• Steel and Composite Structures
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• v.43 no.2
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• pp.139-152
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• 2022

Steel-reinforced concrete (SRC) L-shaped column is the vertical load-bearing member with high spatial adaptability. The seismic behavior of SRC L-shaped column is complex because of their irregular cross sections. In this study, the hysteretic performance of six steel truss reinforced concrete L-shaped columns specimens under the combined loading of compression, bending, shear, and torsion was tested. There were two parameters, i.e., the moment ratio of torsion to bending (γ) and the aspect ratio (column length-to-depth ratio (φ)). The failure process, torsion-displacement hysteresis curves, and bending-displacement hysteresis curves of specimens were obtained, and the failure patterns, hysteresis curves, rigidity degradation, ductility, and energy dissipation were analyzed. The experimental research indicates that the failure mode of the specimen changes from bending failure to bending-shear failure and finally bending-torsion failure with the increase of γ. The torsion-displacement hysteresis curves were pinched in the middle, formed a slip platform, and the phenomenon of "load drop" occurred after the peak load. The bending-displacement hysteresis curves were plump, which shows that the bending capacity of the specimen is better than torsion capacity. The results show that the steel truss reinforced concrete L-shaped columns have good collapse resistance, and the ultimate interstory drift ratio more than that of the Chinese Code of Seismic Design of Building (GB50011-2014), which is sufficient. The average value of displacement ductility coefficient is larger than rotation angle ductility coefficient, indicating that the specimen has a better bending deformation resistance. The specimen that has a more regular section with a small φ has better potential to bear bending moment and torsion evenly and consume more energy under a combined action.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.667-675
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• 2012

Flat plate are being used more in buildings requiring a high level of technical installations or in buildings needing changeable room arrangements during their life time such as office buildings. The main problem in flat plate is its weak resistance against a punching failure at its slab-column connections. Therefore, in this research, an experimental study on full-scale interior slab-column connection was performed. Three types of shear reinforcements were tested to prevent brittle punching shear failure that could lead to collapse of the structure. A series of four flat plate specimens including a specimen without shear reinforcement and three specimens with shear reinforcements were tested. The slabs were tested up to failure using monotonic vertical shear loading. The presences of the shear reinforcements substantially increased punching shear capacity and ductility of the interior slabcolumn connections. The test results showed that a slab that did not have enough bond length failed before shear reinforcement yielded due to anchorage slip. Also, FEM analyses were performed to study an effect of slab thickness and concrete compressive strength on the flat plate slab. The analytical study results were used to propose a method to calculate performance capacity of shear reinforcement in slab-column connection.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.440-447
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• 2020

Masonry structures are used as bearing walls in small buildings, but they are generally considered non-bearing walls. They are used as partition walls that divide the interior spaces of the frame structures of buildings. In addition, wetting techniques that use mortar as an adhesive between blocks or bricks in construction are vulnerable to climatic conditions, especially cracks in mortar, which can cause conduction collapse of the walls in seismic loading. The purpose of this research was to propose a dry concrete block construction method that complements the weak axial shear stiffness and improves the weakness of the wet construction method as well as to investigate its structural behavior. In this study, the material properties of concrete blocks were examined, and the seismic performance of the proposed dry assembly structure was verified by structural behavior tests on horizontal cyclic loads. First, in these study results, concrete blocks can be applied to the dry block construction method instead of wet construction methods because they secure more than C-type blocks in KS regulations. Second, the structural performance of the wall against a horizontal cyclic load indicates that the resisting force of the assembly block wall is increased by increasing the horizontal length of the wall, forming several diagonal cracks. Finally, the proposed dry block wall structure requires a seismic performance assessment considering that the ratio of the shape of the wall by height and length is considered a major influence variable on the structural behavior under a horizontal load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.5
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• pp.577-585
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• 2023

Lateral torsional buckling causessafety accidentssuch as collapse accidents during erection. Therefore, anaccurate safety designshould be conducted. Lateral torsional buckling canbe prevented by reinforcing the end orreducing the unbraced length. The method ofreducing the unbraced length by installing a crossframe has high material and installation costs and low maintenance performance.In addition, structuralsafety may be deteriorated due to cracks. The end reinforcement method using Concrete Filled Half Pipe Stiffeneris a method ofreinforcing the end of a plate girder using a stiffenerin the form of a semi-circular column. This method increasesthewarping strength ofthe girder and increasesthe lateral torsional buckling strength.In thisstudy, the effect ofincreasing the warping strengthof plate girders with concrete filled half pipe stiffeners was confirmed. To verify the effect, the results ofthe designequationand the finite element analysis were compared and verified through a experiment. As a result, the plate girderwithCFHPS increased thewarping strengthand confirmed that the lateral torsional buckling strength was increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2C
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• pp.109-117
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• 2010

Gas hydrate dissociation can generate large amounts of gas and water in gas hydrate bearing sediments, which may eventually escape from a soil skeleton and form voids within the sediments. The loss of fine particles between coarse particles or collapse of cementation due to water flow during heavy or continuous rainfall may form large voids within soil structure. In this study, the effect of void formation resulting from gas hydrate dissociation or loss of some particles within soil structure on the strength of soil is examined. Glass beads with uniform gradation were used to simulate a gas hydrate bearing or washable soil structure. Glass beads were mixed with 2% cement ratio and 7% water content and then compacted into a cylindrical sample with five equal layers. Empty capsules for medicine are used to mimic large voids, which are bigger than soil particle, and embedded into the middle of five equal layers. The number, direction, and length of capsules embedded into each layer vary. After two days curing, a series of unconfined compression tests is performed on the capsule-embedded cemented glass beads. Unconfined compressive strength of cemented glass beads with capsules depends on the volume, direction and length of capsules. The volume and cross section formed by voids are most important factors in strength. An unconfined compressive strength of a specimen with large voids decreases up to 35% of a specimen without void. The results of this study can be used to predict the strength degradation of gas hydrate bearing sediments in the long term after dissociation and loss of fine particles within soil structure.

• Neonatal Medicine
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• v.18 no.2
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• pp.211-220
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• 2011

Purpose: Late-onset hypotension in preterm infants is not a rare condition. Late circulatory collapse due to adrenal insufficiency (AI) is one of the major causes of late-onset hypotension. We assessed the incidence and causes of late-onset hypotension. We also compared the clinical findings according to the presence of AI. Methods: In total, 244 preterm infants with a gestational age ${\leq}$32 weeks and who were admitted to the neonatal intensive care unit (NICU) of Seoul National University Boramae Hospital and Seoul National University Hospital from January 2009 to April 2011 were included. Clinical findings were analyzed retrospectively. Results: Forty-four infants (18%) suffered from late-onset hypotension. Hydrocortisone was administered to 30 infants (68.2%) and AI occurred in 16 infants (36.4%). Cesarean section, sepsis before hypotension, and gastrointestinal surgery were independently associated with late-onset hypotension. Intrauterine growth retardation (IUGR) was less frequent in the hydrocortisonetreated group than in infants not treated with hydrocortisone. The AI group had fewer IUGR infants, and the duration of hospitalization was shorter in the AI group than in infants who were not administered hydrocortisone. Blood pressure tended to normalize more quickly in the AI group, however, the difference was not significant. Conclusion: AI was a major cause of late-onset hypotension, and the use of hydrocortisone shortened the length of hospitalization.

• Journal of Chest Surgery
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• v.38 no.10 s.255
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• pp.717-720
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• 2005

Here we report a case of posterior left ventricular (LV) free wall rupture following postinfarct ventricular septal rupture (VSR). A 58-year-old man was transferred to the hospital under the impression of acute myocardial infarction. Posterior VSR was seen on echocardiographic examination. The intraaortic balloon pump catheter was introduced percutaneously and the emergent operation was proposed. Sudden circulatory collapse was developed shortly after the anesthetic induction and the patient's chest was hurriedly opened while on cardiopulmonary resuscitation. The acute cardiac tamponade was seen and the blood was seen pumping from the longitudinal tear at the mid-level of LV posterior wall, measuring 2 cm in length. The cardiopulmonary bypass was set and LV reconstruction was done. The postoperative recovery was delayed due to the brain injury presumably caused by preoperative cardiac arrest.

• Journal of Trauma and Injury
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• v.28 no.4
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• pp.232-240
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• 2015

Purpose: Thoracic aortic injury is a life-threatening injury that has been traditionally treated by using surgical management. Recently, thoracic endovascular aortic repair (TEVAR) has been conducted pervasively as a better alternative treatment method. Therefore, this study will focus on analyzing the outcome of TEVAR in patients suffering from a blunt thoracic aortic injury. Methods: Of the blunt thoracic aortic injury patients admitted to Eulji University Hospital, this research focused on the 11 patients who had received TEVAR during the period from January 2008 to April 2014. Results: Seven of the 11 patients were male. At the time of admission, the mean systolic pressure was $105.64{\pm}24.60mm\;Hg$, and the mean heart rate was $103.64{\pm}20.02per$ minute. The median interval from arrival to repair was 7 (4, 47) hours. The mean stay in the ICU was $21.82{\pm}16.37hours$. In three patients, a chimney graft technique was also performed to save the left subclavian artery. In one patient, a debranching of the aortic arch vessels was performed. In two patients, the left subclavian artery was totally covered. In one patient whose proximal aortic neck length was insufficient, the landing zone was extended by using a prophylactic left subclavian artery to left common carotid artery bypass before TEVAR. There were no operative mortalities, but a patient who was covered of left subclavian artery died from ischemic brain injury. Complications such as migration, endovascular leakage, collapse, infection and thrombus did not occur. Conclusion: Our short-term outcomes of TEVAR for blunt thoracic aorta injury was feasible. Left subclavian artery may be sacrificed if the proximal landing zone is short, but several methods to continue the perfusion should be considered.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.181-188
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• 2012

The present study on nitrogen-diluted non-premixed counterflow flames with finite burner diameters experimentally investigates the important role of the outer edge flame in flame extinction. Flame stability diagrams mapping the flame extinction response of nitrogen-diluted non-premixed counterflow flames to varying global strain rates in terms of the burner diameter, burner gap, and velocity ratio are explored. There exists a critical nitrogen mole fraction beyond which the flame cannot be sustained, and also the curves of the critical nitrogen mole fraction versus the global strain rate have C-shapes in terms of burner diameter, burner gap, and velocity ratio. In flames with sufficiently high strain rates, the curves of the critical nitrogen mole fractions versus global strain rate collapse into one curve, and the flames can have the 1-D flame response of typical diffusion flames. Three flame extinction modes are identified: flame extinctions through the shrinkage of the outer edge flame with and without an oscillation of the outer edge flame prior to the extinction and flame extinction through a flame hole at the flame center. The measured flame surface temperature and a numerical evaluation of the fractional contribution of each term in the energy equation show that the radial conductive heat loss at the flame edge destabilizes the outer edge flame, and the conductive and convection heat addition to the outer edge from the trailing diffusion flame stabilizes the outer edge flame. The radial conductive heat loss at the flame edge is the dominant extinction mechanism acting through the shrinkage of the outer edge flame.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.609-619
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• 2004

An investigation was conducted on the activities around Europe in order to solve the problem of the thermal bridging of steel studs, which had caused a significant disadvantage. This study included the following: diminishing the contact area between the studs and the sheathing, lengthening the heat transfer route, replacing the steel web with a less conductive material, and placing foam insulation in locations where the thermal shorts are most critical. Although energy efficiency is usually the focus of such foreign cases because their stud application is mostly limited to low-rise residential buildings, both structural and thermal performance are taken into consideration in this study because these target middle-story buildings. A hybrid stud composed of steel and polymer was also developed. This hybrid stud, which is 150 SL in size, is made of a galvanized steel sheet (SGC58) and a glass fiber reinforced polymer (GFRP) withepoxy bonding. A total of 32 specimens were manufactured. Its parameters comprise two types of connection detail,s: the thickness of steel (1.0mm and 1.2mm) and of the GFRP (4mm-4ply and 6mm-6ply), and the ratio of the length to the depth (L/D = 3, 6, 9, 12). Steel stud specimens with the same conditions were compared to the hybrid stud. The test revealed that in the case of the steel specimen with a thickness of 1.0mm, the maximum load of hybrid studs increased an average of 1.62 times comparedto that of the steel stud. In the case of the steel specimen with a thickness of 1.2mm, on the other hand, the average increase was 1.46times. All specimens showed full composite action until the collapse.