• Title, Summary, Keyword: Structural loads

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Nonlinear Response Structural Optimization of a Joined-Wing Using Equivalent Loads (등가하중법을 이용한 접합날개의 기하 비선형 응답 구조최적설계)

  • Kim, Yong-Il;Park, Gyung-Jin
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.321-326
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    • 2007
  • The joined-wing is a new concept of the airplane wing. The fore-wing and the aft-wing arc joined together in the joined-wing. The range and loiter are longer than those of a conventional wing. The joined-wing can lead to increased aerodynamic performances and reduction of the structural weight. The structural behavior of the joined-wing has a high geometric nonlinearity according to the external loads. The gust loads are the most critical loading conditions in the structural design of the joined-wing. The nonlinear behavior should be considered in the optimization of the joined-wing. It is well known that conventional nonlinear response optimization is extremely expensive: therefore, the conventional method is almost impossible to use in large scale structures such as the joined-wing. In this research, geometric nonlinear response structural optimization is carried out using equivalent loads. Equivalent loads are the load sets which generate the same response field in linear analysis as that from nonlinear analysis. In the equivalent loads method, the external loads are transformed to the equivalent loads (EL) for linear static analysis, and linear response optimization is carried out based on the EL.

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Comprehensive Aeromechanics Predictions on Air and Structural Loads of HART I Rotor

  • Na, Deokhwan;You, Younghyun;Jung, Sung N.
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.1
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    • pp.165-173
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    • 2017
  • The aeromechanics predictions of HART I rotor obtained using a computational structural dynamics (CSD) code are evaluated against the wind tunnel test data. The flight regimes include low speed descending flight at an advance ratio of ${\mu}=0.151$ and cruise condition at ${\mu}=0.229$. A lifting-line based unsteady airfoil theory with C81 table look-up is used to calculate the aerodynamic loads acting on the blade. Either rolled-up free wake or multiple-trailer wake with consolidation (MTC) model is employed for the free vortex wake representation. The measured blade properties accomplished recently are used to analyze the rotor for the up-to-date computations. The comparison results on airloads and structural loads of the rotor show good agreements for descent flight and fair for cruise flight condition. It is observed that MTC model generally improves the correlation against the measured data. The structural loads predictions for all measurement locations of HART I rotor are investigated. The dominant harmonic response of the structural loads is clearly captured with MTC model.

Structural Analysis of a Breakwater in Wave and Seismic Loads (파랑하중과 지진하중하의 방파제 구조해석)

  • Cho, Kyu-Nam
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.1
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    • pp.45-52
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    • 2009
  • In this paper, a guideline for designing breakwater in wave loads and in seismic loads is proposed. A simple model structure in breaking wave zone is examined using Morison equation in consideration with the effect of an impact load, for evaluation of the wave loads. As the impact load effect is not significant, pressure distributions according to Goda are applied for evaluation of wave loads on breakwater. Structural behavior of breakwater in wave loads can be obtained using the Goda method, as well. For seismic analysis, Ofunato and Hachinohe models, as well as an artificial seismic acceleration loads model, are adopted. Soil-structure interaction analysis is carried out to find the seismic load effect. It is found that, in certain cases, structural deformation in wave loads is in the same level as deformation that in seismic loads. Thus, it is our recommendation that these two loads are considered at the same level in breakwater design.

Probabilistic Analysis of Design Live Loads on A Refrigeration Store (냉동 창고 상시 적재하중에 관한 확률론적 연구)

  • Kim, Dai-Ho;Jeong, Jae-Hun;Won, Young-SuI;Joo, Kyung-Jai
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.4
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    • pp.109-120
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    • 2001
  • Live load data were collected with a systematic manner from a survey of a refrigeration stores. Using the collected floor live load survey data, the basic statistics, a histogram of the uniformly distributed loads, and the equivalent uniformly distributed loads are computed for various structural members. Based on the above results, the maximum values of a combined live loads during the design life have been estimated and compared with current design live loads. The ultimate goals of this study are to develop probabilistic live load models to analyze survey data of domestic refrigeration stores, and to propose design live loads for structural types.

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Examination of the structural design for SWATH ship (최소 선면쌍동선 구조설계에 대한 고찰)

  • 박명규;신영식
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.1 no.1
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    • pp.95-106
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    • 1995
  • The small-waterplane-area-twin-hull(SWATH) ship has been recognized as a promising high performance ship because of her superior seakeeping characteristics and large deck area for various operations compared to the conventional monohull ship. significant advances in analytical technics for the prediction of the ship motions, wave loads and structural responses, structural fatigue and its prediction, and hull vibration for ship motions, wave loads and structural responses, structural fatigue and its prediction, and hull vibration for SWATH ship have been much developed during the last twenty years. Based on these developments in technology an integrated computational procedures for prediction wave loads and structural responses can be used to get a accurate results. But the major problem of SWATH ship's structural design is the accurate prediction of structural responses by the maximum critical loads likely to be experienced during the life of SWATH. To get a easier and safer computational procedures and the analytical approach for determining the accurate structural responses, a case study has been presented through the project experienced.

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Equivalent static wind loads for stability design of large span roof structures

  • Gu, Ming;Huang, Youqin
    • Wind and Structures
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    • v.20 no.1
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    • pp.95-115
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    • 2015
  • Wind effects on roofs are usually considered by equivalent static wind loads based on the equivalence of displacement or internal force for structural design. However, for large-span spatial structures that are prone to dynamic instability under strong winds, such equivalent static wind loads may be inapplicable. The dynamic stability of spatial structures under unsteady wind forces is therefore studied in this paper. A new concept and its corresponding method for dynamic instability-aimed equivalent static wind loads are proposed for structural engineers. The method is applied in the dynamic stability design of an actual double-layer cylindrical reticulated shell under wind actions. An experimental-numerical method is adopted to study the dynamic stability of the shell and the dynamic instability originating from critical wind velocity. The dynamic instability-aimed equivalent static wind loads of the shell are obtained.

Mathematical Proof for Structural Optimization with Equivalent Static Loads Transformed from Dynamic Loads (동하중에서 변환된 등가정하중에 의한 최적화 방법의 수학적 고찰)

  • Park, Gyung-Jin;Kang, Byung-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.2
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    • pp.268-275
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    • 2003
  • Generally, structural optimization is carried out based on external static loads. All forces have dynamic characteristics in the real world. Mathematical optimization with dynamic loads is extremely difficult in a large-scale problem due to the behaviors in the time domain. The dynamic loads are often transformed into static loads by dynamic factors, design codes, and etc. Therefore, the optimization results can give inaccurate solutions. Recently, a systematic transformation has been proposed as an engineering algorithm. Equivalent static loads are made to generate the same displacement field as the one from dynamic loads at each time step of dynamic analysis. Thus, many load cases are used as the multiple leading conditions which are not costly to include in modern structural optimization. In this research, it is mathematically proved that the solution of the algorithm satisfies the Karush-Kuhn-Tucker necessary condition. At first, the solution of the new algorithm is mathematically obtained. Using the termination criteria, it is proved that the solution satisfies the Karush-Kuhn-Tucker necessary condition of the original dynamic response optimization problem. The application of the algorithm is discussed.

A Study on Live Loads in School (학교교실의 적재하중에 관한 연구)

  • 서극수;박성수
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.61-69
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    • 1994
  • The most fundamental elements in analyzing the structure of building are strength of maerials and value of loads. The applied loads of structural analysis in our country are classified into the dead and live loads. This study, with special reference to live load, is to suggest the stochastic character of live load and the appropriate live load by using the Monte-carlo Simulation method, one of the O. R(Operations Research) techniques acting on school buildings.

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Assessments of Precast Concrete Underground Parking Garage Using Site Instrumentations (현장재하실험을 통한 PC지하주차장 주조물의 거동분석)

  • 곽효경;윤정방;이형진;이석용
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.248-255
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    • 1997
  • The structural behaviors under wheel loads are much different from those under uniform loads which are generally adopted for the design of parking garage. In such a viewpoint, the structural behavior of a Half-PC concrete underground parking garage under wheel loads was investigated using the site instrumentations. The static wheel loads were applied on the structure to evaluate the actual static resistance, and moving load tests were also performed to evaluate the impact factors of the structure. Besides, the impact tests were also conducted to estimate the modal parameters of the structure. Through the experimental investigations, it was found that the structural performance of the underground parking garage can be improved by use of structural type such as Half-PC concrete structures.

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A study on Development of Stress Tolerant Structural System in the Frame of Greenhouses (내재해성이 우수한 비닐하우스골조 구조시스템 개발에 관한 연구)

  • Shim, Jong-Seok;Lee, Choon-Ho
    • Journal of The Korean Digital Architecture Interior Association
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    • v.12 no.1
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    • pp.5-13
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    • 2012
  • The frame of pipe greenhouses in Korea have been collapsed increasingly due to very weak in structure caused by the heavy snow and strong wind. In order to reduce the collapse of green houses, it is urgent to develop the new structural system in stress tolerant greenhouses. Therefore, this paper performed the structural analysis of greenhouse frame in accordance with snow loads and wind loads. Three type models in structural frame configuration of greenhouses, that is, existing type, diagrid type, and honeycomb type are selected. It was classfied the section shape of structural frames in greenhouses into arch style, standard style, and diagonal standard style. As a result of this paper, it was verified that the structural system of diagrid type is better than that of existing type against snow loads and wind loads in the frame of greenhouses.