• 한국공간구조학회논문집
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• 제14권3호
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• pp.57-65
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• 2014

In order to improve the wind performance of buckling-restrained braces (BRBs), Hybrid buckling-restrained braces (H-BRBs) have been studied in Korea. The seismic performance of H-BRBs is different according to the action of VE damper. In this study, the nonlinear time history analyses have been performed on the parameters such as brace types and input earthquakes. The results of the study suggest that H-BRBs meet the BRB's requirement of ANSI/AISC 341-10 only if VE damper is not working during an earthquake.

• Earthquakes and Structures
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• 제7권4호
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• pp.553-570
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• 2014

In this study, nonlinear dynamic analyses were performed in order to evaluate and compare the structural response of different type of moment resisting frame buildings equipped with conventional braces (CBs) and buckling restrained braces (BRBs) subjected to near-field ground motions. For this, the case study frames, namely, ordinary moment-resisting frame (OMRF) and special moment-resisting frame (SMRF) having two equal bays of 6 m and a total height of 20 m were utilized. Then, CBs and BRBs were inserted in the bays of the existing frames. As a brace pattern, diagonal type with different configurations were used for the braced frame structures. For the earthquake excitation, artificial pulses equivalent to Northridge and Kobe earthquake records were taken into account. The results in terms of the inter-story drift index, global damage index, base shear, top shear, damage index, and plastification were discussed. The analysis of the results indicated a considerable improvement in the structural performance of the existing frames with the inclusion of conventional and especially buckling-restrained braces.

• Earthquakes and Structures
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• 제15권2호
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• pp.203-214
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• 2018

Deflection control in tall buildings is a challenging issue. Connecting of the towers is an interesting idea for architects as well as structural engineers. In this paper, two reinforced concrete core-wall towers are connected by a truss bridge with buckling restrained braces. The buildings are 40 and 60-story. The effect of the location of the bridge is investigated. Response spectrum analysis of the linear models is used to obtain the design demands and the systems are designed according to the reliable codes. Then, nonlinear time history analysis at maximum considered earthquake is performed to assess the seismic responses of the systems subjected to far-field and near-field record sets. Fiber elements are used for the reinforced concrete walls. On average, the inter-story drift ratio demand will be minimized when the bridge is approximately located at a height equal to 0.825 times the total height of the building. Besides, because of whipping effects, maximum roof acceleration demand is approximately two times the peak ground acceleration. Plasticity extends near the base and also in major areas of the walls subjected to the seismic loads.

• 국제초고층학회논문집
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• 제7권3호
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• pp.215-221
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• 2018

Buckling-Restrained Braces (BRBs) have been widely applied to tall buildings in seismic areas in the world. In this paper the author summarizes representative types of BRB compositions and shows two cases of special applications of BRBs. In the first case, BRB diagonals for tall building were used to provide stable cyclic nonlinear hysteresis and also used to limit forces generated at columns, connections and walls. The top outriggers are pre-loaded by jacks to resolve long-term differential shortenings between the concrete core wall and concrete-filled steel box columns. The second case is the retrofit work for a communication tower by replacing the insufficiently strong members with BRBs in Japan.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.191-197
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• 2006

In this paper 35- and 72-story tube system and trussed tube system were designed and their seismic performances were evaluated by nonlinear static analysis. According to the analysis results, the tube system structures retained high stiffness and strength; however they showed brittle failure mode due to the yielding of columns. In the case of trussed tube system, columns in the side-side buckled first followed by the buckling of the braces. When buckling-restrained braces were applied, plastic hinges formed in the lower stories gradually spreads to the higher stories, resulting in ductile behavior.

• Earthquakes and Structures
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• 제10권3호
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• pp.589-611
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• 2016

This paper presents an analytical study aimed at evaluating the seismic performance of steel moment resisting frames (MRFs) retrofitted with different approaches. For this, 3, 6 and 12 storey MRFs having four equal bays of 5 m were selected as the case study models. The models were designed with lateral stiffness insufficient to satisfy code drift and hinge limitations in zones with high seismic hazard. Three different retrofit strategies including traditional diagonal bracing system and energy dissipation devices such as buckling restrained braces and viscoelastic dampers were used for seismic upgrading of the existing structures. In the nonlinear time history analysis, a set of ground motions representative of the design earthquake with 10% exceedance probability in fifty years was taken into consideration. Considering the local and global deformations, the results in terms of inter-storey drift index, global damage index, plastic hinge formations, base shear demand and roof drift time history were compared. It was observed that both buckling-restrained braces and viscoelastic dampers allowed for an efficient reduction in the demands of the upgraded frames as compared to traditional braces.

• 한국재난정보학회 논문집
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• 제18권3호
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• pp.646-659
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• 2022

연구목적: 본 연구에서는 기존 소방 시설에 사용되고 있는 흔들림방지버팀대에 비하여 설치 면적을 효율적으로 감소시키고, 안정성과 내진 성능이 우수한 4방향 흔들림방지버팀대를 개발하였다. 개발된 4방향 흔들림방지버팀대의 성능 및 신뢰성을 인장 및 압축 시험과 내진 시험을 통하여 검증하였다. 연구방법: KFI 인증 기준에 따라 정적시험으로서 수평 및 수직 배관에 4방향 흔들림방지버팀태을 설치하여 인장 및 압축 시험을 수행하였으며, 정격 하중에 최대 움직임을 측정하였다. 또한 동적시험으로서 물이 채워진 배관에 4방향 흔들림방지버팀태를 설치하고 가속도센서를 통하여 입력 가진파에 대한 시험응답스펙트럼을 측정하였다. 또한 내진 시험 후 배관 및 흔들림방지버팀대의 이탈, 파손 및 국부변형을 관찰하였다. 연구결과: 인장 및 압축 실험을 수행한 결과, 인장 및 압축 시에 배관의 최대 움직임은 규정 기준 대비 50%~70% 이하로서 4방향 흔들림방지버팀태의 성능이 매우 우수함을 알 수 있었다. 4방향 흔들림방지버팀태의 내진 시험결과, 시험응답스펙트럼이 요구응답스펙트럼을 포괄하고 있음을 알 수 있었다. 시험 종료 후에 배관 및 흔들림방지버팀대의 이탈이나 파손 및 국부변형 등은 발생하지 않았으며, 시설물의 구조적 안정성이 유지됨을 확인할 수 있었다. 결론: 본 연구에서는 정적 실험 및 동적 실험을 통하여, 개발된 4방향 흔들림방지버팀대가 KFI 인중 기준을 만족하고 있음을 알 수 있었고, 기존 흔들림방지버팀대에 비하여 효율성과 경제성 및 안정성과 내진 성능이 우수함을 확인할 수 있었다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.260-267
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• 2001

In this study straightforward design procedure for unbond brace hysteretic dampers is developed. The required amount of equivalent damping to satisfy given performance acceptance criteria is obtained conveniently based on the capacity spectrum method without carrying out time-consuming nonlinear dynamic time history analysis. Then the size of the unbend braces is determined from the required equivalent damping. Parametric study is performed for the design variables such as natural period, yield strength, the stiffness after the first yield, yield stress of the unbond brace.

• Smart Structures and Systems
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• 제21권4호
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• pp.479-491
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• 2018

Shape memory alloys (SMA) exhibit superelasticity which refers to the capability of entirely recovering large deformation upon removal of applied forces and dissipating input energy during the cyclic loading reversals when the environment is above the austenite finish temperature. This property is increasingly favored by the earthquake engineering community, which is currently developing resilient structures with prompt recovery and affordable repair cost after earthquakes. Compared with the other SMAs, NiTi SMAs are widely deemed as the most promising candidate in earthquake engineering. This paper contributes to evaluate the seismic performance of properly designed concentrically braced frames (CBFs) equipped with NiTi SMA braces under earthquake ground motions corresponding to frequently-occurred, design-basis and maximum-considered earthquakes. An ad hoc seismic design approach that was previously developed for structures with idealized SMAs was introduced to size the building members, by explicitly considering the strain hardening characteristics of NiTi SMA particularly. The design procedure was conducted to compliant with a suite of ground motions associated with the hazard level of design-basis earthquake. A total of four six-story CBFs were designed by setting different ductility demands for SMA braces while designating with a same interstory drift target for the structural systems. The analytical results show that all the designed frames successfully met the prescribed seismic performance objectives, including targeted maximum interstory drift, uniform deformation demand over building height, eliminated residual deformation, controlled floor acceleration, and slight damage in the main frame. In addition, this study indicates that the strain hardening behavior does not necessarily impose undesirable impact on the global seismic performance of CBFs with SMA braces.

• Earthquakes and Structures
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• 제18권5호
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• pp.527-542
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• 2020

In traditional eccentrically braced steel frames, damages and plastic deformations are limited to the links and the main structure members are required tremendous sizes to ensure elasticity with no damage based on the force-based seismic design method, this limits the practical application of the structure. The high strength steel frames with eccentric braces refer to Q345 (the nominal yield strength is 345 MPa) steel used for links, and Q460 steel utilized for columns and beams in the eccentrically brace steel frames, the application of high strength steels not only brings out better economy and higher strength, but also wider application prospects in seismic fortification zone. Here, the structures with four type eccentric braces are chosen, including K-type, Y-type, D-type and V-type. These four types EBFs have various performances, such as stiffness, bearing capacity, ductility and failure mode. To evaluate the seismic behavior of the high strength steel frames with variable eccentric braces within the similar performance objectives, four types EBFs with 4-storey, 8-storey, 12-storey and 16-storey were designed by performance-based seismic design method. The nonlinear static behavior by pushover analysis and dynamic performance by time history analysis in the SAP2000 software was applied. A total of 11 ground motion records are adopted in the time history analysis. Ground motions representing three seismic hazards: first, elastic behavior in low earthquake hazard level for immediate occupancy, second, inelastic behavior of links in moderate earthquake hazard level for rapid repair, and third, inelastic behavior of the whole structure in very high earthquake hazard level for collapse prevention. The analyses results indicated that all structures have similar failure mode and seismic performance.