• 한국안전학회지
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• 제29권4호
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• pp.9-14
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• 2014

Self-piercing riveting(SPR) is a mechanical fastening technique which is put pressure on the rivet for joining the sheets. Unlike a spot welding, SPR joining does not make the harmful gas and $CO_2$ and needs less energy consumption. In this study, static and fatigue tests were conducted using tensile-shear specimens with Al-5052 plates for evaluation of fatigue strength of the SPR joints. During SPR joining process for the specimen, using the current sheet thickness and a rivet, the optimal applied punching force was found to be 21 kN. And, the maximum static strength of the specimen produced at the optimal punching force was 3430 N. During the fatigue tests for the specimens, interface failure mode occurred on the top substrate close to the rivet head in the most high-loading range region, but on the bottom substrate close to the rivet tail in the low -loading range region. There was a relationship between applied load amplitude $P_{amp}$ and lifetime of cycle N for the tensile-shear, $P_{amp}=3395.5{\times}N^{-0.078}$. Using the stress-strain curve of the Al-5052 from tensile test, the simulations for fatigue specimens have been carried out using the implicit finite element code ABAQUS. The relation between von-Mises equivalent stress amplitude and number of cycles was found to be ${\sigma}_{eq}=514.7{\times}N^{-0.033}$.

• Steel and Composite Structures
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• 제21권1호
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• pp.137-156
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• 2016

Due to excellent advantages such as better illuminative effects, considerable material savings and ease and rapidness of construction, the bolted ball-cylinder joint which is a new type joint system has been proposed in space truss structures. In order to reveal more information and understanding on the behaviour of bolted ball-cylinder joints, full-scale experiments on eight bolted ball-cylinder joint specimens were conducted. Five joint specimens were subjected to axial compressive force, while another three joint specimens were subjected to axial tensile force. The parameters investigated herein were the outside diameter of hollow cylinders, the height of hollow cylinders, the thickness of hollow cylinders, ribbed stiffener and axial force. These joint specimens were collapsed by excessive deformation of hollow cylinders, punching damage of hollow cylinders, evulsion of bolts, and weld cracking. The strain distributions on the hollow cylinder opening were mainly controlled by bending moments. To improve the ultimate bearing capacity and axial stiffness of bolted ball-cylinder joints, two effective measures were developed: (1) the thickness of the hollow cylinder needed to be thicker; (2) the ribbed stiffener should be adopted. In addition, the axial stiffness of bolted ball-cylinder joints exhibited significant non-linear characteristics.

• 대한치과교정학회지
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• 제38권3호
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• pp.187-201
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• 2008

본 연구는 피질골 천공을 동반한 교정적인 치아이동이 통상의 교정적인 치아이동과 조직 재형성의 정도에 차이가 존재하는지 알아보기 위하여 시행하였다. 실험동물은 15주령 군 300 - 350 g의 자성 백서(Sprague-Dawley Rat)를 사용하였으며 피질골 천공을 동반한 치아이동 실험군(TMC group, n = 16)과 단순 치아이동 대조군(TM group, n = 16)으로 나누었다. 모든 실험동물에 20 gm 이하의 힘으로 전치부를 이개시키는 치아 이동을 시행하였으며, 실험군은 상악전치부의 직후방 구개측에서 치근을 손상시키지 않도록 직경 1.0 mm의 microscrew를 사용하여 피질골 천공을 하였다. 모든 실험동물은 1, 4, 7, 14일에 희생시켜서 matrix metalloproteinase (MMP)-1, -8, -13 효소의 RT-PCR과 I형 교원질(Collagen type I)과 Tissue inhibitor of metalloproteinase-1 (TIMP-1)의 면역조직화학염색(immunohisto-chemistry)을 시행하였다. MMP-1은 실험군에서 4일째에 가장 활발한 발현을 보이다가 7일째와 14일째에 조금씩 감소하는 경향을 보인 반면에, 대조군에서는 실험 7일째에 가장 높은 발현을 보이다가 14일째 들어서 감소하는 양상을 보였다. MMP-8은 실험 1일째부터 실험군이 대조군에 비해서 더 많은 발현을 보였으며, 특히 4일째의 실험군에서는 대조군보다 두 배 이상 발현되었다. MMP-13은 실험 1일째의 실험군에서 가장 높은 발현도를 보였으며, 대조군에서는 오히려 미처치 대조군에 비해 더 낮게 발현되었다. I형 교원질의 면역조직화학염색 결과는 실험 4일째부터 압박측에서는 실험군에서 대조군보다 더 많은 교원질의 소실을 보였고, 인장측에서는 대조군이 실험군보다 더 많은 교원질의 염색 소견을 보였다. TIMP-1은 실험 4일째에는 압박측에서 대조군이 실험군보다 치주인대와 치조골의 골세포에서 좀 더 균일한 염색 소견을 보였다. 이상의 실험 결과에서 피질골 천공은 백서의 실험적 치아이동에 있어 치주인대와 치조골 결합 조직의 재형성 속도를 증가시키는 것으로 판단된다.

• Geomechanics and Engineering
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• 제14권1호
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• pp.61-69
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• 2018

The first part shows the optimal contact surface for T-shaped combined footings to obtain the most economical dimensioning on the soil (optimal area). This paper presents the second part of a new model for T-shaped combined footings, this part shows a the mathematical model for design of such foundations subject to axial load and moments in two directions to each column considering the soil real pressure acting on the contact surface of the footing with one or two property lines restricted, the pressure is presented in terms of an axial load, moment around the axis "X" and moment around the axis "Y" to each column, and the methodology is developed using the principle that the derived of the moment is the shear force. The classic model considers an axial load and a moment around the axis "X" (transverse axis) applied to each column, i.e., the resultant force from the applied loads is located on the axis "Y" (longitudinal axis), and its position must match with the geometric center of the footing, and when the axial load and moments in two directions are presented, the maximum pressure and uniform applied throughout the contact surface of the footing is considered the same. To illustrate the validity of the new model, a numerical example is presented to obtain the design for T-shaped combined footings subjected to an axial load and moments in two directions applied to each column. The mathematical approach suggested in this paper produces results that have a tangible accuracy for all problems.

• 한국구조물진단유지관리공학회 논문집
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• 제12권5호
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• pp.74-80
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• 2008

본 논문은 기둥형상비를 실험 변수로 가지는 무량판 슬래브-기둥 접합부의 내진성능을 평가하는데 있다. 본 연구에서는 무량판 슬래브의 뚫림 전단파괴를 방지하기 위하여 본 연구와 병행하여 진행된 연구에서 개발된 연속 절곡된 전단보강근을 적용하였다. 기둥형상비에 따른 실험체는 각각 FIS1-05(0.5), FIS1- 10(1.0), FIS1-20(2.0) 이다. 실험체의 수평방향으로 정적 수평하중을 가력 하였으며, 중력하중비에 의한 일정 수직 하중을 적용하였다. 실험결과는 슬래브-기둥 접합부의 수평 변위 및 강도를 기준으로 평가하였다. 분석결과, FIS1-05, FIS1-20와 같은 장방형 기둥을 갖는 접합부의 성능이 FIS1-10와 같은 정방형 기둥을 갖는 접합부보다 우수한 것으로 평가되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.241-244
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• 2008

RC 플랫 플레이트 골조는 중력저항 시스템으로 설계하고, 횡력저항 시스템인 전단벽이나 모멘트 골조를 같이 사용하는 것이 일반적이다. 그러나 지진하중과 같은 횡하중은 횡력저항 시스템의 변형을 일으키며 일체로 연결된 중력저항 시스템도 예상치 않았던 횡변위가 발생하여, 접합부에서 큰 불균형 모멘트가 발행하게 된다. 따라서 횡하중에 의해 유발된 불균형모멘트의 고려가 필요하며, �躍꼭患� 파괴를 정확하게 예측할 수 있어야 한다. 본 연구는 RC 플랫 플레이트 골조의 내진성능평가를 위하여 슬래브-기둥 접합부의 비선형 거동을 예측하기 위한 해석모델을 개발하였다. 해석모델의 검증을 위하여 중력전단비가 다른 2개의 2경간 플랫 플레이트 구조물의 실험결과와 해석모델의 결과를 비교하였다. 그 결과 개발된 해석모델은 실험체의 뚤림전단파괴 및 파괴모드를 잘 예측하는 것으로 나타났다.

• Advances in concrete construction
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• 제16권1호
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• pp.21-34
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• 2023

This work presents a complete optimal model for trapezoidal combined footings that support a concentric load and moments around of the "X" and "Y" axes in each column to obtain the minimum area and the minimum cost. The model presented in this article considers a pressure diagram that has a linear variation (real pressure) and the equations are not limited to some cases. The classic model takes into account a concentric load and the moment around of the "X" axis (transverse axis) that is applied due to each column, i.e., the resultant force is located at the geometric center of the footing on the "Y" axis (longitudinal axis), and when the concentric load and moments around of the "X" and "Y" axes act on the footing is considered the uniform pressure applied on the contact surface of the footing, and it is the maximum pressure. Four numerical problems are presented to find the optimal design of a trapezoidal combined footing under a concentric load and moments around of the "X" and "Y" axes due to the columns: Case 1 not limited in the direction of the Y axis; Case 2 limited in the direction of the Y axis in column 1; Case 3 limited in the direction of the Y axis in column 2; Case 4 limited in the direction of the Y axis in columns 1 an 2. The complete optimal design in terms of cost optimization for the trapezoidal combined footings can be used for the rectangular combined footings considering the uniform width of the footing in the transversal direction, and also for different reinforced concrete design codes, simply by modifying the resisting capacity equations for moment, for bending shear, and for the punching shear, according to each of the codes.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.78-79
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• 2014

This study is concerned with the VS shear reinforcement that it can be installed easily in filed as product at the factory and seismic performance can be achieved. The method of study is as follows. first, we researched constructability and economy of existing construction method. Secondly, we made specimen and were examined structural performance tests in order to verify the performance of the shear reinforcement for lateral force like seismic load. As a result, developed VS shear reinforcement increased in shear strength and stiffness of reinforcement, structural safety is judged to be increased.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.956-965
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• 2005

In this paper, the effect on the forced replacement depth of the revetment in soft soil with inter sand layer is analyzed by model test. In the result, the forced replacement occur in 60 second from filling the embankment material. The shape of the forced replacement depth is like to punching shape. Then, in case of thin inter sand layer and near the embankment, the forced replacement depth of inter sand layer case is more than only clayed soil case.

• International Journal of Railway
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• 제2권4호
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• pp.131-138
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• 2009

Static tensile and fatigue tests were conducted using tensile-shear specimens to evaluate the fatigue strength of a SPCC sheet clinch joint. The maximum tensile strength of the specimen produced at the optimal punching force was 1750 kN. The fatigue endurance limit (=760 N) approached 43% of the maximum tensile load (=1750 N) at a load ratio of 0.1, suggesting that the fatigue limit is approximately half of the value of the maximum tensile strength. The FEM analysis showed that at the fatigue endurance limit, the maximum von-Mises stress of 373 MPa is very close to the ultimate tensile strength of the SPCC sheet (=382 MPa).