• 로봇학회논문지
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• 제9권1호
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• pp.11-19
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• 2014

In this paper, an external torque estimation problem in one-degree-of-freedom (1-DOF) flexible-joint robot equipped with a joint-torque sensor is revisited. Since a sensor torque from the joint-torque sensor is distorted by two dynamics having a spring connection, i.e., motor dynamics and link dynamics of a flexible-joint robot, a model-based estimation, rather than a simple linear spring model, should be required to extract external torques accurately. In this paper, an external torque estimation algorithm for a 1-DOF flexible-joint robot is proposed. This algorithm estimates both an actuating motor torque from the motor dynamics and an external link torque from the link dynamics simultaneously by utilizing the flexible-joint robot model and the Kalman filter estimation based on random-walk model. The basic structure of the proposed algorithm is explained, and the performance is investigated through a custom-designed experimental testbed for a vertical situation under gravity.

• Journal of the Korean Wood Science and Technology
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• 제41권2호
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• pp.123-133
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• 2013

This paper presents experimental and numerical tests on a recently developed timber column concealed base joint. This joint was designed to replace the wood-wood connection found in the post-and-beam structure of Hanok, the traditional Korean timber house. The use of metallic connectors provides an increased ductility and energy dissipation for a better performance under reversed loading, especially seismic. In this study, we investigate the performance of the joint under pseudo-static reversed cyclic moment loading through the study of its ductility and energy dissipation. We first perform experimental tests. Results show that the failure occurs in the metallic connector itself because of stress concentrations, while no brittle fracture of wood occur. Subsequent numerical simulations using a refined finite element model confirm these conclusions. Then, using a practical modification of the joint configuration with limited visual impact, we improve the ductility and energy dissipation of the joint while retaining a same level of rotational strength as the originally designed configuration. We conclude that the joint has a satisfying behavior under reversed moment loading for use in earthquake resistant timber structure in low to moderate seismicity areas like Korea.

• 한국지진공학회논문집
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• 제3권3호
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• pp.9-20
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• 1999

프레임 구조물의 접합부 손상을 평가하기 위하여 접합부 손상모델과 신경망기법을 이용한 손상평가기법을 제안하였다 구조물의 보-기둥 접합부를 접합부의 회전강성을 갖는 등가의 스프링요소로 표현하였으며 접합부의 손상도는 손상 전 후의 고정도계수의 감소비율로 정의하였다 손상평가를 위하여 다층퍼셉트론즈 신경망 기법을 제안하였으며 손상평가성능을 향상시키기 위하여 부분구조추정법, 노이즈첨가학습, 자료교란법등의 기법을 적용하였다 10층 프레임 구조물에 대한 수치 예제해석과 2층 프레임 구조물에 대한 실험 예제해석을 통하여 제안기법의 유용성을 평가하였다 계측지점이 일부분으로 제한되어 있고 계측자료에 심한 계측오차가 포함되어 있는 경우에도 손상평가가 합리적으로 이루어질수 있음을 알 수 있었다.

• 구강회복응용과학지
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• 제21권1호
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• pp.1-14
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• 2005

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis of internal connection system(ITI system) according to position and direction of load, under vertical and inclined loading using finite element analysis (FEA). The finite element model of a synOcta implant and a solid abutment with $8^{\circ}$ internal conical joint used by the ITI implant was constructed. The gold crown for mandibular first molar was made on solid abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric cusp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant under both vertical and oblique loading but stresses in the cancellous bone were low under both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. So, the relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 4. In this internal conical joint, vertical and oblique loads were resisted mainly by the implant-abutment joint at the screw level and by the implant collar. Conclusively, It seems to be more important that how long the distance is from center of rotation of the implant itself to the resultant line of force from occlusal contact (leverage). In a morse taper implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. This type of implant-abutment connection can also distribute forces deeper within the implant and shield the retention screw from excessive loading. Lateral forces are transmitted directly to the walls of the implant and the implant abutment mating bevels, providing greater resistance to interface opening.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.575-578
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• 1999

The main objective of this study was to examine structural behavior of reinforced concrete column and steel beam joint. composite specimens about 3/4 of the actual beam column connection assembly were tested by applying cyclic load through actuators. Test variables include face bearing plate(FBP), extended face bearing plate(E-FBP), VIR, U-bar and sub beam. There is not much differenced between specimens with sub beam and without sub beam. Test results also show that the joint strength of test specimen is close to the predicted strength by ASCE guideline.

• 한국산학기술학회논문지
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• 제12권6호
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• pp.2859-2865
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• 2011

본 연구에서는 상수도관의 도 송수관등 대형관(700mm 이상)에 주로 사용되고 있는 도복장강관의 품질 및 시공, 유지관리에 영향을 미치는 용접접합의 현황을 조사 분석하고 용접접합의 개선방안에 대하여 연구하였다. 이를 위해 강관의 사용현황 등의 문제점을 조사하고 용접접합별 특성, 그리고 수동 및 자동 용접접합을 비교 분석하여 기술적, 경제적으로 효과적인 방안을 제시하고자 하였다. 본 연구에서 비교 분석한 용접접합별 특성 검토 결과, 상수도 관로의 관경 700mm - 3,000mm의 현장 시공시 자동용접공법이 수동용접공법에 비해 순공사비 대비 평균 9% 절감되며, 용접공정만 비교시에는 평균 13.5% 이상 절감될 것으로 판단된다. 특히, KS상 강관 진원도에 대한 허용치가 크며 대부분 겹치기 이음으로 되어있는 국내 현실에서 작업환경이 열악한 경우 진원확보를 위한 시간이 무한정 소요될 수 있어 실제적인 절감액은 더욱 차이를 보일 것으로 사료된다.

• Steel and Composite Structures
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• 제20권3호
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• pp.469-486
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• 2016

Codes EN 1993 and EN 1994 require to take into account actual joint characteristics in the global analysis. In order to implement the semi-rigid connection effects in frame design, knowledge of joint rotation characteristics ($M-{\phi}$ relationship), or at least three basic joint properties, namely the moment resistance $M_R$, the rotational stiffness $S_j$ and rotation capacity, is required. To avoid expensive experimental tests many methods for predicting joint parameters were developed. The paper presents a comprehensive analytical model that has been developed for predicting the moment resistance $M_R$, initial stiffness $S_{j.ini}$ and rotation capacity of the minor axis, composite, semi-rigid joint. This model is based on so-called component method included in EN 1993 and EN 1994. Comparison with experimental test results shows that a quite good agreement was achieved. A computer program POWZ containing proposed procedure were created. Based on the numerical simulation made with the use of this program and applying regression analysis, simplified equations for main joint properties were also developed.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.283-289
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• 2000

The panel shear and bearing strengths determining the seismic resistance of reinforced concrete column-to-steel beam connections are predicted by various methods for four previously tested exterior beam-column joints. The analytical approach to model the joint deformation is also examined. Several analyses incorporating the deformations of panel shear and bearing in the joint are demonstrated using a analyses incorporating the deformations of panel shear and bearing in the joint are demonstrated using a fairly simple connection model in the commercial packages such as Drain2dx and IDARC. The strength prediction results indicated that the ASCE method with the modifcation of the comprssion strut contribution is th most accurate. It is also considered that the analytical model presented including the joint deformation can be used for the overall analysis

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.475-480
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• 1998

The composite framed structures, consisting of RC columns and steel beams more popular in korea because of their efficiency and quality. However the force transfer mechanisms between the column and beam may by very complicated since the materials of columns and beams are different. This study develops "the column penetration joint" which the web of steel beam doesn't penetrate and which could improve the strength, deformation, and energy dissipation capacities compared to existing composite joints. It is the concrete-filled square tube joint with the exterior diaphragms and the cruciform stiffening plates. This study evaluated the strength of RC column penetration to steel beam connection by analyzing the results of partial experiments, and reviewed the applicability the strength formula through the comparison of tested results of joint experiment.

• 한국군사과학기술학회지
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• 제10권1호
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• pp.144-149
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• 2007

Behaviour of a thread joint of a rocket motor case show complex structural characteristics. Pre-torque must be applied to the threads to prevent the loosening of the interface from the additional pressure load. During the pressurization of the rocket motor case, the jointing face may be opened if the pre-torque were not set properly or the structure may be failed if the local concentrated stress exceeds the strength of the material. In this paper, the structural behaviour of a thread joint of a rocket motor case were analyzed by the finite element method and the results were compared to the experimental ones. A method to set a pre-torque for a thread joint were proposed to ensure the structural safety.