• 제목/요약/키워드: Design-time history

검색결과 950건 처리시간 0.027초

Ductility-based design approach of tall buildings under wind loads

  • Elezaby, Fouad;Damatty, Ashraf El
    • Wind and Structures
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    • 제31권2호
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    • pp.143-152
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    • 2020
  • The wind design of buildings is typically based on strength provisions under ultimate loads. This is unlike the ductility-based approach used in seismic design, which allows inelastic actions to take place in the structure under extreme seismic events. This research investigates the application of a similar concept in wind engineering. In seismic design, the elastic forces resulting from an extreme event of high return period are reduced by a load reduction factor chosen by the designer and accordingly a certain ductility capacity needs to be achieved by the structure. Two reasons have triggered the investigation of this ductility-based concept under wind loads. Firstly, there is a trend in the design codes to increase the return period used in wind design approaching the large return period used in seismic design. Secondly, the structure always possesses a certain level of ductility that the wind design does not benefit from. Many technical issues arise when applying a ductility-based approach under wind loads. The use of reduced design loads will lead to the design of a more flexible structure with larger natural periods. While this might be beneficial for seismic response, it is not necessarily the case for the wind response, where increasing the flexibility is expected to increase the fluctuating response. This particular issue is examined by considering a case study of a sixty-five-story high-rise building previously tested at the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario using a pressure model. A three-dimensional finite element model is developed for the building. The wind pressures from the tested rigid model are applied to the finite element model and a time history dynamic analysis is conducted. The time history variation of the straining actions on various structure elements of the building are evaluated and decomposed into mean, background and fluctuating components. A reduction factor is applied to the fluctuating components and a modified time history response of the straining actions is calculated. The building components are redesigned under this set of reduced straining actions and its fundamental period is then evaluated. A new set of loads is calculated based on the modified period and is compared to the set of loads associated with the original structure. This is followed by non-linear static pushover analysis conducted individually on each shear wall module after redesigning these walls. The ductility demand of shear walls with reduced cross sections is assessed to justify the application of the load reduction factor "R".

초상화 복식을 중심으로 본 퀸 엘리자베스 1세의 영화 의상에 관한 연구 (A Study of Queen Elizabeth I's Cinema Costumes Viewed from Her Portrait)

  • 성광숙
    • 복식
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    • 제62권8호
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    • pp.55-70
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    • 2012
  • In 16th century, during renaissance time, Britain's queen Elizabeth I, as a means to express her authority, had an exaggerated clothing styles and was the fashion leader of the time. Thus, through a media of Cinema, tried to find out the characteristics and different aspects of the history of clothing styles, of how they changed, ascertained, restored, and reappeared in the modern time. The research was based on the consideration of Elizabeth I's 33 portraits and her clothing styles; and the research is also from analysing the movies from 1937 to 2007, a total of 9 Cinema and 102 clothes. Movie costumes' most important mission is representing the cinema's timely and spatial background. Thus, it is inevitable that ascertaining and restoring Elizabeth I's portrait should be done. However, the movie costume has to show her dramatic lifestyle, dignity, absolute authority, and other visual images. In addition, the costume has to contribute in making artistic effect and thus the creativity of a designer to satisfy all these needs should be added. Based on the findings from the research, the characteristics of Elizabeth I's Cinema costume are first, ascertaining and restoring portraits, second, mixture of silhouette and detail depending on time period, third, partial change on clothing style design, fourth, emphasis of ruff collar, fifth, magnification colors, sixth, avoiding excessive swelling and decoration, and applying modern style on Protective costume. Thus, based on the research, creative design in Cinema clothing, plays an important part in the history of clothing design. I hope this research could work as a foundation reference for clothing design's history.

Improvement on optimal design of dynamic absorber for enhancing seismic performance of nuclear piping using adaptive Kriging method

  • Kwag, Shinyoung;Eem, Seunghyun;Kwak, Jinsung;Lee, Hwanho;Oh, Jinho;Koo, Gyeong-Hoi
    • Nuclear Engineering and Technology
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    • 제54권5호
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    • pp.1712-1725
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    • 2022
  • For improving the seismic performance of the nuclear power plant (NPP) piping system, attempts have been made to apply a dynamic absorber (DA). However, the current piping DA design method is limited because it cannot provide the globally optimum values for the target design seismic loading. Therefore, this study proposes a seismic time history analysis-based DA optimal design method for piping. To this end, the Kriging approach is introduced to reduce the numerical cost required for seismic time history analyses. The appropriate design of the experiment method is used to increase the efficiency in securing response data. A gradient-based method is used to efficiently deal with the multi-dimensional unconstrained optimization problem of the DA optimal design. As a result, the proposed method showed an excellent response reduction effect in several responses compared to other optimal design methods. The proposed method showed that the average response reduction rate was about 9% less at the maximum acceleration, about 5% less at the maximum value of the response spectrum, about 9% less at the maximum relative displacement, and about 4% less at the maximum combined stress compared to existing optimal design methods. Therefore, the proposed method enables an effective optimal DA design method for mitigating seismic response in NPP piping in the future.

계측 지진파 기반 설계응답스펙트럼에 상응하는 설계 지진파 시간이력 생성 기법 개발 (Development of a Design Seismic Wave Time History Generation Technique Corresponding to the Recorded Seismic Wave-Based Design Response Spectrum)

  • 오현주;박형춘
    • 대한토목학회논문집
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    • 제41권6호
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    • pp.687-695
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    • 2021
  • 최근 국내에서 큰 규모의 지진이 발생하게 되면서 내진설계의 중요성이 크게 증가하였다. 내진설계기준에서는 중요구조물 또는 특수구조물에 대해서는 동적시간이력해석을 수행하도록 규정하고 있다. 이러한 중요 또는 특수 구조물의 내진해석 및 설계에 있어 합리적 설계 입력 지진파를 결정하는 것은 해석 및 설계의 신뢰도를 확보하는데 매우 중요한 요소이다. 내진설계기준에서 합리적 설계 지진파는 해당 지역(단층)의 특성을 반영하면서 동시에 내진 성능 수준별 설계응답스펙트럼을 만족해야 한다. 이러한 요구조건은 해당 지역(단층)에서 계측됐던 실 지진파를 설계응답스펙트럼에 상응하게 수정하여 부분적으로 만족시킬 수 있다. 본 연구에서는 하모닉웨이브릿변환(Harmonic Wavelet Transform)을 이용하여 실 계측 지진파를 기반으로 설계응답스펙트럼에 상응하게 지진파시간이력 수정·생성 하는 방법을 제안하였다. 제안한 기법의 적용성 검토를 위해 경주(2016년)와 포항(2017년)에서 발생했던 각 규모 5.8과 5.4의 지진에 제안된 기법을 적용하여 설계응답스펙트럼에 상응한 지진파시간이력을 수정·생성 하였다

An improved time-domain approach for the spectra-compatible seismic motion generation considering intrinsic non-stationary features

  • Feng Cheng;Jianbo Li;Zhixin Ding;Gao Lin
    • Nuclear Engineering and Technology
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    • 제55권3호
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    • pp.968-980
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    • 2023
  • The dynamic structural responses are sensitive to the time-frequency content of seismic waves, and seismic input motions in time-history analysis are usually required to be compatible with design response spectra according to nuclear codes. In order to generate spectra-compatible input motions while maintaining the intrinsic non-stationarity of seismic waves, an improved time-domain approach is proposed in this paper. To maintain the nonstationary characteristics of the given seismic waves, a new time-frequency envelope function is constructed using the Hilbert amplitude spectrum. Based on the intrinsic mode functions (IMFs) obtained from given seismic waves through variational mode decomposition, a new corrective time history is constructed to locally modify the given seismic waves. The proposed corrective time history and time-frequency envelope function are unique for each earthquake records as they are extracted from the given seismic waves. In addition, a dimension reduction iterative technique is presented herein to simultaneously superimpose corrective time histories of all the damping ratios at a specific frequency in the time domain according to optimal weights, which are found by the genetic algorithm (GA). Examples are presented to show the capability of the proposed approach in generating spectra-compatible time histories, especially in maintaining the nonstationary characteristics of seismic records. And numerical results reveal that the modified time histories generated by the proposed method can obtain similar dynamic behaviors of AP1000 nuclear power plant with the natural seismic records. Thus, the proposed method can be efficiently used in the design practices.

Effects of diaphragm flexibility on the seismic design acceleration of precast concrete diaphragms

  • Zhang, Dichuan;Fleischman, Robert B.;Lee, Deuckhang
    • Computers and Concrete
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    • 제25권3호
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    • pp.273-282
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    • 2020
  • A new seismic design methodology for precast concrete diaphragms has been developed and incorporated into the current American seismic design code. This design methodology recognizes that diaphragm inertial forces during earthquakes are highly influenced by higher dynamic vibration modes and incorporates the higher mode effect into the diaphragm seismic design acceleration determination using a first mode reduced method, which applies the response modification coefficient only to the first mode response but keeps the higher mode response unreduced. However the first mode reduced method does not consider effects of diaphragm flexibility, which plays an important role on the diaphragm seismic response especially for the precast concrete diaphragm. Therefore this paper investigated the effect of diaphragm flexibility on the diaphragm seismic design acceleration for precast concrete shear wall structures through parametric studies. Several design parameters were considered including number of stories, diaphragm geometries and stiffness. It was found that the diaphragm flexibility can change the structural dynamic properties and amplify the diaphragm acceleration during earthquakes. Design equations for mode contribution factors considering the diaphragm flexibility were first established through modal analyses to modify the first mode reduced method in the current code. The modified first mode reduced method has then been verified through nonlinear time history analyses.

RFID/USN 기반의 유비쿼터스 제조실행시스템 설계 및 구현 (Design and Implementation of an Ubiquitous Manufacture Execution System based on RFID/USN)

  • 정세훈;김경종;심춘보
    • 디지털산업정보학회논문지
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    • 제6권4호
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    • pp.21-31
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    • 2010
  • A manufacturing execution system in the process according to automation system of installation management has been growing interest about effective system design and effective system manage. In this paper, we propose an ubiquitous Manufacturing Execution System based on RFID/USN for checkup monitoring and history management of installation in manufacturing execution systems. For this, we design and implement installation history and statistics management system based on RFID grafting RFID for efficient installation equipment history and statistics management of ubiquitous Manufacturing Execution System, and was implemented checkup monitoring system based on USN using temperature sensor, humidity sensor, hydraulic pressure sensor for failure prevention of ubiquitous Manufacturing Execution System. And proposed ubiquitous Manufacturing Execution System is implemented based on JSP for access through Web in real time.

도시철도 고가교 및 교량 교각의 연성도 내진설계와 내진성능 평가 (Ductility Demand-Based Seismic Design and Seismic Performance Evaluation of Urban Railway Bridge Pier)

  • 박승희;남민준;윤종구;김진호
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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    • pp.1220-1226
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    • 2011
  • The purpose of this study is to assess the seismic performance of a reinforced concrete pier using ductility demand-based seismic design method and nonlinear earthquake analysis. A computer program named MIDAS/Civil(MIDAS IT,2009) for the analysis of the reinforced concrete pier was used. The bridge pier was designed by the ductility demand-based seismic design. In addition, a seismic performance was evaluated through both capacity spectrum method and nonlinear time history method. In order to determine the seismic performance of the bridge pier, the maximum response values from the capacity spectrum method and nonlinear time history analysis were compared each other.

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내풍설계된 철골조 초고층건물의 선형동적해석에 의한 내진성능평가 (Seismic Perfomance Evaluation of Wind-Designed Steel Highrise Buildings Based on Linear Dynamic Analysis)

  • 이철호;김선웅
    • 한국지진공학회:학술대회논문집
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    • 한국지진공학회 2005년도 학술발표회 논문집
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    • pp.177-184
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    • 2005
  • Even in moderate to low seismic regions like Korean peninsular where wind loading usually governs the structural design of a tall building, the probable structural impact of the design basis earthquake or the maximum credible earthquake on the selected structural system should be considered at least in finalizing the design. In this study, by using response spectrum analysis and time history analysis method, seismic performance evaluation was conducted for wind-designed concentrically braced steel highrise buildings. Input ensemble was normalized to be compatible with expected peak ground acceleration. The analysis results showed that wind-designed concentrically braced steel highrise buildings possess significantly increased elastic seismic capacity due to the system overstrength resulting from the wind-serviceability criterion and the width-to-thickness ratio limits on steel members. The time history analysis tended to significantly underestimated the seismic response as compared to response spectrum analysis. Further detailed studies regarding selection and scaling scheme of input ground motions is needed.

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Study of seismic performance of cable-stayed-suspension hybrid bridges

  • Zhang, Xin-Jun;Yu, Zhou-Jun
    • Structural Engineering and Mechanics
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    • 제55권6호
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    • pp.1203-1221
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    • 2015
  • By taking a cable-stayed-suspension hybrid bridge with main span of 1400 m as example, seismic response of the bridge under the horizontal and vertical seismic excitations is investigated numerically by response spectrum analysis and time history analysis, its seismic performance is discussed and compared to the cable-stayed bridge and suspension bridge with the same main span, and considering the aspect of seismic performance, the feasibility of using cable-stayed-suspension hybrid bridge in super long-span bridges is discussed. Under the horizontal seismic action, the effects of structural design parameters including the cable sag to span ratio, the suspension to span ratio, the side span length, the subsidiary piers in side spans, the girder supporting system and the deck form etc on the seismic performance of the bridge are investigated by response spectrum analysis, and the favorable values of these design parameters are proposed.