이 연구의 목적은 인공신경망 기법을 이용하여 사면의 내진 성능을 비교적 정확하면서도 효율적으로 예측하는 모델을 도 출하는데 있다. 사면의 내진 성능은 지진입력 및 사면모델의 무작위성 및 불확실성으로 인하여 정량화하기 쉽지 않다. 이러한 배경 아래 사면에 대한 확률론적 지진 취약도 분석이 몇몇 연구자에 의해 수행되었고, 이를 기반으로 다중 선형회귀분석 을 통하여 사면 내진성능에 대한 닫힌식이 제안된 바 있다. 그러나 전통적인 통계학적 선형회귀분석은 다양한 조건의 사면과 이에 따른 내진 성능 사이의 비선형적 관계를 정확하게 표현하지 못하는 한계를 보였다. 이에 따라 본 연구에서는 이러한 문제점을 극복하고자 인공신경망 기법을 사면 내진성능 예측 모델을 생성하는데 적용하였다. 도출된 모델의 유효성은 기존 의 다중 선형 및 다중 비선형 회귀분석을 통한 모델과 비교하여 검증하였다. 결과적으로 이전 연구의 전통적인 통계학적 회귀 분석을 통한 모델과 비교 결과, 기본적으로 인공신경망 기법을 통하여 도출된 모델이 사면의 내진성능을 예측하는데 있어 우수한 성능을 보여주었다. 이러한 정확도 높은 모델은 향후 확률에 기반한 사면의 지진취약도 지도를 개발하고, 주요 구 조물의 인근 사면으로 인한 리스크를 효과적으로 평가하는데 활용될 수 있을 것이라 기대된다.

In order to increase the seismic safety of nuclear power plant (NPP) structures, a technique to reduce the seismic load transmitted to the NPP structure by using a seismic isolation device such as a lead-rubber bearing has recently been actively researched. In seismic design of NPP structures, three directional (two horizontal and one vertical directions) artificial synthetic earthquakes (G0 group) corresponding to the standard design spectrum are generally used. In this study, seismic analysis was performed by using three directional artificial synthetic earthquakes (M0 group) corresponding to the maximum-minimum spectrum reflecting uncertainty of incident direction of earthquake load. The design basis earthquake (DBE) and the beyond design basis earthquakes (BDBEs are equal to 150%, 167%, and 200% DBE) of G0 and M0 earthquake groups were respectively generated for 30 sets and used for the seismic analysis. The purpose of this study is to compare seismic responses and seismic fragility curves of seismically isolated NPP structures subjected to DBE and BDBE. From the seismic fragility curves, the probability of failure of the seismic isolation system when the peak ground acceleration (PGA) is 0.5 g is about 5% for the M0 earthquake group and about 3% for the G0 earthquake group.

In the precedent study, the retractable-roof spatial structure was selected as the analytical model and a tuned mass damper (TMD) was installed to control the dynamic response for the earthquake loads. Also, it is analyzed that the installation location of TMD in the analytical model and the optimal number of installations. A single TMD mass installed in the analytical model was set up 1% of the mass of the whole structure, and the optimum installation location was derived according to the number of change. As a result, it was verified that most effective to install eight TMDs regardless of opening or closing. Thus, in this study, eight TMDs were installed in the retractable-roof spatial structure and the optimum mass ratio was inquired while reducing a single TMD. In addition, the optimum mass distribution ratio was identified by redistributing the TMD masses differently depending on the installation position, using the mass ratio of vibration control being the most effective for seismic load. From the analysis results, as it is possible to confirm the optimum mass distribution ratio according to the optimum mass ratio and installation location of the TMD in the the retractable-roof spatial structure, it can be used as a reference in the TMD design for large space structure.

Most school buildings consist of reinforced concrete (RC) moment frames with masonry infills. The longitudinal direction frames of those school buildings are relatively weak due to the short-column effects caused by the partial masonry infills and need to be evaluated carefully. In ‘Manual for Seismic Performance Evaluation and Retrofit of School Facilities’ published in 2018, response modification factor of 2.5 is applied to non-seismic RC moment frames with partial masonry infills, but sufficient verification of the factor has not been reported yet. Therefore, this study conducted seismic performance evaluation of planar RC moment frames with partial masonry infills in accordance with both linear analysis and nonlinear static analysis procedures presented in the manual. The evaluation results from the different procedures are compared in terms of assessed performance levels and number of members not meeting target performance objectives. Finally, appropriate response modification factors are proposed with respect to a shear-controlled column ratio.

This study investigates the seismic performance of a hybrid seismic energy dissipation device composed of a viscoelastic damper and a steel slit damper connected in parallel. A moment-framed structure is designed without seismic load and is retrofitted with the hybrid dampers. The model structure is transformed into an equivalent simplified system to find out optimum story-wise damper distribution pattern using genetic algorithm. The effectiveness of the hybrid damper is investigated by fragility analysis of the structure with and without the dampers. The analysis results show that after seismic retrofit the probability of reaching damage states, especially the complete damage state, of the structure turn out to be significantly reduced.

본 연구에서는 옹벽 구조물의 내진성능 평가를 위해 2차원 유한요소 해석을 수행하였다. 2차원 유한요소 모델은 실제로 시공된 옹벽 구조를 기반으로 2차원 평면변형 요소로 모델링되었으며, 지반은 각각 유한요소와 무한요소로 모델링 하였다. 지진하중은 총 38개의 인공 지진을 생성하여 사용하였고, 생성된 인공 지진파를 11개의 PGA로 나누어 총 418회의 시간이력해석을 수행하였다. 수치해석 결과를 바탕으로 옹벽 구조물의 지진에 대한 취약도를 분석하였다. 취약도 분석 결과 콘크리트 및 철근의 취약도 곡선이 낮은 PGA 수준에서 급격히 변하는 것을 관찰할 수 있었다. 유한요소 해석 결과를 바탕으로 실제 현장의 옹벽 구조에서 상대적으로 낮은 수준의 지진파가 발생하더라도 높은 파괴확률로 인해 지진에 상대적으로 취약함을 확인하였다.

Following a 5.8 magnitude earthquake on September 12, 2016 in Gyeongju Province, a magnitude 5.4 earthquake occurred in the northern region of Pohang City on November 15, 2017 in South Korea. Only 7.9 % of the building structures are earthquake-resistant, according to the recent survey conducted by the government agencies in October 2017. In this paper, the linear analysis seismic performance evaluation procedure of the existing school structures presented in the revised methodology(Seismic Performance Evaluation Procedure and Rehabilitation Manual for School Facilities) was introduced. In this paper, the linear analysis evaluation procedure presented in the revised methodology was introduced and the seismic performance index of the example structure was evaluated using the linear analysis evaluation procedure. The seismic retrofit was verified by the linear and nonlinear dynamic analyses using Perform 3D. The analysis results show that the dissipated inelastic energy is concentrated on the retrofitted shear wall and the maximum inter-story drift of the stadium model structure with damping system satisfies the requirement of the current code.

The main function of the general hospital building is to provide medical facilities and service. However, damage to the non-structural elements such as architectural, medical, mechanical and other components will interrupt those functions after the earthquake. Especially, it is considered that, damage to the non-structural elements is a serious event because it is directly associated with the lives of patients. Therefore, this study evaluated whether the certain non-structural elements of general hospital building has the seismic performance to provide hospital medical services after the earthquake. The evaluation is conducted by selecting the non-structural elements used in general hospital which are sensitive to acceleration, such as cooling towers, air handler, MRI and CT. As a result, the non-structural elements located on the upper floor without suitable support method did not meet the performance objective. Therefore, adequate anchorage against the seismic event is required for such non-structural elements that are acceleration-sensitives.

The curved beam has a complicated behavior compared to a straight beam due to torsional and warping. Therefor, in this study, eigenvalue analysis was performed for curved beam with different shape(I-shape, T-shape, box-shape) corresponding to the same value of the moment of inertia. As a result the curved beam with box-shape section had a larger natural frequency value than the other curved beam. Also, the dynamic analysis results showed that the largest result was obtained at 826.18MPa in the T-shape curved beam when the gyeongju earthquake was applied.

In this study, finite element (FE) analysis was performed to evaluate the seismic performance of the water treatment plant, which is a major state of the art water treatment plant, to predict tensile cracks and compressive failure. The FE model simulation for two facilities of the water purification plant was made considering the initial conditions, boundary conditions and water effect. For the nonlinear dynamic analysis, seismic analysis was performed using ground acceleration. Tensile cracks and compressive failure are analyzed and the effects on the structures are analyzed. As a result of the analysis, tensile cracks can be predicted to occur in the main structure.

The paper presents an experimental study on shear behavior of RC beams retrofitted with Uni-Directional Narrow Fabric to improve seismic performance. Experimental parameters include the type of fiber, spacing of the fiber, and the ratio of transverse reinforcement. Also, Static loading test was performed on twelve shear-critical specimens. An experimental result were analyzed to investigate the contribution of shear strength and failure modes of the specimens retrofitted or strengthened with Uni-Directional Narrow Fabric compared to the non-retrofitted the specimen. In order to derive the shear strength model according to the spacing of the fiber, the experimental results were compared with the conventional shear strength model of RC elements retrofitted with FRP.

As the number of high-rise buildings increases, a mid-story isolation system has been proposed for high-rise buildings. Due to structural problems, an appropriate isolation layer displacement is required for an isolation system. In this study, the mid-story isolation system was designed and the seismic response of the structure was investigated by varying the yield strength and the horizontal stiffness of the seismic isolation system. To do this, a model with an isolation layer at the bottom of 15th floor of a 20-story building was used as an example structure. Kobe(1995) and Nihonkai-Chubu(1983) earthquake are used as earthquake excitations. The yield strength and the horizontal stiffness of the seismic isolation system were varied to determine the seismic displacement and the story drift ratio of the structure. Based on the analytical results, as the yield strength and horizontal stiffness increase, the displacement of the isolation layer decreases. The story drift ratio decreases and then increases. The displacement of the isolation layer and the story drift ratio are inversely proportional. Increasing the displacement of the isolation layer to reduce the story drift ratio can cause the structure to become unstable. Therefore, an engineer should choose the appropriate yield strength and horizontal stiffness in consideration of the safety and efficiency of the structure when a mid-story isolation system for a high-rise building is designed.

‘Seismic Performance Evaluation Method for Existing Buildings (2013)’ developed in accordance with the overseas guidelines ASCE 41 - 06 is the most widely used procedure among domestic seismic performance evaluation guidelines in Korea. However, unlike ASCE 41 - 06, it stipulates that the final performance should be derived as the gravity load distribution ratio of the lateral force resistance system in the guideline. Therefore, in the case of a dual steel structure system with slender braces, where the internal moment frame is mostly responsible for the gravity load, the evaluation of slender braces based on gravity load distribution ratio is difficult to be achieved. In this research, we propose an objective evaluation process for such system by evaluating seismic performance for large-scale factory facilities as an example.

In this study, we conducted a shake table test to verify the seismic performance of the paneling system with steel truss composed of bolt connections. The control group was set to the traditional paneling system with steel truss connected by spot welding method. Test results showed that the bolted connection type paneling system has excellent deformation capacity without cracking or brittle fracture of the steel truss connection parts compared to the welding type paneling system. Furthermore, in the bolted connection type, slight damage occurred at the time of occurrence of the same story drift angle as compared with the existing method, it is considered that it has excellent seismic performance. In compliance with the performance-based design recommended for the current code (ASCE 41-13) on non-structural components, it is judged that in the case of the bolted connection type paneling system, it can be applied to all risk category structures without restriction. However, in the case of traditional paneling system with spot welding method, it is considered that it can be applied limitedly.

본 연구에서는 역량스펙트럼법을 이용해 얻어진 구조물의 성능점을 확률적으로 평가하는 방법을 제시하였다. ATC-40에 따라 역량스펙트럼법을 이용하여 4층 1경간 철골구조물의 성능점을 산정하였다. 요구스펙트럼을 이용하여 구조물의 성능한계를 초과하는지 여부를 분석하기 위해 구조부재의 소성변형각으로부터 정의되는 구조물의 성능한계에 대해 한계변위를 도출하였다. 또한 설계응답스펙트럼과 유사한 응답스펙트럼을 가지는 인공지진파 30개를 선정하여 스펙트럼 가속도에 따른 각 성능한계의 초과여부를 통해 fragility curve를 도출하였다. 관측된 초과확률을 이용하여 fragility curve를 도출하기 위해 maximum likelihood method를 사용하였다. 각 성능한계점에 대응하는 설계응답스펙트럼의 응답가속도값에서 성능한계점을 초과할 확률은 존재하는 것으로 확인되었다. 본 방식은 구조물의 성능점에 대해 지진파의 불확실성을 고려한 확률적 평가가 가능하고, 시간증분해석이 필요하지 않아 해석시간을 상당부분 단축시킬 수 있다는 장점이 있다.

Base isolation system is generally used for low-rise buildings. For high-rise buildings subjected to earthquake loads, a mid-story isolation system was proposed and applied to practical engineering. In this study, seismic responses of high-rise buildings considering the installation story of the mid-story isolation system were evaluated. To do this, the 20-story and 30-story building were used as example structures. Historical earthquakes such as Kobe (1995), Northridge (1994) and Loma Prieta (1989) earthquakes were employed applied as earthquake excitations. The installation location of the mid-story isolation system was changed from the bottom of the 1st floor to the bottom of the top floor. The seismic responses of the example building were investigated by changing the location of the isolation layer. Based on the analytical results, when the seismic isolation system is applied, story drift ratio and acceleration response are reduced compared to the case without the isolation system. When the isolation layer is located on the lower part of the building, it is most effective. However, in that case, the possibility that the structure is unstable increases. Therefore, an engineer should consider both structural efficiency and safety when a mid-story isolation system for a high-rise building is designed.

As an alternative to coupling beam in shear wall system, application of the damper which can dissipate energy is increasing. In this study, lintel beam type steel damper which is simple to construct and change depending on design load was proposed. Cyclic loading test was conducted to compare reinforced concrete coupling beam and lintel beam type steel damper. The test results showed that lintel beam type steel damper has higher initial stiffness and energy dissipation capacity than reinforced concrete coupling beam.

This study develops a new hybrid passive energy dissipation device for seismic rehabilitation of an existing structure. The device is composed of a friction damper combined with a steel plate with vertical slits as a hysteretic damper. Analytical model is developed for the device, and the capacity of the hybrid device to satisfy a given target performance is determined based on the ASCE/SEI 7-10 process. The effect of the device is verified by nonlinear dynamic analyses using seven earthquake records. The analysis results show that the dissipated inelastic energy is concentrated on the hybrid damper and the maximum interstory drift of the SMRF with damping system satisfies the requirement of the current code.

In this study, the seismic performance of concrete-steel composite moment frame structures equipped with seismic retrofitting systems such as seismic reinforcement, base isolators, and bracing members, which are typical earthquake damage mitigation systems, is evaluated through nonlinear dynamic analyses. A total of five frame models were designed and each frame model was developed for numerical analyses. A total of 80 ground acceleration data were used to perform the nonlinear dynamic analysis to measure ground shear force and roof displacement, and to evaluate the behavioral performance of each frame model by measuring inter-story drift ratios. The analysis results indicate that the retrofitting device of the base isolator make a significant contribution to generating relatively larger absolute displacement than other devices due to flexibility provided to interface between ground and column base. However, the occurrence of the inter-story drift ratio, which is a relative displacement that can detect the damage of the structure, is relatively small compared with other models. On the other hand, the seismic reinforced frame model enhanced with the steel plate at the lower part of the column was found to be the least efficient.