The Motion Evaluation of Lumbar Spine Involving the Instantaneous Center of Rotation

2003 ◽  
Vol 2003.7 (0) ◽  
pp. 149-150
Author(s):  
Ko KITAHARA ◽  
Ko TAKANO ◽  
Kazuhiro HASEGAWA ◽  
Toshiaki HARA
Keyword(s):  
Lumbar Spine ◽  
Center Of Rotation ◽  
Instantaneous Center

scholarly journals Instantaneous center of rotation behavior of the lumbar spine with ligament failure

2013 ◽  
Vol 18 (6) ◽  
pp. 617-626 ◽  
Author(s):  
Yunus Alapan ◽  
Cihan Demir ◽  
Tuncay Kaner ◽  
Rahmi Guclu ◽  
Serkan İnceoğlu
Keyword(s):  
Lumbar Spine ◽  
Range Of Motion ◽  
Load Transfer ◽  
Sagittal Plane ◽  
Element Model ◽  
Ligament Injury ◽  
Center Of Rotation ◽  
Lower Lumbar Spine ◽  
Ligament Failure ◽  
Instantaneous Center

Object The goal of this study was to investigate the effect of ligament failure on the instantaneous center of rotation (ICR) in the lower lumbar spine. Methods A 3D finite element model of the L4–5 segment was obtained and validated. Ligament failure was simulated by reducing ligaments in a stepwise manner from posterior to anterior. A pure bending moment of 7.5 Nm was applied to the model in 3 anatomical planes for the purpose of validation, and a 6-Nm moment was applied to analyze the effect of ligament failure. For each loading case, ligament reduction step, and load increment, the range of motion of the segment and the ICR of the mobile (L-4) vertebra were calculated and characterized. Results The present model showed a consistent increase in the range of motion as the ligaments were removed, which was in agreement with the literature reporting the kinematics of the L4–5 segment. The shift in the location of the ICR was below 5 mm in the sagittal plane and 3 mm in both the axial and coronal planes. Conclusions The location of the ICR changed in all planes of motion with the simulation of multiple ligament injury. The removal of the ligaments also changed the load sharing within the motion segment. The change in the center of rotation of the spine together with the change in the range of motion could have a diagnostic value, revealing more detailed information on the type of injury, the state of the ligaments, and load transfer and sharing characteristics of the segment.

Instantaneous Center of Rotation of a Vessel Submitted to Oblique Waves

2020 ◽  
Author(s):  
Daniel de Oliveira Costa ◽  
Joel Sena Sales Junior ◽  
Antonio Carlos Fernandes
Keyword(s):  
Degrees Of Freedom ◽  
Floating Body ◽  
Wave System ◽  
Ocean Engineering ◽  
Wave Condition ◽  
Oblique Waves ◽  
Center Of Rotation ◽  
Instantaneous Center ◽  
6 Degrees Of Freedom ◽  
General Motion

Abstract When under influence of an incident wave system, any freely floating body presents a general motion with all six degrees of freedom. The Instantaneous Center of Rotation, as defined in classical mechanics, is a concept that allows the description of a general motion in 6 degrees of freedom as a pure rotation around such point. This approach, although not widely used in ocean engineering, might be an alternative tool that allows fast and precise analysis in many cases. Recent studies have shown that under specific conditions, such as a heading wave condition, the ICR varies in time but it is always located along a line for one wave frequency. Similar results were presented regarding beam waves as well. The present work continues with the investigation regarding the behavior of ICR under more generic conditions, assuming oblique waves exciting a vessel with typical geometry of a FPSO platform. The study extends the knowledge derived based on 2D approaches from previous works, comparing the results obtained from the different methods. An analytical model is presented, assuming only harmonic motion to all 6 degrees of freedom and showing that, similar to what was observed in the simplified 2D cases, the ICR tends to present dependence on the frequency of motion. Numerical data acquired from commercial codes based on potential theory is also presented.

Analysis for Eccentrically Loaded of Steel Bolted Group

2012 ◽  
Vol 226-228 ◽  
pp. 1441-1444
Author(s):  
Wei Ting Hsu ◽  
Dung Myau Lue ◽  
Cheng Yen Liao
Keyword(s):  
Loading Condition ◽  
Generalized Solution ◽  
Elastic Analysis ◽  
Center Of Rotation ◽  
Vertical Loading ◽  
Rotation Method ◽  
Inclination Angles ◽  
Instantaneous Center ◽  
Made In

Two general approaches for the analysis of eccentrically loaded connections are described in the current AISC Specifications. The first method is the conservative elastic analysis. The second method is the instantaneous center of rotation method which gives more realistic values but is extremely tedious to apply. The 1989 AISC-ASD manual contains design tables intended for vertical loading only. The 2010 AISC manual considers eccentric loading with six specific inclination angles (θ) varying from 0 and to 75 degrees. However, actual loading condition may very likely differ from what has been assumed in the AISC design manual. This study proposes a more generalized solution (75° θ 360°) to overcome the design limitations as inherently made in the design manual. For uncovered cases, AISC Specifications do not offer a guideline on how to handle them. In such situation, engineers have the tendency to use the unjustified elastic method.

Movement of the Instantaneous Center of Rotation and the Position of the Lateral Excursion Center During Lateral Excursion

CRANIO® ◽  
2008 ◽  
Vol 26 (4) ◽  
pp. 253-262 ◽  
Author(s):  
Haruaki Hayasaki ◽  
Issei Saitoh ◽  
Yoko Iwase ◽  
Emi Inada ◽  
Hiroko Hasegawa ◽  
...  
Keyword(s):  
Center Of Rotation ◽  
Instantaneous Center

Résultats d'essais sur des assemblages soudés excentriques en flexion

1985 ◽  
Vol 12 (3) ◽  
pp. 494-506 ◽  
Author(s):  
D. Beaulieu ◽  
A. Picard
Keyword(s):  
Laboratory Tests ◽  
Load Application ◽  
Deformation Characteristics ◽  
Limit States ◽  
Fillet Weld ◽  
Center Of Rotation ◽  
Actual Load ◽  
Simplifying Assumptions ◽  
Instantaneous Center ◽  
Work Done

The development, by Butler and Kulak, of equations for the calculation of fillet weld resistance with relation to the angle of load application has improved the understanding of the limit states behavior of welded connections. For the design of welded connections subjected to shear and moment, Dawe and Kulak developed a method of analysis based on the principle of instantaneous center of rotation, which accounts for the actual load–deformation characteristics of the weld. Due to its complexity, the method of Dawe and Kulak requires the use of a computer. In order to make the method more attractive to the designer, Neis suggested some simplifying assumptions and at the same time criticized the work done by Dawe and Kulak. In the discussions that followed the publication of his results, various researchers expressed diverging opinions on several matters related to the theories.Since the proposed methods were based on the results of only 8 laboratory tests done by Dawe and Kulak, we have carried out a series of 24 tests. The results of these tests were compared with the theoretical ultimate loads obtained from the methods of Dawe and Kulak and Neis, and demonstrate that the proposed methods are adequate as long as they are used within certain limits and respect certain conditions.

Behavior and Mechanisms of Bolt Self-Loosening Under Transverse Load Due to Vibrations of a Washer Along an Arc

2008 ◽  
Author(s):  
Yasuo Fujioka
Keyword(s):  
Fe Analysis ◽  
The Other ◽  
Transverse Load ◽  
Shear Forces ◽  
Center Of Rotation ◽  
Concentric Circles ◽  
Instantaneous Center ◽  
Screw Threads ◽  
External Loads ◽  
Good Agreement

Self-loosening mechanisms of a bolt were investigated by Finite Element Method, under the assumption of a twist at the center of a circular joined structure in which the bolt was set along a certain pitch circle. In this structure, the bolt is loosened by combining the translational and rotational external loads. In the case of a large pitch circle structures in which self-loosening occurs, the directions of friction shear forces on the threads were along concentric circles; however, the instantaneous center of rotation was located one-side near the thread surface, and the center was eccentric with the axis of the bolt. If the radius of the pitch circle is set smaller, the instantaneous center of rotation moves closer to the center of the bolt, and finally reaches to the same position at the center of the bolt. On the other hand, the directions of friction shear forces on pitch diameter of one thread were calculated theoretically using the inclination and friction on a pressure flank. The results were in good agreement with FE analysis. By considering these mechanisms, it was estimated that the number of occurrence of self-loosening in one vibration cycle changes at the border when the diameter value of the pitch circle equals that of the screw threads. If the diameter of the pitch circle becomes smaller than that of the screw threads, the number changes from two to one. With the exception of torsional center-fastened structures, since the pitch circle is very small, self-loosening of general joined structures will occur twice in one vibration cycle.

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