CHOSUN

Inelastic Behavior of Reduced Steel Link-beams for Seismic Resisting Frames

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Author(s)
레마 메론 웁셰트
Issued Date
2017
Keyword
Reduced link beams, PEEQ, Plastic shear rotation, FEM, LCFs, EBFs
Abstract
편심브레이스프레임(Eccentrically braced frames (EBFs))와 linked column frames (LFCs)의 링크빔(Link beam)은 링크빔의 소성변형을 통해서 지진 에너지를 분산 시키는 역할을 한다. 비탄성 변형과 손상은 링크빔의 중심에 집중된다. 기존의 편심브레이스프레임의 링크빔 부분은 주 구조체로부터 분리되지 않기 때문에 지진 후에 링크빔을 교체하는 데 한계가 있다. 이러한 편심브레이스 프레임의 한계를 해결하기 위해 많은 연구자들은 교체 가능한 링크빔을 갖는 EBF를 개발하고자 다양한 디테일을 제안하였다. 지금까지의 연구결과에 따르면 링크빔의 소성변형을 제어하기 위하여 링크빔의 재료강도를 약하게 하거나 링크빔에 연결된 컬렉터 빔에 비해 단면을 감소시켜 설계하는 것으로 해결책을 찾고 있다. 하지만, 컬렉터 빔과 링크빔의 단면적 차이는 시공에 어려움을 초래한다.
이를 해결하기 위해 교체가능하고 단면이 감소된 웨브 링크부와 단면이 감소된 웨브 및 플렌지 링크부를 제안하고, 이를 준정적 재하 실험 및 유한요소 시뮬레이션을 사용하여 구조 성능을 평가했다. 실험 결과는 해당 FE 시뮬레이션과 일치하는 결과를 얻었다. 이는 제안된 링크빔이 AISC-341-10 내진 조항에서 권장된 소성 회전 등급을 만족시키는 결과를 얻었다.
재하실험을 통해 얻은 결과를 바탕으로 검증된 FE 해석 모델을 이용하여 소성힌지의 제어를 위한 플렌지 감소의 유효성을 검증 하였다. 플렌지의 등가소성변형률(PEEQ)은 각각 다른 위치에서 측정되었다. 그 결과 감소된 플렌지에서 측정된 PEEQ가 다른 위치에서 측정 된 PEEQ와 비교할 때 최대인 것으로 나타났다. 이는 감소된 플렌지 섹션에서 소성힌지가 형성되었음을 보여준다. 따라서 링크빔의 단면을 감소시킴으로써 링크플렌지와 기둥간 용접부에서의 발생되었던 응력집중과 소성힌지의 위치가 중앙부로 이동되면서 파괴를 방지할 수 있었다.
|Links in eccentrically braced frames (EBFs) and linked column frames (LCFs) behave as a seismic energy dissipating members. The links dissipate seismic energy through metallic deformation or plastic deformation. The inelastic deformations and damages are supposed to be concentrated at the link. However, the conventional EBFs have a limitation of replacing the link after an earthquake because the link is not isolated from the main structures and also the depth difference between the link beam and the collector beam creates difficulty during slab construction.
In order to address the limitations listed above replaceable reduced I-section and channel-section links were proposed with web perforations, and their structural performance was evaluated using quasi-static loading test and finite element (FE) simulation. The results obtained from the experiment were in good agreement with their corresponding FE analysis. The results show, the proposed links satisfy the plastic rotation limit recommended in AISC-341-10 seismic provision.
Once the FE analysis model was verified through the results obtained from quasi-static loading test, further study was conducted to evaluate the effectiveness of flange reduction to control the plastic hinge using the calibrated FE simulation. The equivalent plastic strain (PEEQ) along the flanges was measured at different locations. The results show that the PEEQ measured at the reduced flange is maximum compared to the PEEQ measured at the link end which indicates that the plastic hinge is formed at reduced flanges sections. Thus, reducing the link beam will also minimize the bending moment and the associated stress at the link to column/end plate connection, and moving the location of maximum plastic strain and the associated deformation away from the column/end plate connection. Finally, the equation defining the plastic shear strength of reduced channel-section link is suggested and it was verified with the results obtained from FE analysis.
Alternative Title
지진저항시프레임 대한 Reduced 링크빔의 비탄성 거동
Alternative Author(s)
Meron Wubshet Lemma
Department
일반대학원 건축공학과
Advisor
최재혁
Awarded Date
2018-02
Table Of Contents
Table of Contents
Table of Contents I
List of Tables IV
List of Figures V
Nomenclatures VIII
Abstract…… X
Abstract in Korean XII
Chapter 1. Introduction 1
1.1 General 1
1.2 Objectives 2
1.3 Organization of thesis 3
Chapter 2. Literature Review and Design Procedures 4
2.1 General 4
2.2 Types of Frames 4
2.2.1 Moment Resisting Frames (MRFs) 4
2.2.2 Eccentrically Braced Frames (EBFs) 5
2.2.3 Linked Column Frames (LCFs) 6
2.3 Link Behavior 8
2.3.1 Link Rotation Capacity 8
2.3.2 Link Stiffeners 11
2.3.3 Link Over-strength 12
2.3.4 Section Compactness 12
2.4 The Behavior of Steel Plates with Circular Hole under Shear Loading 13
2.5 Previous Studies 15
2.5.1 D. Y. Abebe and J. H. Choi, (2016) 15
2.5.2 Nabil et al. (2010) 17
2.5.3 Berman et al. (2010) 18
2.6 Design of Replaceable Reduced Link Sections 18
2.6.1 Design Procedure of Reduced Web Link Sections 18
2.6.2 Design Procedure of Reduced Web and Flange Link Sections 21
Chapter 3. Experimental Program 24
3.1 Introduction 24
3.2 Specimen Design 24
3.3 Experimental Test Setup, Instrumentation and Procedure 29
3.4 Cyclic Loading Protocol 31
3.5 Experimental Results 32
3.5.1 Unreduced Link (ULS-U) 32
3.5.2 Reduced Web Links (Specimens RWS-U5 and RWS-S5) 33
3.5.3 Reduced Web and Flange Links (Specimens RLS-U5 and RLS-S5) 36
3.6 Discussion of Test Results 38
3.7 Summary 45
Chapter 4. Non-Linear FE Analysis 46
4.1 General 46
4.2 Finite Element Analysis 46
4.2.1 Material Modeling and Meshing Type 46
4.2.2 Loading and Boundary Condition 47
4.3 Comparison of Analysis and Test Results for I-section Link Beam 49
4.3.1 Unreduced Link (ULS-U) 49
4.3.2 Reduced Web Links (Specimens RWS-U5 and RWS-S5) 50
4.3.3 Reduced Web and Flange Links (Specimens RLS-U5 and RLS-S5) 53
4.3.4 Summary of Results 56
4.4 Parametric Study for Channel-Section Link Using FE Analysis 59
4.4.1 Specimen Detail 59
4.4.2 Effect of Link Length Factor on Link Performance 61
4.4.3 Effect of Percent of Reduced Web Area on Link Performance 62
4.4.4 Effect of Stiffener on Link Performance 66
Chapter 5. PEEQ Distribution on RLS 68
5.1 General 68
5.2 Design Procedure of RLS 68
5.3 Specimen Detail 72
5.4 Results and Discussions 74
5.5 Summary 86
Chapter 6. Design Recommendation 87
6.1 Introduction 87
6.2 Plastic Shear Strength 87
Chapter 7. Conclusions and Recommendations 91
7.1 Introduction 91
7.2 Conclusions 91
7.3 Recommendations 93
References… 94
APPENDIX A: Hysteresis Responses of Channel Section Link Beam 98
APPENDIX B: Hysteresis Response, PEEQ and Von Mises Stress Distributions of RLS 104
Acknowledgement 113
Degree
Master
Publisher
Chosun University, department of Engineering
Citation
레마 메론 웁셰트. (2017). Inelastic Behavior of Reduced Steel Link-beams for Seismic Resisting Frames.
Type
Dissertation
URI
https://oak.chosun.ac.kr/handle/2020.oak/13382
http://chosun.dcollection.net/common/orgView/200000266506
Appears in Collections:
General Graduate School > 3. Theses(Master)
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