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.

The dome structure is suitable as a roof for large spatial structures because it can maintain the shape without installing columns in the internal space. However, the structure characteristics of the lower and upper structures of the dome structure are different, and damage may occur when an earthquake occurs. Therefore, in this study, mid-story isolation system was applied to the ribbed dome and geodesic dome structures to analyze the seismic response of the lower and upper structures according to the dome shape. As a result of the analysis, the displacement of the ribbed dome increased, but the deformation of the ribbed dome and the response of the lower structure decreased, and the seismic response of the geodesic dome decreased overall. From this result, the effect of the isolator according to the shape of the dome structure was confirmed, and the mid-story isolation is considered effective in reducing the seismic response of the upper and lower structures.

The diagrid structural system has a braced frame that simultaneously resists lateral and vertical loads, and is being applied to many atypical high-rise buildings for aesthetic effects. In this study, a 60-story structure with twisted degrees of 0° to 180° was selected to determine seismic response control performance of twisted high-rise structures whether the diagrid system was applied and according to the reduction of braced frame material quantity. For this purpose, ‘Nor’ model without the diagrid system and the ‘DS’ model with the diagrid system, which was modeled by reducing braced frame member section to 700~400, were modeled. As a result, the 'DS' model showed an seismic response control effect in all Twisted models even when the quantity was reduced, and especially, the Twisted shape model was found to have an superior response control effect compared to the regular structure. In addition, the ‘600DS’ analysis model, which matched the ‘Nor’ model by 99.0% in quantity, showed an increase in seismic response control performance as the rotation angle increased.

본 연구는 수소 탱크를 고정하는 강재 볼트의 부식으로 인한 성능 저하 문제를 해결하기 위해 내부식성 복합재료로 알려진 Glass Fiber Reinforced Polymer (GFRP) 및 Carbon Fiber Reinforced Polymer (CFRP)를 활용한 앵커 시스템을 제안하고, 이를 지진 하 중 하에서의 안전성 평가를 통한 적용 타당성 검토를 수행하였다. 연구에서는 현장 조사를 통해 실제 사용 중인 수소 탱크의 설계 제 원을 확보한 후 이를 바탕으로 유한요소해석을 수행하였으며, AC 156 인공 지진파를 적용하여 FRP 앵커 볼트와 기존 강재 앵커의 성 능을 비교 분석하였다. 주요 분석 결과, FRP 앵커 볼트를 적용한 수소 탱크는 강재 앵커 볼트에 비해 고유 진동수가 21% 증가하여 구 조적 강성이 향상됨을 확인하였다. 또한, 가속도 응답 분석 결과 FRP 앵커 볼트는 상부 가속도를 감소시켜 지진 하중에 대한 저항성을 증진하는 것으로 나타났다. 응력 해석에서는 FRP 앵커 볼트가 강재 앵커 볼트에 비해 유효 응력이 약 91% 감소하여, 구조적 안전성이 크게 개선되었다. 그러나, FRP 앵커 볼트 적용 시 기초 콘크리트에 가해지는 쪼갬 인장 응력이 강재 앵커 대비 최대 3.5배 증가하는 것으로 나타났으며, 이에 따라 FRP 앵커 볼트 사용 시 기초 콘크리트의 보강이 필요할 것으로 사료된다. 이러한 연구 결과는 수치해석 에 국한된 결과로, 향후 실제 지진 하중을 모사한 실험적 검증이 필요하다. FRP 앵커 볼트의 적용 가능성은 향후 연구를 통해 광범위 하게 평가될 것이며, 이를 통해 수소 인프라의 내구성과 안전성을 더욱 강화할 수 있을 것으로 기대된다.

Strong ground motions at specific sites can cause severe damage to structures. Understanding the influence of site characteristics on the dynamic response of structures is crucial for evaluating their seismic performance and mitigating the potential damage caused by site effects. This study investigates the impact of the average shear wave velocity, as a site characteristic, on the seismic response of low-to-medium-rise reinforced concrete buildings. To explore them, one-dimensional soil column models were generated using shear wave velocity profile from California, and nonlinear site response analyses were performed using bedrock motions. Nonlinear dynamic structural analyses were conducted for reinforced concrete moment-resisting frame models based on the regional information. The effect of shear wave velocity on the structural response and surface ground motions was examined. The results showed that strong ground motions tend to exhibit higher damping on softer soils, reducing their intensity, while on stiffer soils, the ground motion intensity tends to amplify. Consequently, the structural response tended to increase on stiffer soils compared to softer soils.

The damage to structures during an earthquake can be varied depending on the frequency characteristics of seismic waves and the geological properties of the ground. Therefore, considering such attributes in the design ground motions is crucial. The Korean seismic design standard (KDS 17 10 00) provides design response spectra for various ground classifications. If required for time-domain analysis, ground motion time series can be either selected and adjusted from motions recorded at rock sites in intraplate regions or artificially synthesized. Ground motion time series at soil sites should be obtained from site response analysis. However, in practice, selecting suitable ground motion records is challenging due to the overall lack of large earthquakes in intraplate regions, and artificially synthesized time series often leads to unrealistic responses of structures. As an alternative approach, this study provides a case study of generating ground motion time series based on the hybrid broadband ground motion simulation of selected scenario earthquakes at sites in the Nakdonggang delta region. This research is significant as it provides a novel method for generating ground motion time series that can be used in seismic design and response analysis. For large-magnitude earthquake scenarios close to the epicenter, the simulated response spectra surpassed the 1000-year design response spectra in some specific frequency ranges. Subsequently, the acceleration time series at each location were used as input motions to perform nonlinear 1D site response analysis through the PySeismoSoil Package to account for the site response characteristics at each location. The results of the study revealed a tendency to amplify ground motion in the mid to long-period range in most places within the study area. Additionally, significant amplification in the short-period range was observed in some locations characterized by a thin soil layer and relatively high shear wave velocity soil near the upper bedrock.

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.

이 논문은 포트 받침이 설치된 3경간 연속 콘크리트 거더교를 대상으로 받침의 노후화가 교량의 지진응답에 미치는 영향을 분석하 였다. 포트 받침은 고정단 및 가동단의 강성을 반영해 교축방향, 교축직각방향, 수직방향의 탄성 스프링으로 모델링하였다. 포트 받침 의 노후화를 고정단 받침의 수평강성 저하와 가동단 받침의 수평강성 증가로 나누어 받침의 노후화가 교량의 지진 거동에 미치는 영 향을 분석하였다. 수치해석으로부터 구한 고유진동수 값과 이 교량의 설계 고유진동수를 비교하여 해석 대상 3경간 연속 거더교의 유 한요소모델이 타당함을 보였으며, 국내 도로교설계기준(한계상태설계법)의 설계응답스펙트럼에 부합하는 인공지진파를 이용해 받 침 강성의 변화에 따른 교량 상부 및 받침의 지진응답을 계산하였다. 지진해석 결과, 받침의 노후화로 인해 고정단 받침의 수평강성이 감소할 경우 지진으로 인한 고정단 받침의 절대최대 상대변위가 증가하였다. 이는 받침을 지지하는 모르타르의 균열과 앵커 볼트의 탈락 가능성이 커짐을 의미한다. 받침의 노후화로 인해 가동단 받침의 수평강성이 증가하는 경우에는 지진으로 인한 고정단 받침의 절대최대 전단력이 감소하였다. 그러나 이 경우 가동단 바로 위 거더 단면에 추가의 휨인장응력이 발생할 수 있으며, 이러한 받침 성능 의 변화로 인하여 지진 시 연속 콘크리트교에 예기치 못한 구조적 손상이 발생할 수 있다.

In the seismic evaluation of underground utility tunnels, selecting an analytical method is critical to estimating reasonable seismic responses. In simplified pseudo-static analysis methods widely applied to typical seismic design and evaluation of underground tunnels in practice, it is essential to check whether the methods provide valid results for cut-and-cover tunnels buried in shallow to medium depth. The differences between the two simplified pseudo-static methods are discussed in this study, and the analysis results are compared to those obtained from FLAC models. In addition to the analysis methods, seismic site classification, overburden soil depth, and sectional configuration are considered variables to examine their effects on the seismic response of underground utility tunnels. Based on the analysis results, the characteristics derived from the concepts and details of each simplified model are discussed. Also, general observations are made for the application of simplified analysis methods.

This study investigated the impact of soil-structure interaction on multi-degree-of-freedom structures using the shallow-foundation Winkler model, known as the BNWF model. The model’s period was determined through eigenvalue analysis and compared to results obtained from FEMA’s formula. Results indicated that considering the soil, the structure’s period increased by up to 8.7% compared to the fixed-base model, aligning with FEMA’s calculations. Furthermore, with adequate ground acceleration, roof displacement increased by 3.4% to 3.8%, while base shear decreased by 4% to 10%. However, roof displacement and base shear increased in some earthquake scenarios due to spectral shape effects in regions with extended structural periods. Foundation damping effects, determined through the foundation’s moment-rotation history, grew with higher ground acceleration. This suggests that accounting for period elongation and foundation damping can enhance the seismic design of multi-degree-of-freedom structures.

In this paper, machine learning models were applied to predict the seismic response of steel frame structures. Both geometric and material nonlinearities were considered in the structural analysis, and nonlinear inelastic dynamic analysis was performed. The ground acceleration response of the El Centro earthquake was applied to obtain the displacement of the top floor, which was used as the dataset for the machine learning methods. Learning was performed using two methods: Decision Tree and Random Forest, and their efficiency was demonstrated through application to 2-story and 6-story 3-D steel frame structure examples.

Machine learning is widely applied to various engineering fields. In structural engineering area, machine learning is generally used to predict structural responses of building structures. The aging deterioration of reinforced concrete structure affects its structural behavior. Therefore, the aging deterioration of R.C. structure should be consider to exactly predict seismic responses of the structure. In this study, the machine learning based seismic response prediction model was developed. To this end, four machine learning algorithms were employed and prediction performance of each algorithm was compared. A 3-story coupled shear wall structure was selected as an example structure for numerical simulation. Artificial ground motions were generated based on domestic site characteristics. Elastic modulus, damping ratio and density were changed to considering concrete degradation due to chloride penetration and carbonation, etc. Various intensity measures 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 and extreme gradient boosting algorithms present good prediction performance.

This study aims to investigate the seismic response of a large span thin shell structures and assess their displacement under seismic loads. The study employs finite element analysis to model a thin shell structure subjected to seismic excitation. The analysis includes eigenvalue analysis and time history analysis to evaluate the natural frequencies and displacement response of the structure under seismic loads. The findings show that the seismic response of the large span thin shell structure is highly dependent on the frequency content of the seismic excitation. The eigenvalue analysis reveals that the tenth mode of vibration of the structure corresponds to a large-span mode. The time history analysis further demonstrates, with 5% damping, that the displacement response of the structure at the critical node number 4920 increases with increasing seismic intensity, reaching a maximum displacement of 49.87mm at 3.615 seconds. Nevertheless, the maximum displacement is well below the allowable limit of the thin shell. The results of this study provide insight into the behaviour of complex large span thin shell structures as elevated foundations for buildings under seismic excitation, based on the displacement contours on different modes of eigenvalues. The findings suggest that the displacement response of the structure is significant for this new application of thin shell, and it is recommended to enhance the critical displacement area in the next design phase to align with the findings of this study to resist the seismic impact.

유체-구조물-지반 상호작용을 고려한 액체저장탱크의 유한요소 모형을 제시하고, 비선형 지진응답 해석기법을 정식화한다. 탱크 구조물은 기하 및 재료 비선형 거동을 고려할 수 있는 쉘 요소로 모델링한다. 유체의 거동은 acoustic 요소로 구현하고, interface 요소 를 사용하여 구조물과 결합한다. 지반-구조물 상호작용을 고려하기 위해 지반의 근역과 원역을 각각 solid 요소와 perfectly matched discrete layer로 모델링한다. 예제 20만 kl급 액체저장탱크의 지진취약도 해석에 적용하여, 유연한 지반에 구조물이 놓인 경우 부지에 서의 암반노두운동의 증폭 및 필터링으로 인해 지진취약도의 중앙값과 대수 표준편차가 감소하는 것을 관찰할 수 있다.

원자력발전소(원전) 내부에 설치되어 있는 주요 기기는 원전의 안정적인 운영을 돕는 주요 2차 구조 물이다. 경주 지진, 포항 지진과 같은 강한 지진이 발생하였을 때, 원전 주요 기기의 손상은 원전의 안정한 정지에 문제를 초래할 수 있다. 따라서, 원전 주요 기기의 지진응답을 저감시키기 위한 연구가 필수적으로 요구된다. 이러한 배경 아래, 본 연구에서는 원전 주요 기기의 내진성능 향상을 위하여 동 흡진장치(Dynamic Absorber)를 활용하였다. 연구에서 사용된 동흡진장치는 스프링, 댐퍼, 및 질량체로 구성된다. 이러한 동흡진장치를 설계하기 위하여 기존에 제안된 방법론들을 활용하였으며, 각 방법론 들을 기반으로 설계된 동흡진장치의 지진응답 저감효과를 비교 및 분석하였다. 구체적으로, 진동대 시 험 결과를 바탕으로 유한요소 모델을 검증하였다. 또한, 이를 기반으로 기존 동흡진장치의 설계방법론 에 따른 원전 주요 기기의 지진응답 저감 효과를 비교 및 분석하였다. 결과적으로 각 방법론들은 원전 주요기기의 가속도, 변위, 응력 응답을 평균적으로 약 30% 정도 감소시키는 효과를 보였다.

This study performed the seismic response analysis of an LNG storage tank supported by a disconnected piled raft foundation (DPRF) with a load transfer platform (LTP). For this purpose, a precise analytical model with simultaneous consideration of Fluid-Structure Interaction (FSI) and Soil-Structure Interaction (SSI) was used. The effect of the LTP characteristics (thickness, stiffness) of the DPRF system on the seismic response of the superstructure (inner and outer tanks) and piles was analyzed. The analytical results were compared with the response of the piled raft foundation (PRF) system. The following conclusions can be drawn from the numerical results: (1) The DPRF system has a smaller bending moment and axial force at the head of the pile than the PRF system, even if the thickness and stiffness of the LTP change; (2) The DPRF system has a slight stiffness of the LTP and the superstructure member force can increase with increasing thickness. This is because as the stiffness of the LTP decreases and the thickness increases, the natural frequency of the LTP becomes closer to the natural frequency of the superstructure, which may affect the response of the superstructure. Therefore, when applying the DPRF system, it is recommended that the sensitivity analysis of the seismic response to the thickness and stiffness of the LTP must be performed.

In this study, the seismic response characteristics of the three analysis model with or without TMD were investigated to find out the effective dome shape. The three analysis models are rib type, lattice type and geodesic type dome structure composed of space frame. The maximum vertical and horizontal displacements were evaluated at 1/4 point of the span by applying the resonance harmonic load and historical earthquake loads (El Centro, Kobe, Northridge earthquakes). The study of the effective TMD installation position for the dome structure shows that seismic response control was effective when eight TMDs were installed in all types of analysis model. The investigation of the efficiency of TMD according to dome shape presents that lattice dome and geodesic dome show excellent control performance, while rib dome shows different control performance depending on the historical seismic loads. Therefore, lattice and geodesic types are desirable for seismic response reduction using TMD compared to rib type.

Non-structural elements, such as equipment, are typically affixed to a building’s floor or ceiling and move in tandem with the structure during an earthquake. Seismic forces acting upon non-structural elements traverse the ground and the building’s structure. Considering this seismic load transmission mechanism, it becomes imperative to account for the interactions between soil, structure, and equipment, establishing seismic design procedures accordingly. In this study, a Soil-Structure-Equipment Interaction (SSEI) model is developed. Through seismic response analysis using this model, how the presence or absence of SSEI impacts equipment behavior is examined. Neglecting the SSEI aspect when assessing equipment responses results in an overly conservative evaluation of its seismic response. This emphasizes the necessity of proposing an analytical model and design methodology that adequately incorporate the interaction effect. Doing so enables the calculation of rational seismic forces and facilitates the seismic design of non-structural elements.

In general, the design response spectrum in seismic design codes is based on the mean-plus-one-standard deviation response spectrum to secure high safety. In this study, response spectrum analysis was performed using seismic wave records adopted in domestic horizontal design spectrum development studies, while three response spectra were calculated by combining the mean and standard deviation of the spectra. Seismic wave spectral matching generated seismic wave sets matching each response spectrum. Then, seismic fragility was performed by setting three damage levels using a single-degree-of-freedom system. A correlation analysis was performed using a comparative analysis of the change in the response spectrum and the seismic fragility concerning the three response spectra. Finally, in the case of the response spectrum considering the mean and standard deviation, like the design response spectrum, the earthquake load was relatively high, indicating that conservative design or high safety can be secured.