• 한국구조물진단유지관리공학회 논문집
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• 제28권2호
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• pp.43-52
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• 2024

내진설계 되지 아니한 조적조 건축물의 내진성능을 평가하고 건축물의 외부에 내진 보강 공법을 채택하여 내진성능을 향상시키고자 하였다. 내진성능을 평가하기 위해 건축물 내진설계 기준 및 해설(KDS 41 17 00 : 2019)과 기존 시설물(건축물) 내진성능 평가요령을 적용하였으며 비선형 정적해석으로 pushover해석을 수행하였다. 해석결과, 우리나라 주택의 내진설계 보급 비율이 낮고 주택의 많은 비중을 차지하고 있는 것이 조적조 건축물임을 고려하면 내진보강이 시급한 것으로 판단되었다. 조적조 건축물에 철골 보-기등+가새 프레임을 보강할 경우 층간 변형각은 X방향 0.043%이며 Y방향 0.047%로 나타나 규정을 만족하였다. 성능 수준별 중력하중 저항능력은 X, Y방향 모두 거주가능으로 판정되어 안전한 것으로 판단되었다. 건축물의 외부에 보강함으로써 주택의 거주성과 편의성을 확보하면서 공사가 가능할 것으로 보여지며 지진성능과 구조물의 거동을 보다 명확하게 예측할 수 있을 것으로 사료 되었다.

• Journal of Trauma and Injury
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• 제18권2호
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• pp.107-111
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• 2005

Backgrounds: To evaluate the effectiveness of conservative treatment in osteoporotic thoraco-lumbar compression fractures and to identify the factors influencing the progression of compression. Materials and Methods: From January 2003 to October 2004, Patients who were admitted to our hospital for osteoporotic thoraco-lumbar compression fractures were reviewed retrospectively with follow-up more than 12 months (ave. 14.6 months). With simple x-ray lateral view, we evaluate wedge compression ratio (WCR) and kyphotic angle (KA) at initial and final follow-up. We separate the patients into two groups baesed on the amount of progression of vertebral compression and evaluate a relation with BMD, vertebral fracture level, initial WCR, initial KA. All datas were statistically analyzed. Results: An average of T-score was -3.5 and the changes of KA between initial and final follow-up were average $3.5^{\circ}$. Compression of anterior column were progressed to 8.5%. The changes between initial and final WCR in Group I (N=24) was 17.8%, and Group II (N=18) was 3.3%. T-score in group I was -3.4 and group II was -3.8 (p=0.228). vertebral fracture level were 10 T12, 12 L1, 2 L2 in group I; 6 T12, 6 L1, 6 L2 in group II (p=0.156). Initail WCR was 0.74 in group I, 0.63 in group II, and there was statistical difference between two groups(p=0002). Initial kyphotic angle was $13.9^{\circ}$in group I, $16.2^{\circ}$in group II repectively (p=0.392). Conclusion: The conservative treatment with short-term bed rest and early embulation is effective and valuable method to patients who have osteoporotic thoraco-lumbar compression fractures. There was no statistical difference between two groups according to BMD, vertebral fracture level, KA. But in comparison with initail WCR between two groups, there was statistical difference. That means, in the case of small initial compression of anterior column, the progression of compression was bigger than else. In these patients, more strict use of appropriate brace and careful follow-up should be needed.

• Journal of Korean Neurosurgical Society
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• 제56권5호
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• pp.431-435
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• 2014

A fifty-year-old female non-smoker with no other specific medical history visited our institute. She complained of axial back pain with no other neurological deficit. Chest X-ray, chest computed tomography (CT) scan, CT-guided needle aspiration biopsy, whole-body positron emission tomography, spine CT and spine magnetic resonance image findings suggested NSCLC with epidermal growth factor receptor (EGFR) mutation, multiple brain metastases, and two isolated metastases to the T3 and L3 vertebral bodies. She underwent chemotherapy with gefitinib ($Iressa^{TM}$) for NSCLC and gamma knife surgery for multiple brain metastases. We performed a two-staged, total en bloc spondylectomy of the T3 and L3 vertebral bodies based on several good prognostic characteristics, such as the lack of metastases to the appendicular bone, good preoperative performance status, and being an excellent responder (Asian, never-smoker and adenocarcinoma histology) to EGFR inhibitors. Improved axial back pain after the surgery enabled her to walk with the aid of a thoracolumbosacral orthosis brace on the third postoperative day. Her Karnofsky performance status score (KPS) was 90 at the time of discharge and has been maintained to date 3 years after surgery. In selected NSCLC patients with good prognostic characteristics, we suggest that locally curative treatment such as total en bloc spondylectomy or radiosurgery should be emphasized to achieve longer term survival for the selected cases.

• Steel and Composite Structures
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• 제34권6호
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• pp.891-907
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• 2020

Many studies reveal that during destructive earthquakes, most of the structures enter the inelastic phase. The amount of hysteretic energy in a structure is considered as an important criterion in structure design and an important indicator for the degree of its damage or vulnerability. The hysteretic energy value wasted after the structure yields is the most important component of the energy equation that affects the structures system damage thereof. Controlling this value of energy leads to controlling the structure behavior. Here, for the first time, the hysteretic behavior and energy dissipation capacity are assessed at presence of elliptical braced resisting frames (ELBRFs), through an experimental study and numerical analysis of FEM. The ELBRFs are of lateral load systems, when located in the middle bay of the frame and connected properly to the beams and columns, in addition to improving the structural behavior, do not have the problem of architectural space in the bracing systems. The energy dissipation capacity is assessed in four frames of small single-story single-bay ELBRFs at ½ scale with different accessories, and compared with SMRF and X-bracing systems. The frames are analyzed through a nonlinear FEM and a quasi-static cyclic loading. The performance features here consist of hysteresis behavior, plasticity factor, energy dissipation, resistance and stiffness variation, shear strength and Von-Mises stress distribution. The test results indicate that the good behavior of the elliptical bracing resisting frame improves strength, stiffness, ductility and dissipated energy capacity in a significant manner.

• Earthquakes and Structures
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• 제17권2호
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• pp.163-173
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• 2019

For Special Concentrically Braced Frame (SCBF), it is common that the damage concentrates at a certain story instead of spreading over all stories. Once the damage occurs, the soft-story mechanism is likely to take place and possibly to result in the failure of the whole system with more damage accumulation. In this study, we use a strongback column which is an additional structural component extending along the height of the building, to redistribute the excessive deformation of SCBF and activate more structural members to dissipate energy and thus avoid damage concentration and improve the seismic performance of SCBF. We tested one-third-scaled, three-story, double-story X SCBF specimens with static cyclic loading procedure. Three specimens, namely S73, S42 and S0, which represent different combinations of stiffness and strength factors ${\alpha}$ and ${\beta}$ for the strongback columns, were designed based on results of numerical simulations. Specimens S73 and S42 were the specimens with the strongback columns, and S0 is the specimen without the strongback column. Test results show that the deformation distribution of Specimen S73 is more uniform and more brace members in three stories perform nonlinearly. Comparing Drift Concentration Factor (DCF), we can observe 29% and 11% improvement in Specimen S73 and S42, respectively. This improvement increases the nonlinear demand of the third-story braces and reduces that of the first-story braces where the demand used to be excessive, and, therefore, postpones the rupture of the first-story braces and enhances the ductility and energy dissipation capacity of the whole SCBF system.

• 한국안전학회지
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• 제35권5호
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• pp.49-58
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• 2020

In domestic construction sites, when installing steel pipe scaffolding and system scaffolding, the guardrails are installed after the installation of the work platforms. This conventional guardrail system (CGS) is always exposed to the risk of falls because the safety railing is installed later. In order to prevent fall disasters during erecting and dismantling scaffolds, it is necessary to introduce the advanced guardrail system (AGS) which installs railings in advance of climbing onto a work platform. For the introduction of the AGS, the structural performance of the system scaffolding applying the CGS and the AGS was compared and evaluated. The structural analysis of the system scaffold (height: 31 m and width: 27.4 m) with AGS confirmed that structural safety was ensured because the maximum stress of each element of the system scaffolding satisfies the allowable stress of each element. As a result of performance comparison of CGS and AGS for each element, the combined stress ratio of vertical posts in AGS was 6.4% lower than that of CGS. In addition, in the case of ledger and transom, the combined stress ratios of AGS and CGS were almost the same. The compression test of the assembled system scaffolding (three-storied, 1 bay) showed that the AGS had better performance than the CGS by 9.7% (8.91 kN). The cross bracing exceeds the limit on slenderness ratio of codes for structural steel design. But the safety factor for the compressive load of the cross bracing was evaluated as meeting the design criteria by securing 3 or more. In actual experiments, it was confirmed that brace buckling did not occur even though the overall scaffold was buckled. Therefore, in the case of temporary structures, it was proposed to revise the standards for limiting on slenderness ratio of secondary or auxiliary elements to recommendations. This study can be used as basic data for the introduction of AGS for installing guardrails in advance at domestic construction sites.

• 해양환경안전학회지
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• 제28권4호
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• pp.601-609
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• 2022

잭업드릴링 리그는 해양 석유와 가스 탐사 산업에서 널리 사용되는 모바일 해양 플랫폼이다. 그것은 시추 및 생산을 위한 캔틸레버 시추 장치가 있는 독립적인 3개의 다리가 있는 자체 승강식 장치이다. 전형적인 잭업리그는 삼각형 선체, 타워형 데릭, 캔틸레버, 잭케이스, 거주구와 다리로 구성되며 여기에는 스퍼드캔 구조, 개방형 트러스, X-교차 구조로 구성된다. 일반적으로 잭업리그는 수심 130m~170m에서만 운용이 되고 있다. 최근 들어 개발 유정이 심해로 이동하면서, 깊은 수심과 가혹한 환경조건을 만족해야 한다. 리그의 작업 상태에서 모든 정적, 동적 하중은 레그(Leg)를 통해서 지탱되는 특징이 있다. 이러한 리그의 중요한 이슈는 순간적으로 큰 충격에너지를 발생시키는 충돌에 대한 레그의 안전성이다. 본 연구에서는 LS-Dyna 프로그램을 이용하여 DNV 선급에서 규정하고 있는 충돌에너지 35MJ 요구사항에 대한 수치해석 및 검증을 수행하였다. 충돌 선박은 배수량 7,500톤 작업 지원선을 사용하였고, 5가지 충돌조건을 선정하였다. 해석결과로부터 모든 충돌조건은 선급 기준을 만족하지 못한다. 코드 방향 충돌조건은 충돌에너지 15MJ, 브레이스 충돌조건은 6MJ이 합리적이다. 따라서 충돌시나리오에 따른 합리적인 충돌에너지 기준의 제정이 필요로 하다.

• 콘크리트학회논문집
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• 제23권5호
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• pp.683-692
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• 2011

필로티형 저층 RC 집합주택에서는 지진 발생 시 필로티층에 손상이 집중된다. 따라서, 이 연구에서는 필로티층의 비틀림과 X, Y방향의 강도와 강성을 증가시키기 위해 좌굴방지가새를 설치함과 동시에, 과도한 변형과 축력의 변동이 발생하는 외부기둥의 연성과 축성능, 전단 성능을 증가시키기 위해 외부기둥을 FRP로 보강하였다. 이와 같은 보강 효과를 실험적으로 검증하기 위해 순수 골조와 FRP와 좌굴방지가새로 보강된 골조에 대한 반복 횡하중 실험을 수행하였다. 실험 결과 항복강도(43.2 kN)는 설계항복강도(30 kN)와 압축부의 강도 증가 때문에 차이가 나타났고, 강성(11.6 kN/mm)은 설계강성(24.2 kN/mm)에 비하여 절반의 값을 가졌다. 이러한 강성의 차이는 골조와 가새의 접합부 사이의 미끄러짐과 기초의 회전 및 횡변위가 원인으로 나타났다. 보강된 골조의 에너지 흡수 능력은 순수 골조에 비해 7.5배 향상되었다. 기초당 설치된 로드셀의 개수를 2개에서 1개로 변화시키면, 횡강성이 11.6 kN/mm에서 6 kN/mm로 줄어 들었고, 이것은 단지 순수 골조의 강성에 3배에 지나지 않는다(2.1 kN/mm).