• 전산구조공학
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• 제9권4호
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• pp.229-237
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• 1996

구조물의 내진설계는 일반적으로 설계시방서의 스펙트럼을 이용하여 이루어지고 있다. 각 시방서에서 제시된 스펙트럼은 여러지역에서 발생한 지진파들을 최대 지반가속도로 정규화하여 평탄한 응답을 구하였으며, 구조물의 특성에 따라 증감하여 사용하고 있다. 구조물은 지진하중에 의하여 소성변형을 보이고 있으며, 이러한 구조물의 소성변형 능력을 고려하여 설계시방서에서는 응답수정계수를 사용하고 있다. 그러나, 이러한 응답수정계수는 모든 구조물의 고유진동주기에 대하여 일정한 값으로 사용되고 있다. 본 연구에서는 각각의 지진파에 대하여 20개의 인공지진파을 작성하여 평탄한 응답스펙트럼을 구하였다. 구하여진 평균 응답 스펙트럼을 사용하여 구조물의 초기항복강도와 감쇠율의 효과를 측정하였으며, 회기분석을 통하여 내진설계시 각 구조물에 요구되는 변위연성도를 얻기 위한 강도계수를 추정하였다. 또한 현재 사용되고 있는 설계시방서의 응답수정계수를 구조물 고유진동주기의 함수로 나타내었다.

• 한국강구조학회 논문집
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• 제19권6호
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• pp.715-723
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• 2007

본 연구에서는 중/저층의 철골모멘트골조를 대상으로 합리적이고 실용적인 변위기반 내진설계절차를 제시하였다. 현행의 내진설계에서는 구조시스템 종별에 따라 경험적이고 획일적으로 규정된 반응수정계수를 토대로 설계가 수행되므로, 접합부가 보유한 회전능력의 적정성 여부를 검증하기가 어렵다. 본 논문에서는 실험적으로 입증된 철골모멘트골조 접합부의 가용 소성회전능력을 주요설계변수로 직접 사용하는 새로운 설계법을 제시하였다. 이 설계방안의 정립을 위해, 우선 지금까지 불분명한 관계로 남아있던 접합부의 가용 소성회전능력과 반응수정계수 사이의 관계를 합리적이고 정량적으로 정의하는 방안을 제시하였다. 이를 토대로 변위에 기반한 단계별 내진설계절차를 제시하고 비선형동적해석에 의해 방안의 타당성을 입증하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.208-213
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• 2002

Near field ground motions contain distinct, large amplitude pulses in both velocity and displacement. This paper presents an investigation on the characteristics of near filed earthquakes and their effects on seismic demands. For this purpose 20 sets of near field ground motion and 20 sets of far filed ground motion are compared with respect to Linear Elastic Response Spectrum(LERS), Response Modification Factor(R), Inelastic Response Spectrum(IRS), and performance point of Capacity Spectum Method(CSM).

• Structural Engineering and Mechanics
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• 제10권4호
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• pp.405-426
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• 2000

Two approximate methods based on mechanism analysis suitable for seismic assessment/design of structural concrete are reviewed. The methods involve use of equal energy concept or equal displacement concept along with appropriate patterns of inelastic deformations to relate structure's maximum lateral displacement to member and plastic deformations. One of these methods (Clough's method), defined here as a ductility-based approach, is examined in detail and a modification for its improvement is suggested. The modification is based on estimation of maximum inelastic displacement using inelastic design response spectra (IDRS) as an alternative to using equal energy concept. The IDRS for demand displacement ductilities are developed for a single degree of freedom model subjected to several accelerograms as functions of response modification factor (R), damping ratios, and strain hardening. The suggested revised methodology involves estimation of R as the ratio of elastic strength demand to code level demand, and determination of design base shear using $R_{design}{\leq}R$ and maximum displacement, determination of plastic displacement using IDRS and subsequent local plastic deformations. The methodology is demonstrated for the case of a 10-story precast wall panel building.

• Earthquakes and Structures
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• 제16권2호
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• pp.185-196
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• 2019

One of the shortcomings of seismic bridge design codes is the lack of clarity in defining the role of different seismic isolation systems with linear or nonlinear behavior in terms of R-factor. For example, based on AASHTO guide specifications for seismic isolation design, R-factor for all substructure elements of isolated bridges should be half of those expressed in the AASHTO standard specifications for highway bridges (i.e., R=3 for single columns and R=5 for multiple column bent) but not less than 1.50. However, no distinction is made between two commonly used types of seismic isolation devices, i.e., elastomeric rubber bearing (ERB) with linear behavior, and lead rubber bearing (LRB) with nonlinear behavior. In this paper, five existing bridges located in Iran with two types of deck-pier connection including ERB and LRB isolators, and two bridge models with monolithic deck-pier connection are developed and their R-factor values are assessed based on the Uang's method. The average R-factors for the bridges with ERB isolators are calculated as 3.89 and 4.91 in the longitudinal and transverse directions, respectively, which are not in consonance with the AASHTO guide specifications for seismic isolation design (i.e., R=3/2=1.5 for the longitudinal direction and R=5/2=2.5 for the transverse direction). This is a clear indicator that the code-prescribed R-factors are conservative for typical bridges with ERB isolators. Also for the bridges with LRB isolators, the average computed R-factors equal 1.652 and 2.232 in the longitudinal and transverse directions, respectively, which are in a good agreement with the code-specified R-factor values. Moreover, in the bridges with monolithic deck-pier connection, the average R-factor in the longitudinal direction is obtained as 2.92 which is close to the specified R-factor in the bridge design codes (i.e., 3), and in the transverse direction is obtained as 2.41 which is about half of the corresponding R-factor value in the specifications (i.e., 5).

• Earthquakes and Structures
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• 제20권2호
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• pp.149-160
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• 2021

Buildings made using the locally available clay materials are amongst the least expensive forms of construction in many developing countries, and therefore, widely popular in remote areas. It is despite the fact that these low-strength masonry structures are vulnerable to seismic forces. Since transporting imported materials like cement and steel in areas inaccessible by motorable roads is challenging and financially unviable. This paper presents, and experimentally investigates, adobe masonry structures that utilize the abundantly available local clay materials with moderate use of imported materials like cement, aggregates, and steel. Shake-table tests were performed on two 1:3 reduce-scaled adobe masonry models for experimental seismic testing and verification. The model AM1 was confined with vertical lightly reinforced concrete columns provided at all corners and reinforced concrete horizontal bands (i.e., tie beams) provided at sill, lintel, and eave levels. The model AM2 was confined only with the horizontal bands provided at sill, lintel, and eave levels. The models were subjected to sinusoidal base motions for studying the damage evolution and response of the model under dynamic lateral loading. The lateral forcedeformation capacity curves for both models were developed and bi-linearized to compute the seismic response parameters: stiffness, strength, ductility, and response modification factor R. Seismic performance levels, story-drift, base shear coefficient, and the expected structural damages, were defined for both the models. Seismic performance assessment of the selected models was carried out using the lateral seismic force procedure to evaluate their safety in different seismic zones. The use of vertical columns in AM1 has shown a considerable increase in the lateral strength of the model in comparison to AM2. Although an R factor equal to 2.0 is recommended for both the models, AM1 has exhibited better seismic performance in all seismic zones due to its relatively high lateral strength in comparison to AM2.

• Tribology and Lubricants
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• 제35권3호
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• pp.158-168
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• 2019

This paper presents the investigation of two types of rotordynamic modeling issues for 2.2 kW-class, rated speed of 1,800 rpm, squirrel-cage type induction motors. These issues include the lamination structure of rotor cores, and the radial clearance of ball bearings that support the shaft of the motor. Firstly, we focus on identifying the effects of rotor core lamination on the rotordynamic analysis via a 2D prediction model. The influence of lamination is considered as the change in the elastic modulus of the rotor core, which is determined by a modification factor ranging from 0 to 1.0. The analysis results show that the unbalanced response of the rotor-bearing system significantly varies depending on the value of the modification factor. Through modal testing of the system, the modification factor of 0.079 is proven to be appropriate to consider the effects of lamination. Next, we investigate the influence of ball bearing clearance on the rotordynamic analysis by establishing a bearing analysis model based on Hertz's contact theory. The analysis results indicate that negative clearance greatly changes the bearing static behavior. Rotordynamic analysis using predicted bearing stiffness with various clearances from -0.005 mm to 0.010 mm reveals that variations in clearance result in a slight difference in the displacement of the system up to 18.18. Thus, considering lamination in rotordynamic analysis is necessary as it can cause serious analysis errors in unbalanced response. However, considering the effect of the bearing clearance is optional because of its relatively weak impact.

• Journal of Electrical Engineering and Technology
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• 제7권3호
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• pp.330-335
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• 2012

The shape optimization of a Thomson coil actuator used in an arc eliminator is done for fast response by adopting topology modification method. The displacement of the plate in a fixed calculation time is taken as the objective function. The objective function and contribution factor are calculated by using an adaptive equivalent circuit method which has been proved accurate and efficient. Both shape optimization and performance analysis are accomplished based on the segmentation of plate. Through the refinement of the sensitive segments a precise optimal plate shape can be obtained. The effectiveness of the proposed method is proved by the comparison of results before and after the shape optimization.

• Journal of Electrical Engineering and Technology
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• 제7권1호
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• pp.58-63
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• 2012

The shape optimization of a Thomson coil actuator used in an arc eliminator is done for fast response by adopting topology modification method. The displacement of the plate in a fixed calculation time is taken as the objective function. The objective function and contribution factor are calculated by using an adaptive equivalent circuit method which has been proved accurate and efficient. Both shape optimization and performance analysis are accomplished based on the segmentation of plate. Through the refinement of the sensitive segments a precise optimal plate shape can be obtained. The effectiveness of the proposed method is proved by the comparison of results before and after the shape optimization.

• 한국구조물진단유지관리공학회 논문집
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• 제11권4호
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• pp.147-151
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• 2007

재하시험은 교량의 내하력을 측정하는 효과적인 방법이다. 국내에서 교량의 내하력평가는 계측값과 해석값을 비교하여 산정된 응답보정계수를 사용하여 산정한다. 본 논문에서는 통행차량에 의한 응답보정계수를 결정하는 방법을 개발하였다. 제안된 방법은 차량효과를 고려하기 위하여 컴퓨터 시뮬레이션의 결과에 기반을 두었다. 제안된 방법과 기존 방법의 비교결과는 제안된 방법이 교량의 공용 내하력을 비교적 잘 예측한다는 것을 알 수 있다.