• Steel and Composite Structures
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• 제28권2호
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• pp.139-147
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• 2018

Moment frames have considerable ductility against cyclic lateral loads and displacements; however, sometimes this feature causes the relative displacement to exceed the permissible limits. This issue can bring unfavorable hysteretic behavior on the frame due to the reduction in the stiffness and resistance against lateral loads. Most of common bracing systems usually control lateral displacements through increasing stiffness while result in decreasing the capacity for energy absorption. This has direct effect on hysteresis curves of moment frames. Therefore, a system that is capable of both having the capacity of energy absorption as well as controlling the displacements without a considerable increase in the stiffness is quite important. This paper investigates retrofitting of a single-storey steel moment frame using a delayed wire-rope bracing system equipped with the ductile middle steel plate. The steel plate is considered at the middle intersection of wire ropes, where it causes cables to be continuously in tension. This integrated system has the advantage of reducing considerable stiffness of the frame compared to cross bracing systems as a result of which it could also preserve the frame's energy absorption capacity. In this paper, FEM models of a delayed wire-rope bracing system equipped by steel plates with different geometries have been studied, validated, and compared with other researchers' laboratory test results.

• 한국강구조학회 논문집
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• 제14권5호통권60호
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• pp.577-591
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• 2002

지진 하중에 대한 강재 모멘트 골조의 합성 슬래브를 포함한 강재 보의 비탄성 거동을 모델하기 위한 합성 보 요소가 제안되고 강재 모멘트 골조의 지진 거동에 대한 합성 슬래브의 효과가 조사된다. 합성 보 요소는 단일 직렬 힌지 모델로 간주 될 수 있고, 그 해석 결과는 실험결과와 매우 합리적인 상관 관계를 보였다. 합성 보 요소는 기존의 강재 보 요소보다 상당히 좋은 거동을 보이고, 합성모델은 지진 하중 하에서의 구조물의 국부변형과 전체 응답을 기존의 강재 모델보다 정밀하게 예측할 수 있다. 합성 슬래브는 강재 모멘트 골조의 국부 및 전체 해석 응답에 상당히 큰 효과를 나타낸다.

• Steel and Composite Structures
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• 제47권4호
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• pp.489-502
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• 2023

The strong column-weak beam (SCWB) moment ratio is specified in AISC 341 to prevent an abrupt column sway in steel special moment frames (SMFs) during earthquakes. Even when the SCWB requirement is satisfied for an SMF, a column-sway can develop in the SMF. This is because the contribution of the composite beam action developed in the concrete floor slab and its supporting beams was not included while calculating the SCWB moment ratio. In this study, we developed a new method for calculating the SCWB moment ratio that included the contribution of composite beam action. We evaluated the seismic collapse performance of the SMFs considering various risk categories and building heights. We demonstrated that the collapse performance of the SMFs was significantly improved by using the proposed SCWB equation that also satisfied the target performance specified in ASCE 7.

• Steel and Composite Structures
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• 제11권4호
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• pp.273-290
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• 2011

In current ductility-based earthquake-resistant design, the estimation of design forces continues to be carried out with the application of response modification factors on elastic design spectra. It is well-known that the response modification factor (R) takes into account the force reduction, strength, redundancy, and damping of structural systems. The key components of the response modification factor (R) are force reduction ($R_{\mu}$) and strength ($R_S$) factors. However, the response modification and strength factors for structural systems presented in design codes were based on professional judgment and experiences. A numerical study has been accomplished to evaluate force reduction, strength, and response modification factors for special steel moment resisting frames. A total of 72 prototype steel frames were designed based on the recommendations given in the AISC Seismic Provisions and UBC Codes. Number of stories, soil profiles, seismic zone factors, framing systems, and failure mechanisms were considered as the design parameters that influence the response. The effects of the design parameters on force reduction ($R_{\mu}$), strength ($R_S$), and response modification (R) factors were studied. Based on the analysis results, these factors for special steel moment resisting frames are evaluated.

• 국제강구조저널
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• 제18권5호
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• pp.1684-1698
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• 2018

Fragility functions are determined for braced steel moment frames (SMFs) with plans such as square-, T-, L-, U-, trapezoidal-, and semicircular-shaped, subjected to blast. The frames are designed for gravity and seismic loads, but not necessarily for the blast loads. The blast load is computed for a wide range of scenarios involving different parameters, viz. charge weight, standoff distance, and blast location relative to plan of the structure followed by nonlinear dynamic analysis of the frames. The members failing in rotation lead to partial collapse due to plastic mechanism formation. The probabilities of partial collapse of the SMFs, with and without bracing system, due to the blast loading are computed to plot fragility curves. The charge weight and standoff distance are taken as Gaussian random input variables. The extent of propagation of the uncertainties in the input parameters onto the response quantities and fragility of the SMFs is assessed by computing Sobol sensitivity indices. The probabilistic analysis is conducted using Monte Carlo simulations. The frames have least failure probability for blasts occurring in front of their corners or convex face. Further, the unbraced frames are observed to have higher fragility as compared to counterpart braced frames for far-off detonations.

• Steel and Composite Structures
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• 제50권3호
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• pp.249-263
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• 2024

This article presents a comparative analysis of seismic behavior in steel-beam reinforced concrete column (RCS) frames versus steel and reinforced concrete frames. The study evaluates the seismic response and collapse behavior of RCS frames of varying heights through nonlinear modeling. RCS, steel, and reinforced concrete special moment frames are considered in three height categories: 5, 10, and 20 stories. Two-dimensional frames are extracted from the three-dimensional structures, and nonlinear static analyses are conducted in the OpenSEES software to evaluate seismic response in post-yield regions. Incremental dynamic analysis is then performed on models, and collapse conditions are compared using fragility curves. Research findings indicate that the seismic intensity index in steel frames is 1.35 times greater than in RCS frames and 1.14 times greater than in reinforced concrete frames. As the number of stories increases, RCS frames exhibit more favorable collapse behavior compared to reinforced concrete frames. RCS frames demonstrate stable behavior and maintain capacity at high displacement levels, with uniform drift curves and lower damage levels compared to steel and reinforced concrete frames. Steel frames show superior strength and ductility, particularly in taller structures. RCS frames outperform reinforced concrete frames, displaying improved collapse behavior and higher capacity. Incremental Dynamic Analysis results confirm satisfactory collapse capacity for RCS frames. Steel frames collapse at higher intensity levels but perform better overall. RCS frames have a higher collapse capacity than reinforced concrete frames. Fragility curves show a lower likelihood of collapse for steel structures, while RCS frames perform better with an increase in the number of stories.

• 한국디지털건축인테리어학회논문집
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• 제4권1호
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• pp.36-45
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• 2004

Allowable stress design method have been most widely used in steel structure in Korea. Recently, not only high-rise buildings but also medium or low-rise buildings were designed as steel structure. Most of low-rise steel buildings are designed as ordinary moment resisting frames(MRF). But MRFs don't have any lateral force resisting devices such as bracing in braced frames. This study focuses mainly on nonlinear seismic response analyses of small scale steel frames which will be used later as specimens for the evaluation of MRF's seismic performances. The main parameters of analyses are arrangement of column axis, $P-{\Delta}$ effect, acceleration factor etc. The object of this paper is to estimate the seismic performances of MRFs, which are mostly designed in Korea, through the results of response analyses.

• Steel and Composite Structures
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• 제25권3호
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• pp.271-286
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• 2017

The use of Hollow Structural Sections (HSS) provides an alternative for steel buildings in seismic zones, with the advantage over WF columns that the HSS columns have similar resistance along both axes and enhanced performance under flexure, compression and torsion with respect to other columns sections. The HSS columns have shown satisfactory performance under seismic loads, such as observed in buildings with steel moment frames in the Honshu earthquake (2011). The purpose of this research is to propose a new moment connection, EP-HSS ("End-plate to Hollow Structural Section"), using a wide flange beam and HSS column where the end plate falls outside the range of prequalification established in the ANSI/AISC 358-10 Specification, as an alternative to the traditional configuration of steel moment frames established in current codes. The connection was researched through analytical, numerical (FEM), and experimental studies. The results showed that the EP-HSS allowed the development of inelastic action on the beam only, avoiding stress concentrations in the column and developing significant energy dissipation. The experiments followed the qualification protocols established in the ANSI/AISC 341-10 Specification satisfying the required performance for highly ductile connections in seismic zones, thereby ensuring satisfactory performance under seismic actions without brittle failure mechanisms.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.233-238
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• 2000

The purpose of this study is to outline the analysis procedure for evaluating the performance of moment resisting steel frames. For this purpose, three ordinary moment resisting frames are designed in compliance to UBC 1994. The evaluation is performed by nonlinear static procedures using two analytical models. Only one analytical model using panel element can reflect the panel zone deformation explicitly. The limit values in FEMA 273 are used as guidelines of predicted demand parameters by which the performance of OMRFs may be assessed.

• 한국지진공학회논문집
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• 제16권4호
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• pp.1-8
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• 2012

국내 철골모멘트골조를 이전 KBC2005 및 현 KBC2009 기준에 따라 설계한 후 비선형동적해석을 이용하여 FEMA355F의 내진성능평가 절차에 따라 성능을 평가하였다. 그 결과 비선형정적 Push-over 해석을 이용한 역량스펙트럼법과 차이가 있었다. 특히 국내 철골모멘트골조는 약패널존을 가지기 때문에 비선형동적해석을 통해서만 보다 정확한 거동을 예측할 수 있었다. 국내 철골모멘트골조는 지반 조건 SB 또는 SC에 위치한다면 층수 및 R값에 관계없이 성능목표를 만족하는 것으로 나타났다. 하지만 지반 조건 SD 또는 SE에 위치한다면 성능목표 만족 여부는 명확하지 않았다. 따라서 KBC2005나 KBC2009 어떤 기준을 사용하더라도 지반 조건이 상대적으로 좋다면 국내 철골모멘트골조는 내진성능을 충분히 확보하고 있다고 볼 수 있다.