• Title/Summary/Keyword: Rigid Bearing

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Effect of connection stiffness on the earthquake-induced progressive collapse

  • Ali, Seyedkazemi;Mohammad Motamedi, Hour
    • Earthquakes and Structures
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    • v.23 no.6
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    • pp.503-515
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    • 2022
  • Global or partial damage to a structure due to the failure of gravity or lateral load-bearing elements is called progressive collapse. In the present study, the alternate load path (ALP) method introduced by GSA and UFC 4-023-03 guidelines is used to evaluate the progressive collapse in special steel moment-resisting frame (SMRF) buildings. It was assumed that the progressive collapse is due to the earthquake force and its effects after the removal of the elements still remain on the structures. Therefore, nonlinear dynamic time history analysis employing 7 earthquake records is used to investigate this phenomenon. Internal and external column removal scenarios are investigated and the stiffness of the connections is changed from semi-rigid to rigid. The results of the analysis performed in the OpenSees program show that the loss of the bearing capacity of an exterior column due to a seismic event and the occurrence of progressive collapse can increase the inter-story drift of the structure with semi-rigid connections by more than 50% and make the structure unable to satisfy the life safety performance level. Furthermore, connection stiffness severely affects the redistribution of forces and moments in the adjacent elements of the removed column.

A Studyon the Drawing of Rectangular Rod from Round Bar by using Rigid Plastic FEM and Neural Network (강소성 유한요소법과 신경망을 이용한 직사각재 인발공정에 관한 연구)

  • Kim, Y.C.;Choi, Y.;Kim, B.M.;Choi, J.C.
    • Transactions of Materials Processing
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    • v.8 no.4
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    • pp.331-339
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    • 1999
  • In this study, to analyze the shaped drawing process from round bar, the practical conical die with considering die radius and bearing was defined by a mathematical expression, and also a simple technique for initial mesh generation to the shaped drawing process was proposed. The drawing of rectangular section from round bar, one of the shaped drawing process, has been simulated by using non-steady state 3D rigid plastic finite element method in order to evaluate the influence of semi-die angle and reduction in area to corner filling. Other process variables such as friction constant, rectangular ratio, die radius and bearing length were fixed during the simulation. An artificial neural network has been introduced to obtain the optimal process conditions which gave rise to a fast simulation.

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Foundation size effect on the efficiency of seismic base isolation using a layer of stone pebbles

  • Banovic, Ivan;Radnic, Jure;Grgic, Nikola
    • Earthquakes and Structures
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    • v.19 no.2
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    • pp.103-117
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    • 2020
  • The effect of the foundation size on the efficiency of seismic base isolation using a layer of stone pebbles is experimentally investigated. Four scaled models of buildings with different stiffnesses (from very stiff to soft) were tested, each with the so-called small and large foundation, and exposed to four different accelerograms (different predominant periods and durations). Tests were conducted so that the strains in the model remained elastic and afterwards the models were tested until collapse. Each model was tested for the case of the foundation being supported on a rigid base and on an aseismic layer. Compared to the smaller foundation, the larger foundation results in a reduced rocking effect, higher earthquake forces and lower bearing capacity of the tested models, with respectable efficiency (reduced strain/stress, displacement and increase of the ultimate bearing capacity of the model) for the considered seismic base isolation compared to the foundation on a rigid base.

An Approximate Time-Effective Finite Element Method for Analyzing a Rotary Forging Process (회전단조공정 해석을 위한 실용적 유한요소법)

  • Moon H. K.;Lee M. C.;Chung J. H.;Joun M. S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.05a
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    • pp.117-121
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    • 2005
  • In this paper, an approximate time-effective approach to rigid-plastic finite element method is presented with its solution scheme and a volume compensation method is proposed to simulate rotary forging processes. The applicability is examined by comparing the results obtained by the presented approach with those by the conventional approach. The approach is applied to simulation of a rotary forging process fur a wheel bearing assembly. The analyzed results are compared with the experimental results.

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Model Validation and Controller Design for Vibration Suppression of Flexible Rotor Using AMB

  • Soo Jeon;Ahn, Hyeong-Joon;Han, Dong-Chul
    • Journal of Mechanical Science and Technology
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    • v.16 no.12
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    • pp.1583-1593
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    • 2002
  • This paper discusses the model validation and vibration suppression of an AMB flexible rotor via additional LQG controller. The main difficulty in the vibration suppression of the flexible rotor using AMB is to realize a controller that can minimize resonance without injuring the stabilized rigid modes. In order to solve this problem, simple scheme for system modeling and controller design are developed. Firstly, the AMB flexible rotor is stabilized with a PID controller, which leads to a new stable rotor-bearing system. Then, authors propose the model validation procedure using measured open-loop frequency responses to obtain an accurate model of the AMB flexible rotor system. After that, LQG controller with modal weighting is designed to suppress resonances of the stable rotor-bearing system. Due to the poor controllability and observability of flexible modes compared to rigid ones, balancing of two Gramians is prerequisite for the fair LQG controller design. Simulation with step disturbance and experimental results of unbalance response up to 10,000 rpm verified the effectiveness of the proposed scheme.

An Instrumented Workstation to Evaluate Weight-Bearing Distribution in the Sitting Posture

  • Moriguchi, Cristiane S.;Sato, Tatiana O.;Coury, Helenice J.C.G.
    • Safety and Health at Work
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    • v.10 no.3
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    • pp.314-320
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    • 2019
  • Background: Sitting posture may be related to risk factors, including inadequate weight-bearing support, particularly when maintained for long periods. Considering that body weight is loaded in a closed support system composed of the seat, backrest, floor and working surface, the aims of the present study were to describe the development of an ergonomic sitting workstation to continuously record weight-bearing at the seat, chair, backrest, work surface, and floor and to test its measurement properties: reproducibility, criterion-related validity, and sensitivity. Methods: Rigid bodies (1 to 30 kg) and participant weights were recorded to evaluate the workstation measurement properties. Results: Rigid body tests showed variation values less than 0.050 kg on reproducibility test and errors below 5% of measured value on criterion validity tests. Participant tests showed no statistically significant differences between repeated measures ($p{\geq}0.40$), errors were less than 2% of participant weights an sensitivity presented statistically significant changes (p = 0.007). Conclusion: The sitting workstation proposed showed to be reliable, valid and sensitive for use in future ergonomic studies to evaluate the sitting posture.

Three-Dimensional Rigid-Plastic Finite Element Analysis of Nonsteady State Shaped Drawing Process (비정상상태 이형재 인발공정의 3차원 강소성 유한요소해석)

  • Kim, Ho-Chang;Choi, Young;Kim, Byung-Min
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.7
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    • pp.119-128
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    • 1998
  • In this paper, nonsteady state shaped drawing process has been investigated using the three-dimensional rigid-plastic finite element method. In order to analyze the shaped drawing process, a method to define straight converging die considering straight die part, die radius part and bearing part has been proposed. In addition, the modeling of initial billet and the generation procedure of mesh system have been suggested. The three-dimensional rigid-plastic finite element simulation has been performed for a square sectional drawing process and its result has been confirmed in comparison with the existing experimental one. Also, for the same process conditions, the effect of perimeter ratio in the shaped drawing process has been investigated.

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An Analysis of the Stability of Externally Pressurized Air-Lubricated Journal Bearings (외부가압 공기윤활 저어널베어링의 안정성에 관한 해석)

  • 임종락;김경웅;김금모
    • Tribology and Lubricants
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    • v.6 no.1
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    • pp.74-81
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    • 1990
  • The threshold of instability for a rigid rotor supported in externally pressurized airlubricated circular or non-circular journal bearings of finite length is theoretically analyzed. The analysis is performed for a bearing having one feeding plane, no recess volume, which is assumed to be a line source, and is based on a first order perturbation of journal center motion about steady state position. And then linearized system dynamic analysis is carried out. Numerical results are given, showing the threshold of instability as a function of supply pressure ratio, feeding parameter and load. It is shown that the region that 2-lobe bearing is more stable than circular bearing exists and whirl ratio of 2-lobe bearing is less than that of the other types of bearing.

Dynamic Characteristics Analysis of the Carriage Structure Supported by Air Bearing (공기베어링으로 지지된 캐리지 구조물의 동특성 해석)

  • 정순철;김덕수;유충준;장승환
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.11
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    • pp.1059-1065
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    • 2004
  • In this paper, the dynamic characteristic analysis of carriage structure supported by air bearings were performed. Toward this end, the characteristics of air bearing were numerically analyzed to estimate the stiffness of the air bearing and the clearance between air bearing and guide surface. The modal analysis of the carriage structure was performed by using finite element method, and the experimental modal analysis was also performed to validate the finite element model, where rigid body modes were compared to validate the stiffness of the air bearings. From the results, the air spring stiffness can be estimated within the range of acceptable accuracy under any pressure and clearance condition.

Dynamic Characteristics Analysis of the Carriage Structure Supported by Air Bearing (에어베어링으로 지지된 캐리지 구조물의 동특성 해석)

  • 정순철;김덕수;유충준;장승환;이재응
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.1107-1114
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    • 2003
  • In this thesis, the dynamic characteristic analysis of carriage structure supported by air bearings were peformed. Toward this end, the characteristics of air bearing were numerically analyzed to estimate the stiffness of the air bearing and the clearance between air bearing and guide surface. The modal analysis of the carriage structure was peformed by using finite element method, and the experimental modal analysis was also performed to validate the finite element model, where rigid body modes were compared to validate the stiffness of the air bearings. From the results, the air spring stiffness can be estimated within the range of acceptable accuracy under any pressure and clearance condition.

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