• Earthquakes and Structures
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• 제15권3호
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• pp.319-334
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• 2018

In this paper, an analytical study was carried out to propose an optimum base-isolated system for the design of steel structures equipped with lead rubber bearings (LRB). For this, 5 and 10-storey steel moment resisting frames (MRFs) were designed as Special Moment Frame (SMF). These two-dimensional and three-bay frames equipped with a set of isolation systems within a predefined range that minimizes the response of the base-isolated frames subjected to a series of earthquakes. In the design of LRB, two main parameters, namely, isolation period (T) and the ratio of strength to weight (Q/W) supported by isolators were considered as 2.25, 2.5, 2.75 and 3 s, 0.05, 0.10 and 0.15, respectively. The Force-deformation behavior of the isolators was modelled by the bi-linear behavior which could reflect the nonlinear characteristics of the lead-plug bearings. The base-isolated frames were modelled using a finite element program and those performances were evaluated in the light of the nonlinear time history analyses by six natural accelerograms compatible with seismic hazard levels of 2% probability of exceedance in 50 years. The performance of the isolated frames was assessed in terms of roof displacement, relative displacement, interstorey drift, absolute acceleration, base shear and hysteretic curve.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.698-703
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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 piecewise 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.

• Earthquakes and Structures
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• 제10권1호
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• pp.73-89
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• 2016

The seismic performance of moment frames could vary according to the rotation capacity of their connections. The minimum rotation capacity of moment connections for steel intermediate moment frames (IMF) was defined as 0.02 radian in AISC 341-10. This study evaluated the seismic performance of IMF frames with connections having a rotation capacity of 0.02 radian. For this purpose, thirty IMFs were designed according to current seismic design provisions considering different design parameters such as the number of stories, span length, and seismic design categories. The procedure specified in FEMA P695 was used for conducting seismic performance evaluation. It was observed that the rotation capacity of 0.02 radian could not guarantee the satisfactory seismic performance of IMFs. This study also conducted seismic performance evaluation for IMFs with connections having the rotation capacity of 3% and ductile connections for proposing the minimum rotation capacity of IMF connections.

• 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.

• 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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• 제44권1호
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• pp.49-63
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• 2022

This study aims to develop ensemble machine learning (ML) models for estimating the peak floor acceleration and maximum top drift of steel moment frames. For this purpose, random forest, adaptive boosting, gradient boosting regression tree (GBRT), and extreme gradient boosting (XGBoost) models were considered. A total of 621 steel moment frames were analyzed under 240 ground motions using OpenSees software to generate the dataset for ML models. From the results, the GBRT and XGBoost models exhibited the highest performance for predicting peak floor acceleration and maximum top drift, respectively. The significance of each input variable on the prediction was examined using the best-performing models and Shapley additive explanations approach (SHAP). It turned out that the peak ground acceleration had the most significant impact on the peak floor acceleration prediction. Meanwhile, the spectral accelerations at 1 and 2 s had the most considerable influence on the maximum top drift prediction. Finally, a graphical user interface module was created that places a pioneering step for the application of ML to estimate the seismic demands of building structures in practical design.

• Steel and Composite Structures
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• 제49권1호
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• pp.47-64
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• 2023

Due to their efficient use of materials, hybrid reinforced concrete-steel (RCS) systems provide more practical and economic advantages than traditional steel and concrete moment frames. This study evaluated the seismic design factors and response modification factor 'R' of RCS composite moment frames composed of reinforced concrete (RC) columns and steel (S) beams. The current International Building Code (IBC) and ASCE/SEI 7-05 classify RCS systems as special moment frames and provide an R factor of 8 for these systems. In this study, seismic design parameters were initially quantified for this structural system using an R factor of 8 based on the global methodology provided in FEMA P695. For analyses, multi-story (3, 5, 10, and 15) and multi-span (3 and 5) archetypes were used to conduct nonlinear static pushover analysis and incremental dynamic analysis (IDA) under near-field and far-field ground motions. The analyses were performed using the OpenSees software. The procedure was reiterated with a larger R factor of 9. Results of the performance evaluation of the investigated archetypes demonstrated that an R factor of 9 achieved the safety margin against collapse outlined by FEMA P695 and can be used for the design of RCS systems.

• 한국강구조학회 논문집
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• 제21권2호
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• pp.155-164
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• 2009

본 논문에서는 용접철골모멘트골조의 비선형 동적 연쇄붕괴 해석을 위해 인장-휨 거동을 반영한 효율적인 병렬 소성힌지를 제안하였다. 본 목적을 위해 재료적/기하학적 비선형 유한요소해석을 이용한 변수연구를 통해 기둥이 손실된 2경간 보의 항복후 휨거동과 모멘트-축인장력 상호작용을 살펴보았다. 유한요소해석결과를 토대로 보의 모멘트-축인장력 상호작용 관계를 일련의 선형으로 근사화한 소성힌지모델을 제안하고, 이를 OpenSees 프로그램에 적용하여 용접철골모멘트골조의 비선형 동적 연쇄붕괴해석을 수행하였다. 비선형 동적 유한요소해석을 통하여 본 연구에서 제안한 힌지모델의 효율성과 정확도를 검증하였다. 또한 본 연구 결과는 연쇄붕괴 해석 및 설계에 적절한 현수작용효과의 포함여부가 중요함을 보여준다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.947-952
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• 2001

This study is to evaluate seismic performance of ordinary moment concrete frames. Base shear and roof displacement relations are obtained from the experiment of 3 story ordinary moment resisting concrete frame. The frame was designed only for gravity loads. The performance of the building is evaluated using capacity spectrum method. Five different seismic zones and three different soil types are considered. For each condition of seismic zone and soil type, ten earthquake ground motions are used to establish the demand spectrum.

• 한국강구조학회 논문집
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• 제21권3호
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• pp.267-275
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• 2009

본 논문에서는 기둥이 손실된 철골모멘트골조의 2경간 보의 동적거동 특성을 고찰하고 철골모멘트골조의 연쇄붕괴 예비평가를 위한 비선형 동적 근사해석법을 제안하였다. 기둥이 손실된 2경간 부분골조 모델의 동적거동의 분석을 통하여, 2경간 보의 중력하중과 보스팬-대-보춤 비가 최대 동적 변형요구의 지배적인 요소임을 확인하였다. 이를 토대로 2경간 보의 중력하중 변수와 최대 현회전각과의 관계를 기술하는 붕괴스펙트럼 개념을 새로이 제안하고 이의 활용법을 예시하였다. 3차원 비선형 동적 유한요소해석결과와 비교하여, 본 연구에서 제안한 방안이 용접 철골모멘트골조의 비선형 연쇄붕괴거동을 신속히 평가하는데 정확하면서도 매우 효율적임을 입증하였다.