• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.454-457
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• 2011

본 논문에서는 국내에서 아직 기준이 마련되지 않은 제진설계에 대한 접근을 소개하였다. ASCE 7-05 기준에 근거하여 국내 5층 규모의 철근콘크리트 신축 건물에 제진 설계를 수행하였다. 우리나라의 현행 기준을 만족하면서 효과적인 제진 시스템 설계를 위한 방법을 소개한다. ASCE 7-05 기준에서는 제진 구조물 해석 시 부재력이 공칭강도의 1.5배를 초과하지 않은 경우 경계비선형 해석을 허용하고 있다. 이 때의 제진 설계 프로세스는 기존의 중력하중 및 등가정적하중의 75%에 의한 단면을 가정하여 부재설계를 실시하고, 선형 시간이력 해석을 통해 제진장치 및 가새를 설계한다. 이후 우리나라 실정에 맞도록 보정된 인공 지진파를 입력하여 경계비선형 해석을 실시하고, 밑면 전단력 및 층간변위 등의 만족여부를 검토한다. 이 때 목표성능을 완전탄성설계 또는 유사탄성설계로 정하여 목표성능을 만족하는지도 검토하여야 한다. 본 논문에 적용한 신축 건물은 유사탄성 설계를 위해 경계비선형 해석을 실시하였고, 가장 효과적인 제진 설계를 위해 댐퍼의 종류, 설치방법, 개수, 변위 증폭비 등을 변수로 한 case study를 진행하였다. 해석 결과 목표성능을 만족하는 범위 내에서 가장 효과적인 제진 설계는 점성댐퍼, 이층 토글형태, 증폭비 2.0, 총 8개의 댐퍼를 설치하는 것으로 나타났다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.742-745
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• 2010

본 논문은 초고층구조물의 해석방법으로 탄성변형과 아울러 시간의존성을 가진 크리프와 건조수축에 의한 비탄성변형을 고려한 비선형 시공단계 해석법을 제시한다. 기존의 초고층구조물 해석에서 주로 행하는 기둥 축소량 해석은 실무자의 경험과 프로그램을 통한 간략화에 맞추어져 있다. 이는 실제 시공 시 발생하는 구조해석 요소들을 충분히 반영하지 못하여 계산 값과 실제 값 사이에 오차가 발생된다. 비선형 시공단계 해석은 실제 시공 때 발생되는 해석변수들을 고려한 단계별 해석의 수행이 가능하며, 시간의 의존성을 가진 creep과 shrinkage의 효과를 함께 고려하여 일괄해석의 문제점을 구조해석 단계에서 실제상황에 가까운 해석을 가능하게 할 수 있다. 이를 위해 시공단계해석이 가능한 범용 프로그램을 이용한 50층 규모의 3차원 골조 프레임 모델 예제 해석을 통하여 기존 해석법들과의 비교, 분석으로 시간의 의존성을 고려한 시공단계해석의 필요성을 제시한다. 본 논문에는 범용프로그램인 SAP2000(ver.14)와 CEB-FIP모델 코드를 사용 하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.89-92
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• 2009

본 논문에서는 비선형구조물의 위상최적화를 위하여 개발된 요소 연결 매개법 (Element Connectivity Parameterization Method)을 이용하여 기하비선형 구조물의 고유진동수(Eigenfrequency)를 최적화하는 연구를 소개한다. 기존의 밀도를 기반으로 한 위상최적화기법은 비선형 구조물의 위상최적화를 수행할 때 약한 탄성계수를 가지는 요소가 대변형을 일으켜 전체 강성행렬(Tangent Stiffness Matrix)이 양정정성(Positive definiteness)를 잃어버리는 문제점이 있어서 위상최적화를 수행하기 어렵다. 이 문제점을 해결하기 위하여 최근에 요소 연결 매개법(Element Connectivity Parameterization Method)이 개발되었다. 이 요소 연결 매개법은 요소의 강성을 설계하는 것이 아니라 요소의 연결성을 설계하는 기법으로 이를 이용하여 비선형 구조물의 위상최적화를 효과적으로 수행할 수 있다. 이 연구에서는 요소 연결 매개법을 동적인 문제에 적용하기 위한 연구를 수행하며 이를 이용하여 비선형 구조물의 고유진동수를 최적화 하는 위상최적화 문제에 적용하였다. 비선형 수치 예제를 통하여 기하 비선형 구조물의 고유진동수를 최대화를 통하여 기하 비선형 구조물의 강성최대화 문제와 같은 결과를 얻을 수 있었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.6
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• pp.45-53
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• 2011

The purpose of this study was to propose a design procedure for a damped structure with a friction damper for an existing structure. The target displacement of the damped structure was determined using the maximum displacement of the existing structure. The displacement of the damped structures was predicted using a proposed equation for the inelastic displacement ratio. For this study, we conducted a nonlinear response history analysis using 80 earthquake ground motions to verify the validity of the proposed design procedure by comparing the responses of the damped and undamped structures. Based on the dynamic analysis results, it was concluded that the predicted displacement of the damped structure using the proposed design procedure matched well with the analysis results.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.197-206
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• 2003

The optimal design method in cooperation with a nonlinear elastic analysis method was presented. The proposed nonlinear elastic method overcame the drawback of the conventional LRFD method this approximately accounts for the nonlinear effect caused by using the moment amplification factors of and. The genetic algorithm uses a procedure based on the Darwinian notions of the survival of the fittest, where selection, crossover, and mutation operators are used to look for high performance among the sections of the database. They satisfy constraint functions and give the lightest weight to the structure. The objective function was set to the total weight of the steel structure. The constraint functions were load-carrying capacities, serviceability, and ductility requirement. Case studies for a two-dimensional frame, a three-dimensional frame, and a three-dimensional steel arch bridge were likewise presented.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.103-113
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• 2005

In the present study, the Direct Inelastic Design (DID) for steel structures developed in the previous study was improved to expand it applicability. The proposed design method can perform inelastic designs that address the design characteristics of steel structures: Group member design, discrete member sizes, variation of moment-carrying capacity according to axial force, connection types, and multiple design criteria and load conditions. The design procedure for the proposed method was established, and a computer program incorporating the design procedure was developed. The design results from the conventional elastic method and the DID were compared and verified by the existing computer program for nonlinear analysis. Compared with the conventional elastic design, the DID addressing the inelastic behavior reduced the total weight of steel members and enhanced the deformability of the structure. The proposed design method is convenient because it can directly perform inelastic design by using linear analysis for secant stiffness. Also, it can achieve structural safety and economical design by controlling deformations of the plastic hinges.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.2
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• pp.69-80
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• 2008

In this study, improved capacity spectrum method (CSM) is proposed. The method can account for higher mode contribution to the seismic response of MDOF systems. The CSM has been conveniently used for determining maximum roof displacement using both demand spectrum and capacity curve of equivalent SDOF system. Unlike the conventional CSM, the maximum roof displacement is determined without iteration using inelastic displacement ratio and R factor calculated from demand spectrum and capacity curve. Three moment resisting steel frames of 3-, 9- and 20-stories are considered to test the accuracy of the proposed method. Nonlinear response history analysis (NL-RHA) for three frames is also conducted, which is considered as an exact solution. SAC LA 10/50 and 2/50 sets of ground motions are used. Moreover, this study estimates maximum story drift ratios (IDR) using ATC-40 CSM and N2-method and compared with those from the proposed method and NL-RHA. It shows that the proposed CSM estimates the maximum IDR accurately better than the previous methods.

• Journal of Korean Association for Spatial Structures
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• v.9 no.4
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• pp.73-80
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• 2009

It is very important that predict the inelastic seismic behavior exactly for seismic performance evaluation of a building in the performance based seismic design. But, it is difficulty that predict the building behavior of actual and exact in simplified load-deformation relation of structural material and members. In this study, system ductility and story ductility capacity of building structure used to the Backbone hinge Model are estimated and compared considering the characteristics of load-deformation relation of structural material and members. Analyses results, bilinear hinge model has lower system ductility and story ductility demands than those of backbone hinge model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1509-1521
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• 2013

Social demand for the stability of structures lead to the development of the technology to accomplish it. The non-destructive seismic technique, which is able to assess structural integrity of infrastructures, belongs to this category. Seismic technique is focused on the measurement of seismic velocity propagating through the material, and has to utilize sensors coupled to material surface, which does not allow the testing to be performed on the fly. In this paper, a general vocal microphone, which works as a non-contact sensor, was adopted to facilitate seismic testing with mobility and efficiency improved. The target of using microphones was oriented toward quality assessment of compacted subgrade, stiffness evaluation and health monitoring of concrete structures. Experimental parametric study and field applications were performed to investigate reliability and efficiency of microphones. Finally, the optimal test configuration of microphones was suggested for resonance tests and surface-wave tests.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.5
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• pp.35-44
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• 2011

PGA (Peak Ground Acceleration) is the parameter which indicates the peak value for strong ground motion and is mainly due to the intensity of the seismic wave. Usually, seismic waves can consist of different characteristics and can have different effects on structures. Therefore, it may be undesirable that the effects of a seismic wave are evaluated only based on the PGA. In this study, time history analysis was executed with a single degree of freedom model for inelastic seismic analysis. The numerical model was assumed to be a perfect elasto-plastic model. Input accelerations were made with El Centro NS (1940), other earthquake records and artificial earthquakes. The displacement ductility demand and cumulative dissipated energy, which were calculated from other artificial earthquakes, were compared. As a result, different responses from other seismic waves which have the same PGA were identified. Therefore, an index which could reflect both seismic and structural characteristics is needed. The SI (Spectrum Intensity) scale which could be obtained from integration by parts of the velocity response spectrum could be an index reflecting the inelastic seismic response of structures. It can be possible to identify from correlation analysis among the SI scale, displacement ductility demand and cumulative dissipated energy that the SI scale is sufficient to be an index for the inelastic response of structures under seismic conditions.