• 한국구조물진단유지관리공학회 논문집
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• 제14권3호
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• pp.201-208
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• 2010

본 연구에서는 현장타설 철근콘크리트 구조체에 대한 국내외 허용오차 관련기준을 검토하여, 현행 국내 허용오차 기준의 수준을 검토함과 동시에 합리적인 시공오차 측정방법과 측정기기를 제시하였다. 또한 국내 공동주택을 대상으로 철근콘크리트 구조 부재의 시공오차를 조사하여 현재 국내 시공오차 허용범위 만족도를 검토하고, 구조체의 저항능력 평가 시, 부재크기 오차의 불확실성을 고려한 합리적인 안전성 평가를 위한 자료를 제공한다.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.395-406
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• 2020

Many prefabricated concrete frame joints have been proposed, and most of them showed good seismic performance. However, there are still some limitations in the proposed fabricated joints. For example, for prefabricated prestressed concrete joints, prefabricated beams and prefabricated columns are assembled as a whole by the pre-stressed steel bar and steel strand in the beams, which brings some troubles to the construction, and the reinforcement in the core area of the joints is complex, and the mechanical mechanism is not clear. Based on the current research results, a new type of fabricated joint of prestressed concrete beams and confined concrete columns is proposed. To study the seismic performance of the joint, the quasi-static test is carried out. The test results show that the nodes exhibit good ductility and energy dissipation. According to the experimental fitting method and the "fixed point pointing" law, the resilience model of this kind of nodes is established, and compared with the experimental results, the two agree well, which can provides a certain reference for elasto-plastic seismic response analysis of this type of structure. Besides, based on the analysis of the factors affecting the shear capacity of the node core area, the formula of shear capacity of the core area of the node is proposed, and the theoretical values of the formula are consistent with the experimental value.

• 한국지반신소재학회논문집
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• 제17권4호
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• pp.199-212
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• 2018

본 연구에서는 깊은 굴착에 따른 인접구조물의 손상 평가 및 벽체 구조물의 안정성 평가를 하기 위한 지표의 거동 및 벽체 부재력의 효율적인 예측기법에 대한 내용을 다루었다. 우선적으로 지표의 거동 및 벽체 부재력에 영향을 미치는 매개 변수에 대한 연구를 수행하였고, 이를 토대로 다양한 굴착 조건에 대해 수치해석을 실시한 결과를 통해 데이터베이스를 구축하였다. 구축된 데이터베이스를 토대로 벽체의 부재력과 지표의 거동 각각의 해석 결과에 대한 인공신경망 엔진 학습을 수행하였으며 학습된 인공신경망을 이용하여 예측된 결과와 사용된 데이터베이스의 결과를 비교하여 인공신경망 엔진이 벽체의 부재력 및 지표의 거동예측에 효율적임을 검증하였다.

• 화약ㆍ발파
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• 제37권1호
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• pp.34-47
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• 2019

본 사례연구는 인천 학익동에 위치한 디씨알이 인천공장 발파해체 프로젝트에 관한 것이다. 대상건물은 건물내부에 위치한 굴뚝형태의 강구조 설비들이 가동 시 내뿜었던 수백도의 고열과 해풍 등의 영향으로 주요 구조체에 극심한 노후화가 진행되었다. 이로 인해 기둥과 보의 콘크리트들이 탈락하여 녹이 슨 철근들이 노출되어 있었고, 일부 슬래브들은 커다랗게 구멍이 뚫려있어 작업 인원의 접근도 힘들 만큼 구조물이 위험한 상태였다. 따라서 중장비가 건물 내부로 진입하여 작업하는 기계식 철거방법의 적용이 불가능하여 건물 내부의 설비구조물들을 그대로 두고 해체 할 수 있는 발파해체공법을 적용하였다. 발파순서는 (1)탄화탑 ${\rightarrow}$ (2)연돌 2 ${\rightarrow}$ (3)연돌 1의 순서로 진행되도록 계획하였다. 탄화탑과 연돌들에 설치된 폭약을 순차적으로 기폭시키는 데에는 총 406개의 전자뇌관(Unitronic 600)이 사용되었다.

• Structural Engineering and Mechanics
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• 제71권1호
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• pp.57-63
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• 2019

During the last two decades, much joint research regarding vibration based methods has been done, leading to developing various algorithms and techniques. These algorithms and techniques can be divided into modal methods and signal methods. Although modal methods have been widely used for health monitoring and damage detection, signal methods due to higher efficiency have received considerable attention in various fields, including aerospace, mechanical and civil engineering. Signal-based methods are derived directly from the recorded responses through signal processing algorithms to detect damage. According to different signal processing techniques, signal-based methods can be divided into three categories including time domain methods, frequency domain methods, and time-frequency domain methods. The frequency domain methods are well-known and interest in using them has increased in recent years. To determine dynamic behaviours, to identify systems and to detect damages of bridges, different methods and algorithms have been proposed by researchers. In this study, a new algorithm to detect seismic damage in the bridge's piers is suggested. To evaluate the algorithm, an analytical model of a bridge with simple spans is used. Based on the algorithm, before and after damage, the bridge is excited by a sine force, and the piers' responses are measured. The dynamic specifications of the bridge are extracted by Power Spectral Density function. In addition, the Least Square Method is used to detect damage in the bridge's piers. The results indicate that the proposed algorithm can identify the seismic damage effectively. The algorithm is output-only method and measuring the excitation force is not needed. Moreover, the proposed approach does not need numerical models.

• 화약ㆍ발파
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• 제36권4호
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• pp.48-61
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• 2018

본 사례연구는 성남시 분당구에 위치한 한국가스공사(KOGAS) 분당사옥 건물의 발파해체 프로젝트에 관한 것이다. 대상건물은 긴 경간을 갖는 보 구조물이라는 특징 때문에 프로젝트 초기에는 잭 서포트를 이용한 기계식 해체공법이 고려되었다. 하지만 과도한 보강비용과 안전상의 불확실성, 그리고 공사기간의 장기화 우려 때문에 발파해체공법을 대안공법으로 적용하였다. 폭약의 기폭순서는 붕괴과정 중에 주변의 건물 및 시설물 방호를 목적으로 정교하게 설계하였으며, 대상건물은 왼쪽 전방을 향해 붕괴되도록 유도하였다. 1층, 2층 및 5층에 위치한 발파기둥들에 설치된 폭약을 순차적으로 기폭시키는 데에는 총 550개 이상의 전자뇌관(Unitronic 600)이 사용되었다. 분진발생을 저감하기 위해 각각의 발파대상 기둥과 바닥에는 작은 물주머니와 큰 물주머니를 각각 설치하였다. 이와 같이 본 프로젝트에서는 대상건물의 발파해체 시에 발생될 것으로 예상되는 소음, 분진 및 충격진동을 경감시키기 위해 총체적인 노력을 경주하였다.

• The Journal of Advanced Prosthodontics
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• 제11권2호
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• pp.95-104
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• 2019

PURPOSE. To evaluate the effect of surface treatments and repair materials on the shear bond strength and to measure the fracture toughness of CAD/CAM provisional restoration materials. MATERIALS AND METHODS. Four CAD/CAM (3D printing: Nextdent C&B and ZMD-1000B Temporary, CAD/CAM resin block: Yamahachi PMMA disk and Huge PMMA block) and four conventional (monometacrylate: Jet and Alike, dimetacrylate: Luxatemp and Protemp 4) materials were selected to fabricate disk-shaped specimens and divided into six groups according to surface treatment (n=10). CAD/CAM materials were repaired with Jet or Luxatemp, while conventional materials were repaired with their own materials. The shear bond strength was measured by using universal testing machine. Ten rectangular column-shaped specimens for each material were fabricated to measure the fracture toughness by single edge v notched beam technique. Statistical analysis was performed by one-way ANOVA. RESULTS. The highest shear bond strength of CAD/CAM materials was achieved by SiC paper + sandblasting. It was also accomplished when repairing 3D printing materials with Luxatemp, and repairing CAD/CAM resin blocks with Jet. Yamahachi PMMA disk showed the highest fracture toughness. Nextdent C&B showed the lowest fracture toughness value but no statistically significant difference from Alike and Luxatemp (P>.05). CONCLUSION. In order to successfully repair the CAD/CAM provisional restoration, mechanical surface treatment and appropriate repair material according to the CAD/CAM material type should be selected. The CAD/CAM provisional materials have proper mechanical properties for clinical use as compared to conventional materials.

• 대한건축학회논문집:구조계
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• 제33권12호
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• pp.37-44
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• 2017

Due to structural characteristics, construction costs and duration of a modular system would be saved by minimizing the schedule on the job site. As such, it is crucial to develop a connection that can guarantee stiffness while allowing for simple assembling. Particularly, the mid- to high-rise construction of the modular system necessitates the securing of the structural stability and seismic performance of multi-unit frames and connections, and thus, the stiffness of unit-assembled structures needs to be re-evaluated and designed. However, evaluating a frame consisting of slender members and reinforcing materials is a complicated process. Therefore, the present study aims to examine the structural characteristics of a modular unit connection based a method for reinforcing connection brackets and hinges while minimizing the loss of the cross section. Toward this end, the study modeled the beam-to-column connection of a modular system with the proposed connection, and produced a specimen which was used to perform a cycling loading test. The study compared the initial stiffness, the attributes of the hysteretic behavior, and the maximum flexural moment, and observed whether the model acquired the seismic performance, compared to the flexural strength of the steel moment frame connection that is required by the Korean Building Code. The test results showed that the proposed connection produced a similar initial stiffness value to that of the theoretical equation, and its maximum strength exceeded the theoretical strength. Furthermore, the model with a larger ceiling bracket showed higher seismic performance, which was further increased by the reinforcement of the plate.

• 대한건축학회논문집:구조계
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• 제34권3호
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• pp.19-28
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• 2018

Key factors that ensure competitiveness of modular unit include consistent high quality and connection condition that ensures high structural performance while minimizing the overall scale of the on-site process. However, it is difficult to evaluate the structural performance of the connection of modular unit, and its structural analysis and design method can be different depending on the connection to its development, which affects the seismic performance of its final design. In particular, securing the seismic performance is the key to designing modular systems of mid-to-high-rise structure. In this paper, therefore, the seismic performance of the modular system with bracket-typed fully restrained moment connections according to stiffness and the shapes of various connection members was evaluated through experimental and analytical methods. To verify the seismic performance, a cyclic loading test of the connection joint of the proposed modular system was conducted. As a result of this study, theoretical values and experimental results were compared with the initial stiffness, hysteresis behavior and maximum bending moment of the modular system. Also, the connection joint was modeled, using the commercial program ANSYS, which was then followed by finite element analysis of the system. According to the results of the experiment, the maximum resisting force of the proposed connection exceeded the theoretical parameters, which indicated that a rigid joint structural performance could be secured. These results almost satisfied the criteria for connection bending strength of special moment frame listed on KBC2016.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.182-192
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• 2022

취성파괴는 구조물의 파괴거동 중 하나로서 구조재료의 내진성능에 큰 영향을 미친다. 하중속도는 취성파괴의 주요 발생원인 중 하나로 작용하며, 특히 지진과 같은 상황에서 건축물에 높은 하중속도가 작용하게 된다. 하지만 현재 국내·외 강구조 보-기둥 접합부의 내진성능평가는 대부분 정적실험을 통해 수행되고 있다. 따라서 기존 내진성능평가에서는 지진 시의 높은 하중속도에 의한 재료 인성 저하 및 최대변형률 감소 등의 요소에 따른 취성파괴가 충분히 고려되지 않았을 가능성이 존재한다. 본 연구에서는 기존 실험방법에 따른 낮은 하중속도에서의 정적실험과 진동대를 이용한 높은 하중속도에서의 동적실험을 각각 실시한다. 각 실험결과에 따른 파괴형상 및 구조성능 등을 비교·분석하고 최종적으로 하중속도의 크기가 접합부의 내진성능에 미치는 영향을 분석한다.