• Title, Summary, Keyword: analytical substructure

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Semi-analytical numerical approach for the structural dynamic response analysis of spar floating substructure for offshore wind turbine

  • Cho, Jin-Rae;Kim, Bo-Sung;Choi, Eun-Ho;Lee, Shi-Bok;Lim, O-Kaung
    • Structural Engineering and Mechanics
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    • v.52 no.3
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    • pp.633-646
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    • 2014
  • A semi-analytical numerical approach for the effective structural dynamic response analysis of spar floating substructure for offshore wind turbine subject to wave-induced excitation is introduced in this paper. The wave-induced rigid body motions at the center of mass are analytically solved using the dynamic equations of rigid ship motion. After that, the flexible structural dynamic responses of spar floating substructure for offshore wind turbine are numerically analyzed by letting the analytically derived rigid body motions be the external dynamic loading. Restricted to one-dimensional sinusoidal wave excitation at sea state 3, pitch and heave motions are considered. Through the numerical experiments, the time responses of heave and pitch motions are solved and the wave-induced dynamic displacement and effective stress of flexible floating substructure are investigated. The hydrodynamic interaction between wave and structure is modeled by means of added mass and wave damping, and its modeling accuracy is verified from the comparison of natural frequencies obtained by experiment with a 1/100 scale model.

Development, implementation and verification of a user configurable platform for real-time hybrid simulation

  • Ashasi-Sorkhabi, Ali;Mercan, Oya
    • Smart Structures and Systems
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    • v.14 no.6
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    • pp.1151-1172
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    • 2014
  • This paper presents a user programmable computational/control platform developed to conduct real-time hybrid simulation (RTHS). The architecture of this platform is based on the integration of a real-time controller and a field programmable gate array (FPGA).This not only enables the user to apply user-defined control laws to control the experimental substructures, but also provides ample computational resources to run the integration algorithm and analytical substructure state determination in real-time. In this platform the need for SCRAMNet as the communication device between real-time and servo-control workstations has been eliminated which was a critical component in several former RTHS platforms. The accuracy of the servo-hydraulic actuator displacement control, where the control tasks get executed on the FPGA was verified using single-degree-of-freedom (SDOF) and 2 degrees-of-freedom (2DOF) experimental substructures. Finally, the functionality of the proposed system as a robust and reliable RTHS platform for performance evaluation of structural systems was validated by conducting real-time hybrid simulation of a three story nonlinear structure with SDOF and 2DOF experimental substructures. Also, tracking indicators were employed to assess the accuracy of the results.

Vibration Analysis of Shaft-Bladed Disk Systems (축-익 붙임 원판 계의 진동해석)

  • 전상복
    • Journal of KSNVE
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    • v.8 no.1
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    • pp.99-111
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    • 1998
  • An analytical method using the substructure synthesis and assumed modes method is developed to investigate the effect of flexibility of bladed disk assembly on vibrational modes of flexible rotor system. In modeling the system, Coriolis forces, gyroscopic moments, and centrifugal stiffening effects are taken into account. Then the coupled vibrations between the shaft and bladed disk are extensively investigated using simplistic models, as the shaft rotational speed and the pretwist and stagger angles of blade are varied.

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The Influence of Vanadium Addition on Fracture Behavior and Martensite Substructure in a Ni-36.5at.%Al Alloy (Ni-36.5at.%Al 합금에서 V 첨가가 파괴거동 및 마르텐사이트 내부조직에 미치는 영향)

  • Kim, Young Do;Choi, Ju;Wayman, C. Marvin
    • Analytical Science and Technology
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    • v.5 no.2
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    • pp.203-211
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    • 1992
  • Fracture behavior and martensite substructure of Ni-36.5at.%Al alloy were investigated with the addition of vanadium which is known as scavenging element of grain boundary. The fracture surfaces were examined by scanning electron microscopy and the EDX spectrometer was applied for composition analysis of fracture surfaces. The substructure of martensite was studied by transmission electron microscopy. By addition of vanadium, fracture surfaces show mixed modes of intergranular and transgranular fracture and more Al content is found on the grain boundaries. For Ni-36.5at.%Al alloy, the planar faults observed in the martensite plates are the internal twins. By increasing the vanadium content, the modulated structure with stacking faults and dislocations dominates while the twinned martensite disappears. The stacking fault is determined to be extrinsic due to the substitution of V for Al. It is concluded that the segregation of sulfur on the high-energy state stacking fault area suppresses the intergranular fracture.

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Vibration Analysis of Structures Using the Transfer Stiffness Coefficient Method and the Substructure Synthesis Method (전달강성계수법과 부분구조합성법을 이용한 구조물의 진동해석)

  • Choi, Myung-Soo
    • Journal of the Korea Society For Power System Engineering
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    • v.5 no.4
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    • pp.24-30
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    • 2001
  • The substructure synthesis method(SSM) is developed for overcoming disadvantages of the Finite Element Method(FEM). The concept of the SSM is as follows. After dividing a whole structure into several substructures, every substructures are analyzed by the FEM or experiment. The whole structure is analyzed by using connecting condition and the results of substructures. The concept of the transfer stiffness coefficient method(TSCM) is based on the transfer of the nodal stiffness coefficients which are related to force vectors and displacement vectors at each node of analytical mode1. The superiority of the TSCM to the FEM in the computation accuracy, cost and convenience was confirmed by the numerical computation results. In this paper, the author suggests an efficient vibration analysis method of structures by using the TSCM and the SSM. The trust and the validity of the present method is demonstrated through the numerical results for computation models.

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A Simplified Soil-Structure Interaction Analytical Technique of Embedded Structure and Structure on Layered Soil Sites (매입구조물(埋入構造物)과 층상지반상(層狀地盤上) 구조물(構造物)에 대한 지반(地盤)-구조물(構造物) 상호(相互) 작용(作用)의 단순해석(單純解析))

  • Joe, Yang Hee;Lee, Yong Il;Kim, Jong Soo
    • Journal of The Korean Society of Civil Engineers
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    • v.7 no.2
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    • pp.45-57
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    • 1987
  • The dynamic behavior of a structure by earthquake is considerably affected by the flexibility of the base soil. This phenomenon is called dynamic soil-structure interaction effect. There are two broad categories of soil-structure interaction analytical technique: direct method and substructure method. Substructure method, in contrast to direct method, has many limitations in applying to embedded structures or structures on layered soil sites, while it is relatively simple. In this paper, a simplified soil-structure interaction analytical procedure using substructure method is proposed to eliminate its original limitations. The proposed method is well applicable to embedded structures or structures on layered soil sites with as good results as FLUSH.

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Structural Dynamic Modification Using substructure Response Function Sensitivity Method(SRFSM) (부분구조응답함수감소법을 이용한 동적구조변경)

  • Ji, Tae-Han;Park, Yeong-Pil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.12
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    • pp.3782-3791
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    • 1996
  • A great deal of effert has been invested in upgrading the performance and the efficiency of mechanical structures. Using experimental modal analysis(EMA) or finite element analysis(FEA) data of mechanical structures, this performance and efficiency can be effectively evaluated. In order to analyze complex structures such as automobiles and aircraft, for the sake of computing efficiency, the dynamic substructuring techniques that allow to predict the dynamic behavior of a structure based on that of the composing structures, are widely used. By llinking a modal model obtained from EMA and an analytical model obtained from FEA, the best conditioned structures can be desinged. In this paper, a new algorithm for structural dynamic modification-SRFSM (substructure response function sensitivity method) is proposed by linking frequency responce function synthesis and response function sensitivity. A mehtod to obtain response function sensitivity using direct derivative of mechanical impedance, is also used.

Vibration and Noise Control of the Simply Supported Slab Using the Multi-tuned Mass Damper (다중동조질량감쇠기를 이용한 단순지지 슬래브의 진동 및 소음저감에 관한 연구)

  • Hwang, Jae-Seung;Hong, Geon-Ho;Park, Hong-Gun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.10
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    • pp.1006-1013
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    • 2008
  • In this study, it is outlined that heavy weight floor impact noise induced by the vibration of slab can be reduced using multi tuned mass damper(MTMD) effectively. Substructure synthesis is utilized to develope analytical model of the slab coupled with MTMD and acoustic power is introduced to evaluate the performance of noise control for simplicity. Numerical analysis is carried out to investigate the effect of the properties of MTMD on the vibration and noise control of the simply supported slab. Numerical analysis shows that mass ratio of MTMD is critical on the vibration and noise control of the slab and it is also essential to reduce the vibration in higher modes of slab in the light of its great effect on the radiation of sound.

Vibration and noise control of slab using the multi-tuned mass damper (다중질량감쇠기를 이용한 슬래브의 진동 및 소음저감에 관한 연구)

  • Hwang, Jae-Seung;Kim, Hong-Jin;Kang, Kyung-Soo;Hong, Gun-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.659-664
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    • 2008
  • In this study, it is outlined that heavy weight floor impact noise induced by the vibration of slab can be reduced by multi tuned mass damper(MTMD) effectively. Substructure synthesis is utilized to develope analytical model of slab coupled with MTMD and acoustic power is introduced to evaluate the performance of noise control for simplicity. Numerical analysis is carried out to investigate the effect of the properties of MTMD on the vibration and noise control. Numerical analysis shows that mass ratio of MTMD is critical on the vibration and noise control of the slab and it is essential to reduce the vibration in higher modes of slab because it has a great effect on the radiation of sound.

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Seismic performance of a rocking bridge pier substructure with frictional hinge dampers

  • Cheng, Chin-Tung;Chen, Fu-Lin
    • Smart Structures and Systems
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    • v.14 no.4
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    • pp.501-516
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    • 2014
  • The rocking pier system (RPS) allows the columns to rock on beam or foundation surfaces during the attacks of a strong earthquake. Literatures have proved that seismic energy dissipated by the RPS through the column impact is limited. To enhance the energy dissipation capacity of a RPS bridge substructure, frictional hinge dampers (FHDs) were installed and evaluated by shaking table tests. The supplemental FHDs consist of two brass plates sandwiched by three steel plates. The strategy of self-centering design is to isolate the seismic energy by RPS at the columns and then dissipate the energy by FHDs at the bridge deck. Component tests of FHD were first conducted to verify the friction coefficient and dynamic characteristic of the FHDs. In total, 32 shaking table tests were conducted to investigate parameters such as wave forms of the earthquake (El Centro 1940 and Kobe 1995) and normal forces applied on the friction dampers. An analytical model was also proposed to compare with the tested damping of the bridge sub-structure with or without FHDs.