• 한국지진공학회논문집
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• 제15권2호
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• pp.11-22
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• 2011

개발된 완전 조립식 교량 하부구조에 대한 설계비교와 비선형 해석을 수행하였다. 조립식 교량 하부구조는 현행설계법과 하중저항계수설계법으로 설계하였다. 설계시에는 현 도로교설계기준에 규정된 DB-24 및 DL-24 설계활하중을 적용하였다. 이 연구는 비선형 유한요소해석을 통해서 완전 조립식 교량 하부구조의 현행 설계법인 KHBD (2005)와 AASHTO-LRFD (2007)를 평가하였다. 사용된 프로그램은 철근콘크리트 구조물의 해석을 위한 RCAHEST이다.

• 한국구조물진단유지관리공학회 논문집
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• 제14권2호
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• pp.82-88
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• 2010

본 연구의 목적은 내진규준이 적용되기 이전에 건설된 역사건물의 내진성능 평가 및 내진보강이다. 이를 위하여 2층 RC 역사건물의 내진성능이 평가되었다. 동적해석에 의한 층간변위비 및 층전단력 평가결과, 층전단력이 설계기준의 밑면전단력을 초과하는 것으로 평가되어 적절한 내진보강이 필요한 것으로 평가되었다. 내진성능 향상을 위하여 총 4개의 강재댐퍼가 사용되었다. 해석 변수는 강재댐퍼 형상 및 설치 방법이다. 동적해석결과 역 K가새로 설치되는 슬릿댐퍼가 다른 댐퍼 형상 및 설치 방법보다 우수한 내진성능을 가진 것으로 평가되었다.

• 국제초고층학회논문집
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• 제5권1호
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• pp.1-12
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• 2016

The 1100 foot [335 m] tall Wilshire Grand Center tower under construction in Los Angeles illustrates many key outrigger issues. The tower has a long, narrow floor plan and slender central core. Outrigger braces at three groups of levels in the tower help provide for occupant comfort during windy conditions as well as safety during earthquakes. Because outrigger systems are outside the scope of prescriptive code provisions, Performance Based Design (PBD) using Nonlinear Response History Analysis (NRHA) demonstrated acceptability to the Los Angeles building department and its peer review panel. Buckling Restrained Brace (BRB) diagonals are used at all outrigger levels to provide stable cyclic nonlinear behavior and to limit forces generated at columns, connections and core walls. Each diagonal at the lowest set of outriggers includes four individual BRBs to provide exceptional capacities. The middle outriggers have an unusual 'X-braced Vierendeel' configuration to provide clear hotel corridors. The top outriggers are pre-loaded by jacks to address long-term differential shortening between the concrete core and concrete-filled steel perimeter box columns. The outrigger connection details are complex in order to handle large forces and deformations, but were developed with contractor input to enable practical construction.

• 전산구조공학
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• 제10권4호
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• pp.281-290
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• 1997

현행 내진설계 규준에서 사용하고 있는 반응수정계수는 설계지진하중과 유사한 지진발생시 구조물이 비선형 거동을 하도록 탄성응답에서 요구되는 밑면전단력 값을 낮추는 계수라 할 수 있다. 따라서 반응수정계수는 하중저감계수(force reduction factor)라고 할 수 있으며, 이러한 값들은 경험적으로 결정된 것이어서 예상지진에 대하여 구조설계자가 설계한 건물이 어느정도의 비선형 거동을 할지는 예측하기가 힘들다. 본 연구에서는 목표가 되는 연성비(target ductility ratio)에 따라 요구되는 밑면전단력의 값을 구하고 이를 규준에서 요구하는 값과 비교할 것이다. 만약 요구되는 값이 규준 값 보다 크다면 이는 구조물이 가지는 부가강도(overstrength)나 잉여력(redundancy)이 담당해야 한다. 모멘트연성골조 건물을 설계한 후 이를 push-over 해석에 의하여 부가강도를 찾아 보아 요구강도와 비교할 것이다.

• Structural Engineering and Mechanics
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• 제60권5호
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• pp.761-779
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• 2016

Design of safe structures with resistance to progressive collapse is of paramount importance in structural engineering. In this paper, an efficient optimization technique is used for optimal design of steel moment frames subjected to progressive collapse. Seismic design specifications of AISC-LRFD code together with progressive collapse provisions of UFC are considered as the optimization constraints. Linear static, nonlinear static and nonlinear dynamic analysis procedures of alternate path method of UFC are considered in design process. Three design examples are solved and the results are discussed. Results show that frames, which are designed solely considering the AISC-LRFD limitations, cannot resist progressive collapse, in terms of UFC requirements. Moreover, although the linear static analysis procedure needs the least computational cost with compared to the other two procedures, is the most conservative one and results in heaviest frame designs against progressive collapse. By comparing the results of this work with those reported in literature, it is also shown that the optimization technique used in this paper significantly reduces the required computational effort for design. In addition, the effect of the use of connections with high plastic rotational capacity is investigated, whose results show that lighter designs with resistance to progressive collapse can be obtained by using Side Plate connections in steel frames.

• 대한기계학회논문집B
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• 제26권6호
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• pp.795-804
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• 2002

The optimal design code of an axial flow pump has been developed to determine geometric and fluid dynamic variables under hydrodynamic as well as mechanical design constraints. The design code includes the optimization of the complete radial distribution of the geometry by determining the coefficients of 2$^{nd}$ order polynomials to represent the three-dimensional geometry. The optimization problem has been formulated with a nonlinear multivariable objective function, maximizing the efficiency and stall margin, while minimizing the net positive suction head required. Calculation of the objective function is based on the mean streamline analysis and through-flow analysis using the present state-of-the-art model. The optimal solution is calculated using the penalty function method in which the genetic optimizer is employed. The optimized efficiency and design variables are presented in this paper as a function of non-dimensional specific speed in the range, 2$\leq$ $n_{s}$ $\leq$10. The results can be used in preliminary design of axial flow pumps.

• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.355-371
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• 2016

In this study seismic performance of reinforced concrete staggered wall system structures were investigated and their behavior factors such as overstrength factors, ductility factors, and the response modification factors were evaluated from the overstrength and ductility factors. To this end, 5, 9, 15, and 25-story staggered wall system (SWS) structures were designed and were analyzed by nonlinear static and dynamic analyses to obtain their nonlinear force-displacement relationships. The response modification factors were computed based on the overstrength and the ductility capacities obtained from capacity envelopes. The analysis results showed that the 5- and 9-story SWS structures failed due to yielding of columns and walls located in the lower stories, whereas in the 15- and 25-story structures plastic hinges were more widely distributed throughout the stories. The computed response modification factors increased as the number of stories decreased, and the mean value turned out to be larger than the value specified in the design code.

• Structural Engineering and Mechanics
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• 제76권3호
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• pp.355-365
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• 2020

In this study, considering the hydroelastic response represented by the springing and whipping phenomena, we propose a method of estimating the fatigue damage in the longitudinal connections of ships. First, we screened the design sea states using a load transfer function based on the frequency domain. We then conducted a time domain fluid-structure interaction (FSI) analysis using WISH-FLEX, an in-house code based on the weakly nonlinear approach. To obtain an effective and robust analytical result of the hydroelastic response, we also conducted an experimental model test with a 1/50-scale backbone-based model of a ship, and compared the experimental results with those obtained from the FSI analysis. Then, by combining the results obtained from the hydroelastic response with those obtained from the numerical fatigue analysis, we developed a fatigue damage estimation method. Finally, to demonstrate the effectiveness of the developed method, we evaluated the fatigue strength for the longitudinal connections of the real ship and compared it with the results obtained from the model tests.

• 전자공학회논문지A
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• 제32A권12호
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• pp.220-228
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• 1995

An optimized 4-stage 12-bit pipelined CMOS analog-to-digital converter (ADC) architecture is proposed to obtain high linearity and high yield. The ADC based on a multiplying digital-to-analog converter (MDAC) selectively employs a binary-weighted-capacitor (BWC) array in the front-end stage and a unit-capacitor (UC) array in the back-end stages to improve integral nonlinearity (INL) and differential nonlinearity (DNL) simultaneously whil maintaining high yield. A digital-domain nonlinear error calibration technique is applied in the first stage of the ADC to improve its accuracy to 12-bit level. The largest DNL error in the mid-point code of the ADC is reduced by avoiding a code-error symmetry observed in a conventional digitally calibrated ADC is reduced by avoiding a code-error symmetry observed in a conventional digitally calibrated ADC is simulated to prove the effectiveness of the proposed ADC architecture.

• Steel and Composite Structures
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• 제20권2호
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• pp.399-412
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• 2016

This paper evaluates the seismic response of three dimensional steel space buildings using the spread plastic hinge approach. A numerical study was carried out in which a sample steel space building was selected for pushover analysis and incremental nonlinear dynamic time history analysis. For the nonlinear analysis, three earthquake acceleration records were selected to ensure compatibility with the design spectrum defined in the Turkish Earthquake Code. The interstorey drift, capacity curve, maximum responses and dynamic pushover curves of the building were obtained. The analysis results were compared and good correlation was obtained between the idealized dynamic analyses envelopes with and static pushover curves for the selected building. As a result to more accurately account response of steel buildings, dynamic pushover envelopes can be obtained and compared with static pushover curve of the building.