• Steel and Composite Structures
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• 제5권4호
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• pp.271-287
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• 2005

The seismic behavior of two steel moment-resisting frames, which satisfy all the current seismic design requirements, are evaluated and compared in the presence of pre-Northridge connections denoted as BWWF and an improved post-Northridge connections denoted as BWWF-AD. Pre-Northridge connections are modeled first as fully restrained (FR) type. Then they are considered to be partially restrained (PR) to model their behavior more realistically. The improved post-Northridge connections are modeled as PR type, as proposed by the authors. A sophisticated nonlinear time-domain finite element program developed by the authors is used for the response evaluation of the frames in terms of the overall rotation of the connections and the maximum drift. The frames are excited by ten recorded earthquake time histories. These time histories are then scaled up to produce some relevant response characteristics. The behaviors of the frames are studied comprehensively with the help of 120 analyses. Following important observations are made. The frames produced essentially similar rotation and drift for the connections modeled as FR type and PR type represented by BWWF-AD indicating that the presence of slots in the web of beams in BWWF-AD is not detrimental to the overall response behavior. When the lateral displacements of the frames are significantly large, the responses are improved if BWWF-AD type connections are used in the frames. This study analytically confirms many desirable features of BWWF-AD connections. PR frames have longer periods of vibration in comparison to FR frames and may attract lower inertia forces. However, calculated periods of the frames of this study using FEMA 350 empirical equation is longer than those calculated using dynamic characteristics of the frames. This may result in even lower design forces and may adversely influence the design.

• Steel and Composite Structures
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• 제23권2호
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• pp.143-152
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• 2017

This paper focuses on the seismic performance of pallet-type steel storage rack structures in their down aisle direction. As evidenced by experimental research, the seismic response of storage racks in the down-aisle direction is strongly affected by the nonlinear moment-rotation response of the beam-to-column connections. In their down-aisle direction, rack structures are designed to resist lateral seismic loads with typical moment frames utilizing proprietary beam-to-column moment-resisting connections. These connections are mostly boltless hooked type connections and they exhibit significantly large rotations resulting in large lateral frame displacements when subjected to strong ground motions. In this paper, typical hooked boltless beam-to-column connections are studied experimentally to obtain their non-linear reversed cyclic moment-rotation response. Additionally, a compound type connection involving the standard hooks and additional bolts were also tested under similar conditions. The simple introduction of the additional bolts within the hooked connection is considered to be a practical way of structural upgrade in the connection. The experimentally evaluated characteristics of the connections are compared in terms of some important performance indicators such as maximum moment and rotation capacity, change in stiffness and accumulated energy levels within the cyclic loading protocol. Finally, the obtained characteristics were used to carry out seismic performance assessment of rack frames incorporating the tested beam-to-column connections. The assessment involves a displacement based approach that utilizes a simple analytical model that captures the seismic behavior of racks in their down-aisle direction. The results of the study indicate that the proposed method of upgrading appears to be a very practical and effective way of increasing the seismic performance of hooked connections and hence the rack frames in their down-aisle direction.

• 한국강구조학회 논문집
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• 제16권2호통권69호
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• pp.247-255
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• 2004

본 실험프로그램은 슬래브가 있는 합성보의 내진성능향상을 위해 기존 모멘트접합부의 내진보강 방법을 개발을 목적으로 수행하였다. 반복하중을 통해 5개의 실대형 합성실험체에 대한 실험을 수행하였다. 각형강관기둥과 H형강보로 이루어진 기존의 다이아프램접합부가 RBS 또는 개량수평스티프너를 통해서 하부플랜지에만 내진 보강되었다. 제안한 보강접합부의 효율성을 조사하였다. 실험결과 하부플랜지에만 RBS를 적용한 접합부는 부족한 변형성능을 나타냈지만, 개량스티프너를 적용한 합성보 접합부는 내진성능을 향상시켰다.

• Structural Engineering and Mechanics
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• 제24권4호
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• pp.463-478
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• 2006

The design of structural frameworks for buildings is constantly evolving and is dependent on regional issues such as loading and constructability. One of the most promising recent developments for low to medium rise construction in terms of efficiency of construction, robustness and aesthetic appearance utilises concrete-filled steel tubular sections as the columns in a moment-resisting frame. These are coupled to rigid or semi-rigid connections to composite steel-concrete beams. This paper includes the results of a pilot experimental programme leading towards the development of economical, reliable connections that are easily constructed for this type of frame. The connections must provide the requisite strength, stiffness and ductility to suit gravity loading conditions as well as gravity combined with the governing lateral wind or earthquake loading. The aim is to develop connections that are stiffer, less expensive and easier to construct than those in current use. A proposed fabricated T-stub connection is to be used to connect the beam flanges and the column. These T-stubs are connected to the column using "blind bolts" with extensions, allowing installation from the outside of the tube. In general, the use of the extensions results in a dramatic increase in the strength and stiffness of the T-stub to column connection in tension, since the load is shared between membrane action in the tube wall and the anchorage of the bolts through the extensions into the concrete.

• Steel and Composite Structures
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• 제25권4호
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• pp.443-456
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• 2017

Many authors have established the usefulness of concrete filled steel tubular (CFST) sections as compression members while few have proved their utility as flexural members. To explore their prospective as part of CFST frame structures, two types of connections using extended end plate and seat angle are proposed for exterior joints of CFST beams and CFST columns. To investigate the performance and failure modes of the proposed bolted connections subjected to static loads, an experimental program has been executed involving ten specimens of exterior beam-to-column joints subjected to monotonically increasing load applied at the tip of beam, the performance is appraised in terms of load deformation behaviour of joints. The test parameters varied are the beam section type, type and diameter of bolts. To validate the experimental behaviour of the proposed connections in CFST beam-column joints, finite element analysis for the applied load has been performed using software ATENA-3D and the results of the proposed models are compared with experimental results. The experimental results obtained agree that the proposed CFST beam-column connections perform in a semi-rigid and partial strength mode as per specification of EC3.

• 한국강구조학회 논문집
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• 제20권4호
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• pp.529-537
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• 2008

본 논문의 목적은 슬래브가 있는 RHS 기둥-H 형강보 접합부의 내진보강설계방법을 제안하는 것이다. 모멘트접합부의 내진보강에 관한 이전 연구를 참조하면, 보강된 RBS(SR) 또는 연장된 수평스티프너(LH)를 가진 접합부는 응력/변형도 집중의 저감에 매우 효과적인 것으로 밝혀졌다. 따라서 두개의 내진보강방법, 즉, 보강된 RBS(SR)과 연장된 수평스티프너(LH)를 사용한 새로운 설계절차를 제시하였다: 게다가 본 논문에는 접합부의 내진보강방법을 향상시키기 위한 다양한 상세 및 방법 등이 기술되었다. 끝으로 설계방법의 검증을 위해서 파일럿테스트를 실시하였다.

• Structural Engineering and Mechanics
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• 제72권3호
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• pp.367-382
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• 2019

This paper presents experimental and analytical investigations on additional fixed-end rotations resulting from the strain penetration of high-strength reinforcement in reinforced concrete (RC) beam-column connections under monotonic loading. The experimental part included the test of 18 interior beam-column connections with straight long steel bars and 24 exterior beam-column connections with hooked and headed steel bars. Rebar strains along the anchorage length were recorded at the yielding and ultimate states. Furthermore, a numerical program was developed to study the effect of strain penetration in beam-column connections. The numerical results showed good agreement with the test results. Finally, 87 simulated specimens were designed with various parameters based on the test specimens. The effect of concrete compressive strength ($f_c$), yield strength ($f_y$), diameter ($d_b$), and anchorage length ($l_{ah}$) of the reinforcement in the beam-column connection was examined through a parametric study. The results indicated that additional fixed-end rotations increased with a decrease in $f_c$ and an increase in $f_y$, $d_b$ and $l_{ah}$. Moreover, the growth rate of additional fixed-end rotations at the yielding state was faster than that at the ultimate state when high-strength steel bars were used.

• 한국강구조학회 논문집
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• 제30권2호
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• pp.77-85
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• 2018

각형강관 기둥을 이용한 모멘트 접합부는 주로 관통형 다이어프램 형식으로 사용되고 있으나, 제작 및 시공과정이 복잡하여 적용하는데 어려움이 있다. 본 연구에서 제안하는 강구조물 시스템은 단위 유닛 모듈(각형강관 기둥, H형강 보, 원웨이 볼트)을 현장으로 반입하여 볼트조립만으로 완성되는 것이다. 따라서 이 연구에서는 내부보강판의 길이, 내부보강판의 형상을 변수로 설정하여 제안된 기둥-보 접합부의 내력 및 강성, 연성능력, 에너지 소산능력을 비교 분석하여 제시된 강구조물 시스템을 평가하였다.

• Steel and Composite Structures
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• 제22권1호
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• pp.113-139
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• 2016

The nonlinear seismic responses of steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF) are estimated, modeling the interior connections first as perfectly pinned (PPC), and then as partially restrained (PRC). Two 3D steel building models, twenty strong motions and three levels of the PRC rigidity, which are represented by the Richard Model and the Beam Line Theory, are considered. The RUAUMOKO Computer Program is used for the required time history nonlinear dynamic analysis. The responses can be significantly reduced when interior connections are considered as PRC, confirming what observed in experimental investigations. The reduction significantly varies with the strong motion, story, model, structural deformation, response parameter, and location of the structural element. The reduction is larger for global than for local response parameters; average reductions larger than 30% are observed for shears and displacements while they are about 20% for bending moments. The reduction is much larger for medium- than for low-rise buildings indicating a considerable influence of the structural complexity. It can be concluded that, the effect of the dissipated energy at PRC should not be neglected. Even for connections with relative small stiffness, which are usually idealized as PPC, the reduction can be significant. Thus, PRC can be used at IGF of steel buildings with PMRF to get more economical construction, to reduce the seismic response and to make steel building more seismic load tolerant. Much more research is needed to consider other aspects of the problem to reach more general conclusions.

• 한국강구조학회 논문집
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• 제15권5호통권66호
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• pp.519-529
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• 2003

최근에 스틸하우스나 고층아파트 지붕에 경량형강 지붕트러스의 사용이 증가하는 추세이다. 그러나 현재 지붕트러스와 하부구조의 앵커 접합부의 설계는 거의 경험에 의존하는 실정이다. 본 논문에서는 냉간성형형강 지붕트러스 앵커 접합부의 구조적인 거동에 관한 실험적인 연구를 서술하였다. 트러스부재와 접합철물은 스크류로 접합하였으며, 하부구조의 구조재료에 따라 시공성 및 구조적인 성능이 우수한 단순한 형태의 접합철물을 사용하여 철근콘크리트구조인 경우 케미컬 앵커볼트 그리고 강구조인 경우는 용접 및 DX-Pin을 사용하여 하부구조와 연결하였다. 다양한 접합부 형태에 대한 인발실험을 수향하여 접합부의 강도 및 강성을 측정하였으며, 이를 AISI시방서(1996) AISC시방서(1989)규정에 근거한 설계강도와 비교하였다. 또한 스크류 연결부의 최대전단강도식을 제안하여 실험결과와 비교하였다.