• Structural Engineering and Mechanics
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• v.77 no.5
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• pp.601-612
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• 2021

To study the vibration characteristics of a high-speed railway continuous girder bridge-track coupling system (HSRCBT), a coupling vibration analysis model of an m-span continuous girder bridge-subgrade-track system with n-span approach bridge was established. The model was based on the energy and its variational method, where both the interlaminar slip and shear deformation effects were considered. In addition, the free vibration equations and natural boundary conditions of the HSRCBT were derived. Further, according to the coordination principle of deformation and mechanics, an analytical method for calculating the natural vibration frequencies of the HSRCBT was obtained. Three typical bridge-subgrade-track coupling systems of high-speed railway were taken and the results of finite element analysis were compared to those of the analytical method. The errors between the simulation results and calculated values of the analytical method were less than 3%, thus verifying the analytical method proposed in this paper. Finally, the analytical method was used to investigate the influence of the number of the approach bridge spans and the interlaminar stiffness on the natural vibration characteristics of the HSRCBT based on the degree of sensitivity. The results suggest the approach bridges have a critical number of spans and in general, the precision requirements of the analysis could be met by using 6-span approach bridges. The interlaminar vertical compressive stiffness has very little influence on the low-order natural vibration frequency of HSRCBT, but does have a significant influence on higher-order natural vibration frequency. As the interlaminar vertical compressive stiffness increases, the degree of sensitivity to interlaminar stiffness of each of the HSRCBT natural vibration characteristics decrease and gradually approach zero.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.249-252
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• 2005

Prediction of damage caused by low-velocity impact in laminated composite plate is an important problem faced by designers using composites. Not only the inplane stresses but also the interlaminar normal and shear stresses playa role in estimating the damage caused. The work reported here is an effort in getting better predictions of damage in composite plate using DNS approach. In the DNS model, we discretize the composite plates through separate modeling of fiber and matrix for the local microscopic analysis. Through comparison with the homogenized model. In the view of microscopic mechanics with DNS model, interlaminar stress behaviors in the inside of composite materials is investigated and compared with the results of the homogenized model which has been used in the conventional approach of impact analysis.

• Journal of Korean Neurosurgical Society
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• v.40 no.2
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• pp.79-83
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• 2006

Objective : The purpose of this study was to describe a surgical technique of axillary approach of percutaneous endoscopic interlaminar discectomy for L5-S1 disc herniation and its preliminary results. Methods : From July 2002 to September 2003, 101 patients with lumbar radiculopathy due to L5-S1 disc herniation, who were treated by percutaneous interlaminar endoscopic discectomy, were retrospectively reviewed. There were 57 males and 44 females with a mean age of 44.8 years [range, 18 to 62 years]. The surgery consisted of needle insertion into the epidural space via the interlaminar space, sequential dilatation, and endoscopic discectomy through the axillary area of the S1 root. Results : The mean follow-up period was 14.5 months and the average surgical time was 41 min. According to the modified Macnab criteria, 44 patients [43.6%] had excellent outcomes, 49 [48.5%] had good results and only 8 [78%] had fair or poor outcomes. Four patients had a revision microdiscectomy due to incomplete removal of disc fragment. There were no major complications related to this surgical approach. Conclusion : Axillary approach of percutaneous endoscopic interlaminar discectomy is safe and effective procedure for the treatment of L5-Sl disc herniation. It combines the advantages of MED and conventional percutaneous endoscopic discectomy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.8
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• pp.317-323
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• 2017

This study was conducted to investigate the differences in magnetic resonance imaging (MRI) findings after lumbar epidural nerve block using the transforaminal approach and the interlaminar approach in patients with low back pain. This study was an observational analysis study of abnormal findings of MRI after epidural nerve block. This study included 78 patients who underwent MRI at approximately 24 h after lumbar epidural nerve block at a pain clinic of a university hospital between January 2007 and December 2016. Among patients who received epidural nerve block, 36 used the interlaminar approach and 42 used the transforaminal approach. The incidence of patients with abnormal changes in MRI findings was higher among patients using the interlaminar approach (53%) than those using the transforaminal approach (7%). Abnormal MRI findings included epidural air or fluid, needle tracks, and soft tissue changes, with epidural air being the most frequent abnormal finding (72%). We recommend use of the transforaminal approach to reduce the possibility of misreading or difficulty in interpretation of images of patients who underwent MRI at approximately 24 h after lumbar epidural nerve block. Practitioners should consider the possibility of abnormal findings such as epidural air on MRI in cases of epidural nerve block using the interlaminar approach.

• Journal of Korean Neurosurgical Society
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• v.42 no.1
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• pp.11-15
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• 2007

Objective : Lumbar foraminal stenosis is an important etiology of lumbar radicular symptomatology and frequent causes of remained symptoms after decompressive surgery. This study was conducted to determine the precise clinical and radiologic diagnosis of lumbar foraminal stenosis, and to demonstrate thorough treatment by decompressive surgery using a minimally invasive technique. Methods : Seven patients with established unilateral lumbar foraminal stenosis according to clinical and radiologic diagnosis were retrospectively studied. All patients underwent combined interlaminar and paraisthmic procedure with partial facetectomy. The outcome of surgery was evaluated and classified into excellent, good, fair and poor. Results : The results were excellent in four patients, good in two, and fair in one during the follow-up. There were no surgery-related complications. Conclusion : Minimally invasive combined interlaminar and paraisthmic approach provides good outcome in carefully selected patients with symptomatic lumbar foraminal stenosis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.887-902
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• 1994

Within the framework of anisotropic thermoelasticity, the problem of an interlaminar crack in a laminated fiber-reinforced composite subjected to a uniform heat flow is investigated. Under a state of generalized plane deformation, dissimilar anisotropic half-spaces with different fiber orientations are considered to be bound together by a matrix interlayer containing the crack. The interlayer models the matrix-rich interlaminar region of the fibrous composite laminate. Based on the flexibility/stiffness matrix approach, formulation of the current crack problem results in having to solve two sets of singular integral equations for temperature and thermal stress analyses. Numerical results are obtained, illustrating the parametric effects of laminate stacking sequence, relative crack size, crack location, crack surface partial insulation, and fiber volume fraction on the values of mixed mode thermal stress intensity factors.

• Steel and Composite Structures
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• v.17 no.4
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• pp.387-403
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• 2014

This paper presents a high accuracy Finite Element approach for delamination modelling in laminated composite structures. This approach uses multi-layered shell element and cohesive zone modelling to handle the mechanical properties and damages characteristics of a laminated composite plate under low velocity impact. Both intralaminar and interlaminar failure modes, which are usually observed in laminated composite materials under impact loading, were addressed. The detail of modelling, energy absorption mechanisms, and comparison of simulation results with experimental test data were discussed in detail. The presented approach was applied for various models and simulation time was found remarkably inexpensive. In addition, the results were found to be in good agreement with the corresponding results of experimental data. Considering simulation time and results accuracy, this approach addresses an efficient technique for delamination modelling, and it could be followed by other researchers for damage analysis of laminated composite material structures subjected to dynamic impact loading.

• The Korean Journal of Pain
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• v.31 no.2
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• pp.87-92
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• 2018

Background: An epidural steroid injection (ESI) is a commonly administered procedure in pain clinics. An unintentional lumbar facet joint injection during interlaminar ESI was reported in a previous study, but there has not been much research on the characteristics of an unintentional lumbar facet joint injection. This study illustrated the imaging features of an unintentional lumbar facet joint injection during an interlaminar ESI and analyzed characteristics of patients who underwent this injection. Methods: From December 2015 to May 2017, we performed 662 lumbar ESIs and we identified 24 cases (21 patients) that underwent a lumbar facet joint injection. We gathered data contrast pattern, needle approach levels and directions, injected facet joint levels and directions, presence of lumbar spine disease as seen on magnetic resonance images (MRI), and histories of lumbar spine surgeries. Results: The contrast pattern in the facet joint has a sigmoid or ovoid contrast pattern confined to the vicinity of the facet joint. The incidence of unintentional lumbar facet joint injection was 3.6%. The mean age was 68.47 years. Among these 21 patients, 14 (66.7%) were injected in the facet joint ipsilaterally to the needle approach. Among the 20 patients who received MRI, all (100%) had central stenosis and 15 patients (75%) had severe stenosis. Conclusions: When the operator performs an interlaminar ESI on patients with central spinal stenosis, the contrast pattern on the fluoroscopy during interlaminar ESI should be carefully examined to distinguish between the epidural space and facet joint.

• Structural Engineering and Mechanics
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• v.7 no.4
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• pp.377-386
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• 1999

The stress distribution in a symmetrically laminated composite plate subjected to in-plane compression are evaluated using finite element analysis. Six different finite element models are created for the study of stresses in the plate after buckling. Two finite element modelling approaches are adopted to obtain the stress distribution. The first approach starts with a full model of shell elements from which sub-models of solid elements are spin-off The second approach adopts a full model of solid elements at the beginning from which sub-models of solid elements are created. All sub-models have either 1-element thickness or 14-element thickness. Both techniques show high interlaminar direct and shear stresses at the free edges. The study also provides vital information of the distribution of all components of stresses along the unloaded edges in length direction and also in the thickness direction of the plate.

• Structural Engineering and Mechanics
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• v.43 no.5
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• pp.657-678
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• 2012

The mismatch of ply orientations in composite laminates can cause high interlaminar stress concentrations near the free edges. Evaluation of these interlaminar stresses and their role in the progressive damage analysis of laminates is desirable. Recently, the authors developed a new method to relate the physically based micromechanics approach with the meso-scale CDM considering matrix cracking and induced delamination. In this paper, the developed method is applied for the analysis of edge effects in various angle-ply laminates such as $[10/-10]_{2s}$, $[30/-30]_{2s}$ and $[45/-45]_{2s}$ and comparing the results with available traditional CDM and experimental results. It is shown that the obtained stress-strain behaviors of laminates are in good agreement with the available experimental results and even in better agreement than the traditional CDM results. Variations of the stresses and stiffness components through the laminate thickness and near the free edges are also computed and compared with the available CDM results.