• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.57-64
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• 1998

This paper presents the cyclic seismic performance of slip-critically designed, high-strength bolted-beam splice in steel moment frame. Before the moment connection reaching its plastic strength, unexpected premature slippage occurred at the slip-critically designed beam splice during the test. The experimentally observed frictional coefficients were as low as about 50% to 60% of nominal (code) value. Nevertheless, the bearing type behavior mobilized after the slippage transferred the increasing cyclic loads successfully, i.e., the consequence of slippage into bearing was not catastrophic to the connection behavior. The test result seems to indicate that the traditional beam splice design basing upon (bolt-hole deducted) effective flange area criterion may not be sufficient in developing the plastic strength of moment connections under severe earthquake loading. New procedure for achieving slip-critical beam splice design is proposed based on capacity design concept.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.267-282
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• 2020

The seismic performance and failure modes of the dual system of moment resisting frames and thin steel plate shear walls (TSPSWs) without and with one or two outrigger trusses are studied in this paper. These structural systems were utilized to resist vertical and lateral loads of 40-storey buildings. Detailed Finite element models associated with nonlinear time history analyses were used to examine seismic capacity and plastic mechanism of the buildings. The analyses were performed under increased levels of earthquake intensities. The models with one and two outriggers showed good performance during the maximum considered earthquake (MCE), while the stress of TSPSWs in the model without outrigger reached its ultimate value under this earthquake. The best seismic capacity was in favour of the model with two outriggers, where it is found that increasing the number of outriggers not only gives more reduction in lateral displacement but also reduces stress concentration on thin steel plate shear walls at outrigger floors, which caused the early failure of TSPSWs in model with one outrigger.

• Structural Engineering and Mechanics
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• 제54권4호
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• pp.809-827
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• 2015

In this paper, seismic energy response of inelastic steel structures under earthquake excitations is investigated. For this purpose, a numerical procedure based on nonlinear dynamic analysis is developed by considering material, geometric and connection nonlinearities. Material nonlinearity is modeled by the inversion of Ramberg-Osgood equation. Nonlinearity caused by the interaction between the axial force and bending moment is also defined considering stability functions, while the geometric nonlinearity caused by axial forces is described using geometric stiffness matrix. Cyclic behaviour of steel connections is taken into account by employing independent hardening model. Dynamic equation of motion is solved by Newmark's constant acceleration method in the time history domain. Energy response analysis of space frames is performed by using this proposed numerical method. Finally, for the first time, the distribution of the different energy types versus time at the duration of the earthquake ground motion is obtained where in addition error analysis for the numerical solutions is carried out and plotted depending on the relative error calculated as a function of energy balance versus time.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.268-275
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• 2000

A hybrid mass damper that combines a tuned mass damper and an actuator has been recognized to be one of the most promising devices for vibration control of a tall building subjected to dynamic loads such as wind and earthquake. In this paper, in order to reduce vibration levels of a 5-story test structure, a hybrid mass damper using AC-servomotor was designed and developed. And control performances using HMD and TMD under random and earthquake excitations are compared through experimental test. It is confirmed that it is more effective to reduce the vibration levels of the test structure using HMD especially for earthquake excitation.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.519-526
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• 2006

This paper compares the seismic response control performance of linear and non-linear models fer tuned liquid damper (TLD). The existing linear and nonlinear TLD models were used for the numerical analysis of single degree of freedom (SDOF) and multi degree of freedom (MDOF) systems with TLD. The nonlinear model considers the variation of the frequency and damping of the TLD with varying excitation amplitude while the linear one has the invariant parameters. Numerical analysis results from SDOF systems indicate that the nonlinear model shows about 5% better control performance than linear one when the mass ratio is 2% and the optimal parameters for reducing peak responses are dependent on the characteristics of the excitation earthquake loads.

• Structural Engineering and Mechanics
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• 제76권5호
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• pp.643-651
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• 2020

Generally, it is necessary to perform transient structural analysis in order to verify and improve the seismic performance of high-rise buildings and bridges against earthquake loads. In this paper, we propose the model order reduction (MOR) method using the Krylov vectors to perform seismic analysis for linear and elastic systems in an efficient way. We then compared the proposed method with the mode superposition method (MSM) by using the limited numbers of modal vectors (or eigenvectors) calculated from the modal analysis. In the calculation, the data of the El Centro earthquake in 1940 were adopted for the seismic loading in the transient analysis. The numerical accuracy and efficiency of the two methods were compared in detail in the case of a simplified high-rise building.

• 한국지진공학회논문집
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• 제9권4호
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• pp.19-28
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• 2005

대공간의 쇼핑몰, 오피스 등과 같이 낮은 고유진동수를 가지는 구조물들은 사람의 활동에 의하여 큰 동적응답이 발생할 수 있다. 이러한 활동은 한 사람의 경우보다는 여러 사람에 의한 경우가 더 일반적이다. 본 연구의 목적은 구조물의 모드형상을 이용하여 보행자 전용 구조물과 같이 무리하중을 받는 구조물의 응답을 간단하게 평가하는 것이다. 이를 위하여 사람간의 상관관계가 고려된 무리하중을 받는 구조물의 응답에 관한 식을 유도하였다. 그리고 무리하중을 구성하는 개개의 하중의 연관성을 파악하기 위하여 두 개의 로드셀을 이용하여 하중간의 상관관계를 조사하였다. 구조물의 모드와 하중간의 상관관계에 대한 식을 이용하여 무리하중에 의한 응답을 구조물의 모드형상만으로 평가하는 방법을 제시하였다. 이 방법의 효율성을 확인하기 위하여 보와 바닥판의 예를 들어 무리하중을 동조시킨 경우와 그렇지 않은 경우에 대하여 응답을 평가하였으며 마지막으로 실제 사용중인 구조물을 대상으로 무리하중을 동조시킨 경우와 그렇지 않은 경우에 대하여 응답을 계측하고 이를 제시한 방법과 비교하였다.

• 한국지진공학회논문집
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• 제10권3호
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• pp.65-75
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• 2006

건물의 지진응답을 평가하기 위하여 비선형 푸시오버 해석을 수행한다. 구조물의 비탄성 지진응답을 정확히 예측하기 위해서는, 비선형해석에 사용되는 층하중분포가 구조물의 시간이력 지진응답 동안 실제로 발생되는 지진하중분포를 나타낼 수 있어야 한다. 본 연구에서는 건축물의 지진하중분포를 예측하기 위하여 새로운 모드조합법을 개발하였다. 개발된 모드조합법에서는 모드조합계수를 곱한 각 모드의 스펙트럼응답을 조합하여 다수의 지진하중분포를 예측한다. 모멘트 골조와 켄틸레버 벽체에 대한 변수연구를 수행하였다. 변수연구 결과를 토대로, 각 고유모드가 구조물의 지진응답에 미치는 영향을 나타내는 모드조합계수를 정의하였다. 다양한 정형 및 수직 비정형 구조물에 대하여 제안된 계수모드조합법을 적용하였다. 그 결과 제안된 모드조합법은 시간이력 응답 동안 구조물에 실제로 발생되는 지진하중분포를 정확히 예측할 수 있었다.

• Smart Structures and Systems
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• 제15권1호
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• pp.1-13
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• 2015

This paper proposes an analytical mode decomposition (AMD) and Hilbert transform method for structural nonlinearity quantification and damage detection under earthquake loads. The measured structural response is first decomposed into several intrinsic mode functions (IMF) using the proposed AMD method. Each IMF is an amplitude modulated-frequency modulated signal with narrow frequency bandwidth. Then, the instantaneous frequencies of the decomposed IMF can be defined with Hilbert transform. However, for a nonlinear structure, the defined instantaneous frequencies from the decomposed IMF are not equal to the instantaneous frequencies of the structure itself. The theoretical derivation in this paper indicates that the instantaneous frequency of the decomposed measured response includes a slowly-varying part which represents the instantaneous frequency of the structure and rapidly-varying part for a nonlinear structure subjected to earthquake excitations. To eliminate the rapidly-varying part effects, the instantaneous frequency is integrated over time duration. Then the degree of nonlinearity index, which represents the damage severity of structure, is defined based on the integrated instantaneous frequency in this paper. A one-story hysteretic nonlinear structure with various earthquake excitations are simulated as numerical examples and the degree of nonlinearity index is obtained. Finally, the degree of nonlinearity index is estimated from the experimental data of a seven-story building under four earthquake excitations. The index values for the building subjected to a low intensity earthquake excitation, two medium intensity earthquake excitations, and a large intensity earthquake excitation are calculated as 12.8%, 23.0%, 23.2%, and 39.5%, respectively.

• Earthquakes and Structures
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• 제7권5호
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• pp.779-796
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• 2014

This experimental investigation was conducted to examine the behavior and response of high-strength material (HSM) reinforced concrete (RC) columns under combined high-axial and cyclic-increasing lateral loads. All the columns use high-strength concrete ($f_c{^{\prime}}$=100MPa) and high-yield strength steel ($f_y$=685MPa and $f_y$=785MPa) for both longitudinal and transverse reinforcements. A total of four full-scale HSM columns with amount of transverse reinforcement equal to 100% more than that required by earthquake resistant design provisions of ACI-318 were tested. The key differences among those four columns are the spacing and configuration of transverse reinforcements. Two different constant axial loads, i.e. 60% and 30% of column axial load capacity, were combined with cyclically-increasing lateral loads to impose reversed curvatures in the columns. Test results show that columns under 30% of axial load capacity behaved much more ductile and had higher lateral deformational capacity compared to columns under the 60% of axial load capacity. The columns using closer transverse reinforcement spacing have slightly higher ductility than columns with larger spacing.