• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.10
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• pp.3199-3210
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• 1996

The buckling and postbuckling behaviors were sutdied analytically and experimentally for stiffened laminated composite panels under compression loading. The panels with I-, blade, -and hat-shapeed stiffeners were investigated. In the analysis, the stiffened panels were anlyzed using the nonlinear finite element method combined with an improved arc-length method. The progressive failure analysis was done by adopting the maximum stress criterion and complete unloading failure model. The effects of the fiber angles were investigated on the buckling and postbuckling behaviors. In the experiment, the web and the lower cap of each stiffener were formed by the continuous lay-up of the skin for cocuring the stiffened panels. Therefore, the separation between stiffener and skin was not found in the junction part even after postbuckling ultimate load and the stiffened panels had excellent postbuckling load carrying capacity. A shadow moire thchnique was used to monitor the out-of-plane deformations of the panels. The piezoelectric films were attached to the panels to get the failure characteristics of the panel. The analytical results on the buckling load, postbuckling ultimate load, and failure pattern showed good agreement with the experimental results.

• Journal of the Korean Geotechnical Society
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• v.26 no.3
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• pp.35-45
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• 2010

The mechanism of load transfer by punching shear in pile-supported embankments is investigated. Based on the geometric configuration of the punching shear observed in sand fills on soft ground, a theoretical analysis is carried out to predict the embankment loads transferred on a cap beam according to punching shear developed in pile-supported embankments. The equation presented by the theoretical analysis was able to consider the effect of various factors affecting the vertical loads transferred on the cap beam. The reliability of the presented theoretical equation is investigated by comparing it with the results of a series of model tests. The model tests were performed on cap beams, which had two types of width; one is narrow width and the other is wide width. Sand filling was performed through seven steps. Two types of loading pattern were applied at each filling step; one is the long-term loading, in which sand fills at each filling step were kept for 24 hours, the other is the short-term loading, in which sand fills at each filling step were kept for 2 hours. The vertical loads measured in all model tests show good agreement with the ones predicted by the theoretical equation. Finally, the predicted vertical loads also show good agreement with the vertical loads measured in a well-instrumented pile-supported embankment in field, where cap beams were placed on too wide space.

• The Journal of Engineering Geology
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• v.7 no.1
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• pp.37-52
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• 1997

This paper discribes the practical application of stability analysis on the revetment structures, and four different sections of revetment structures are considered in this study. As a result of stability analysis, the the section of inclined revetment with T.T.P. block shows the highest safety factor against to the sliding failure of cap concrete block, while the section of inclined revetment with rubble stone shows the highest safety factor against to the straight and circular sliding failure. And the safety factors are increased by increasing of the rigidity of covered materials and by decreasing of the slope angle. For the safety factor of overturnning and bearing capacity, the section of inclined revetment structures shows higher safety factors than the section of vertical structures, and the safety factors are increased by decreasing of the slope angle and by increasing of the bottom width of the structures.

• Computers and Concrete
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• v.20 no.3
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• pp.329-338
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• 2017

A new simple and practical strut-and-tie model (STM) for predicting the shear strength of RC pile caps is proposed in this paper. Two approaches are adopted to take into account the concrete softening effect. In the first approach, a concrete efficiency factor based on compression field theory is employed to determine the effective strength of a concrete strut, assumed to control the shear strength of the whole member. The second adopted Kupfer and Gerstle's biaxial failure criterion of concrete to derive the simple nominal shear strength of pile caps containing the interaction between strut and tie capacity. The validation of these two methods is investigated using 110 RC pile cap test results and other STMs available in the literature. It was found that the failure criterion approach appears to provide more accurate and consistent predictions, and hence is chosen to be the proposed STM. Finally, the predictions of the proposed STM are also compared with those obtained by using seven other STMs from codes of practice and the literature, and were found to give better accuracy and consistency.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.1
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• pp.42-48
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• 2011

To define ice as a solid material, mathematical and physical characteristics and their application examples are investigated for several materials' yield functions which include isotropic elastic, isotropic elastic-plastic, classical Drucker-Prager, Drucker-Prager Cap, Heinonen's elliptic, Derradji-Aouat's elliptic, and crushable foam models. Taking into account brittle failure mode of ice subject to high loading rate or extremely low temperature, isotropic elastic model can be better practicable than isotropic elastic-plastic model. If a failure criterion can be properly determined, the elastic model will provide relatively practicable impact force history from ice-hull interactions. On the other hand, it is thought that the soil models can better predict the ice spalling mechanism, since they contain both terms of shear stress-induced and hydrostatic stress-induced failures in the yield function.

• Structural Engineering and Mechanics
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• v.85 no.3
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• pp.407-417
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• 2023

Precast assembled bridge piers with hybrid connection (PASP) use both tendons and socket connections. To study the seismic performance of PASP, a full-scale in-situ test was performed based on an actual bridge project. The elastic-plastic fiber model of PASP was established using finite element software, and numerical analyses were performed to study the influence of prestress degree and socket depth on the PASP seismic performance. The results show that the typical failure mode of PASP under horizontal load is bending failure dominated by concrete cracking at the joint between the column and cushion cap. The cracking of the pier concrete and opening of joints depend on the prestress degree and socket depth. The prestressing tendons and socket connection can provide enough ductility, strength, restoration capability, and bending strength under small horizontal displacements. Although the bearing capacity and post yield stiffness of the pier can be improved to some extent by increasing the prestressing force, ductility is reduced, and residual deformation is increased. Overall, there are reasonable minimum socket depths to ensure the reliability of the socket connection.

• Tuberculosis and Respiratory Diseases
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• v.66 no.5
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• pp.358-364
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• 2009

Background: The appropriate empirical antimicrobial choice in the treatment of community-acquired pneumonia (CAP) should be advocated by community-based information on the etiologic pathogens, their susceptibility to antimicrobials, clinical characteristics and outcomes. Jeju is a geographically isolated and identical region in Korea. However, there is no regional reference on adult CAP available. This study investigated the etiologic agents and clinical outcomes of adult patients diagnosed with CAP in Jeju, Korea, to help guide the empirical antimicrobial choice. Methods: A prospective observational study for one year in a referral hospital in Jeju, Korea. Patients diagnosed with CAP were enrolled with their clinical characteristics. Microbiological evaluations to identify the etiologic agents in the adult patients with CAP were performed with blood culture, expectorated sputum smear and culture, antibody tests for mycoplasma, chlamydophila, and antigen tests for legionella and pneumococcus. The clinical outcomes of the initial empirical treatment were analyzed. Results: Two hundred and three patients with mean age of 64 and 79 females were enrolled. Ten microbials from 90 cases (44.3%) were isolated and multiple isolates were confirmed in 30. Among the microbial isolates, S. pneumoniae (36.3%) was the most common, followed by M. pneumoniae (23.0%), C. pneumoniae (17.0%), S. aureus (9.6%) and P. aeruginosa (5.9%). The initial treatment failure (23.8%) was related to the isolation of polymicrobial pathogens, elevated inflammatory markers, and the presence of pleural effusion. Among the 30 isolates of S. pneumoniae, 16 (53.3%) were not susceptible to penicillin, and 19 isolates (63.3%) to erythromycin and clarithromycin. However, 29 isolates (96.7%) were susceptible to levofloxacin and ceftriaxone. Conclusion: S. pneumoniae, M. pneumoniae, S. aureus, and P. aeruginosa are frequent etiologic agents of adult CAP in Jeju, Korea. The clinical characteristics and antibiotic resistance should be considered when determining the initial empirical antimicrobial choice. Respiratory quinolone or ceftriaxone is recommended as an empirical antimicrobiotic in the treatment of adult CAP in Jeju, Korea.

• Computers and Concrete
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• v.6 no.5
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• pp.377-390
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• 2009

In this paper an improved one-dimensional frame element for modelling of reinforced concrete beams and columns subjected to impact is presented. The model is developed in the framework of a flexibility fibre element formulation that ignores the shear effect at material level. However, a simple shear cap is introduced at section level to take account of possible shear failure. The effect of strain rate at the fibre level is taken into account by using the dynamic increase factor (DIF) concept for steel and concrete. The capability of the formulation for estimating the element response history is demonstrated by some numerical examples and it is shown that the developed 1D element has the potential to be used for dynamic analysis of large framed structures subjected to impact of air blast and rigid objects.

• Tuberculosis and Respiratory Diseases
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• v.60 no.4
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• pp.419-425
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• 2006

Background : Severe community-acquired pneumonia (CAP) can develop into respiratory failure that requires mechanical ventilation (MV), which is associated with a higher rate of mortality. It was recently reported that a hydrocortisone infusion in severe CAP patients was associated with a significant reduction in the length of the hospital stay and mortality. This study evaluated efficacy of a hydrocortisone infusion for patients with severe CAP requiring MV. Methods : From February 2005 to July 2005, 13 patients (M : F = 10 : 3, mean age: $68.6{\pm}14.1years$), who were diagnosed with severe CAP and required MV, were enrolled in this study. Hydrocortisone was administered as an intravenous 200mg loading bolus, which was followed by an infusion at a rate of 10mg/hour for 7 days. The control group was comprised of patients with severe CAP requiring MV but in whom corticosteroid was not used before study period. The clinical and physiologic parameters on or by day 8 and the outcome in the hydrocortisone infusion group were compared with those in the control group. Results : 1) There was no significant difference in age, gender ratio, SAPS II, SOFA score, temperature, leukocyte count, PaO2/FiO2 (P/F) ratio, the number of patients with P/F ratio < 200, chest radiograph score, lung injury score and catecholamine-dependent septic shock between the hydrocortisone infusion group and control group at day 1. 2) At day 8, the proportion of patients with an improvement in the P/F ratio ${\geq}100$ and the chest radiograph score was significantly higher in the hydrocortisone infusion group than in the control group (61.5% vs. 15.4%, 76.9% vs. 23.1%, p< 0.05). However, there was no significant difference in the other clinical and physiologic parameters. 3). There was no significant difference in the duration of the MV, ICU stay, hospital stay and 10th and 30th day mortality between the two groups. Conclusion : Hydrocortisone infusion for patients with severe CAP requiring invasive mechanical ventilation may be effective in improving the level of oxygenation and the chest radiograph score.

• Journal of Audiology & Otology
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• v.23 no.2
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• pp.112-117
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• 2019

Background and Objectives: The purpose of this study was to evaluate the efficacy of revision cochlear implant (CI) surgery for better speech comprehension targeting patients with low satisfaction after first CI surgery. Subjects and Methods: Eight patients who could not upgrade speech processors because of an too early CI model and who wanted to change the whole system were included. After revision CI surgery, we compared speech comprehension before and after revision CI surgery. Categoies of Auditory Performance (CAP) score, vowel and consonant confusion test, Ling 6 sounds, word and sentence identification test were done. Results: The interval between surgeries ranged from eight years to 19 years. Same manufacturer's latest product was used for revision surgery in six cases of eight cases. Full insertion of electrode was possible in most of cases (seven of eight). CAP score (p-value=0.01), vowel confusion test (p-value=0.041), one syllable word identification test (p-value=0.026), two syllable identification test (p-value=0.028), sentence identification test (p-value=0.028) had significant improvement. Consonant confusion test (p-value=0.063), Ling 6 sound test (p-value=0.066) had improvement but it is not significant. Conclusions: Although there are some limitations of our study design, we could identify the effect of revision (upgrade) CI surgery indirectly. So we concluded that if patient complain low functional gain or low satisfaction after first CI surgery, revision (device upgrade) CI surgery is meaningful even if there is no device failure.