In the case of a school building, even though it is a regular structure in terms of plan shape, if the masonry infill wall acts as a lateral load resisting element, it can be determined as a torsionally irregular building. As a result, the strength and ductility of the structure are reduced, which may cause additional earthquake damage to the structure. Therefore, in this study, a structure similar to a school building with torsional irregularity was selected as an example structure and the damping performance of the PC-BRB was analyzed by adjusting the eccentricity according to the amount of masonry infilled wall. As a result of nonlinear dynamic analysis after seismic reinforcement, the torsional irregularity of each floor was reduced compared to before reinforcement, and the beams and column members of the collapse level satisfied the performance level due to the reduction of shear force and the reinforcement of stiffness. The energy dissipation of PC-BRB was similar in the REC-10 ~ REC-20 analytical models with an eccentricity of 20% or less. REC-25 with an eccentricity of 25% was the largest, and it is judged that it is effective to combine and apply PC-BRB when it has an eccentricity of 25% or more to control the torsional behavior.

In this paper, based on the finite element analysis model verified in previous studies, a new model of a buckling restrained brace reinforced with a steel plate was proposed. A design formula was proposed for the new model to dissipate energy without buckling the steel core under load protocol, and the performance of the model satisfying the design formula was evaluated by comparing it with the previous model through the results of hysteresis loop, bi-linear curve, cumulative energy dissipation capacity, and equivalent viscous damping.

The precast-buckling restrained braces(PC-BRB) reinforced with engineering plastics that can compensate for the disadvantages in the manufacturing process of the existing buckling restrained brace. In this study, to examine the applicability of PC-BRB to actual structures, example structures similar to school facilities were selected and the reinforcement effect was analyzed analytically according to the damping design procedure of PC-BRB. Load-displacement curve through the incremental loading test appeared similar to the bilinear curve. Applying test result, Analytical model of PC-BRB model was constructed and applied to the example structure. As a result of the analysis, the PC-BRB showed stable hysteresis behavior without lowering the strength, and the inter story drift ratio and the shear force were reduced due to the damping effect. In addition, the reduction ratio of the shear force was similar to the reduction ratio assumed when designing the damping device.

In this study, the Buckling restrained braces reinforced with engineering plastics that can compensate for the disadvantages in the manufacturing process of the existing buckling restrained brace. The proposed PC-BRB was fabricated to evaluate the reinforcement effect by carrying out a structural performance test and a full-scale two-layer frame test through cyclic loading test. As a result of PC-BRB's incremental and cyclic loading test, stable hysteresis behavior was achieved within the target displacement, and the compressive strength adjustment coefficient satisfied the recommendation. As a result of the real frame experiment, the strength of the reinforced specimen increased compared to the unreinforced specimen, and the ductility and energy dissipation increased.

본 논문에서는 커코프 판이론과 폰-칼만 비선형 변형율-변위 관계를 이용하여 서형화된 좌굴해석을 수행하였다. 평면응력과 좌굴문제에서 영률과 두께에 관한 설계민감도식을 유도하였고, 고유치를 최대화하면서 컴플라이언스를 최소화하는 위상최적설계 기법을 정식화하였다. 좌굴해석에서의 프리스트레스를 이용하여 판 좌굴문제에 적용할 수 있는 위상최적설계 기법을 개발하였다. 폰-칼만 비선형 변형률을 사용하여 좌굴문제의 응력행렬을 구성하는데 프리스트레스가 필요하므로 면외로의 운동을 도입하였다. 위상최적설계를 위하여 정규재료밀도를 설계변수로 하고, 목적함수는 최소 컴플라이언스와 최대 고유진동수로 하였으며 제한조건은 허용되는 재료량이다. 여러 수치예제를 통하여 개발된 설계민감도 해석법은 유한차분 민감도와 비교하여 매우 정확한 값을 가지고, 위상최적설계는 물리적으로 의미있는 결과를 제공함을 확인하였다.

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.

본 연구의 목적은 볼접합부를 갖는 원형강관의 좌굴실험 결과를 토대로 하여 국내외 압축재 설계규준과 비교 평가함으로써 부재의 좌굴내력 및 좌굴길이 계수의 안전성과 합리성을 조사하는 것이다. 좌굴성능 평가를 위해 선정된 원형강관은 ∅48.6×2.8t와 ∅60.5×3.2t 및 ∅ 76.3×3.2t이다. 국내외 압축재 설계를 위해 우리나라의 하중저항계수 설계법(LRFD), 일본의 한계상태 설계법(LSD) 및 영국의 BS5950 규준을 적용하였다. 본 연구에서는 선행연구의 실험결과와 국내외 설계규준과의 좌굴성능을 비교 분석하였다. 그 결과를 요약해 보면 다음과 같다. 각 국의 압축재 설계규준에서 부재의 전체길이를 좌굴길이로 적용한 결과 실험에 의한 좌굴내력의 64%∽89% 정도로 나타났다. 따라서 안전을 위해 현재 설계 규준식에 준하여 부재설계를 수행하는 것이 바람직하다고 판단되었다. 실험결과 측정된 좌굴내력은 우리나라, 일본 및 영국의 압축재 설계규준에서 좌굴길이를 순수 원형강관만으로 고려한 좌굴내력 값에 비해 1.02배∽1.43배 높은 것으로 나타났다. 따라서 스페이스 프 레임 구조물 설계에 있어 개별부재 좌굴내력은 절점 간 길이가 아닌 순수 원형강관의 길이로 좌굴계수를 고려할 필요가 있을 것으로 보여진다.

The conventional brace system is generally accepted lateral load resisting system for steel structures due to efficient story drift control and economic feasibility by frame materials decrease. But the lateral stiffness of the brace decreases following buckling in this system and buckling causes unstable structures with strength deterioration hysteresis performance. Buckling restrained brace system that performs stable behavior after yielding of core element prevented from buckling by tube element is better than conventional brace system in point of earthquake energy absorbing capacity. In this study, the seismic performance of the multi-story steel frames applied for brace and buckling restrained brace is respectively analyzed, so that, the damage of two systems is quantitatively evaluated by analyzing energy absorption capacity.

본 연구에서는 원형강관 가새의 국부좌굴에 의한 내력감소를 배제하기 위하여, 가새의 국부좌굴 거동을 파악하고 좌굴제어 방법을 찾고자 한다. 좌굴을 제어하기 위한 방법으로, 하나는 좌굴 영역에 커버플레이트를 설치하여 좌굴을 구속함으로써 변형능력을 확보하고자 하는 것이며, 다른 하나는 가새 중앙부에 강봉과 스프링을 이용한 수축장치를 삽입하여 압축 시 좌굴의 위험을 배제하는 것이다. 본 연구의 목적은 국부좌굴을 구속하거나 배제하기 위한 좌굴제어시스템을 제안하고, 실험을 통하여 제안한 방법의 적용성을 조사, 검토하는 것이다. 또한 좌굴제어에 따른 성능향상을 정량적으로 평가하는 것이다.