• Earthquakes and Structures
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• 제10권1호
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• pp.163-178
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• 2016

Composite Lightweight (CL) insulated walls have gained wide adoption recently because the exterior claddings of steel building frames have their cost effectiveness, good thermal and structural efficiency. To investigate the seismic behavior, lateral stiffness, ductility and energy dissipation of steel frames with the CL infill walls, five one-story one-bay steel frames were fabricated and tested under cyclic loads. Test results showed that the bolted connections allow relative movement between CL infill walls and steel frames, enabling the system to exhibit satisfactory performance under lateral loads. Additionally, it is found that the addition of diagonal steel straps to the CL infill wall significantly increases the initial lateral stiffness, load-carrying capacity, ductility and energy dissipation capacity of the system. Furthermore, the test results indicate that the lateral stiffness values of the frames with the CL infill wall are similar to those of the bare steel frames in large lateral displacement.

• Steel and Composite Structures
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• 제43권5호
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• pp.553-564
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• 2022

Many existing reinforced concrete (RC) structures need to be strengthening for reason such as poor construction quality, low ductility or designing without considering seismic effects. One of the strengthening methods is strengthening technique with eccentrically braced frames (EBFs). The characteristic element of these systems is the link element and its length is very important in terms of seismic behavior. The link element of Y shaped EBF systems (YEBFs) is designed as a short shear element. Different limits are suggested in the literature for the link length. This study to aim experimentally investigate the effect of the link length for the suggested limits on the behavior of the RC frame system and efficiency of strengthening technique. For this purpose, a total of 5 single story, single span RC frame specimens were produced. The design of the RC frames was made considering seismic design deficiencies. Four of the produced specimens were strengthened and one of them remained as bare specimen. The steel YEBFs were used in strengthening the RC frame and the link was designed as a shear element that have different length with respect to suggested limits in literature. The length of links was determined as 50mm, 100mm, 150mm and 200mm. All of the specimens were tested under cyclic loads. The obtained results show that the strengthening technique improved the energy consumption and lateral load bearing capacities of the bare RC specimen. Moreover, it is concluded that the specimens YB-2 and YB-3 showed better performance than the other specimens, especially in energy consumption and ductility.

• 한국지진공학회논문집
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• 제28권1호
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• pp.11-20
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• 2024

The ductility of the system based on the capacity of each structural member constituting the seismic force-resisting system is a significant factor determining the structure's seismic performance. This study aims to provide a procedure to supplement the current seismic design criteria to secure the system's ductility and improve the seismic performance of the steel ordinary moment frames. For the study, a nonlinear analysis was performed on the 9- and 15-story model buildings, and the formation of collapse mechanisms and damage distribution for dynamic loads were analyzed. As a result of analyzing the nonlinear response and damage distribution of the steel ordinary moment frame, local collapse due to the concentration of structural damage was observed in the case where the influence of the higher mode was dominant. In this study, a procedure to improve the seismic performance and avoid inferior dynamic response was proposed by limiting the strength ratio of the column. The proposed procedure effectively improved the seismic performance of steel ordinary moment frames by reducing the probability of local collapse.

• 한국구조물진단유지관리공학회 논문집
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• 제10권3호
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• pp.106-114
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• 2006

본 논문에서는 역강성법을 비좌굴 가새골조시스템의 내진설계에 적용하여 목표 변위를 만족시키는 비좌굴 가새의 단면적을 산정하였으며, 기존 연구와 비교하여 타당성을 검토하였다. 본 설계 방법은 개념이 직관적이고 적용이 간편하며, 고차모드 고려가 가능하고 각 층의 연성도를 개별적으로 조절할 수 있는 장점이 있다. 각 모델에 본 설계법을 적용한 결과, 전반적으로 목표변위 증가에 따라 가새 단면적이 감소하지만 층수와 연성도의 증가에 따라 일부층에서 오히려 가새 단면적이 증가하는 것을 확인하였다. 또한 항복 후 강성비의 변화가 단면적에 끼치는 영향은 가새의 항복 후 강성비가 작은 경우 더 민감한 차이를 보이는 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제23권3호
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• pp.143-149
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• 2019

U-형 복합보는 공작물 주차장으로 사용하기 위한 목적으로 개발되었다. 복합보를 공작물로 적용할 때, 가장 우선적으로 고려하여야 할 사항은 낮은 층고와 장경간이다. 또한, 철근 콘크리트 및 강구조가 혼합된 구조이기 때문에 일체성을 확보하고, 소요강도 이상의 구조성능을 확보하여야 한다. 본 연구는 철근 콘크리트 슬래브와 U-형 강판으로 이루어진 복합보의 구조성능을 파악하기 위한 것이다. 복합보의 구조성능을 파악하기 위해 주차장용으로 사용되는 일반적인 U-형 복합보를 기준실험체로 설정하고, 기준실험체 대비 하중방향, U-형 복합보의 춤 및 폭을 변화시킨 실험체를 제작하여 실험을 실시하였다. 실험체 지점간 거리는 4.5m 이며, 하중은 순수 휨구간이 1.5m가 되도록 중앙부 2점가력 하였다. 이론값 산정을 위해 U-형 중앙부의 철근, 강재, 콘크리트 등에 변형게이지를 부착하였으며, 하중점 및 측면에 변위계를 설치하였다. 실험결과, 주차장용으로 계획된 기준실험체의 초기 항복강도는 U-형 강재 밑면에서 처음 발생되었다. 항복강도 이후에는 U-형 강재의 항복구간이 점점 확대되면서 최대강도에 도달되었으며, 최대강도 이후에는 RC 슬래브 콘크리트가 압괴되면서 최종파괴 되었다. 춤을 증가시킨 실험체의 구조성능은 기준실험체와 비교하여 강도 및 연성이 매우 향상된 것을 알 수 있다. 또한, 하중방향에 따른 저항 성능은 부가력으로 가력했을 때 휨성능은 저하되나 연성거동은 증가하므로 휨성능 및 연성을 고려한 설계가 이루어져야 할 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.140-154
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• 1992

The objective of the research stated here was aimed at providing the information needed to establish the Korean Seismic Design Code Recommendations and Guides for precast concrete (P.C) large panel apartment buildings. This was accomplished by investigation and analysis of the response of P.C large panel structures subjected to shaking table excitation simulating earthquake ground motion. one of the test specimens used was 1/3-scaled 3-story box P.C model provided by Sam-Hwan Camus Corporation. The 4m $\times$4m shaking table was used to simulate the earthquake ground motion. the employed input accelerogram was the one recorded as Taft N21E component and the peak ground acceleration(PGA) was scaled depending on the desired level of seismic severity and the time according to dynamic similitude rule. Based on results obtained from shaking table test of this P.C model, the following conclusions were drawn . (1) As far as test specimen is concerned, the seismic safety factors turns out to be 7~8. (2)P.C model has damping ratio of about8% which is twice larger than in-situ R.C. structure. And (3)this model has global displacement ductility ratio of 2~3 through the energy dissipation by opening and sliding of joints.

• 한국강구조학회 논문집
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• 제14권2호
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• pp.339-348
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• 2002

본 논문에서는 비선형 해석을 이용한 강뼈대 구조물의 자동화설계를 수행한다. 기하학적 비선형은 안정함수를 사용하여 고려한다. 보-기둥 부재에 대하여 전단변형 효과를 고려한다. 자동화 설계 기법으로는 직접 탐색법을 사용한다. LRFD의 상관방정식으로 각각의 부재의 상관 계수 값을 계산하여 가장 큰 상관 계수 값을 가지는 부재의 크기를 데이터베이스에서 단계별로 증가시킨다. 목적함수는 강뼈대 구조물의 중량을 사용하며, 계약조건식은 하중-저항능력, 처짐, 층간 수평변위 및 연성도를 고려한다. 2차원과 3차원 2층 강뼈대구조물에 대한 예제 해석을 수행한다.

• Steel and Composite Structures
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• 제37권5호
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• pp.571-587
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• 2020

In this article the seismic demand and performance of two recent braced steel frames named steel moment frames with the elliptic bracing (ELBRFs) are assessed through a laboratory program and numerical analyses of FEM. Here, one of the specimens is without connecting bracket from the corner of the frame to the elliptic brace (ELBRF-E), while the other is with the connecting brackets (ELBRF-B). In both the elliptic braced moment resisting frames (ELBRFs), in addition to not having any opening space problem in the bracing systems when installed in the surrounding frames, they improve structure's behavior. The experimental test is run on ½ scale single-story single-bay ELBRF specimens under cyclic quasi-static loading and compared with X-bracing and SMRF systems in one story base model. This system is of appropriate stiffness and a high ductility, with an increased response modification factor. Moreover, its energy dissipation is high. In the ELBRF bracing systems, there exists a great interval between relative deformation at the yield point and maximum relative deformation after entering the plastic region. In other words, the distance from the first plastic hinge to the collapse of the structure is fairly large. The experimental outcomes here, are in good agreement with the theoretical predictions.

• 한국지진공학회논문집
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• 제25권1호
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• pp.1-9
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• 2021

Most commercial buildings among existing RC buildings in Korea have a multi-story wall-frame structure where RC shear wall is commonly used as its core at stairways or elevators. The members of the existing middle and low-rise wall-frame buildings are likely arranged in ordinary details considering building occupancy, and the importance and difficulty of member design. This is because there are few limitations, considerations, and financial burdens on the code for designing members with ordinary details. Compared with the intermediate or unique details, the ductility and overstrength are insufficient. Furthermore, the behavior of the member can be shear-dominated. Since shear failure in vertical members can cause a collapse of the entire structure, nonlinear characteristics such as shear strength and stiffness deterioration should be adequately reflected in the analysis model. With this background, an 8-story RC wall-frame building was designed as a building frame system with ordinary shear walls, and the effect of reflecting the shear failure mode of columns and walls on the collapse mechanism was investigated. As a result, the shear failure mode effect on the collapse mechanism was evident in walls, not columns. Consequently, it is recommended that the shear behavior characteristics of walls are explicitly considered in the analysis of wall-frame buildings with ordinary details.

• Structural Engineering and Mechanics
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• 제88권5호
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• pp.463-480
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• 2023

The buckling-restrained braced frames with eccentric configurations (BRBF-Es) exhibit stable cyclic behavior and possess a high energy absorption capacity. Additionally, they offer architectural advantages for incorporating openings, much like Eccentrically Braced Frames (EBFs). However, studies have indicated that significant residual drifts occur in this system when subjected to earthquakes at the Maximum Considered Earthquake (MCE) hazard level. Consequently, in order to mitigate these residual drifts, it is recommended to employ self-centering systems alongside the BRBF-E system. In our current research, we propose the utilization of the Direct Displacement-Based Seismic Design method to determine the design base shear for a hybrid system that combines BRBF with an eccentric configuration and a self-centering frame. Furthermore, we present a methodology for designing the individual components of this composite system. To assess the effectiveness of this design approach, we designed 3-, 6-, and 9-story buildings equipped with the BRBF-E-SCF system and developed finite element models. These models were subjected to two sets of ground motions representing the Maximum Considered Earthquake (MCE) and Design Basis Earthquake (DBE) seismic hazard levels. The results of our study reveal that although the combined system requires a higher amount of steel material compared to the BRBF-E system, it substantially reduces residual drift. Furthermore, the combined system demonstrates satisfactory performance in terms of story drift and ductility demand.