• Title, Summary, Keyword: analytical substructure

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Efficient Analysis for Vertical Vibration of Multistory Buildings (다층 건축구조물의 효율적인 연직진동해석)

  • 이동근;안상경
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.129-136
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    • 1999
  • This research proposes an effective analytical methodology for vertical vibration of three dimensional frame structures including slabs. The consideration of slabs, although allows more precise results, requires large amount of computer time and memory space due to the use of plane stress elements. In consideration of these problems, a method to properly manage nodal points and degrees of freedom is proposed based on matrix condensation technique. Also studied is the use of substructure method to obtain fast and reliable results with simple input data when they are applied to conventional building structures.

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A Study on the Finite Element Modeling and Analytical Parameters for the Dynamic Stiffness Evaluation of Shipboard Equipment Foundations (선박 장비 받침대의 동강성 평가를 위한 유한요소 모델링과 해석 인자에 관한 연구)

  • Kim, Kook-Hyun;Kim, Yun-Hwan;Choi, Tae-Muk;Choi, Sung-Won;Cho, Dae-Seung
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.6
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    • pp.808-812
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    • 2010
  • This paper studies the finite element modeling and analytical parameters for the numerical evaluation of dynamic stiffness of large foundation for shipboard equipments such as marine diesel engine. For the purpose, numerical method and procedure to evaluate the dynamic stiffness are established based on the impact test method, which are applied for the dynamic stiffness evaluation of a real diesel generator foundation of ship. Numerical investigations compared with the measured data are carried out to evaluate the effects of modeling ranges of ship substructure, finite element sizes, lower support structures and damping coefficients. From the results, modeling and analytical parameters for proper evaluation of dynamic stiffness of large foundation of shipboard equipment are suggested.

Modeling of the lateral stiffness of masonry infilled steel moment-resisting frames

  • Lemonis, Minas E.;Asteris, Panagiotis G.;Zitouniatis, Dimitrios G.;Ntasis, Georgios D.
    • Structural Engineering and Mechanics
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    • v.70 no.4
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    • pp.421-429
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    • 2019
  • This paper presents an analytical model for the estimation of initial lateral stiffness of steel moment resisting frames with masonry infills. However, rather than focusing on the single bay-single storey substructure, the developed model attempts to estimate the global stiffness of multi-storey and multi-bay frames, using an assembly of equivalent springs and taking into account the shape of the lateral loading pattern. The contribution from each infilled frame panel is included as an individual spring, whose properties are determined on the basis of established diagonal strut macro-modeling approaches from the literature. The proposed model is evaluated parametrically against numerical results from frame analyses, with varying number of frame stories, infill openings, masonry thickness and modulus of elasticity. The performance of the model is evaluated and found quite satisfactory.

Effectiveness of Isolation-System on Reduction of Seismic Response of Primary and Secondary Structures (주구조물 및 부구조물에 대한 감진장치의 지진응답 감소 효율성)

  • Kim, Young Sang;Lee, Dong Guen
    • Journal of The Korean Society of Civil Engineers
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    • v.12 no.4_1
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    • pp.9-21
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    • 1992
  • The effectiveness of the isolation system installed at the base of the primary structure and at the support of the substructure mounted on the primary structure is evaluated for reducing of structural responses under different earthquakes in this paper. The structural responses are analyzed to identify its behavior due to the input motion characteristics such as various peak acceleration and frequency content. Three analytical models are used to evaluate the effectiveness of the isolation system in this study as follows: fixed-base primary structure with support-fixed substructure, base-isolated primary structure with support-fixed substructure, and fixed-base primary structure with support-isolated substruciure. A computer code (KBISAP) is used for numerical integration of equation of motion considering the interaction between the primary structure and the secondary structure. The matrix condensation technique and constant average acceleration method are utilized in this program. And also, the effective stiffness of the base-isolator on reducing the structural response are evaluated for various earthquakes through the relationship of the acceleration - displacement.

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Seismic performance of prefabricated bridge columns with combination of continuous mild reinforcements and partially unbonded tendons

  • Koem, Chandara;Shim, Chang-Su;Park, Sung-Jun
    • Smart Structures and Systems
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    • v.17 no.4
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    • pp.541-557
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    • 2016
  • Prefabricated bridge substructures provide new possibility for designers in terms of efficiency of creativity, fast construction, geometry control and cost. Even though prefabricated bridge columns are widely adopted as a substructure system in the bridge construction project recently, lack of deeper understanding of the seismic behavior of prefabricated bridge substructures cause much concern on their performance in high seismic zones. In this paper, experimental research works are presented to verify enhanced design concepts of prefabricated bridge piers. Integration of precast segments was done with continuity of axial prestressing tendons and mild reinforcing bars throughout the construction joints. Cyclic tests were conducted to investigate the effects of the design parameters on seismic performance. An analytical method for moment-curvature analysis of prefabricated bridge columns is conducted in this study. The method is validated through comparison with experimental results and the fiber model analysis. A parametric study is conducted to observe the seismic behavior of prefabricated bridge columns using the analytical study based on strain compatibility method. The effects of continuity of axial steel and tendon, and initial prestressing level on the load-displacement response characteristics, i.e., the strain of axial mild steels and posttensioned tendon at fracture and concrete crushing strain at the extreme compression fiber are investigated. The analytical study shows the layout of axial mild steels and posttensioned tendons in this experiment is the optimized arrangement for seismic performance.

Real-time Hybrid Testing a Building Structure Equipped with Full-scale MR dampers and Application of Semi-active Control Algorithms (대형 MR감쇠기가 설치된 건축구조물의 실시간 하이브리드 실험 및 준능동 알고리즘 적용)

  • Park, Eun-Churn;Lee, Sung-Kyung;Lee, Heon-Jae;Moon, Suk-Jun;Jung, Hyung-Jo;Min, Kyung-Won
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.21 no.5
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    • pp.465-474
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    • 2008
  • The real-time hybrid testing method(RT-HYTEM) is a structural testing technique in which the numerical integration of the equation of motion for a numerical substructure and the physical testing for an experimental substructure are performed simultaneously in real-time. This study presents the quantitative evaluation of the seismic performance of a building structure installed with an passive and semi-active MR damper by using RT-HYTEM. The building model that was identified from the force-vibration testing results of a real-scaled 5-story building is used as the numerical substructure, and an MR damper corresponding to an experimental substructure is physically tested by using the universal testing machine(UTM). The RT-HYTEM implemented in this study is validated because the real-time hybrid testing results obtained by application of sinusoidal and earthquake excitations and the corresponding analytical results obtained by using the Bouc-Wen model as the control force of the MR damper respect to input currents were in good agreement. Also for preliminary study, some semi-active control algorithms were applied to the MR damper in order to control the structural responses optimally. Comparing between the test results of semi-active control using RT-HYTEM and numerical analysis results show that the RT-HYTEM is more resonable than numerical analysis to evaluate the performance of semi-active control algorithms.

Experimental evaluation of an inertial mass damper and its analytical model for cable vibration mitigation

  • Lu, Lei;Fermandois, Gaston A.;Lu, Xilin;Spencer, Billie F. Jr.;Duan, Yuan-Feng;Zhou, Ying
    • Smart Structures and Systems
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    • v.23 no.6
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    • pp.589-613
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    • 2019
  • Cables are prone to vibration due to their low inherent damping characteristics. Recently, negative stiffness dampers have gained attentions, because of their promising energy dissipation ability. The viscous inertial mass damper (termed as VIMD hereinafter) can be viewed as one realization of the inerter. It is formed by paralleling an inertial mass part with a common energy dissipation element (e.g., viscous element) and able to provide pseudo-negative stiffness properties to flexible systems such as cables. A previous study examined the potential of IMD to enhance the damping of stay cables. Because there are already models for common energy dissipation elements, the key to establish a general model for IMD is to propose an analytical model of the rotary mass component. In this paper, the characteristics of the rotary mass and the proposed analytical model have been evaluated by the numerical and experimental tests. First, a series of harmonic tests are conducted to show the performance and properties of the IMD only having the rotary mass. Then, the mechanism of nonlinearities is analyzed, and an analytical model is introduced and validated by comparing with the experimental data. Finally, a real-time hybrid simulation test is conducted with a physical IMD specimen and cable numerical substructure under distributed sinusoidal excitation. The results show that the chosen model of the rotary mass part can provide better estimation on the damper's performance, and it is better to use it to form a general analytical model of IMD. On the other hand, the simplified damper model is accurate for the preliminary simulation of the cable responses.

Vibrational Analysis of Rotor Model considering the Dynamic Characteristics of the Support Structure (지지구조물의 동특성을 고려한 회전축 모델의 진동해석)

  • Choe, Bok-Rok;Park, Jin-Mu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.4
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    • pp.555-563
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    • 2001
  • Support dynamics are often important in rotordynamic analyses. It may well happen in real situation of machines such as centrifugal pumps or turbines operating on flexible structure. This paper presents the applications of the impedance coupling method and the improved rotor model for including the support effects on the interaction with the rotor. The impedance coupling techniques are based on the FRFs of each substructure. Its dynamic stiffness matrix can be assembled to generate the system matrix, which satisfy the constraint conditions in the connection coordinates. And, the improved rotor uses the simplified spring-mass models as support properties. The equivalent support models are directly incorporated into the finite element rotor model. To verify the suggested analytical procedures, the results are compared to those of the pump system.

Dynamic Analysis of Harmonically Excited Non-Linear System Using Multiple Scales Method

  • Moon, Byung-Young;Kang, Beom-Soo
    • Journal of Mechanical Science and Technology
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    • v.16 no.6
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    • pp.819-828
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    • 2002
  • An analytical method is presented for evaluation of the steady state periodic behavior of nonlinear systems. This method is based on the substructure synthesis formulation and a MS (multiple scales) procedure, which is applied to the analysis of nonlinear responses. The proposed procedure reduces the size of large degrees-of-freedom problem in solving nonlinear equations. Feasibility and advantages of the proposed method are illustrated with the nonlinear rotating machine system as an example of large mechanical structure systems. In addition, its efficiency for nonlinear response prediction will be shown by comparison of other conventional methods.

Effects of Stagger and Pretwist Angles on the Vibration of Flexible Shaft-Bladed Disk Systems (탄성 축-익 붙임 원판 계의 진동에 있어서 엇각 및 비틀림각의 영향)

  • 전상복;이종원
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.101-109
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    • 1997
  • An analytical procedure on the base of the substructure synthesis and assumed modes method is developed to investigate the flexibility effect 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. The coupled vibrations between the shaft and bladed disk are then extensively investigated through the numerical simulation of simplified models, with varying the shaft rotational speed and the pretwist and stagger angles of the blade. It is found that the Coriolis and inertia forces and the inertia torque, which are induced by the one nodal diameter modes of the bladed disk and vary depending upon the stagger and pretwist angles, lead to the coupled motions of the shaft and the bladed disk.

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