• 한국강구조학회 논문집
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• 제18권3호
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• pp.361-371
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• 2006

최근 전통적인 구조 최적화 알고리즘의 단점을 극복하기 위해서 부재 변위기여도를 이용뼈 부재 사이즈를 조절함으로써 건물의 변위을 만족시키는 재분배기법이 실용적인 고층 건물 변위설계법으로 인식되고 있다. 재분배 기법을 이용한 변위 설계법은 변위에 효과적인 부재는 물량은 증가시키고, 변위제어에 효과적이지 못한 부재의 물량은 감소시키는 방법으로 변위를 제어한다. 기존 연구에서 재분배 기법은 동적 변위기여도에 근거하여 지진하중을 받는 철골 구조물의 변위를 효과적으로 제어할 수 있었다 기존의 연구에서 재분배 기법은 정하중과 지진하중을 받는 고층 건물의 변위를 효과적으로 제어할 수 있었으나, 재분배 기법으로 설계된 구조물의 비선형 성능에 대한 평가는 이루어 지지 못했다. 본 연구에서는 변위 제어 뿐 만 아니라 비선형 특성을 함께 개선할 수 있는 재분배 기법을 개발하기 위한 기초 연구로서, 재분배 기법의 비선형 특성 평가 모델을 개발하고, 이를 구조 시스템 중에서 가장 단순한 형태인 철골 모멘트 저항 골조 예제에 적용히여 철골 모멘트 저항 골조에 대한 재분배 기법의 비선형 특성을 평가하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.367-374
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• 2000

This study investigates the effect of hysteretic characteristics to the Inelastic Demand Spectrum (IDS) which was expressed by an acceleration(Sa) and a displacement response spectrum (Sd). Elasto Perfectly Plastic(EPP) model is used in this study and inelastic demand spectrum (Sa vs, Sd) are obtained from a given target ductility ratio. For a given target ductility ratio IDS can be obtained by using nonlinear time history analysis of single degree of system with forth five recorded earthquake ground motions for stiff soil site. The effect EPP model under demand spectrum is investigated by ductility factor and natural frequency. According to the results obtained in this study IDS has dependency on ductility factor and natural frequency.

• Structural Engineering and Mechanics
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• 제26권5호
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• pp.545-556
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• 2007

In this paper, a hybrid boundary element technique is implemented to analyze nonlinear transient pile soil interaction in Gibson type nonhomeogenous soil. Inelastic modeling of soil media is presented by introducing a rational approximation to the continuum with nonlinear interface springs along the piles. Modified $\ddot{O}$zdemir's nonlinear model is implemented and systems of equations are coupled at interfaces for piles and pile groups. Linear beam column finite elements are used to model the piles and the resulting governing equations are solved using an implicit integration scheme. By enforcing displacement equilibrium conditions at each time step, a system of equations is generated which yields the solution. A numerical example is performed to investigate the effects of nonlinearity on the pile soil interaction.

• 한국지진공학회논문집
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• 제20권7_spc호
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• pp.495-502
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• 2016

In this paper, time and frequency domain characteristics of Gyeong-ju earthquakes were investigated, and nonlinear time history analyses were conducted for bi-linear hysteretic structures excited by short-duration ground accelerations. Previous studies showed that larger inelastic displacements than the peak displacement of the corresponding elastic system were observed especially for the structures with structural period shorter than 0.3s, and the similar results could be obtained when long-duration ground accelerations were used as excitation loads. For the short-duration earthquakes, however, the inelastic displacements were not so large and almost identical to the peak elastic displacements.

• Earthquakes and Structures
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• 제20권3호
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• pp.239-260
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• 2021

Torsional response of buildings is attributed to poor structural configurations in plan, which arises due to two factors - torsional eccentricity and torsional flexibility. Usually, building codes address effects due to the former. This study examines both of these effects. Buildings with torsional eccentricity (e.g., those with large eccentricity) and with torsional flexibility (those with torsional mode as a fundamental mode) demand large deformations of vertical elements resisting lateral loads, especially those along the building perimeter in plan. Lateral-torsional responses are studied of unsymmetrical buildings through elastic and inelastic analyses using idealised single-storey building models (with two degrees of freedom). Displacement demands on vertical elements distributed in plan are non-uniform and sensitive to characteristics of both structure and earthquake ground motion. Limits are proposed to mitigate lateral-torsional effects, which guides in proportioning vertical elements and restricts amplification of lateral displacement in them and to avoid torsional mode as the first mode. Nonlinear static and dynamic analyses of multi-storey buildings are used to validate the limits proposed.

• Structural Engineering and Mechanics
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• 제41권2호
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• pp.157-181
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• 2012

The paper presents a review of the application of the newly proposed mixed finite element model for seismic simulation of different types of composite frame structures. To evaluate the performance of the element, a comparison with displacement-based and force-based models is conducted. The study revealed that the mixed model is superior to the others in terms of both speed of convergence and numerical stability, and is therefore considered the most practical approach for modeling of composite structures. In this model, the element is derived using independent force and displacement shape functions. The nonlinear response of the frame element is based on the section discretization into fibers with uniaxial material models. The interfacial behavior is modeled using an inelastic interface element. Numerical examples to clarify the advantages of the model are presented for the following structural applications: anchored reinforcing bar problems, composite steel-concrete girders with deformable shear connectors, beam on elastic foundation elements, R/C girders strengthened with FRP sheets, R/C beam-columns with bond-slip, and prestressed concrete girders. These studies confirmed that the model represents a major advancement over existing elements in simulating the inelastic behavior of composite structures.

• Earthquakes and Structures
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• 제20권4호
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• pp.457-471
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• 2021

This study aims at providing a simple and effective methodology to define a meaningful characteristic period for special class of earthquake records named "pulse-like ground motions". In the proposed method, continuous wavelet transform is employed to extract the large pulse of ground motions. Then, Fourier amplitude spectra obtained from the original ground motion and the residual motion is simply compared. This comparison permits to define a threshold pulse-period (Tp∗) as the threshold period above which the pulse component has negligible contributions to the Fourier amplitude spectrum. The effect of pulse on frequency content of motions was discussed on the light of this definition. The advantage and superior features of the new definition were related to the inelastic displacement ratio (IDR) for single-degree-of-freedom systems with period equal to one half of the threshold period. Analyses performed for the proposed period at three ductility levels u=2,4,6 were compared with the results obtained at half of pulse period derived from wavelet analysis, peak-point method and the peak of product of the velocity and the displacement response spectra (Sv x Sd). According to the results, pulse effects on inelastic displacement ratio seem to be more important when $\frac{T_p^*}{T}=2$ (T is the fundamental vibration period of system). The results showed that utilizing of the proposed definition could facilitate an enhanced understanding of pulse-like records features.

• 한국지진공학회논문집
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• 제19권5호
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• pp.239-246
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• 2015

Reinforced concrete shear walls are effective for resisting lateral loads imposed by wind or earthquakes. Observed damages of the shear wall in recent earthquakes in Chile(2010) and New Zealand(2011) exceeded expectations. Various analytical models have been proposed in order to incorporate such response features in predicting the inelastic response of RC shear walls. However, the model has not been implemented into widely available computer programs, and has not been sufficiently calibrated with and validated against extensive experimental data at both local and global response levels. In this study, reinforced concrete shear walls were modeled with fiber slices, where cross section and reinforcement details of shear walls can be arranged freely. Nonlinear analysis was performed by adding nonlinear shear spring elements that can represent shear deformation. This analysis result will be compared with the existing experiment results. To investigate the nonlinear behavior of reinforced concrete shear walls, reinforced concrete single shear walls with rectangular wall cross section were selected. The analysis results showed that the yield strength of the shear wall was approximately the same value as the experimental results. However, the yielding displacement of the shear wall was still higher in the experiment than the analysis. The analytical model used in this study is available for the analysis of shear wall subjected to high axial forces.

• Structural Engineering and Mechanics
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• 제27권6호
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• pp.697-711
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• 2007

Though extensive research has been carried out for the ultimate strength of steel reinforced concrete (SRC) members under static and cyclic load, there was only limited information on the applied analysis models. Modeling of the inelastic response of SRC members can be accomplished by using a microcosmic model. However, generally used microcosmic model, which usually contains a group of parameters, is too complicated to apply in the nonlinear structural computation for large whole buildings. The intent of this paper is to develop an effective modeling approach for the reliable prediction of the inelastic response of SRC columns. Firstly, five SRC columns were tested under cyclic static load and constant axial force. Based on the experimental results, normalized trilinear skeleton curves were then put forward. Theoretical equation of normalizing point (ultimate strength point) was built up according to the load-bearing mechanism of RC columns and verified by the 5 specimens in this test and 14 SRC columns from parallel tests. Since no obvious strength deterioration and pinch effect were observed from the load-displacement curve, hysteresis rule considering only stiffness degradation was proposed through regression analysis. Compared with the experimental results, the applied analysis model is so reasonable to capture the overall cyclic response of SRC columns that it can be easily used in both static and dynamic analysis of the whole SRC structural systems.

• 한국산학기술학회논문지
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• 제10권4호
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• pp.838-845
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• 2009

본 논문은 내진성능평가를 위해 사용되는 비탄성해석의 신뢰도와 정확도에 있어 결정적인 영향을 미치는 다양한 이력모델의 특성과 구조물의 내진거동에 미치는 영향을 분석하고자 한다. 연구대상은 표준학교건물로서 외국의 지진 가속도와 우리나라 규준에 맞는 인공지진 가속도 3가지를 건물의 장 단변방향 평면골조에 가한 후, 다양한 이력 모델을 적용하여 2차원 시간이력해석을 수행하고 비탄성응답을 구하고 층전단력, 층간변위비, 층변위를 비교하고 힌지의 발생 상태를 분석해 이력모델이 건물의 비탄성거동에 미치는 영향을 분석하였다. 그 결과, 단변방향에서는 층전 단력과 층간변위비 모두 최대값은 수정다케다모델에서, 최소값은 외국지진에 대해서는 클라프모델, 국내지진에 대해서는 강성저감 삼선형모델과 수정다케다모델에서 각각 발생하는 것으로 평가되었다. 하지만, 장변방향에서 외국지진은 강성저감 삼선형모델이, 국내지진은 수정다케다모델이 최대 층전단력을 보였고 층간변위비는 최대값은 수정다케다 모델에서, 최소값은 외국지진의 경우 클라프모델에서, 국내지진의 경우 다케다모델에서 나타났다. 장변방향에서 외국지진은 층전단력와 층간변위가 클라프모델에서 안전율을 낮게 보는 반면 국내지진에서는 수정다케다모델이 안전율을 낮게 평가하는 상이한 결과가 발생했다.