• Title, Summary, Keyword: Flexible load

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Theoretical analysis on vibration characteristic of a flexible tube under the interaction of seismic load and hydrodynamic force

  • Lai, Jiang;He, Chao;Sun, Lei;Li, Pengzhou
    • Nuclear Engineering and Technology
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    • v.52 no.3
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    • pp.654-659
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    • 2020
  • The reliability of the spent fuel pool instrument is very important for the security of nuclear power plant, especially during the earthquake. The effect of the fluid force on the vibration characteristics of the flexible tube of the spent fuel pool instrument needs comprehensive analysis. In this paper, based on the potential flow theory, the hydrodynamic pressures acting on the flexible tube were obtained. A mathematical model of a flexible tube was constructed to obtain the dynamic response considering the effects of seismic load and fluid force, and a computer code was written. Based on the mathematical model and computer code, the maximum stresses of the flexible tube in both safe shutdown earthquake and operating basis earthquake events on the spent fuel pool with three typical water levels were calculated, respectively. The results show that the fluid force has an obvious effect on the stress and strain of the flexible tube in both safe shutdown earthquake and operating basis earthquake events.

Modeling and Parameter Identification of the Slung Load System of an Unmanned Rotorcraft using a Flexible Cable

  • Lee, Byung-Yoon;Moon, Gun-Hee;Lee, Dong-Yeon;Tahk, Min-Jea;Oh, Hyun-Shik
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.2
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    • pp.365-377
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    • 2017
  • In this paper, we propose a method to identify the parameters of a rotorcraft slung load system using the modal characteristics of a flexible cable. The proposed method estimates the length of the cable and the mass of the payload by means of a frequency analysis. Dynamic equations of the slung load system with the flexible cable are derived using Udwadia-Kalaba equation (UKE) in order to build a simulation program, and the similarity of the simulated slung load movement is verified by comparison with flight test results. Using the computer simulation program, we show that the proposed method works well within various parameter ranges.

Evaluating a Load Limit on Heavy Vehicles in Flexible Pavements (아스팔트 포장구조체에 대한 중차량 제한하중 평가)

  • Park, Seong-Wan;Hwang, Jung Joon
    • Journal of The Korean Society of Civil Engineers
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    • v.30 no.1D
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    • pp.53-60
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    • 2010
  • The objective of this paper is to evaluate a performance-based load zoning procedure in flexible pavements. Long-term performance in flexible pavements will be evaluated using VESYS type rutting model and Miner s theory on fatigue cracking. Permanent deformation properties such as alpha and gnu, and fatigue cracking properties such as k1 and k2 in asphalt concrete were used respectively. The data from the literatures were also used in predicting performance in flexible pavements for evaluating load restrictions as well as parametric study. Finally, a performance-based load zoning procedure and a simple load limit procedure for load zoning were assessed.

Dynamic Behavior Analysis of Floating Offshore Wind Turbine Including Flexible Effects of Tower and Blade (타워와 블레이드의 탄성효과를 고려한 부유식 해상풍력발전기의 동적거동해석)

  • Jung, Hye-Young;Sohn, Jeong-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.8
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    • pp.905-911
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    • 2012
  • To establish a floating offshore wind turbine simulation model, a tension leg platform is added to an onshore wind turbine. The wind load is calculated by using meteorological administration data and a power law that defines the wind velocity according to the height from the sea surface. The wind load is applied to the blade and wind tower at a regular distance. The relative Morison equation is employed to generate the wave load. The rated rotor speed (18 rpm) is applied to the hub as a motion. The dynamic behavior of a 2-MW floating offshore wind turbine subjected to the wave excitation and wind load is analyzed. The flexible effects of the wind tower and the blade are analyzed. The flexible model of the wind tower and blade is established to examine the natural frequency of the TLP-type offshore wind turbine. To study the effect of the flexible tower and blade on the floating offshore wind turbine, we modeled the flexible tower model and flexible tower-blade model and compared it with a rigid model.

The analytical solution for buckling of curved sandwich beams with a transversely flexible core subjected to uniform load

  • Poortabib, A.;Maghsoudi, M.
    • Structural Engineering and Mechanics
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    • v.52 no.2
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    • pp.323-349
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    • 2014
  • In this paper, linear buckling analysis of a curved sandwich beam with a flexible core is investigated. Derivation of equations for face sheets is accomplished via the classical theory of curved beam, whereas for the flexible core, the elasticity equations in polar coordinates are implemented. Employing the von-Karman type geometrical non-linearity in strain-displacement relations, nonlinear governing equations are resulted. Linear pre-buckling analysis is performed neglecting the rotation effects in pre-buckling state. Stability equations are concluded based on the adjacent equilibrium criterion. Considering the movable simply supported type of boundary conditions, suitable trigonometric solutions are adopted which satisfy the assumed edge conditions. The critical uniform load of the beam is obtained as a closed-form expression. Numerical results cover the effects of various parameters on the critical buckling load of the curved beam. It is shown that, face thickness, core thickness, core module, fiber angle of faces, stacking sequence of faces and openin angle of the beam all affect greatly on the buckling pressure of the beam and its buckled shape.

The use of load pressure feedback in designing high performance electro-hydraulic speed controller for a flexible structure (대부하 탄성 구조물의 부하압력 피이드백에 관한 연구)

  • 김영대;정인수;김종규
    • 제어로봇시스템학회:학술대회논문집
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    • pp.310-314
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    • 1988
  • In designing a high performance electrohydraulic control system for a large flexible structure, several flexible structural modes should be taken into account in a range of hydraulic control system bandwidth. The procedures of modeling a flexible mode control system and designing the high pass filter of load pressure feedback are presented. Example analysis varifies the presented analysis.

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A Study on the Dynamic Stress Analysis of an Engine Block using Flexible-body Dynamic Analysis (유연체 동역학적 해석을 이용한 엔진블록의 동응력 해석에 관한 연구)

  • Son, Chang-Su;Cheon, Ho-Jeong;Seong, Hwal-Gyeong;Yoon, Keon-Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.7
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    • pp.805-813
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    • 2011
  • The dynamic stress of the diesel engine block is analyzed by using flexible-body dynamic analysis. Multiple loadings including the pressure load due to gas combustion, thermal load, and dynamic load are considered. Thermal load is assumed constant, however, pressure load and dynamic load are treated as time dependent. The present work is focused on the dynamic stress analysis, especially on finding critical points of the engine block. The analysis model includes four parts - engine block, generator, bed, and mounts. On the other hand, crank shaft, pistons, and main bearings are excluded from the model. However, their dynamic effects are applied by dynamic forces, obtained in the separate analysis. Dynamic stress is found by using flexible body dynamic analysis, and compared to the measured data.

Nonlinear analysis of interaction between flexible pile group and soil

  • Liu, Jie;Li, Q.S.;Wu, Zhe
    • Structural Engineering and Mechanics
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    • v.20 no.5
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    • pp.575-587
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    • 2005
  • Using the nonlinear load transfer function for pile side soil and the linear load transfer function for pile end soil, a combined approach of the incremental load transfer matrix method and the approximate differential equation solution method is presented for the nonlinear analysis of interaction between flexible pile group and soil. The proposed method provides an effective approach for the solution of the nonlinear interaction between flexible pile group under rigid platform and surrounding soil. To verify the accuracy of the proposed method, a static load test for a nine-pile group under a rigid platform is carried out. The finite element analysis is also conducted for comparison purposes. It is found that the results from the proposed method match very well with those from the experimental test and are better in comparison with the finite element method.

Generalized load cycles for dynamic wind uplift evaluation of rigid membrane roofing systems

  • Baskaran, A.;Murty, B.;Tanaka, H.
    • Wind and Structures
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    • v.14 no.5
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    • pp.383-411
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    • 2011
  • Roof is an integral part of building envelope. It protects occupants from environmental forces such as wind, rain, snow and others. Among those environmental forces, wind is a major factor that can cause structural roof damages. Roof due to wind actions can exhibit either flexible or rigid system responses. At present, a dynamic test procedure available is CSA A123.21-04 for the wind uplift resistance evaluation of flexible membrane-roofing systems and there is no dynamic test procedure available in North America for wind uplift resistance evaluation of rigid membrane-roofing system. In order to incorporate rigid membrane-roofing systems into the CSA A123.21-04 testing procedure, this paper presents the development of a load cycle. For this process, the present study compared the wind performance of rigid systems with the flexible systems. Analysis of the pressure time histories data using probability distribution function and power spectral density verified that these two roofs types exhibit different system responses under wind forces. Rain flow counting method was applied on the wind tunnel time histories data. Calculated wind load cycles were compared with the existing load cycle of CSA A123.21-04. With the input from the roof manufacturers and roofing associations, the developed load cycles had been generalized and extended to evaluate the ultimate wind uplift resistance capacity of rigid roofs. This new knowledge is integrated into the new edition of CSA A123.21-10 so that the standard can be used to evaluate wind uplift resistance capacity of membrane roofing systems.

Biomechanical Efficacy of a Combined Flexible Cage with Pedicle Screws with Spring rods: A Finite Element Analysis (Spring rod를 사용한 척추경 나사못과 동반 시술된 Flexible cage의 생체역학적 효과)

  • Kim, Y.H.;Park, E.Y.;Kim, W.H.;Hwang, S.P.;Park, K.W.;Lee, Sung-Jae
    • Journal of Biomedical Engineering Research
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    • v.38 no.1
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    • pp.9-15
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    • 2017
  • Recently, flexible cages have been introduced in an attempt to absorb and reduce the abnormal load transfer along the anterior parts of the spine. They are designed to be used with the pedicle screw systems to allow some mobility at the index level while containing ROM at the adjacent level. In this study, a finite element (FE) study was performed to assess biomechanical efficacies of the flexible cage when combined with pedicle screws with flexible rods. The post-operated models were constructed by modifying the L4-5 of a previously-validated 3-D FE model of the intact lumbar spine (L2-S1): (1) Type 1, flexible cage only; (2) Type 2, pedicle screws with flexible rods; (3) Type 3, interbody fusion cage plus pedicle screws with rigid rods; (4) Type 4, interbody fusion cage plus Type 2; (5) Type 5, Type 1 plus Type 2. Flexion/extension of 10 Nm with a compressive follower load of 400N was applied. As compared to the Type 3 (62~65%) and Type 4 (59~62%), Type 5 (53~55%) was able to limit the motion at the operated level effectively, despite moderate reduction at the adjacent level. It was also able to shift the load back to the anterior portions of the spine thus relieving excessively high posterior load transfer and to reduce stress on the endplate by absorbing the load with its flexible shape design features. The likelihood of component failure of flexble cage remained less than 30% regardless of loading conditions when combined with pedicle screws with flexible rods. Our study demonstrated that flexible cages when combined with posterior dynamic system may help reduce subsidence of cage and degeneration process at the adjacent levels while effectively providing stability at the operated level.