• Steel and Composite Structures
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• 제50권3호
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• pp.337-345
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• 2024

This research proposed a particle swarm optimization (PSO) based seismic retrofit design of moment frame structures using a steel frame assembly. Two full scale specimens of the steel frame assembly with different corner details were attached to one-story RC frames for seismic retrofit, and the lateral load resisting capacities of the retrofitted frames subjected to cyclic loads were compared with those of a bare RC frame. The open source software framework Opensees was used to develop an analytical model for validating the experimental results. The developed analytical model and the optimization scheme were applied to a case study structure for economic seismic retrofit design, and its seismic performance was assessed before and after the retrofit. The results show that the developed steel frame assembly was effective in increasing seismic load resisting capability of the structure, and the PSO algorithm could be applied as convenient optimization tool for seismic retrofit design of structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.953-958
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• 2001

A retrofit method “Steel Ring Confinement Retrofit” was proposed and discussed on the material and member characteristics through experiments. Steel Ring Confinement Retrofit consist of confining steel ring and expansive concrete. The steel ring is set on the footing, surrounding the base of the pier. By placing expansive concrete between the pier and steel ring, chemical prestress is introduced in the members. Chemical prestressed ring concrete enlarge the pier section and enhance both the strength and ductility of the pier. It was confirmed that Various Ring Confinement Retrofit improved the strength of the pier up to 30% ~ 100% with experiments.

• 품질경영학회지
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• 제45권3호
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• pp.393-401
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• 2017

Purpose: The purpose of this study is to propose retrofit measures for KDX-II KVLS hull crack, also, enhance safety and quality of ship. Also, this study suggest to how to retrofit about hull crack of the ship and how to improve operability of the ship. Methods: Retrofit measures of KDX-II KVLS hull crack reach a conclusion through global structure analysis and fatigue analysis. Concerned about thermal deformation due to welding around the KVLS, in addition to, verify to safety of KVLS. Results: Based on result of global structure analysis establish retrofit measures for KDX-II KVLS hull crack. Additionally, through fatigue analysis establish final retrofit measures. The results of retrofit measures are allowed both stress level and fatigue life. Conclusion: Retrofit measures for ship hull crack based on global structure analysis and fatigue analysis improves operability and quality of the ship. Especially, KDX-II ship is the best battleship in our country. Considering the importance of KDX-II, this study improves both Korea navy's combat power and ability to carry out the mission.

• 토지주택연구
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• 제13권3호
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• pp.83-102
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• 2022

경주·포항 지진이후 국내 건축물의 내진성능에 대한 국민들의 관심이 고조되고 있으며, 특히 지진하중에 취약한 필로티형 건축물의 내진성능확보에 대한 시의성이 높아지고 있다. 이 연구에서는 LH가 보유한 필로티형 건축물의 유형별 내진보강방안을 제시하였다. 내진보강방안에는 내진보강우선순위, 코어의 위치에 따른 내진보강방안이 제시되어있다. 제시된 내진보강방안의 유효성을 검증하기 위하여 필로티형 건축물의 코어의 유형에 따라 전산해석을 수행하였으며, 그 결과 제시된 내진보강방안으로 내진보강을 수행 할 경우, 내진성능이 향상됨을 확인하였다.

• Structural Engineering and Mechanics
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• 제82권5호
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• pp.557-569
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• 2022

The retrofit of existing structures in high seismic zones is a crucial issue in the earthquake engineering field. The interest of the research community is particularly high for the structures that do not respect current seismic codes and present structural deficiencies such as poor detailing and lack of capacity design provisions. A reinforced concrete (RC) school building is used as case study to show the influence of different knowledge levels on the seismic retrofitting cost assessment. The safety assessment of the case study building highlights deficiencies under both vertical and seismic loads. By considering all the possible knowledge levels defined by the Italian such as by the European codes in order to derive the mechanical properties of the school building constitutive materials, the retrofit operations are designed to achieve different seismic safety thresholds. The retrofit structural costs are calculated and summed up to the costs for in-situ in tests. The paper shows how for the case study building the major costs spent for a large number of in-situ tests allows to save a consistent amount of money for retrofit operations. The hypothesis of demolition and reconstruction of the building is also compared in terms of costs with all the analyzed retrofit options.

• Earthquakes and Structures
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• 제24권5호
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• pp.345-352
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• 2023

This paper studied the effect of soil-structure interaction (SSI) on the seismic response and retrofit of a reinforced concrete structure with a soft-first story for different soil types. A 5-story structure built on a 30m deep homogeneous soil mass was considered as a case study structure, and steel column jacketing and steel bracing were chosen as seismic retrofit methods. Seismic responses of a fixed-base and a flexible base structure subjected to seven scaled earthquake records were obtained using the software OpenSees to investigate the effect of soil on seismic response and retrofit. The nonlinearBeamColumn elements with the fiber sections were used to simulate the nonlinear behavior of the beams and columns. Soil properties were defined based on shear wave velocity according to categorized site classes defined in ASCE-7. The finite element model of the soil was made using isoparametric four-noded quadrilateral elements and the nonlinear dynamic responses of the combined system of soil and structure were calculated in the OpenSees. The analysis results indicate that the soil-structure interaction plays an important role in the seismic performance and retrofit of a structure with a soft-first story. It was observed that column steel jacketing was effective in the retrofit of the model structure on a fixed base, whereas stronger retrofit measures such as steel bracing were needed when soil-structure interaction was considered.

• 한국지진공학회논문집
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• 제26권2호
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• pp.59-69
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• 2022

The use of dampers is being considered a means to improve the seismic performance of buildings. It may take considerable time and effort to find an optimal design solution since repeated three-dimensional nonlinear time history analyses are required. Therefore, a preliminary design procedure for seismic retrofit using hysteretic dampers was proposed in this study. In the proposed procedure, the amount of retrofit (required number of dampers) is estimated from the capacity curve of the building before retrofit and allowable story drift of the building. In combining the capacity curves of the building and the dampers, the deformation demand for the dampers can be easily checked against their deformation capacity. The equations to transform the device displacement to roof displacement for the combination of capacity curves are developed. The proposed procedure was applied to the seismic retrofit design of sample buildings. The study found that the estimated capacity curve was very close to the actual capacity curve obtained from the pushover analysis, which can determine an appropriate configuration to meet the required seismic performance.

• Steel and Composite Structures
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• 제51권2호
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• pp.173-183
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• 2024

This study investigates a new seismic retrofit system that utilizes rotational friction dampers and axial springs. The retrofit system involves a steel frame with rotational friction dampers (RFD) at beam-column joints and linear springs at the corners, providing energy dissipation and self-centering capabilities to existing structures. The axial spring acts as a self-centering mechanism that eliminates residual deformations, while the friction damper mitigates seismic damage. To evaluate the seismic performance of the proposed retrofit system, a series of cyclic loading tests were carried out on a steel beam-column subassembly equipped with the proposed devices. An analytical model was then developed to validate the experimental results. A performance point ratio (PPR) was presented to optimize the design parameters of the retrofit system, and a performance-based seismic design strategy was developed based on the PPR. The retrofit system's effectiveness and the presented performance-based design approach were evaluated through case study models, and the analysis results demonstrated that the developed retrofit system and the performance-based design procedure were effective in retrofitting structures for multi-level design objectives.

• 한국구조물진단유지관리공학회 논문집
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• 제16권1호
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• pp.18-26
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• 2012

최근 FRP를 이용한 철근콘크리트 구조물의 보강방법으로서, 표면매입 보강 (Near-Surface-Mounted Retrofit, NSMR)방법의 연구가 활발히 진행되고 있다. 이 방법은 콘크리트에 홈을 형성하는 추가의 작업이 필요하지만 보강효과를 높일 수 있고 FRP가 표면에 노출되지 않기 때문에 환경의 영향을 저감시킬 수 있다. 본 연구에서는 이와 같은 표면매입 보강공법 즉, FRP판을 세워서 표면에 매입보강하는 공법의 보강효과를 실험적으로 규명하고자 하였다. 이를 위하여 철근콘크리트 보를 제작한 뒤 기존의 표면부착 보강과 표면매입 보강을 실시한 뒤 실험을 통하여 보강성능을 비교하였다. 또한 매입보강의 경우에는 중앙부를 부분적으로 비부착시켜 그 효과를 관찰하였다. 연구결과, FRP판을 이용한 철근콘크리트 부재의 휨보강방법으로서 FRP판을 세워서 표면에 매입하는 보강방법은 기존의 판 부착보강에 비하여 높은 보강성능을 발휘하는 것으로 나타났다. ACI 440-2R의 휨보강시 내력산정방법을 따르고 정착부분의 세가지 파괴형태를 고려함으로써 표면매입 보강된 부재의 내력을 평가할 수 있는 것으로 나타났다.

• Steel and Composite Structures
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• 제25권4호
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• pp.473-484
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• 2017

In this study a seismic retrofit scheme for a building structure was presented using steel plate slit dampers. The energy dissipation capacity of the slit damper used in the retrofit was verified by cyclic loading test. Genetic algorithm was applied to find out the optimum locations of the slit dampers satisfying the target displacement. The seismic retrofit of the model structure using the slit dampers was compared with the retrofit with enlarging shear walls. A simple damper distribution method was proposed using the capacity spectrum method along with the damper distribution pattern proportional to the inter-story drifts. The validity of the simple story-wise damper distribution procedure was verified by comparing the results of genetic algorithm. It was observed that the capacity-spectrum method combined with the simple damper distribution pattern leaded to satisfactory story-wise distribution of dampers compatible with the optimum solution obtained from genetic algorithm.