• Earthquakes and Structures
• /
• 제26권3호
• /
• pp.203-218
• /
• 2024

Beam-column joints in the frame structure are at high risk of brittle shear failure which would lead to significant residual deformation and even the collapse of the structure during an earthquake. In order to improve the damage issue and enhance the recoverability of the beam-column joints, a sector lead rubber damper (SLRD) has been developed. The SLRD can increase the bearing capacity and energy dissipation capacity, and also demonstrating recoverability of seismic performance following cyclic loading. In this paper, the hysteretic behavior of SLRD was experimentally investigated in terms of the regular hysteretic behavior, large deformation behavior and fatigue behavior. Furthermore, a parametric analysis was performed to study the influence of the primary design parameters on the hysteretic behavior of SLRD. The results show that SLRD resist the exerted loading through the shear capacity of both rubber parts coupled with the lead cores in the pre-yielding stage of lead cores. In the post-yielding phase, it is only the rubber parts of the SLRD that provide the shear capacity while the lead cores primarily dissipate the energy through shear deformation. The SLRD possesses a robust capacity for large deformation and can sustain hysteretic behavior when subjected to a loading rotation angle of 1/7 (equivalent to 200% shear strain of the rubber component). Furthermore, it demonstrates excellent fatigue resistance, with a degradation of critical behavior indices by no more than 15% in comparison to initial values even after 30 cycles. As for the designing practice of SLRD, it is recommended to adopt the double lead core scheme, along with a rubber material having the lowest possible shear modulus while meeting the desired bearing capacity and a thickness ratio of 0.4 to 0.5 for the thin steel plate.

• Archives of Plastic Surgery
• /
• 제46권6호
• /
• pp.589-593
• /
• 2019

Post-traumatic defects of the distal third of the leg often require skipping a few steps of the well-established reconstructive ladder, due to the limited local reliable reconstructive options. In rare cases, the reconstructive plan and flap choice may encounter challenges when the patient has psychiatric illness affecting compliance with postoperative care. We describe a case of a patient with severe intellectual disability and an open fracture of the distal lower limb. After fracture management and debridement of devitalized tissues, the resultant soft tissue defect was covered with a free gracilis flap. On postoperative day 7, the patient ripped out the newly transplanted flap. The flap was too traumatized for salvage, so a contralateral free gracilis muscle flap was used. The patient showed good aesthetic and functional outcomes at a 1-year follow-up. When planning the postoperative management of patients with psychiatric illness, less complex and more robust procedures may be preferred over a long and complex surgical reconstruction requiring good compliance with postoperative care. The medical team should be aware of the risk of postoperative collapse, focus on the prevention of pain, and be wary of drug interactions. Whenever necessary, free tissue transfer should be performed despite potential compliance issues.

• Journal of Chest Surgery
• /
• 제15권4호
• /
• pp.432-439
• /
• 1982

Congenital posterolateral diaphragmatic hernia [Bochdalek hernia] is the result of a congenital diaphragmatic defect in the posterior costal part of the diaphragm in the region of the tenth and eleventh ribs. There is usually free communication between the thoracic and abdominal cavities. The defect is most commonly found on the left [90%], but may occurs on the right, where the liver often prevents detection. The male to female ratio is 2:1. Owing to the negative intrathoracic pressure, herniation of abdominal contents through the defects occurs, with resultant collapse of the lung. Shifting of mediastinum to the opposite side and compression of the opposite lung occurs. Most often these hernias are manifestated by acute respiratory distress in the newborn. A second, but less well recognized, group of patient with Bochdalek hernia survive beyond the neonatal period, usually present at a later time with "failure of thrive, intermittent vomiting, or progressive respiratory difficulty. " The diagnosis can often be made on clinical ground from the presence of respiratory distress, absence of breath sounds on the chest presence of bowel sounds over the chest . Roentgenogram of the chest confirm the diagnosis. Obstruction and strangulation have been reported but are rare. Treatment consists of early reliable identification of these congenital diaphragmatic hernia with high risk and surgical repairment. and postoperative pharmacological management with extracorporeal membranous oxygenation [=ECMO] support in the period of intensive care. On the surgical approach, for defects on left side, an abdominal incision is preferred, because of the high incidence of malrotation and obstructing duodenal bands. In the neonate, the operative mortality may be appreciable, but, later repair almost always is successful. During the period from 1972 to 1982, 4 cases of congenital Bochdalek hernia were experienced at the Kyung-Hee University Hospital.

• 한국항해항만학회지
• /
• 제33권7호
• /
• pp.469-476
• /
• 2009

Recent collapse of shipping market right after unprecedent surge clearly demonstrates that shipping industry is extremely risky. Due to the volatile movements of the freight rates, investors tend to ask higher rate of return; higher required return reduces the total net present value of the investment project. For several decades, the Discounted Cash Flow(DCF hereafter) analysis has been the most frequently used valuation technique. However, the main problem of the DCF analysis is its assumption that the discount rate would stay the same during the project life. In other words, it usually does not address the decisions that managers have after a project has been accepted. The purpose of this study is investigate a new valuation method of investment: the Real Option Analysis(ROA hereafter) on ship investment. By replacing the existing valuation methods with the new one, the research will present a new perspective on investment with uncertainty. While uncertainty increases risk of investment and consequently discounts the value of it in the traditional feasibility analysis, in the ROA, a new valuation method which will be addressed in the research, uncertainty means some additional value of flexibility so that the tool can help investors produce more accurate decisions. Contrary to the DCF analysis, the ROA takes managerial flexibilities into account. In reality, capital budgeting and project management is typically dynamic, rather than static in nature. The ROA finds and assesses the values of managerial flexibilities or real options in the investments. The main structures of the research will be as follows: (1) overview of the ship investment project, (2) evaluation of the project by the Net Present Value analysis, (3) evaluation of the same project by the Real Option Analysis, (4) comparision of the two techniques.

• Structural Monitoring and Maintenance
• /
• 제10권1호
• /
• pp.87-105
• /
• 2023

Seismic regulations have been updated from time to time to accommodate an increase in seismic hazards. Comparison of seismic fragility of the existing bridges in Indonesia from different historical periods since the era before 1990 will be the basis for seismic assessment of the bridge stock in Indonesia, most of which are located in earthquake-prone areas, especially those built many years ago with outdated regulations. In this study, seismic fragility curves were developed using incremental non-linear time history analysis and more holistically according to the actual strength of concrete and steel material in Indonesia to determine the uncertainty factor of structural capacity, βc. From the research that has been carried out, based on the current seismic load in SNI 2833:2016/Seismic Map 2017 (7% probability of exceedance in 75 years), the performance level of the bridge in the era before SNI 2833:2016 was Operational-Life Safety whereas the performance level of the bridge designed with SNI 2833:2016 was Elastic - Operational. The potential for more severe damage occurs in greater earthquake intensity. Collapse condition occurs at As = F_PGA x PGA value of bridge Era I = 0.93 g; Era II = 1.03 g; Era III = 1.22 g; Era IV = 1.54 g. Furthermore, the fragility analysis was also developed with geometric variations in the same bridge class to see the effect of these variations on the fragility, which is the basis for making bridge risk maps in Indonesia.

• 지질공학
• /
• 제17권2호
• /
• pp.253-261
• /
• 2007

집중강우에 의해 주로 발생되는 절토사면 붕괴는 인적, 물적 피해를 초래한다. 한국건설기술연구원은 예방 수단으로서 위험사면을 집중관리하고 있다. 지속적인 사면관리에도 불구하고 지구환경의 변화로 절토사면의 붕괴발생 빈도는 점차적으로 증가하고 있다. 이에 대책공법 적용이 어려운 절토사면에 대하여 상시계측시스템을 설치하고 있다. 상시계측시스템의 운용은 대인 대물 피해에 대한 조치로서 활용될 수 있으나, 강우시 절토사면의 붕괴 징후를 인지하더라도 관리자가 현장관리 작업을 수행함에 있어서 시공간적 제약으로 인한 한계가 있다. 낙석신호등은 상시계측시스템을 통하여 사면 위험 징후가 발견될 시, 도로이용자에게 낙석발생에 대한 위험을 주지시키고, 붕괴시 도로관리자의 현장 도착 전까지 자동적으로 또는 수동적으로 도로를 차단시킴으로서 사면붕괴에 의한 피해를 예방하는 관리시스템의 일종이다.

• 한국재난정보학회 논문집
• /
• 제11권1호
• /
• pp.63-72
• /
• 2015

본 연구는 수학여행과 같은 단체 테마 현장체험학습의 사고 현황과 문제점을 분석하고 안전관리에 대한 개선점과 안전관리대책을 제시하여 안전사고를 예방하는데 목적이 있다. 이를 위해서 단체 현장체험학습에서의 안전사고 사례인 세월호침몰사고, 경주 마우나 오션리조트 체육관 붕괴사고를 분석하는 사례 연구방법과 지금까지 연구되었던 선행연구들과 신문, 인터넷 검색자료, 관련 법률 등을 참고하는 문헌고찰을 주로 활용하였고 또한 관계 부처와 협조하여 자료를 수집하고 안전관리의 방안을 모색하였다. 두 가지 사례를 분석한 결과 각각의 문제점에 대한 개선점(법제도의 체계적인 개선, 국민 안전의식 고취, 안전관리자의 육성 및 교육, 재난대응 조직구성, 중앙구조본부 및 구조 구급대 설치, 재난대응체계의 혼선에 따른 정비, 국가의 자체적인 대응능력 강화, 재난훈련의 의무화 및 제재강화, 대비 대응절차의 특성에 따른 평가절차의 마련 등)을 바탕으로 안전한 사회를 위한 법제도적 기반 마련 및 재난관리체계 및 위험관리시스템의 정비를 기여할 수 있다는 결론을 내렸다.

• Geomechanics and Engineering
• /
• 제36권5호
• /
• pp.417-426
• /
• 2024

Shield tunneling method is widely used to build tunnels in complex geological environment. Stability control of tunnel face is the key to the safety of projects. To improve the excavation efficiency or perform equipment maintenance, the excavation chamber sometimes is not fully filled with support medium, which can reduce the load and increase tunneling speed while easily lead to ground collapse. Due to the high risk of the face failure under non-fully support mode, the tunnel face stability should be carefully evaluated. Whether compressive air is required for compensation and how much air pressure should be provided need to be determined accurately. Based on the upper bound theorem of limit analysis, a non-fully support rotational failure model is developed in this study. The failure mechanism of the model is verified by numerical simulation. It shows that increasing the density of supporting medium could significantly improve the stability of tunnel face while the increase of tunnel diameter would be unfavorable for the face stability. The critical support ratio is used to evaluate the face failure under the nonfully support mode, which could be an important index to determine whether the specific unsupported height could be allowed during shield tunneling. To avoid of face failure under the non-fully support mode, several charts are provided for the assessment of compressed air pressure, which could help engineers to determine the required air pressure for face stability.

• Journal of Animal Science and Technology
• /
• 제59권3호
• /
• pp.5.1-5.10
• /
• 2017

Background: Bovine respiratory disease (BRD) is one of the leading causes of economic losses in the beef and dairy industry. Reliable antemortem tools for diagnosing BRD would improve the efficacy of treatment and reduce costs. Here we examined whether the relatively simple technique of thoracoscopy can support BRD diagnosis under field conditions. We also compared various equipment set-ups in order to optimize the safety and efficacy of the procedure. A total of 24 thoracoscopic procedures were performed in 17 calves diagnosed with BRD and in 2 healthy control calves. Rigid and flexible endoscopes and industrial videoscopes were tested using various insertion approaches. The suitability of the technique was assessed in terms of duration, volume of air extracted, visualization score, and image quality. Safety was assessed in terms of rectal temperature, body weight, breaths/min, presence of fibrinogen, pain score, recovery time, intraoperative complications and risk of laceration or threatening collapse. Results: Insertion of a flexible endoscope via a right, dorso-caudal approach at the $5^{th}$ intercostal space allowed complete examination of the right lung in 15 min, as well as identification of main lung lesions and adherences in calves with BRD, without compromising calf welfare. While the dorso-caudal approach was optimal, it was associated with substantial discomfort when rigid endoscopes were used, minimal complications or mortality due to thoracoscopy were observed up to 28 days after the procedure. Videoscopes were as safe and easy to use as endoscopes, but endoscopes provided better image quality. Conclusion: This study provides the first field evidence that thoracoscopy can be safe to explore BRD-diseased calves. These results justify a larger study to rigorously assess the diagnostic performance of the technique.

• 한국세라믹학회지
• /
• 제52권4호
• /
• pp.253-263
• /
• 2015

Ordinary Portland cement is a widely favored construction material because of its good strength and durability and its reasonable price; however, spalling behaviour during fire exposure can be a serious risk that can lead to strength degradation or collapse of a building. Geopolymers, which can be synthesized by mixing aluminosilicate source materials such as metakaolin and fly ash, and alkali activators, are resistant to fire. Because the chemical composition of geopolymers controls the properties of the geopolyers, geopolymers with various Si:Al ratios were synthesized and evaluated as fire resistant construction materials. Rejected fly ash generated from a power plant was quantitatively analyzed and mixed with alkali activators to produce geopolymers having Si:Al ratios of 1.5, 2.0, and 3.5. Compressive strength of the geopolymers was measured at 28 days before and after heating at $900^{\circ}C$. Geopolymers having an Si:Al ratio of 1.5 presented the best fire resistance, with a 44% increase of strength from 29 MPa to 41 MPa after heating. This material also showed the least expansion-shrinkage characteristics. Geopolymer mortar developed no spalling and presented more than a 2 h fire resistance rating at $1,050^{\circ}C$ during the fire testing, with a cold side temperature of $74^{\circ}C$. Geopolymers have high potential as a fire resistant construction material in terms of their increased strength after exposure to fire.