental data for data-driven ground motion models. To address this limitation, we investigated the suitability of the hybrid ground motion simulation method that Graves and Pitarka (2010, 2015) proposed for simulating earthquake ground motions in South Korea. The hybrid ground motion simulation method used in this study relies on region-specific parameters to accurately model phenomena associated with the seismic source and the wave propagation. We initially employed relevant models and parameters available in the literature as a practical approach. We incorporated a three-dimensional velocity model developed by Kim et al. (2017) and a one-dimensional velocity model presented by Kim et al. (2011) to account for the crustal velocity structure of the Korean peninsula. To represent the earthquake source, we utilized Graves and Pitarka’s rupture generator algorithm along with a magnitude-area scaling relationship developed for SCR by Leonard (2014). Additionally, we assumed the stress and attenuation parameters based on studies of regional seismicity. Using the implemented platform, we simulated the 2016 Mw5.57 Gyeongju earthquake and the 2017 Mw5.4 Pohang earthquake. Subsequently, we compared results with recorded accelerations and an empirical ground motion prediction equation at strong motion stations. Our simulations had an overall satisfactory agreement with the recorded ground motions and demonstrated the potential of broadband hybrid ground motion simulation for engineering applications in South Korea. However, limitations remain, such as the underestimation of long-period ground motions during the 2017 Pohang earthquake and the lack of a model to predict the ground motion amplification associated with the near-surface site response accurately. These limitations underscore the importance of careful validation and refinement of region-specific models and parameters for practically implementing the simulation method.

In stable continental regions, selecting appropriate ground motions for seismic design and dynamic response analysis presents significant challenges. This study evaluates the liquefaction potential of the Nakdonggang delta region, South Korea, by generating synthetic ground motion scenarios and applying a scenario-based liquefaction assessment approach. We utilized a hybrid broadband ground motion simulation method proposed by Graves and Pitarka (2010, 2015) to create bedrock ground motions for three hypothetical earthquakes (Mw 6.2 and 6.0) occurring along the Dongrae and Miryang faults. The generated synthetic ground motions were used as input for onedimensional nonlinear site response analyses, incorporating shear wave velocity profiles derived from surface wave inversion. The simulated ground motions demonstrated higher responses at short periods and relatively weaker responses at long periods compared to the Korean design spectra. This amplification of long-period components was attributed to the dynamic response of deep sedimentary layers, while high-frequency components were generally deamplified due to damping effects in shallow silty layers. Liquefaction susceptibility was assessed using surface ground motions derived from the site response analyses, following the SPT-based simplified method proposed by Idriss and Boulanger (2008). Results indicated high liquefaction potential across most sites for the Dongrae earthquake scenario, while liquefaction was unlikely for all sites under the Miryang-1 scenario. For the Miryang-2 scenario, liquefaction was predicted at some sites. Overall, liquefaction is expected at PGA values of approximately 0.13 g or higher, with sites exhibiting lower shear wave velocities being more vulnerable to liquefaction

In order to design a seismic safety of a cabinet affected by an earthquake, vibration analysis was performed using a model cabinet. In order to analyze the vibration characteristics of the cabinet under earthquake conditions, 3D finite element analysis was performed using ANSYS Workbench and SolidWorks. The modal analysis of the cabinet showed nine natural modes and natural frequencies, and showed the deformation and vibration of the cabinet panel for each mode. The frequencies of the 1st and 2nd modes, which are low modes, were 10% of the natural frequency value of the 9th mode, so it was easy to predict the possibility of resonance occurrence. The response spectrum due to the earthquake showed that the displacement, acceleration, and stress distribution of the cabinet had different behaviors in the x, y, and z directions, and especially showed very large values in the z direction. Although the vibration characteristics of the structure were evaluated using the modal characteristics and response spectrum for the cabinet, research on the application of a tuned mass damper is necessary for the dynamic characteristics process of the cabinet due to an earthquake and resonance reduction.