• 한국공간구조학회논문집
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• 제22권4호
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• pp.89-98
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• 2022

The recent earthquake in Korea caused a lot of damage to reinforced concrete (RC) columns with non-seismic details. The nonlinear analysis enables predicting the hysteresis behavior of RC columns under earthquakes, but the analytical model used for the columns must be accurate and practical. This paper studied the nonlinear analysis models built into a commercial structural analysis program for the existing RC columns. The load-displacement relationships, maximum strength, initial stiffness, and energy dissipation predicted by the three analysis models were compared and analyzed. The results were similar to those tested in the order of the fiber, Pivot, and Takeda models, whereas the fiber model took the most time to build. For columns subjected to axial load, the Pivot model could predict the behavior at a similar level to that of the fiber model. Based on the above, it is expected that the Pivot model can be applied most practically for existing RC columns.

• Steel and Composite Structures
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• 제46권2호
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• pp.237-252
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• 2023

The article describes the development of a novel dissipative bracing connection device (identified by the acronym DRBrC) for concentrically braced frames in steel and composite structures. The origins of the device trace back to the seminal work of Kelly, Skinner and Heine (1972), and, more directly related, to the PIN-INERD device, overcoming some of its limitations and greatly improving the replaceability characteristics. The connection device is composed of a rigid housing, connected to both the brace and the beam-column connection (or just the column), in which the axial force transfer is achieved by four-point bending of a dissipative pin. The experimental validation stages, presented in detail, consisted of a preliminary testing campaign, resulting in successive improvements of the original device design, followed by a systematic parametric testing campaign. That final campaign was devised to study the influence of the constituent materials (S235 and Stainless Steel, for the pin, and S355 and High Strength Steel, for the housing), of the geometry (four-point bending intermediate spans) and of the loading history (constant amplitude or increasing cyclic alternate). The main conclusions point to the most promising DRBrC device configurations, also presenting some suggestions in terms of the replaceability requirements.

• Structural Engineering and Mechanics
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• 제72권5호
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• pp.643-652
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• 2019

Protection of cultural heritage and carrying it to the future are at the top of the significant topics of research and implementation in engineering in the 21st century. There are several historical structures in the district of Ahlat located in the east of Turkey on the Lake Van Basin that has harbored many civilizations. Some of such works are the gravestones that are found in the Ahlat Seljuk Cemetery, which is the oldest and largest cemetery in the district. This study firstly provides information about the Ahlat Seljuk Cemetery and the gravestones found in it. Observation-based structural analyses were carried out on these gravestones that are found in this area that are known to have belonged to different civilizations based on their physical and constructional characteristics. These stones were built out of Ahlat stone as single pieces. Information is provided on the damages that have occurred on the gravestones in time and their causes. In general, losses of mass, abrasions, separations, collapses and calcifications due to natural conditions, as well as vegetative formations, were observed in the gravestones. To provide an example of other gravestones within the context of the study, the gravestone that is known to belong to the person named Nureddin Ebu Hasan was selected. As a result of the modeling that was carried out for this gravestone by using the finite elements method, modal analyses were carried out. With these analyses, for the gravestone, period, effective mass participation rates and stress values were calculated. The stress values that were obtained in this study were compared to the material safety stress values that were obtained in previous studies. Additionally, QR code application was created for the gravestone that was selected as an example in the study, and information on this gravestone was transferred to an electronic environment. The QR code application includes different language options, visuals of the gravestone and information on the gravestone. The QR application was also supported with a video of the cemetery where the gravestone is located. With this application, access to information about gravestones will be possible by using tablets and smartphones. With a QR code to be created for each gravestone, these gravestones will obtain identity cards.

• Earthquakes and Structures
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• 제11권6호
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• pp.1101-1121
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• 2016

Base isolation, one of the popular seismic protection approaches proven to be effective in practical applications, has been widely applied worldwide during the past few decades. As the techniques mature, it has been recognised that, the biggest issue faced in base isolation technique is the challenge of great base displacement demand, which leads to the potential of overturning of the structure, instability and permanent damage of the isolators. Meanwhile, drain, ventilation and regular maintenance at the base isolation level are quite difficult and rather time- and fund- consuming, especially in the highly populated areas. To address these challenges, a number of efforts have been dedicated to propose new isolation systems, including segmental building, additional storey isolation (ASI) and mid-storey isolation system, etc. However, such techniques have their own flaws, among which whipping effect is the most obvious one. Moreover, due to their inherent passive nature, all these techniques, including traditional base isolation system, show incapability to cope with the unpredictable and diverse nature of earthquakes. The solution for the aforementioned challenge is to develop an innovative vibration isolation system to realise variable structural stiffness to maximise the adaptability and controllability of the system. Recently, advances on the development of an adaptive magneto-rheological elastomer (MRE) vibration isolator has enlightened the development of adaptive base isolation systems due to its ability to alter stiffness by changing applied electrical current. In this study, an innovative semi-active storey isolation system inserting such novel MRE isolators between each floor is proposed. The stiffness of each level in the proposed isolation system can thus be changed according to characteristics of the MRE isolators. Non-dominated sorting genetic algorithm type II (NSGA-II) with dynamic crowding distance (DCD) is utilised for the optimisation of the parameters at isolation level in the system. Extensive comparative simulation studies have been conducted using 5-storey benchmark model to evaluate the performance of the proposed isolation system under different earthquake excitations. Simulation results compare the seismic responses of bare building, building with passive controlled MRE base isolation system, building with passive-controlled MRE storey isolation system and building with optimised storey isolation system.

• 한국재난정보학회 논문집
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• 제16권3호
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• pp.458-471
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• 2020

연구목적: 우리나라에서는 최근 지진의 발생빈도와 횟수가 매년 증가하고 있다.따라서 본 연구에서는 우리나라와 일본지진의 특성과 사례 및 이에 대한 복구체계에 대해서 비교분석하고, 우리나라 지진 방재정책의 개선사항 제안하는 데 목적을 두었다. 연구방법: 본 연구에서는 고베 대지진과 동일본 대지진 두 사례에서의 일본의 대응을 조사 및 평가하고, 경주 지진과 포항 지진 두 사태에서 우리나라의 대응책을 조사 및 평가한 후, 이를 비교하였다. 연구결과: 우리나라와 일본의 복구체계를 비교했을 때, 크게 도로교통망 복구를 위한 계획, 지역방재계획 과 BCP 개념의 도입에서 유의미한 차이를 보였다. 결론: 우리나라의 지진 위험지역과 수도의 물리적 거리를 고려할 때 시일이 소요될 수밖에 없는 현재의 중앙정부 집중형의 하향식 대응에서 벗어나 기능연속성계획(COOP)의 세부 수립을 통해 지역에서의 즉각적인 지진 대응력을 높이고, 행정BCP 개념 도입을 통해 재해 발생 시 행정기능이 정상적으로 발휘되도록, 이를 담보하기 위한 대처방안을 조속히 마련해야 할 것이다.

• 한국화재소방학회논문지
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• 제27권6호
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• pp.21-25
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• 2013

대형화, 초고층 및 고스팬에 부응하기 위한 강재 기술개발의 노력으로 용접성능과 내진성능 그리고 내화성능이 부여된 새로운 강재인 Thermo-mechanical control process (TMCP) 내화강재가 개발되었다. TMCP 내화강재는 기존의 내화강재 생산과정 시 압연과 동시에 정밀한 열처리를 병행함으로 인장력과 용접성을 향상시킬 수 있는 새로운 기술인 TMCP 방법으로 개발되었으며, 화재와 같은 고온에서의 구조적 안전성에 관한 내력평가가 요구되었다. 따라서 본 연구에서는 고온 시 TMCP 내화강재의 내력평가를 목적으로 고온 시 항복강도, 탄성계수를 평가하고 각각에 대한 온도영역별 실험식을 제시하였으며, 이를 일반 내화강재의 고온 특성과 비교, 분석하였다. 또한 각각의 소재로 설정된 H형강 기둥부재를 대상으로 고온 시의 내력을 계산하여 그 안전성을 확인한 결과, TMCP 내화강재의 고온 시 내력특성은 일반강 내화강재의 고온 내력저하 특성보다 열위인 것으로 나타났다.

• Computers and Concrete
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• 제20권5호
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• pp.545-553
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• 2017

A pounding tuned mass damper (PTMD) can be considered as a passive device, which combines the merits of a traditional tuned mass damper (TMD) and a collision damper. A recent analytical study by the authors demonstrated that the PTMD base on the energy dissipation during impact is able to achieve better control effectiveness over the traditional TMD. In this paper, a PTMD prototype is manufactured and applied for seismic response reduction to examine its efficacy. A series of shaking table tests is conducted in a three-story building frame model under single-dimensional and two-dimensional broadband earthquake excitations with different excitation intensities. The ability of the PTMD to reduce the structural responses is experimentally investigated. The results show that the traditional TMD is sensitive to input excitations, while the PTMD mostly has improved control performance over the TMD to remarkably reduce both the peak and root-mean-square (RMS) structural responses under single-dimensional earthquake excitation. Unlike the TMD, the PTMD is found to have the merit of maintaining a stable performance when subjected to different earthquake loadings. In addition, it is also indicated that the performance of the PTMD can be enhanced by adjusting the initial gap value, and the control effectiveness improves with the increasing excitation intensity. Under two-dimensional earthquake inputs, the PTMD controls remain outperform the TMD controls; however, the oscillation of the added mass is observed during the test, which may induce torsional vibration modes of the structure, and hence, result in poor control performance especially after a strong earthquake period.

• Structural Monitoring and Maintenance
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• 제2권3호
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• pp.269-282
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• 2015

Civil structures should be designed with the lowest cost and longest lifetime possible and without service failure. The efficient and sustainable use of materials in building design and construction has always been at the forefront for civil engineers and environmentalists. Timber is one of the best contenders for these purposes particularly in terms of aesthetics; fire protection; strength-to-weight ratio; acoustic properties and seismic resistance. In recent years, timber has been used in commercial and taller buildings due to these significant advantages. It should be noted that, since the launch of the modern building standards and codes, a number of different structural systems have been developed to stabilise steel or concrete multistorey buildings, however, structural analysis of high-rise and multi-storey timber frame buildings subjected to lateral loads has not yet been fully understood. Additionally, timber degradation can occur as a result of biological decay of the elements and overloading that can result in structural damage. In such structures, the deficient members and joints require strengthening in order to satisfy new code requirements; determine acceptable level of safety; and avoid brittle failure following earthquake actions. This paper investigates performance assessment and damage assessment of older multi-storey timber buildings. One approach is to retrofit the beams in order to increase the ductility of the frame. Experimental studies indicate that Sprayed Fibre Reinforced Polymer (SFRP) repairing/retrofitting not only updates the integrity of the joint, but also increases its strength; stiffness; and ductility in such a way that the joint remains elastic. Non-linear finite element analysis ('pushover') is carried out to study the behaviour of the structure subjected to simulated gravity and lateral loads. A new global index is re-assessed for damage assessment of the plain and SFRP-retrofitted frames using capacity curves obtained from pushover analysis. This study shows that the proposed method is suitable for structural damage assessment of aged timber buildings. Also SFRP retrofitting can potentially improve the performance and load carrying capacity of the structure.

• 융합신호처리학회논문지
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• 제22권4호
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• pp.199-205
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• 2021

수배전반의 경우 지면 또는 건물의 바닥 면에 바로 설치되며 지진과 같은 진동이나 외부 충격 발생 시 수배전반의 내부 전력기기, 배선 그리고 보호계전기 등의 전기부품 손상, 오동작 발생 가능성이 커지게 된다. 이러한 이유로 최근 내진형 수배전반의 필요성이 대두되고 있으며, 제진기능을 갖는 수배전반의 연구 개발 및 제품 출시가 이루어지고 있다. 본 논문에서는 제진형 배전반의 진동, 온도, 습도 등을 측정할 수 있는 제진형 배전반의 진동 및 환경 데이터수집을 위한 IoT 시스템을 구현하였다. 제진형 배전반에 진동이 발생하였을 때 진동 정도 및 온습도 데이터를 측정하고 신뢰성 있는 메시징 전송을 위한 MQTT 프로토콜을 사용하였고, 모니터링과 데이터 저장은 Node-RED를 통해 MySQL DB에 데이터를 저장하고, 시각화를 진행하였다. 제진형 배전반에 IoT 기기를 부착하여 테스트를 진행 하였으며, 데이터를 실시간으로 수집하고 Node-RED의 대시보드 UI에서 진동 및 환경 데이터의 변화를 모니터링 하였다.

• Structural Engineering and Mechanics
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• 제90권1호
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• pp.19-26
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• 2024

In recent years, an increasing number of experimental studies have shown that the practical application of mature active control systems requires consideration of robustness criteria in the design process, including the reduction of tracking errors, operational resistance to external disturbances, and measurement noise, as well as robustness and stability. Good uncertainty prediction is thus proposed to solve problems caused by poor parameter selection and to remove the effects of dynamic coupling between degrees of freedom (DOF) in nonlinear systems. To overcome the stability problem, this study develops an advanced adaptive predictive fuzzy controller, which not only solves the programming problem of determining system stability but also uses the law of linear matrix inequality (LMI) to modify the fuzzy problem. The following parameters are used to manipulate the fuzzy controller of the robotic system to improve its control performance. The simulations for system uncertainty in the controller design emphasized the use of acceleration feedback for practical reasons. The simulation results also show that the proposed H∞ controller has excellent performance and reliability, and the effectiveness of the LMI-based method is also recognized. Therefore, this dynamic control method is suitable for seismic protection of civil buildings. The objectives of this document are access to adequate, safe, and affordable housing and basic services, promotion of inclusive and sustainable urbanization, implementation of sustainable disaster-resilient construction, sustainable planning, and sustainable management of human settlements. Simulation results of linear and non-linear structures demonstrate the ability of this method to identify structures and their changes due to damage. Therefore, with the continuous development of artificial intelligence and fuzzy theory, it seems that this goal will be achieved in the near future.