• 한국강구조학회 논문집
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• 제21권2호
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• pp.105-113
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• 2009

가새골조 성능을 개선하기 위해 연결부 (거싯 플레이트) 강도, 강성, 연성이 골조 디자인에 직접적으로 고려되어야 한다. 연결부의 강도는 지진력에 저항하도록 디자인 되어야하고 필요한 골조시스템의 연성을 확보하는데 기여해야한다. 그리고 연결부의 강성은 구조요소와 연결부의 동적 반응과 변위 요구에 영향을 준다. 이 논문에서 지난 실험 결과를 이용하여 거싯 플레이트 연결부에 대한 현 디자인 모델을 검토하고 평가한다. 현 디자인 모델은 연결부 디자인 가이드라인을 주기엔 적절하지 못하고 실제 거싯 플레이트의 응력과 변위 상태는 비선형이고 굉장히 복잡하다. 구조 디자이너들은 시스템과 연결부의 성능을 대략적으로 예측하기 위해 보와 기둥을 포함한 단순한 모델을 원한다. 이를 위해 단순화한 디자인 모델이 개발되고 평가된다. 이 모델은 비교적 정확하고 신뢰성 있는 연결부 강성 평가를 제공한다.

• 한국전산구조공학회논문집
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• 제24권6호
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• pp.629-636
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• 2011

최근 들어 여러 테러에 의한 폭발사건에서 유발된 위험상황에서 보듯이 폭발에 의한 인명피해나 시설물의 손상은 우리가 고려하는 재해수준을 넘는 비참한 결과를 항상 수반한다. 하지만 폭발에 대한 구조물의 설계는 그 연구나 대책이 상당히 미비한 실정이다. 이에 미국건물설계기준(UBC94)을 바탕으로 내진설계(Welded Moment Resistant Frame)된 10층 건물의 폭발에 대한 해석적 모델을 제공하고자 한다. 현재 폭발하중의 정량적인 결과는 미국 육군(U.S.Department of Army)에서 개발된 경험적 방법에 기반을 둔 프로그램을 통해 폭간거리에 따른 하중의 크기와 분포를 알 수 있다. 본 연구에 사용된 폭원의 성격은 반구형 표면 폭발(Hemispherical Surface Burst)의 경우를 사용하였으며, 또한 선형 및 비선형 시간 이력해석을 통해 건물의 변위, 상대변위, 요구/수행비 및 비선형 거동에 대한 해석적 결과를 제공하였다. 또한 현재 사용되고 있는 내진기준(FEMA356)에 적용하여 소성힌지의 거동을 통해 폭발에 대한 건물의 성능수준을 예상하였다.

• Structural Engineering and Mechanics
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• 제51권3호
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• pp.487-502
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• 2014

In buildings structures, the flexural stiffness reduction of beams and columns due to concrete cracking plays an important role in the nonlinear load-deformation response of reinforced concrete structures under service loads. Most Seismic Design Codes do not precise effective stiffness to be used in seismic analysis for structures of reinforced concrete elements, therefore uncracked section properties are usually considered in computing structural stiffness. But, uncracked stiffness will never be fully recovered during or after seismic response. In the present study, the effect of concrete cracking on the lateral response of structure has been taken into account. Totally 120 cases of 3 Dimensional Dynamic Analysis which considers the real and accidental torsional effects are performed using ETABS to determine the effective structural system across the height, which ensures the performance and the economic dimensions that achieve the saving in concrete and steel amounts thus achieve lower cost. The result findings exhibits that the dual system was the most efficient lateral load resisting system based on deflection criterion, as they yielded the least values of lateral displacements and inter-storey drifts. The shear wall system was the most economical lateral load resisting compared to moment resisting frame and dual system but they yielded the large values of lateral displacements in top storeys. Wall systems executes tremendous stiffness at the lower levels of the building, while moment frames typically restrain considerable deformations and provide significant energy dissipation under inelastic deformations at the upper levels. Cracking found to be more impact over moment resisting frames compared to the Shear wall systems. The behavior of various lateral load resisting systems with respect to time period, mode shapes, storey drift etc. are discussed in detail.

• 한국전산구조공학회논문집
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• 제25권3호
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• pp.259-266
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• 2012

본 논문에서는 벽식 구조시스템의 일부 전단벽을 제거하여 공간의 가변성을 높인 무량복합 구조시스템의 내진성능을 ATC-63에 제시되어 있는 절차에 따라 파악하였으며, 동일한 규모의 벽식 구조시스템의 내진성능과 비교하였다. 해석모델로 12층 무량복합 및 벽식 구조시스템을 KBC 2009에 따라 설계하고 비선형 정적 및 비선형 증분 동적해석(IDA)을 수행하여 지진응답 및 붕괴거동을 파악하였다. 무량복합 시스템은 벽식 구조시스템 보다 적은 양의 콘크리트 물량으로 설계되었으며, 동일한 지진하중에 대하여 좀 더 큰 변위응답을 보이는 것으로 나타났다. IDA 해석결과 얻어진 붕괴 여유비(CMR)는 ATC-63에 제시된 한계상태를 만족하여 설계지진하중에 대하여 충분한 내진성능을 보유한 것으로 나타났다.

• 한국농공학회지
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• 제39권3호
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• pp.72-82
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• 1997

In all inelastic deformations time rate effects are always present to some degree. Whether or not their exclusion has a significant influence on the prediction of the material behaviour depends upon several factors. In the study of structural components under static loading conditions at normal temperature it is accepted that time rate effects are generally not important. However metals, especially under high temperatures, exhibit simultaneously the phenomena of creep and viscoplasticity. In this study, elastoplastic and elasto-viscoplastic models include nonlinear geometrical effects were developed and several numerical examples are also included to verify the computer programming work developed here in this work. Comparisons of the calculated results, for the elasto-viscoplastic analysis of an internally pressurised thick cylinder under plane strain condition, have shown that the model yields excellent results. The results obtained from the numerical examples for an elasto-viscoplastic analysis of the Nuclear Reinforced Concrete Containment Structure(NRCCS) subjected to an incrementally applied internal pressure were summarized as follows : 1. The steady state hoop stress distribution along the shell layer of dome and dome wall junction part of NRCCS were linearly behave and the stress in interior surfaces was larger than that in exterior. 2.However in the upper part of the wall of NRCCS the steady state hoop stress in creased linearly from its inner to outer surfaces, being the exact reverse to the previous case of dome/dome-wall junction part. 3.At the lower part of wall of NRCCS, the linear change of steady state hoop stress along its wall layer began to disturb above a certain level of load increase.

• Earthquakes and Structures
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• 제16권4호
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• pp.469-485
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• 2019

A numerical investigation regarding local (${\mu}_L$) and story (${\mu}_S$) ductility demand evaluation of steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF), is conducted in this study. The interior connections are modeled, firstly as perfectly pinned (PP), and then as semi-rigid (SR). Three models used in the SAC steel project, representing steel buildings of low-, mid-, and high-rise, are considered. The story ductility reduction factor ($R_{{\mu}S}$) as well as the ratio ($Q_{GL}$) of $R_{{\mu}S}$ to ${\mu}_L$ are calculated. ${\mu}_L$ and ${\mu}_S$, and consequently structural damage, at the PMRF are significant reduced when the usually neglected effect of SR connections is considered; average reductions larger than 40% are observed implying that the behavior of the models with SR connections is superior and that the ductility detailing of the PMRF doesn't need to be so stringent when SR connections are considered. $R_{{\mu}S}$ is approximately constant through height for low-rise buildings, but for the others it tends to increase with the story number contradicting the same proportion reduction assumed in the Equivalent Static Lateral Method (ESLM). It is implicitly assumed in IBC Code that the overall ductility reduction factor for ductile moment resisting frames is about 4; the results of this study show that this value is non-conservative for low-rise buildings but conservative for mid- and high-rise buildings implying that the ESLM fails evaluating the inelastic interstory demands. If local ductility capacity is stated as the basis for design, a value of 0.4 for $Q_{GL}$ seems to be reasonable for low- and medium-rise buildings.

• Earthquakes and Structures
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• 제21권5호
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• pp.551-562
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• 2021

In this study, the generalized intensity measure (IM) named I_Npg is analyzed. The recently proposed proxy of the spectral shape named N_pg is the base of this intensity measure, which is similar to the traditional N_p based on the spectral shape in terms of pseudo-acceleration; however, in this case the new generalized intensity measure can be defined through other types of spectral shapes such as those obtained with velocity, displacement, input energy, inelastic parameters and so on. It is shown that this IM is able to increase the efficiency in the prediction of nonlinear behavior of structures subjected to earthquake ground motions. For this work, the efficiency of two particular cases (based on acceleration and velocity) of the generalized I_Npg to predict the peak floor acceleration demands on steel frames under 30 earthquake ground motions with respect to the traditional spectral acceleration at first mode of vibration Sa(T₁) is compared. Additionally, a 3D reinforced concrete building and an irregular steel frame is used as a basis for comparison. It is concluded that the use of velocity and acceleration spectral shape increase the efficiency to predict peak floor accelerations in comparison with the traditional and most used around the world spectral acceleration at first mode of vibration.

• 한국농공학회지
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• 제39권4호
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• pp.106-113
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• 1997

Dynamic loading of structures often causes excursions of stresses well into the inelastic range, and the influence of the geometric changes on the dynamic response is also significant in many cases. Therefore, both material and geometric nonlinearity effects should be considered in case that a dynamic load acts on the structure. A structure in a nuclear power plant is a structure of importance which puts emphasis on safety. A nuclear container is a pressure vessel subject to internal pressure and this structure is constructed by a reinforced concrete or a pre-stressed concrete. In this study, the material nonlinearity effect on the dynamic response is formulated by the elasto-viscoplastic model highly corresponding to the real behavior of the material. Also, the geometrically nonlinear behavior is taken into account using a total Lagrangian coordinate system, and the equilibrium equation of motion is numerically solved by a central difference scheme. The constitutive relation of concrete is modeled according to a Drucker-Prager yield criterion in compression. The reinforcing bars are modeled by a smeared layer at the location of reinforcements, and the steel layer model under Von Mises yield criteria is adopted to represent an elastic-plastic behavior. To investigate the dynamic response of a nuclear reinforced concrete containment structure, the steel-ratios of 0, 3, 5 and 10 percent, are considered. The results obtained from the analysis of an example were summarized as follows 1. As the steel-ratio increases, the amplitude and the period of the vertical displacements in apex of dome decreased. The Dynamic Magnification Factor(DMF) was some larger than that of the structure without steel. However, the regular trend was not found in the values of DMF. 2. The dynamic response of the vertical displacement and the radial displacement in the dome-wall junction were shown that the period of displacement in initial step decreased with the steel-ratio increases. Especially, the effect of the steel on the dynamic response of radial displacement disapeared almost. The values of DMF were 1.94, 2.5, 2.62 and 2.66, and the values increased with the steel-ratio. 3. The characteristics of the dynamic response of radial displacement in the mid-wall were similar to that of dome-wall junction. The values of DMF were 1.91, 2.11, 2.13 and 2.18, and the values increased with the steel-ratio. 4. The amplitude and the period of the hoop-stresses in the dome, the dome-wall junction, and the mid-wall were shown the decreased trend with the steel-ratio. The values of DMF were some larger than those of the structure without steel. However, the regular trend was not found in the values of DMF.

• 한국전산구조공학회논문집
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• 제26권6호
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• pp.455-462
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• 2013

최근에 지어진 건축물의 경우 지진에 대한 안전성을 확보하고 있지만, 내진설계 도입 이전의 건축물은 지진에 대해 매우 취약하다. 본 연구에서는 내진성능이 부족한 기존 저층 RC구조물의 지진 발생 시 안전성 확보를 위한 내진보강 방안으로 격자강판 전단벽을 제안하고 내진성능평가를 수행하였다. 횡력저항요소로 사용된 격자강판 전단벽의 탄소성 이력특성값은 실험결과를 토대로 횡력저항 기여도등을 평가하여 작성된 이선형곡선을 적용하였다. 비탄성 정적해석을 통해 대상구조물의 성능점을 찾아내어 적용 지진하중에 대한 응답과 성능수준을 평가하였다. 격자강판 전단벽을 적용한 경우, 보강 전에 비하여 응답변위가 약 42% 저감되는 것을 확인할 수 있었으며, 성능점에서 거의 탄성거동을 보여주고 있어 목표성능인 인명안전수준을 만족시켰다. 또한 반응수정계수를 산정하여 내진보강 효과를 검증하였으며, 보강 전과 후에 각각 2.17에서 3.25로 증가하여 설계기준을 초과하였다. 따라서 격자강판 전단벽에 의해 대상 구조물의 강도 및 강성보강이 적절히 수행된 것으로 판단된다.

• 한국강구조학회 논문집
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• 제17권1호통권74호
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• pp.63-71
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• 2005

최근 기존의 합성 기둥들이 가지는 단점은 보완하고 장점은 유지시킬 수 있는 효율적인 기둥 시스템으로 철골-콘크리트 합성 기둥(SC 합성 기둥)에 대한 연구가 수행되고 있다. 본 연구자는 선행 실험 연구를 통해 SC 합성 기둥의 압축 내력을 평가하였지만, 실험실의 용량 부족으로 대형 기둥에서의 실험은 수행하지 못하였다. 따라서 이 연구에서는 실험 연구의 후속 연구로서 범용 유한요소 해석프로그램을 이용하여 콘크리트와 철골의 상호 작용 및 비조밀단면을 가진 철골 플랜지의 국부좌굴을 반영할 수 있도록 하였다. 이러한 유한요소해석 모델은 기 수행된 압축 실험값과 비교하여 적합성을 검증하였다. 또한 이렇게 검증된 해석적 모델을 이용하여 대형 크기의 기둥에 대해 비선형 해석을 수행하여 단면 증대에 따른 SC 합성 기둥의 비선형 거동에 대해 비교 분석하였다. 비선형 해석 결과 SC 합성 기둥의 철골 단면의 폭-두께비는 25.0을 초과하지 않아야 하고, 연결재의 단면적은 $0.025d{\cdot}t$ 이상, 연결재의 간격은 d/2 또는 최대 300mm이하로 설치하는 것이 바람직하다는 결론을 얻었다.