• 국제초고층학회논문집
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• 제3권1호
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• pp.9-19
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• 2014

In this study the seismic performances of reinforced concrete apartment buildings with Y- and box-shaped plans having central core are investigated. Three types of model structures are designed for each shape depending on the amount of shear partition walls: structures with all shear walls, structures with all columns except the core walls, and structures with shear walls and columns combined. The required amount of concrete to satisfy the specified design loads is the largest in the all shear wall structures, and decreases as more and more shear walls are replaced with columns. The amount of re-bars increased significantly in the flat plate structures. According to nonlinear static and dynamic analysis results, the structures with all shear walls and all columns turn out to have the largest and the smallest strengths, respectively. However it is observed that even the all-column structures with shear core have proper load resisting capacity for design level seismic load.

• Earthquakes and Structures
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• 제16권5호
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• pp.533-546
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• 2019

This study presents an experimental investigation on six beam-column joint specimens under the lateral cyclic loading. The aim was to explore the effectiveness of steel fiber-reinforced concrete (SFRC) in reducing the transverse shear stirrups in beam-column joints of the reinforced concrete (RC) frames with strong-columns and weak-beams. Two RC and four SFRC specimens with different types of reinforcement detailing and steel fibers of volume fraction in the range of 0.75-1.5% were tested under gradually increasing cyclic displacements. The main parameters investigated were lateral load-resisting capacity, hysteresis response, energy dissipation capacity, stiffness degradation, viscous damping variation, and mode of failure. Test results showed that the diagonally bent configuration of beam longitudinal bars in the beam-column joints resulted in the shear failure at the joint region against the flexural failure of beams having straight bar configurations. However, all SFRC specimens exhibited similar lateral strength, energy dissipation potential and mode of failure even in the absence of transverse steel in the beam-column joints. Finally, a methodology has been proposed to compute the shear strength of SFRC beam-column joints under the lateral loading condition.

• Steel and Composite Structures
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• 제16권2호
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• pp.221-231
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• 2014

The purpose of this study was to evaluate the cyclic behavior of steel column-tree moment connections used in steel moment resisting frames. These connections are composed of shop-welded stub beam-to-column connection and field bolted beam-to-beam splice. In this study, the effects of beam splice length on the seismic performance of column-tree connections were experimentally investigated. The change of the beam splice location alters the bending moment and shear force at the splice, and this may affect the seismic performance of column-tree connections. Three full-scale test specimens of column-tree connections with the splice lengths of 900 mm, 1,100 mm, and 1,300 mm were fabricated and tested. The splice lengths were roughly 1/6, 1/7, 1/8 of the beam span length of 7,500 mm, respectively. The test results showed that all the specimens successfully developed ductile behavior without brittle fracture until 5% radians story drift angle. The maximum moment resisting capacity of the specimens showed little differences. The specimen with the splice length of 1,300 mm showed better bolt slip resistance than the other specimens due to the smallest bending moment at the beam splice.

• Steel and Composite Structures
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• 제20권3호
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• pp.545-569
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• 2016

Stiffeners have widely been used in lateral load resisting systems to improve the buckling stability of shear panels in steel frames. However, due to major differences between plate girders and steel plate shear walls (SPSWs), use of plate girder equations often leads to uneconomical and, in some cases, incorrect design of stiffeners. Hence, this paper uses finite element analysis (FEA) to describe the effect of the rigidity and arrangement of stiffeners on the buckling behavior of plates. The procedures consider transverse and/or longitudinal stiffeners in various practical configurations. Subsequently, curves and formulas for the design of stiffeners are presented. In addition, the influence of stiffeners on the inward forces subjected to the boundary elements and the tension field angle is investigated as well. The results indicate that the effective application of stiffeners in SPSW systems not only improves the structural behavior, such as stiffness, overall strength and energy absorption, but also leads to a reduction of the forces that are exerted on the boundary elements.

• 한국지진공학회논문집
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• 제27권2호
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• pp.91-99
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• 2023

Structural vibration induced by earthquake hazards is one of the most significant concerns in structure performance-based design. Structural hazards evoked from seismic events must be properly identified to make buildings resilient enough to withstand extreme earthquake loadings. To investigate the effects of combined earthquake-resistant systems, shear walls and five types of dampers are incorporated in nineteen structural models by altering their arrangements. All the building models were developed as per ACI 318-14 and ASCE 7-16. Seismic fragility curves were developed from the incremental dynamic analyses (IDA) performed by using seven sets of ground motions, and eventually, by following FEMA P695 provisions, the collapse margin ratio (CMR) was computed from the collapse curves. It is evident from the results that the seismic performance of the proposed combined shear wall-damper system is significantly better than the models equipped with shear walls only. The scrutinized dual seismic resisting system is expected to be applied practically to ensure a multi-level shield for tall structures in high seismic risk zones.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.61-64
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• 2008

콘크리트충전 강관기둥(Concrete Filled steel Tube Column)과 RC 무량판 슬래브의 조합은 거푸집을 사용하지 않는다는 것만으로도 초고층 건물의 공기단축에 상당한 영향을 미칠 수 있다. 뿐만 아니라 기둥의 내력 증진으로 인한 기둥 크기의 축소, 그로 인한 공간 활용도의 증가, 층간 소음문제 해결 등 많은 장점이 잠재되어 있다. 하지만 접합부의 성능을 정확히 밝혀내는 것이 우선 이루어져야 하며, 본 논문에서는 기존에 수행된 CFT 기둥-RC 무량판 슬래브의 내부접합부에 대한 중력 실험과 횡하중 실험을 바탕으로 외부접합부에 대한 실물대 실험을 수행하였다. 외부접합부 실험 결과, 내부접합부 실험체에 비하여 동일한 조건에서 설계된 외부접합부 실험체는 최대 모멘트강도가 $50%{\sim}65%$ 감소하였고, 내진밴드가 추가된 CFT-E2 실험체는 BME 실험체에 비하여 20%의 최대모멘트 증진과 탁월한 연성능력, 에너지 흡수능력을 보유한 것으로 나타났다. 또한 CFT-E2는 내진밴드의 사용으로 슬래브의 휨거동 영역이 확장되었으며 모든 실험체가 설계기준에서 요구하는 0.4V$_c$중력하중 하에서 1.5% 횡변 위비를 만족하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.65-68
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• 2008

RC 무량판 구조시스템은 여러 구조적 장점들로 인해 그 사용이 증가하는 추세이지만 횡방향 변위성능, 변형성능에 대한 약점을 지니고 있고, 고층화에 따라 기둥 크기가 증가하는 단점을 가지고 있다. 이러한 구조적 단점들은 CFT기둥의 사용을 통해 어느 정도 보완될 수 있으나 현재 CFT 기둥과 RC 무량판 접합부의 상세 및 설계법은 명확하게 제시된 바가 없다. 따라서 본 논문은 실물대 실험을 통해 일반 RC 기둥-무량판 접합부와 비교하여 CFT 기둥-RC 무량판 접합부의 횡저항 성능을 검증하고, 횡하중-변위비 성능에 따른 접합부의 모멘트 성능과 연성 능력을 파악하였다. 각기 다른 변수를 지닌 4개의 실험체를 제작하여 횡력 실험을 수행한 결과 다음과 같은 결론을 도출하였다. CFT 실험체는 전단머리의 영향으로 위험단면이 확장되었으며 일반 RC 기둥 실험체에 비해 초기강성은 35%, 모멘트는 25${\sim}$35% 증가하였고, 모멘트의 증가로 인한 에너지 흡수율이 증가하였다. 모든 실험체는 슬래브의 전단거동이 지배하였지만 내진밴드로 보강된 CFT 실험체는 슬래브의 휨거동 영역이 확장되었고, 연성비와 에너지 흡수율 또한 증가하였다.

• 콘크리트학회논문집
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• 제27권5호
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• pp.489-499
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• 2015

내진 보강 공법의 보강효과 파악을 위해선 이에 대한 이론적 규명이 필요하다. 이에 본 연구는 단부에 기둥 부재를 증타한 단근 배근된 전단벽체를 대상으로 해 보강되는 기둥의 상세와 일체화 거동을 고려한 전단강도 모델을 제안했다. 이 모델은 증타된 기둥부재의 전단변형이 집중되는 길이를 가정해 이를 일체화된 벽체 내에 발생하는 스트럿 두께 산정에 이용했다. 뿐만 아니라 이 길이 내에 집중 발생하는 전단변형률을 유도, 이를 일체화 거동을 고려한 적합성 조건을 기존 전단벽체의 해석 알고리즘에 도입함으로써 증타 보강된 벽체의 해석 알고리즘을 새로이 제안했다. 또한 제안된 알고리즘을 통해 계산된 전단강도로 횡력 저항 메커니즘을 단일 스트럿 화 시켜줌으로써 보강부재의 초기강성을 제안하였다. 본 연구에서 제안한 방법의 타당성을 확인하기 위해 해석 결과 값을 본 연구에서 수행한 증타 보강된 벽체를 대상으로 한 실험뿐만 아니라 기존 RC 골조 내에 RC 전단벽체를 신설해 보강한 실험의 결과와 비교해 본 결과, 기둥부재의 상세를 고려하면서 동시에 기존 기준들에 비해 실험결과에 가깝게 예측할 수 있음을 확인했다.

• Steel and Composite Structures
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• 제32권2호
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• pp.199-212
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• 2019

This paper presents an investigation on seismic behavior of out-of-code Q690 circular high-strength concrete-filled thin-walled steel tubular (HCFTST) columns made up of high-strength (HS) steel tubes (yield strength $f_y{\geq}690MPa$). Eight Q690 circular HCFTST columns with various diameter-to-thickness (D/t) ratios, concrete cylinder compressive strengths ($f_c$) and axial compression ratios (n) were tested under the constant axial loading and reversed cyclic lateral loading. The obtained lateral load-displacement hysteretic curves, energy dissipation, skeleton curves and ductility, and stiffness degradation were analyzed in detail to reflect the influences of tested parameters. Subsequently, a simplified shear strength model was derived and validated by the test results. Finally, a finite element analysis (FEA) model incorporating a stress triaxiality dependent fracture criterion was established to simulate the seismic behavior. The systematic investigation indicates the following: compared to the D/t ratio and axial compression ratio, improving the concrete compressive strength (e.g., the HS thin-walled steel tube filled with HS concrete) had a slight influence on the ductility but an obvious enhancement of energy dissipation and peak load; the simplified shear strength model based on truss mechanism accurately predicted the shear-resisting capacity; and the established FEA model incorporating steel fracture criterion simulated well the seismic behavior (e.g., hysteretic curve, local buckling and fracture), which can be applied to the seismic analysis and design of Q690 circular HCFTST columns.

• Steel and Composite Structures
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• 제51권5호
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• pp.563-573
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• 2024

This research experimentally evaluated the local stress distribution along the cross-section of composite beams under both positive and negative moments. The experiment utilized a large-scale, two-story, two-by-three bay steel gravity frame with a concrete on metal deck floor system. The composite shear connections, which are nominally assumed to be pinned under gravity loading, can develop non-negligible moment-resisting capacity when subjected to lateral loads. This paper discusses the local stress distribution, orshear lag effects, observed near the beam-to-column connections when subjected to combined gravity and lateral loading. Strain gauges were used for measurements along the beam depth at varying distances from the connection. The experimental data showed amplified shear lag effects near the unconnected region of the beam web and bottom flange under the applied loading conditions. These results indicate that strain does not vary linearly across the beam cross-section adjacent to the connection components. This insight has implications for the use of experimental strain gauge data in estimating beam demands near the connections. These findings can be beneficial in informing instrumentation plans for future experimental studies on composite beams.