• Title/Summary/Keyword: 철골골조

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Inelastic Time History Analysis of a Five-Story Steel Framed Structure Considering Rigidity of TSD Connection (TSD 접합부의 강성을 고려한 5층 철골골조구조물의 비탄성 시간이력해석)

  • Kang, Suk-Bong;Lee, Jae-Hwan
    • Journal of Korean Society of Steel Construction
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    • v.22 no.3
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    • pp.281-291
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    • 2010
  • In this study, a five-story steel frame was designed in accordance with KBC2005 to evaluate the effects of the beam-column connection on the structural behavior. The connections were designed as fully rigid and semi-rigid. The fiber model was used to describe the moment-curvature relationship of the steel beam and the column, the power model for the moment-rotation angle of the semi-rigid connection and the three-parameter model for the hysteretic behavior of the steel beam, column, and connection. The structure was idealized as separate 2-D frames and as connected 2-D frames. The peak ground accelerations of four earthquake records were modified in a time-history analysis for the levels of the mean return period and for the maximum base-shear force in a pushover analysis. The top story displacement, base-shear force, story drift, demanded ductility ratio for the semi-rigid connection, maximum bending moment of the column, beam, and connection, and distribution of the plastic hinge were examined in the time-history analysis. The frame with the semi-rigid connection yielded a lower base-shear force, less magnitude, and increasing ratio in the bending moment of the column, beam, and connection than the frame with a fully rigid connection. The TSD connection was deemed to have secured the economy and safety of the sample structure that was subjected to seismic excitation for the Korean design level.

Seismic Retrofit of Reinforced Concrete Structures Using Steel Braces and Moment Frames (가새와 강골조를 이용한 저층 RC 구조물의 내진보강)

  • Huynh, Chanh Trung;Park, Kyoung-Hoon;Kim, Jin-Koo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.5
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    • pp.509-516
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    • 2010
  • In this study a seismic retrofit scheme for the reinforced concrete moment framed structures was investigated using steel bracing and moment frames. The analysis model structure is a 3-story 3-bay moment frame structure designed only for gravity load. The stress/strain concentration in brace-RC frame connection was investigated using finite element analysis. To prevent premature joint failure, steel moment frames were placed inside of middle bay of the RC frame. Two types of braces, steel braces and buckling restrained braces(BRBs), were used for retrofit, and the ductility and the strength of the structure before and after the retrofit were compared using nonlinear static and dynamic analyses. According to the analysis results, the strength and ductility of the structure retrofitted by the moment frames and braces increased significantly. The added steel frame did not contribute significantly to the increase of lateral strength mainly because the size is relatively small.

Seismic Analysis of Mid Rise Steel Moment Resisting Frames with Relative Stiffness of Connections and Beams (접합부와 보의 상대강성을 고려한 중층 철골 모멘트 골조의 내진해석)

  • Ha, Sung-Hwan;Kang, Cheol-Kyu;Han, Hong-Soo;Han, Kweon-Gyu;Choi, Byong-Jeong
    • Journal of Korean Society of Steel Construction
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    • v.23 no.5
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    • pp.595-606
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    • 2011
  • This study was conducted to investigate the seismic behavior of steel member resisting frames considering the relative stiffness of the connection and beams. Six-story steel moment frames were designed to study the seismic behavior. The connections were classified into Double Web-Angle connections (DWAs), Top- and Seat-angles with double Web-angles (TWSs), FEMA-Test Summary No. 28, Specimen ID: UCSD-6 (SAC), and Fully Restrained (FR). The rotational stiffness of the semi-rigid connections was estimated using the Three-Parameter Power Model adopted by Chen and Kishi. The relative stiffness, which is the ratio of the rotational stiffness of the connections to the stiffness of the beams, was used. Push-over, repeated loading, and time history analysis were performed for all the frames. The seismic behavior of each frame was analyzed with the story drift, plastic hinge rotation, and hysteretic energy distribution.

Simplified Nonlinear Static Progressive Collapse Analysis of Steel Moment Frames (철골모멘트골조의 비선형 정적 연쇄붕괴 근사해석)

  • Lee, Cheol Ho;Kim, Seon Woong
    • Journal of Korean Society of Steel Construction
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    • v.19 no.4
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    • pp.383-393
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    • 2007
  • A simplified model which incorporates the moment-axial tension interaction of the double-span beams in a column-removed steel frame is presented in this paper. To this end, material and geometric nonlinear parametric finite element analyses were conducted for the double-span beams by changing the beam span to depth ratio and the beam size within some practical ranges. The beam span to depth ratio was shown to be the most influential factor governing the catenary action of the double-span beams. Based on the parametric analysis results, a simplified piece-wise linear model which can reasonably describe the vertical resisting force versus the beam chord rotation relationship was proposed. It was also shown that the proposed method can readily be used for the energy-based progressive collapse analysis of steel moment frames.

Risk-Targeted Seismic Performance of Steel Ordinary Concentrically Braced Frames Considering Seismic Hazard (지진재해도를 고려한 철골 보통중심가새골조의 위험도기반 내진성능)

  • Shin, Dong-Hyeon;Hong, Suk-Jae;Kim, Hyung-Joon
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.5
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    • pp.371-380
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    • 2017
  • The risk-targeted seismic design concept was first included in ASCE/SEI 7-10 to address problems related to the uniform-hazard based seismic concept that has been constructed without explicitly considering probabilistic uncertainties in the collapse capacities of structures. However, this concept is not yet reflected to the current Korean building code(KBC) because of insufficient strong earthquake data occurred at the Korean peninsula and little information on the collapse capacities of structures. This study evaluates the risk-targeted seismic performance of steel ordinary concentrically braced frames(OCBFs). To do this, the collapse capacities of prototype steel OCBFs are assessed with various analysis parameters including building locations, building heights and soil conditions. The seismic hazard curves are developed using an empirical spectral shape prediction model that is capable of reflecting the characteristics of earthquake records. The collapse probabilities of the prototype steel OCBFs located at the Korean major cities are then evaluated using the risk integral concept. As a result, analysis parameters considerably influence the collapse probabilities of steel OCBFs. The collapse probabilities of taller steel OCBFs exceed the target seismic risk of 1 percent in 50 years, which the introduction of the height limitation of steel OCBFs into the future KBC should be considered.

Evaluation of Ductility Factors for MDOF Systems in Special Steel Moment Resisting Frames (철골 연성 모멘트 골조에 대한 다자유도 시스템의 연성계수 평가)

  • Kang, Cheol-Kyu;Han, Young-Cheol
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.6 s.40
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    • pp.13-22
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    • 2004
  • Ductiluty factor has played an important role in seismic design as it is key component of response modification factor(R). In this stuty, ductility factors() are calculated by multiplying ductility factor for SDOF systems() and MDOF modification factors(). Ductility factors() for SDOF systems are computed from nonlinear dynamic analysis undergoing different level of displacement ductiluty demands and period when subjected to a large number of recorded earthquake ground motions. The MDOF modification factors() are proposed to account for the MDOF systems, based on previous studies. A total of 108 prototype steel frames are designed to investigate the ductility factors considering the number of stories(4, 8 and 16-stories), framing system(Perimeter Frames, PF and Distributed Frames, DF), failure mechanism(Strong-Column Weak-Beam, SCWB and Weak-Column Strong-Beam, WCSB), soil profiles(SA, SC and SE in UBC 1997) and seismic zone factors(Z=0.075, 0.2 and 0.4 in UBC 1997). It is shown that the number of stories, failure mechanisms (SCWB, WCSB), and soil profiles have great influence on the ductility factors, however, the structural system(Perimeter frames, Distributed frames), and seismic zones have no influence on the ductility factors.

Study on the Nonlinear Analysis Model for Seismic Performance Evaluation of School Buildings Retrofitted with Infilled Steel Frame with Brace (철골 끼움가새골조로 보강된 학교건물의 내진성능평가를 위한 비선형 해석 모델에 관한 연구)

  • Yoo, Suk-Hyeong;Ko, Kwan-Wook
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.4
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    • pp.65-72
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    • 2022
  • Recently, damage to buildings due to earthquakes in Korea occurred mainly in school buildings and Piloti-type multi-family houses, highlighting the need for seismic retrofit for buildings of the same type. In the early days of the seismic retrofit project for school facilities, various patented methods using dampers as a ductile seismic retrofit method were applied without sufficient verification procedures. However, in 「School Facility Seismic Performance Evaluation and Retrofit Manual, 2021」, when the patented method is applied, it must be applied through a separate strict verification procedure, and instead, the strength/stiffness retrofit method was induced as a general method. In practice,when evaluating seismic performance for retrofit by infilled steel frame with brace, the analysis model is constructed by directly connecting only the steel brace to the existing RC member. However, if the frame is removed from the analysis model of the infilled steel frame with brace, the force reduction occurring on the existing RC member near the retrofit is considered to be very large, and this is judged to affect the review of whether to retrofit the foundation or not. Therefore, in this study, preliminary analysis with variables such as whether or not steel frame is taken into account and frame link method for the analysis model of RC school building retrofitted by infilled steel frame with brace and nonlinear analysis for actual 3-story school building was performed, and basic data for rational analysis model setting were presented by comparing preliminary analysis and pushover analysis results for each variable.

An Experiemetal Study for Improvement of Seismic Performance of Steel Beam-to-Column Connections (철골 보-기둥 접합부의 내진성능 개선을 위한 실험적 연구)

  • 이승준;김원기;이정웅
    • Journal of the Earthquake Engineering Society of Korea
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    • v.3 no.4
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    • pp.61-70
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    • 1999
  • Cracking was observed in beam-to-column connections of many steel building frames during the 1994 Northridge and 1995 Kobe earthquakes. Thus extensive experimental researches are currently being conducted to improve the seismic performance of steel frames. A value of 0.015 radian was considered as a reasonable estimate of beam plastic rotation demand in steel moment-resisting frames subjected to severe earthquakes. The objective of this research is to develop a type of connection detail which moves the plastic hinge region in the beam away from the face of the column and can prevent cracking at the welded flange of the beam-to-column connection under seismic loading. An experimental investigation was undertaken on five beam-to-column connection specimens to study the performance of the connections with proposed details. The experiemental results showed that the flexural strength and rotational ductility of the beam connections were adequate for the seismic resistance steel frames to prevent possible cracks at the connections.

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Response Characteristics of the Steel Moment Resisting Frame According to the Stiffness Variation of Pontoo (플로팅 함체의 강성변화에 따른 철골모멘트연성골조의 응답 특성)

  • Lee, Young-Wook;Park, Jeong-Ah;Chae, Ji-Yong;Choi, Ji-Hun
    • Journal of Navigation and Port Research
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    • v.36 no.3
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    • pp.215-223
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    • 2012
  • To examine the interaction of the floating pontoon with a steel moment resisting frame, the static structural analysis is carried out, in which the pressure load are calculated from the forgoing fluid dynamic analysis, varying the period of wave from 3 to 15 second and for 3 cases of depth of pontoon, 1.5, 2.0, 2.5m. As results, it has shown that RAO-pitch has the linear relationship with the increase of moment of the frame and the curvature of pontoon is reversely proportional to the stiffness of pontoon. By synthesizing these results, an estimation method is proposed, which predicts the moment of frame of the different depth of pontoon based on the analysis result of an arbitrary depth of a floating pontoon. The estimation result shows considerably good agreement, compared with the analysis result.

A Parallel Axial-Flexural Hinge Model for Nonlinear Dynamic Progressive Collapse Analysis of Welded Steel Moment Frames (용접 철골모멘트골조의 비선형 동적 연쇄붕괴해석을 위한 병렬 소성힌지 모델의 개발)

  • Lee, Cheol Ho;Kim, Seon Woong;Lee, Kyung Koo
    • Journal of Korean Society of Steel Construction
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    • v.21 no.2
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    • pp.155-164
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    • 2009
  • In this study, a computationally efficient parallel axial-flexural plastic hinge model is proposed for nonlinear dynamic progressive collapse analysis of welded steel moment frames. To this end, post-yield flexural behavior and the interaction of bending moment and axial force of the double-span beams in the column's missing event was first investigated by using material and geometric nonlinear parametric finite element analysis. A piece-wise linear parallel point hinge model that captures the moment-axial tension interaction was then proposed and applied to nonlinear dynamic progressive collapse analysis of welded steel moment frames with the use of the OpenSees Program. The accuracy as well as the efficiency of the proposed model was verified based on the inelastic dynamic finite element analysis results. The importance of including the catenary action effects for proper progressive collapse resistant analysis and design was also emphasized.