• Title, Summary, Keyword: Slender braces

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Seismic Performance Evaluation of Steel Moment Frame Factory Building with Slender Braces (세장한 가새가 사용된 철골모멘트골조 공장시설물의 내진 성능평가)

  • Kim, Dong Yeon;Cho, Jae Chul;Hwang, Sunwoo;Kim, Taejin;Kim, Jong Ho
    • Journal of the Earthquake Engineering Society of Korea
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    • v.22 no.1
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    • pp.33-43
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    • 2018
  • 'Seismic Performance Evaluation Method for Existing Buildings (2013)' developed in accordance with the overseas guidelines ASCE 41 - 06 is the most widely used procedure among domestic seismic performance evaluation guidelines in Korea. However, unlike ASCE 41 - 06, it stipulates that the final performance should be derived as the gravity load distribution ratio of the lateral force resistance system in the guideline. Therefore, in the case of a dual steel structure system with slender braces, where the internal moment frame is mostly responsible for the gravity load, the evaluation of slender braces based on gravity load distribution ratio is difficult to be achieved. In this research, we propose an objective evaluation process for such system by evaluating seismic performance for large-scale factory facilities as an example.

Mid-length lateral deflection of cyclically-loaded braces

  • Sheehan, Therese;Chan, Tak-Ming;Lam, Dennis
    • Steel and Composite Structures
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    • v.18 no.6
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    • pp.1569-1582
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    • 2015
  • This study explores the lateral deflections of diagonal braces in concentrically-braced earthquake-resisting frames. The performance of this widely-used system is often compromised by the flexural buckling of slender braces in compression. In addition to reducing the compressive resistance, buckling may also cause these members to undergo sizeable lateral deflections which could damage surrounding structural components. Different approaches have been used in the past to predict the mid-length lateral deflections of cyclically loaded steel braces based on their theoretical deformed geometry or by using experimental data. Expressions have been proposed relating the mid-length lateral deflection to the axial displacement ductility of the member. Recent experiments were conducted on hollow and concrete-filled circular hollow section (CHS) braces of different lengths under cyclic loading. Very slender, concrete-filled tubular braces exhibited a highly ductile response, undergoing large axial displacements prior to failure. The presence of concrete infill did not influence the magnitude of lateral deflection in relation to the axial displacement, but did increase the number of cycles endured and the maximum axial displacement achieved. The corresponding lateral deflections exceeded the deflections observed in the majority of the previous experiments that were considered. Consequently, predictive expressions from previous research did not accurately predict the mid-height lateral deflections of these CHS members. Mid-length lateral deflections were found to be influenced by the member non-dimensional slenderness (${\bar{\lambda}}$) and hence a new expression was proposed for the lateral deflection in terms of member slenderness and axial displacement ductility.

A Study on the Development of Force Limiting Devices of Folded Plate Type (절판형 응력제한 기구의 개발에 관한 연구)

  • Kim, Cheol Hwan;Chae, Won Tak
    • Journal of Korean Society of Steel Construction
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    • v.26 no.6
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    • pp.571-579
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    • 2014
  • The steel braces are used to control the lateral drift of high rise buildings. The braces are designed as tensile members since the braces consisted of slender member can not resist compressive loads by elastic buckling. To resolve this problem, a lot of research were performed to develop the non-buckling member. The force limiting device (FLD.) is one of them. The purpose of this study is the development of FLD. to prevent a elastic buckling for a slender member. The folded plate type is proposed to induce the yielding before occurring elastic buckling. In this study, member test and FEM analysis for proposed type were performed. Further, It is verified that the structure with FLD member is stable by high energy absorption. The proposed folded plate type FLD could be effective to preserve the compressive member from the elastic buckling.

Compressive Behavior of H-section Brace Strengthened by Non-welded Cold-Formed Element (무용접 냉간성형 조립재로 보강한 H형강 가새의 압축거동)

  • Kim, Sun Hee;Kim, Do Bum;Choi, Sung Mo
    • Journal of Korean Society of Steel Construction
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    • v.27 no.2
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    • pp.169-180
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    • 2015
  • Recently, Seismic performance of the building built in the past is required to review, because the code for seismic design have been reinforced. In 2009, if the revised latest criteria of seismic design is applied, the majority the steel structure of the low-rise concentrically braced system is short of the seismic performance. Also, when the steel braces are subject to compressive load, which causes unstable behavior of the structure. In order to verify the compressive behavior of the reinforced braces, structural performance test was conducted with variables of slenderness ratio and the amount of reinforcement. Therefore, this study suggests restraining the bending buckling of slender H-shaped braces to resist compressive force. In order to verify the compressive behavior of the reinforced braces, structural performance test was conducted with variables of slenderness ratio and the amount of reinforcement.

Wilshire Grand: Outrigger Designs and Details for a Highly Seismic Site

  • Joseph, Leonard M.;Gulec, C. Kerem;Schwaiger, Justin M.
    • International Journal of High-Rise Buildings
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    • v.5 no.1
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    • pp.1-12
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    • 2016
  • The 1100 foot [335 m] tall Wilshire Grand Center tower under construction in Los Angeles illustrates many key outrigger issues. The tower has a long, narrow floor plan and slender central core. Outrigger braces at three groups of levels in the tower help provide for occupant comfort during windy conditions as well as safety during earthquakes. Because outrigger systems are outside the scope of prescriptive code provisions, Performance Based Design (PBD) using Nonlinear Response History Analysis (NRHA) demonstrated acceptability to the Los Angeles building department and its peer review panel. Buckling Restrained Brace (BRB) diagonals are used at all outrigger levels to provide stable cyclic nonlinear behavior and to limit forces generated at columns, connections and core walls. Each diagonal at the lowest set of outriggers includes four individual BRBs to provide exceptional capacities. The middle outriggers have an unusual 'X-braced Vierendeel' configuration to provide clear hotel corridors. The top outriggers are pre-loaded by jacks to address long-term differential shortening between the concrete core and concrete-filled steel perimeter box columns. The outrigger connection details are complex in order to handle large forces and deformations, but were developed with contractor input to enable practical construction.