• Maxillofacial Plastic and Reconstructive Surgery
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• 제34권5호
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• pp.311-319
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• 2012

Purpose: The aim of this study is to evaluate the vertical changes of the lip and perioral soft tissue, following orthognathic surgery in skeletal class III patients by a cephalometric analysis of a cone beam computed tomography (CBCT). Methods: A total of 20 skeletal class III patients, who had bimaxillary surgery with Le Fort 1 osteotomy and bilateral sagittal split ramus osteotomy, were included in this study. The surgical plan for maxilla was posterosuperior impaction with the anterior nasal spine, as the rotation center. Further, the surgical plan for mandible was also posterosuperior movement. The soft tissue changes between lateral cephalogram and CBCT were compared. And the correlations between independent variables and dependent variables were evaluated. Results: There were no significant differences of the soft tissues changes between lateral cephalogram and CBCT. Upper lip philtrum length (SnLs), nasolabial angle increased and upper lip vermilion length (LsStms), lower lip length (StmiB'), lower lip vermilion length (StmiLi), lower lip philtrum length (LiB') and soft tissue lower facial height (SnMe') decreased after surgery. Change of SnLs (${\Delta}$SnLs) was influenced by vertical change of menton (${\Delta}$MeV), and change of LsStms (${\Delta}$LsStms) was influenced by upper lip thickness (ULT). Change of StmiLi' (${\Delta}$StmiLi') were influenced by preoperative overjet. Change of StmiB' (${\Delta}$StmiB') were influenced by preoperative overjet, vertical change of lower incisor (${\Delta}$L1V) and horizontal change of posterior nasal spine (${\Delta}$PNSH). Change of LiB' (${\Delta}$LiB') was influenced by ${\Delta}$L1V and ${\Delta}$PNSH. Change of SnMe' (${\Delta}$SnMe') was influenced by ${\Delta}$MeV, horizontal change of upper incisor (${\Delta}$U1H) and horizontal change of lower incisor (${\Delta}$L1H). ${\Delta}$Nasolabial angle was influenced by change of ULT (${\Delta}$ULT). Conclusion: Both soft tissues and hard tissues can be evaluated by CBCT. Posterosuperior rotation of maxillomandibular complex resulted in increase of upper lip philtrum length and nasolabial angle, while the upper lip vermilion length, lower lip philtrum length, lower lip vermilion length, and soft tissue lower facial height showed a decrease.

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.104-111
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• 2009

This paper shows the behaviors of macro- and micro-structures and mechanical properties for specimen's welding region welded by FSW. according to welding conditions with 5mm thickness aluminum 5083O alloy plate. It apparently results in defect-free weld zone in case traverse speed was changed to 32 mm/min under conditions of anti-clockwise direction and tool rotation speed such as 800 and 1250 rpm with tool's pin diameter of 5 ${\Phi}mm$ and shoulder diameter of 20 ${\Phi}mm$, pin length of 4.5 mm and tilting angle of $2^{\circ}$. The ultimate stress of ${\sigma}_T=331$ MPa and the yield point of 147 MPa are obtained at the condition of the travel speed of 32 mm/min with the tool rotation speed of 1250 rpm. There is neither voids nor cracks on bended surface of $180^{\circ}$ after bending test. The improvement of toughness after impact test was found. The lower rotating and traverse speed became, the higher were yield point, maximum stress and elongation(%) with the stresses and the elongation(%) versus the traverse speed diagram. Vickers hardness for cross section of welding zone were also presented. The typical macro-structures such as dynamically recrystallized zone, thermo-mechanically affected zone and heat affected zone and the micro-structures of the transverse cross-section were also showed. However, the author found out that the region of 6mm far away from shoulder circumference was affected by friction heat comprehensively, that is, hardness softened and that part of micro-structures were re-solid-solution or recrystallized, the author also knew that there is no mechanically deformation on heat affected zone but there are the flow of plastic deformation of $45^{\circ}$ direction on thermo-mechanically affected zone and the segregation of Al-Mg on nugget. The solid solution wt(%) of parent material as compared against of friction stir welded zone was comprehensively changed.

• 한국정밀공학회지
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• 제32권12호
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• pp.1073-1080
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• 2015

A drive shaft is used to transmit torque and rotation through the connection of components of a drive train. Recently, a monobloc drive shaft without welding regions is developed to improve the safety of the drive shaft. The drive shaft bears the shear stress induced by torque. The objective of this paper is to investigate into the structural safety of a monobloc tubular drive shaft subjected to torque. Elasto-plastic finite element (FE) analysis is performed to estimate the deformation behavior of the drive shaft and stress-strain distribution in the drive shaft. Several techniques are used to create finite element (FE) model of the monobloc tubular drive shaft subjected to torque. Through the comparison of the results of FE analyses with those of experiments from the viewpoint of rotational angle, appropriate correction coefficients for different load conditions are estimated. The safety of the tubular drive shaft is examined using the results of FE analyses for different load conditions. Finally, it is noted that the designed tubular drive shaft has a sufficient structural safety.

• Steel and Composite Structures
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• 제24권4호
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• pp.441-453
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• 2017

In Y-shaped eccentrically braced frame fabricated with high strength steel (Y-HSS-EBF), link uses conventional steel while other structural members use high strength steel. Cyclic test for a 1:2 length scaled one-bay and one-story Y-HSS-EBF specimen and shake table test for a 1:2 length scaled three-story Y-HSS-EBF specimen were carried out to research the seismic performance of Y-HSS-EBF. These include the failure mode, load-bearing capacity, ductility, energy dissipation capacity, dynamic properties, acceleration responses, displacement responses, and dynamic strain responses. The test results indicated that the one-bay and one-story Y-HSS-EBF specimen had good load-bearing capacity and ductility capacity. The three-story specimen cumulative structural damage and deformation increased, while its stiffness decreased. There was no plastic deformation observed in the braces, beams, or columns in the three-story Y-HSS-EBF specimen, and there was no danger of collapse during the seismic loads. The designed shear link dissipated the energy via shear deformation during the seismic loads. When the specimen was fractured, the maximum link plastic rotation angle was higher than 0.08 rad for the shear link in AISC341-10. The Y-HSS-EBF is a safe dual system with reliable hysteretic behaviors and seismic performance.

• Earthquakes and Structures
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• 제10권6호
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• pp.1467-1486
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• 2016

This research focuses on seismic performance of a class of single pier skewed bridges with three different pier-deck connections; skew angles vary from $0^{\circ}$ to $60^{\circ}$. A well-documented four span continuous deck bridge has been modeled and verified. Seat-type connections with fixed and sliding bearings plus monolithic pier-deck connections are studied. Shear keys are considered either fully operational or ineffective. Seismic performances of the bridges and the structural components are investigated conducting bidirectional nonlinear time history analysis in OpenSees. Several global and intermediate engineering demand parameters (EDP) have been studied. On the basis of results, the values of demand parameters of skewed bridges, such as displacement and rotation of the deck plus plastic deformation and torsional demand of the piers, increase as the skew angle increases. In order to eliminate the deck collapse probability, the threshold skew angle is considered as $30^{\circ}$ in seat-type bridges. For bridges with skew angles greater than $30^{\circ}$, monolithic pier-deck connections should be applied. The functionality of shear keys is critical in preventing large displacements in the bearings. Pinned piers experience considerable ductility demand at the bottom.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.67-72
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• 2001

The LBB behavior and the crack opening displacement after a crack penetrated wall thickness of statically indeterminate piping system were investigated in this study, compared with statically determinate piping system. The reduction of ultimate strength caused by a crack was relatively small in the statically indeterminate piping system. The statically indeterminate piping system has more safety margin for LBB behavior than the statically determinate piping system. The crack opening displacement could be evaluated by using the plastic rotation angle proposed to evaluate the crack opening displacement after crack penetration in pipe with a non-penetrating crack.

• 한국강구조학회 논문집
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• 제23권5호
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• pp.595-606
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• 2011

본 연구는 기둥-보 접합부의 강성에 따른 철골 모멘트 골조의 동적특성의 차이를 파악하는데 목적이 있다. 6층의 철골 모멘트 골조를 설계하였으며, 접합부는 DWA (Double Web-Angle Connection), TSW (Top-and Seat-Angle Connection with Double Web-Angle), FEMA(SAC-Test Summary No.28, Specimen ID : UCSD-6) 접합부를 사용하였고, 완전강접합부의 동적거동특성과 상호 비교 검토하였다. 반강접 접합부의 회전강성은 Chen 과 Kishi 에 의해 제안된 3매개변수파워모델을 사용하여 구하였다. 접합부의 회전 강성을 보의 강성으로 나누어 상대강성으로 정의하여 사용하였다. 모든 골조에 대하여 비선형 정적해석(push over analysis), 반복하중 해석 및 시간이력해석을 수행하였다. 각 접합부의 강성에 따른 내진거동은 층간변위, 소성힌지 및 이력 에너지 분배의 항목별로 비교 분석하였다.

• 한국재난정보학회 논문집
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• 제15권3호
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• pp.418-426
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• 2019

연구목적: 내진성능이 부족한 중 저층의 RC 격자 구조물의 내진능력을 해석한 후, 보와 기둥의 내진성능 개선을 위해 강재 슬래브 이력형 댐퍼(SSHD)를 설치하고, 지진이 발생할 때 구조물의 손상 및 인적피해를 최소화 하는 방안을 제시하는 데 그 목적이 있다. 연구방법: 내진설계가 되지 않은 격자 형태의 전철 역사를 대상으로 내진성능을 파악하고, 내진성능이 부족할 경우 공기를 최소화 할 수 있는 방법인 SSHD 시스템을 설치하는 것으로 가정하여 구조물의 내진성능 평가 및 보강을 검토한다. 연구결과: SSHD를 적용하여 구조물을 보강한 후, 고유치 해석을 수행한 결과 장변방향으로는 0.548s의 고유주기를 나타내었으며, 단변방향으로는 0.593s의 고유주기를 가지고 있는 것으로 나타났다. 결론: SSHD에 대하여 반복하중 실험을 수행 한 결과, 댐퍼의 전단강성은 103%, 에너지소산량은 111% 및 109%로 나타나고, 모든 기둥과 보 부재의 소성회전각은 $I_o$수준을 만족하는 것으로 나타나 보강효과가 충분할 것으로 판단된다.

• 대한건축학회논문집:구조계
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• 제35권4호
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• pp.135-146
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• 2019

Deep beam has high section modules compared with shallow beam of the same weight. However, deep beam has low rotational capacity and high possibility of brittle failure so it is not possible to apply deep beams with a long span to intermediate moment frames, which should exhibit a ductility of 0.02rad of a story drift angle of steel moment frames. Accordingly, KBC and AISC limit the beam depth for intermediate and special moment frame to 750mm and 920mm respectively. The purpose of this paper is to improve the seismic performance of intermediate moment frame with 1200mm depth beam. In order to enhance vulnerability of plastic deformation capacity of deeper beam, Multi-Reduced Taper Beam(MRTB) shape that thickness of beam flange is reinforced and at the same time some part of the beam flange width is weakened are proposed. Based on concept of multiple plastic hinge, MRTB is intended to satisfy the rotation requirement for intermediate moment frame by dividing total story drift into each hinge and to prevent the collapse of the main members by inducing local buckling and fracture at the plastic hinge location far away from connection. The seismic performance of MRTB is evaluated by cyclic load test with conventional connections type WUF-W, RBS and Haunch. Some of the proposed MRTB connection satisfies connection requirements for intermediate moment frame and shows improved the seismic performance compared to conventional connections.

• 한국지반공학회지:지반
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• 제13권4호
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• pp.149-162
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• 1997

주응력회전시 모래의 강도특성을 연구하기 위하여 일련의 응력경로에 대해 시험을 실시하였다. 이들 결과는 공시체의 높이에 따라 25cm와 40cm로 분류할 수 있으며 공시체에 작용된 토르 크(Torque)는 시계방향으로만 작용시켰다. 본 연구에서는 비 틀림전단시험시 주응력비에 대한 모래의 강도특성이 조사되었고 그 결과를 Lade의 파괴규준과 비교하여 보았다. 그리고 공시체높 이에 대한 영향을 고려하였다. 이들 시험결과로 부터 모래의 내부마찰각은 축차주응력비 $b:(\sigma_2 -\sigma_s)/(\sigma_2,-\sigma_3)$에 많은 영향을 받는 것으로 나타났다. 모래의 파괴강도는 응력경로에 영향을 받지 않고 현재의 응력상태에 의해 결정 되어지며 25cm와 40cm 높이의 공시체에 대한 비교로부터 단부구속의 영향은 발견할 수 없었다. 그리고 신장력이 작용된 b=0.5 이상인 시험에서는 변형을 국부현상에 의한 Necking현상이 발견되었다.