• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.6
• /
• pp.86-93
• /
• 2023

As the hysteretic behavior of reinforced concrete members under cyclic loading progresses, the energy dissipation ability decreases due to a decrease in stiffness and strength and pinching effects. However, the guideline "Nonlinear Analysis Model for Performance-Based Seismic Design of Reinforced Concrete Building Structures, 2021" requires calculating a single energy dissipation factor for each member and all histeric step, so the decrease in energy dissipation capacity according to histeric step cannot be considered. It is judged that Therefore, in this study, the energy dissipation factor according to the histeric step was examined by comparing the existing experimental results and the nonlinear time history analysis results for a general beam under cyclic loading. The energy dissipation factor was calculated as the ratio of the energy dissipation amount of the actual specimen to the energy dissipation amount of the idealized elastoplastic behavior obtained as a result of nonlinear time history analysis. In the existing experiment results, the energy dissipation factor was derived by calculating one cycle for each histeric step, and the energy dissipation factor was derived based on the nonlinear modeling process in the guidelines. In the existing experimental study, the energy dissipation factor was calculated by setting each histeric step (Y-L-R), and the energy dissipation factor was found to be 0.36 in the Y-L step and 0.28 in the L-R step, and the energy dissipation factor in the guideline was found to be 0.31. This shows that the energy dissipation factor calculation formula in the guidelines does not indicate a decrease in the energy dissipation capacity of reinforced concrete members.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.28 no.1
• /
• pp.12-23
• /
• 2024

In this study, a structural concrete square beam was developed using the centrifugal molding technique. In order to secure the bending stiffness of the cross section, the hollow rate of the cross section was set to 10% or less. Instead of using the current poor mixture of concrete and a concrete mixing ratio with a high slump (150-200) and a design strength of 100 MPa or more was developed and applied. In order to investigate the durability of centrifugally formed PSC square beams to be used as the superstructure of the avalanch tunnel or ramen bridge, the durability performance of ultra-high-strength centrifugally formed concrete with a compressive strength of 100 MPa was evaluated in terms of deterioration and chemical resistance properties.Concrete durability tests, including chloride penetration resistance, accelerated carbonation, sulfate erosion resistance, freeze-thaw resistance, and scaling resistance, were performed on centrifugally formed square beam test specimens produced in 2022 and 2023. Considering the information verified in this study, the durability of centrifugally molded concrete, which has increased watertightness in the later manufacturing stage, was found to be superior to that of general concrete.

• The Journal of Korean Orthopaedic Ultrasound Society
• /
• v.7 no.1
• /
• pp.20-27
• /
• 2014

Purpose: The purpose of this study was to evaluate coracohumeral distance (CHD) in patients with or without subcoracoid impingement with hypothesis that patients with subcoracoid impingement would have narrower CHD. Materials and Methods: One hundred twenty-four patients with subacromial impingement were evaluated. The subjects with subcoracoid impingement which was affirmed clinically and confirmed by ultrasound guided subcoracoid injection (n=28) was compared with patients with subacromial impingement only (n=96). Patients with stiffness and rotator cuff tear were excluded. Absolute CHD was measured on magnetic resonance imaging (MRI) axial images and on ultrasound with the humerus in neutral position and internal rotation. Also relative ratio of distance difference (RRDD) defined as the difference of CHD in neutral position and internal rotation compared with absolute CHD in neutral on ultrasound was also measured. Results: The distance measured in neutral position was similar between US imaging and MRI (p>0.05) and both measurements did not have significant difference between the two groups (p>0.05). On ultrasound, the difference in CHD in internal rotation between the two groups nearly met the level of significance (p=0.07). No significant difference of CHD difference in two humeral positions was seen between the two groups. However, RRDD value was significantly greater in subcoracoid impingement group (p<0.05). Conclusion: No significant difference of CHD was seen between the subcoracoid impingement group and the control group. RRDD value was greater in subcoracoid impingement group suggesting that individualized coracohumeral distance in internal rotation should be taken into account when assessing patients with subcoracoid impingement.

• Clinical and Experimental Pediatrics
• /
• v.50 no.4
• /
• pp.363-368
• /
• 2007

Purpose : It has been reported that deep neck abscesses are recently increasing again. We analyzed pediatric cases with deep neck abscesses during the last several years to contribute to the treatment of the disease. Methods : The clinical data of 30 children under 16 years of age with deep neck abscess from February 2001 to July 2006 were analysed retrospectively. Results : The mean age was 9 years (2-16 years), and the male/female ratio was 19/11. Abscesses in the peritonsillar space were most common (57%), followed by the retropharyngeal (30%) and parapharyngeal (13%) spaces. Upper respiratory infection in 10 cases (33%), dental infection in four case (14%), cervical lymphadenitis in three case (10%) and sinusitis in two case (6%) contributed to the development of deep neck infections. The frequent symptoms were fever in 16 case (53%), sore throat in 15 case (50%), poor oral intake in 10 (33%), odynophagia in eight (27%), and neck pain in eight (27%). Unilateral tonsillar hypertrophy and displacement in 15 case (50%) were most common. Neck mass in 13 patients (43%), neck stiffness in three (10%) and trismus in three (10%) were also found. Bacteria were isolated in 8 among 10 pus cultures; Streptococcus species 7 and Micrococcus luteus 1. All of those bacteria except Micrococcus luteus were sensitive to penicillin G. Surgical intervention was applied to 12 cases (40%), and the remaining 18 patients (60%) were treated with antibiotics only. There were no differences between the two groups in the duration of admission and antibiotic treatment. No complicated cases were observed. Conclusion : Peritonsillar abscesses were most frequent. Upper respiratory infection was the most common predisposing factor, followed by dental infection and sinusitis. Symptoms of respiratory tract obstruction were not found. The most common pathogens were Streptococcus species. Deep neck abscesses in children, if diagnosed at the early stage, possibly can be treated by antibiotics only, without surgical intervention.

• Journal of the Korean GEO-environmental Society
• /
• v.15 no.5
• /
• pp.47-56
• /
• 2014

In winter season, the pore water inside the ground freezes and thaws repetitively due to the cold air temperature. When the freezing-thawing processes are repeated on the ground, the change in soil particle structure occurs and thus the damage of the infrastructure may be following. This study was performed in order to investigate the stiffness change of soils due to the freeze-thaw by using elastic waves. Sand-silt mixtures are prepared with in the silt fraction of 40 %, 60 % and 80 % in weight and in the degree of saturation of 40 %. The specimens are placed into the square freezing-thawing cell by the temping method. For the measurement of the elastic waves, a pair of the bender elements and a pair of piezo disk elements are installed on the cell, and a thermocouple is inserted into soils for the measurement of the temperature. The temperature of the mixtures is decreased from $20^{\circ}C$ to $-10^{\circ}C$ during freezing, is maintained at $-20^{\circ}C$ for 18 hours, is gradually increased up to the room temperature of $20^{\circ}C$ to thaw the specimens. The shear waves, the compressional waves and the temperature are measured during the freeze-thaw process. The experimental result indicates that the shear and the compressional wave velocities after thawing are smaller than those of before freezing. The velocity ratio of after thawing to before freezing of shear wave is smaller than that of the compressional wave. As silt fraction increases from 40 % to 80 %, the shear and compressional wave velocities are gradually increased. This study suggests that the freezing-thawing process in unsaturated soil loosens the soil particle structure, and the shear wave velocity reflects the effect of freezing-thawing more sensitively than the compressional wave velocity.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.2
• /
• pp.167-176
• /
• 2021

When producing recycled asphalt mix, it is important that the old binder of reclaimed asphalt pavement(RAP) should be well melted during blending in the mixer. The recycled asphalt mix is produced by instant mixing(IM) of all materials(RAP, virgin asphalt and new aggregates) all together in the mixer. However, in the same recycled mix, the binder around RAP aggregate was found to show higher oxidation level than the binder coated around the virgin aggregate because the old binder of RAP was not rejuvenated properly while instant mixing. The partially-rejuvenated RAP binder is assumed to be a high stiffness point in IM recycled mix. In this study, the stage mixing(SM) method was introduced; blending RAP and virgin asphalt for the first stage, and then mixing all together with hot new aggregates for the second stage. To compare the effect of the two mixing methods on moisture resistance of recycled mixes, a statistical t-test was performed between SM and IM using indirect tensile strength(ITS) and tensile strength ratio(TSR). Three conditioning methods were used; a 16-h freezing and then 24-h submerging, 48-h submerging, and 72-h submerging in 60℃ water. It was found that the TSR(=ITS_wet/ITS_dry) values of the mixes prepared by SM was clearly higher than the IM mixes, and coefficients of variation of SM mixes were lower than the IM mixes. It was also observed that the ITS_WET of SM was significantly different from the IM at α=0.05 level by statistical t-test. The ITS_WET of SM mix was reduced less than the IM mix in severer conditioned mixes. Therefore, it was concluded that the stage mixing method was an important blending technique for producing better-quality of recycled asphalt mixes, which would show higher moisture resistance than the recycled mixes produced by conventional instant mixing.

• Pediatric Infection and Vaccine
• /
• v.4 no.1
• /
• pp.64-72
• /
• 1997

Purpose : The incidence of tuberculous meningitis in Korean children has been markedly decreased after 1980s, but this disease has still occurred with low rate. Therefore, it may be suspected that delayed diagnosis and treatment will be happened because of lacking of clinical experiences and indistinguishable other meningitis, so it is important to make early diagnosis and treatment of tuberculous meningitis concerning with the prognosis. In this aspect, we conducted study to concern and investigate sustainly about the diagnostic criteria, clinical characteristics, radiological findings, complications, and prognosis of typical or atypical tuberculous meningitis in children. Methods : Forty four children who were hospitalized and treated due to tuberculous meningitis in pediatric wards of Our Lady of Mercy Hospital, St. Holy Hospital, St. Vincent Hospital and Uijungbu St. Mary Hospital from January 1985 to June 1996 were included in this study. We reviewed medical records of these patients retrospectively. Results : 1) The tuberculous meningitis has occured continuosly since mid-1980s. The highest 2) The diagnosis was made by contact history of active tuberculous patients, positive tuberculin test, responses of antituberculous antibiotics and discovery of Mycobacterium tuberculosis from CSF or other specimens. Among patients, 7 children(16%) were not vaccinated with BCG, and only 18 children(40%) were positive in tuberculin test. 3) The symptoms and signs of our patients on initial examinations were fever, vomiting, headache, lethargy, poor feeding, weight loss, neck stiffness, convulsion, abdominal pain and motor deficits. 4) The findings of initial CSF samples revealed leukocyte $239.5/mm^3$(mean) with lymphocyte predominant, elevated protein levels(mean;259.5mg%) and low sugar level(mean;40.7mg%). And the ratio of CSF/blood sugar was 0.407. But, atypical CSF findings were seen in 31.8% patients. 5) On brain imaging study, 34 out of 39 children had findings of hydrocephalus, basilar meningeal enhancement, infarction and subarachnoidal inflammations etc. On chest X-ray, the findings of miliary tuberculosis(34.1%), normal finding(29.5%), parenchymal infiltrations (11.4%) and calcifications(9.1%) were showed. 6) In neurological clinical stage, there were twenty-six children(59%) in stage 1, fourteen children(32%) in stage 2 and four children(9%) in stage 3. The late sequeles were encountered by 29.5% with mild and 4.6% with severe neurological injury. The most common neurological injury was quadriplegia and the mortality rate was 6.8%. 7) The SIADH was developed in 20 children(45.5%) after the 4th hospital day. Half of all SIADH patients were symptomatic. Conclusion : Tuberculosis meningitis is still an important extrapulmonary disease with high morbidity and mortality. Early diagnosis with clinical contact history of active tuberculosis and radiological imaging examinations and early treatments are essential in order to prevent and decrase the rate of late sequeles and death.