• Structural Engineering and Mechanics
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• 제7권4호
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• pp.413-432
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• 1999

A macro-element model is developed to account for shear deformation and bond slip of reinforcement bars in the beam-column joint region of reinforced concrete structures. The joint region is idealized by two springs in series, one representing shear deformation and the other representing bond slip. The softened truss model theory is adopted to establish the shear force-shear deformation relationship and to determine the shear capacity of the joint. A detailed model for the bond slip of the reinforcing bars at the beam-column interface is presented. The proposed macro-element model of the joint is validated using available experimental data on beam-column connections representing exterior joints in ductile and nonductile frames.

• 대한토목학회논문집
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• 제28권5A호
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• pp.691-697
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• 2008

강구조물의 현장연결 방식으로 널리 사용되고 있는 고장력볼트 마찰이음은 연결부의 부식 방지를 위해 도장을 실시하는 것이 일반적으로 허용되고 있다. 고장력볼트 이음부의 마찰면에 도장을 실시하는 경우에는 도장의 정도가 이음부의 미끄러짐 내력에 미치는 영향이 문제로 된다. 본 연구는 마찰면에 새로운 도장형식인 세라믹계 도장사양을 적용한 경우의 고장력볼트 마찰이음부의 미끄러짐 거동을 파악하기 위한 목적으로 실시하였다. 실험은 소정의 세라믹 도장사양을 적용한 고장력볼트 마찰이음 시험편을 대상으로 미끄러짐 시험을 실시하여 미끄러짐 하중 및 미끄러짐 계수를 측정하였으며, 이로부터 세라믹계 도장사양을 실시한 고장력볼트 연결부의 안전성 및 사용성을 검토하였다. 그 결과 미끄러짐 발생시의 하중-변위 특성은 각 도료사별로 다소의 차이가 발생하였으나, 평균 미끄러짐 계수는 도로교표준시방서의 설계기준인 마찰계수 0.4를 초과하는 결과를 나타내고 있다. 그러나 세라믹계 도장을 실시한 고장력볼트 연결부의 안전성과 사용성을 확보하기 위해서는 상세 도장조건에 대한 기준의 제정 및 시방서의 개정이 필요할 것으로 판단된다.

• Journal of the Korean Wood Science and Technology
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• 제17권4호
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• pp.35-43
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• 1989

Nailed joints, which are commonly used in Wooden structures, transmit loads from one member to another and induce partial composite actions between members. Long-term loads induce creep slip in nailed joints and affect load sharing and partial composite action, which may reduce joint stiffness. Two theoretical viscous-viscoelastic models were developed for nailed joints to predict creep behavior under long-term variable loads. Those models were also used to predict stiffness changes under long-term variable loads. The stiffness of nailed joint is defined as a Secant modulus which is called the joint modulus or slip modulus. Input data for the models are the results of constant load tests under three different load levels. To verify the models, nailed joints were also tested under two long-term variable load functions. The predictions of the models were very close to the experimental data. Therefore, the theoretical viscous-viscoelastic models and procedures developed in this study can be applied to predict creep slip and the changes in joint moduli of nailed joints under long-term variable loads.

• 구강회복응용과학지
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• 제21권2호
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• pp.113-132
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• 2005

The purpose of this study was to assess the stress-induced pattern at the supporting bone, the implant fixture, the abutment and the abutment screw according to a friction-fit joint (Astra; Model 1) or slip- fit joint (Frialit-2; Model 2) in the internal connection system under vertical and inclined loading using finite element analysis. In conclusion, in the internal connection system of the implant and the abutment connection methods, the stress-induced pattern at the supporting bone, the implant fixture, the abutment and the abutment screw according to the abutment connection form had difference among them, and the stress distribution pattern usually had a widely distributed tendency along the inner surface of the implant fixture contacting the abutment post. The magnitude of the stress distributed in the supporting bone, the implant fixture, the abutment and the abutment screw was higher in the friction-fit joint than in the slip-fit joint. But it is considered that the further study is necessary about how this difference in the magnitude of the stress have an effect on the practical clinic.

• 터널과지하공간
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• 제15권4호
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• pp.288-295
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• 2005

암반은 여러 가지 지질학적 요인에 기인한 역학적 결함을 많이 포함하고 있기 때문에 이방성 거동을 보이는 경우가 대부분이다. 그러므로 안정한 암반구조물이나 암반기초의 설계를 위해서는 이방성 암반에서 응력분포의 특성을 이해하는 것이 매우 중요하다. 이 연구에서는 반무한 평면이방성 지반의 표면에 선하중이 작용할 때 지반에 야기되는 탄성응력 분포의 특성을 고찰하였다. 절리의 강성과 절리의 간격, 경사각이 응력분포 형태에 미치는 영향이 검토되었다. 절리면의 미끄러짐 조건으로 Mohr-Coulomb 식을 가정할 경우, 절리면을 통한 미끄러짐이 발생할 수 있는 영역에 대한 고찰도 수행되었다.

• 대한토목학회논문집
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• 제26권2A호
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• pp.285-292
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• 2006

이 연구는 탄소섬유쉬트-콘크리트 부착이음 실험 결과로부터 국부적인 부착모텔(부착응력-미끄럼 모델)을 결정하는 방법을 제안하고, 실제 실험 결과와 비교하여 이러한 부착 조건에 적용 기능한 부착모델을 제시한다. 부착모델의 형상은 임의의 곡선 형태를 고려할 수 있도록 디중선형곡선(multi-linear curve)으로 가정하였으며, 수치적인 방법으로 부착이음의 해를 계산하여 실험 결과와 오차를 최소화하는 방법으로 부착모델을 결정하였다. 이중선형곡선(bilinear curve)을 도입한 부착모델 역시 최적화를 수행하여 다중선형모텔과 비교하였다. 최적화의 대상은 동일 조건의 부착모텔에 대해 여러 실험체로부터 구한 극한하중-부착길이 곡선과 개별 실험체의 하중-변위 곡선이다. 최적화를 위한 정식화는 physical programming을 사용하였으며 최적화 방법은 유전알고리즘(genetic algorithm)을 이용하였다.

• 로봇학회논문지
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• 제6권3호
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• pp.284-291
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• 2011

This paper presents the estimation of the frictional coefficient of the wheel-legged robot with hip joint actuation producing maximum tractive force. Slip behavior for wheel-legged robot is analytically explored and physically understood by identification of the non-slip condition and derivation of the torque limits satisfying it. Utilizing results of the analysis of slip behavior, the frictional coefficients of the wheel-legged robot during stance phase are numerically estimated and finally this paper suggests the pseudo-algorithm which can not only estimate the frictional coefficients of the wheel-legged robot, but also produce the candidate of the touch down angle for the next stance.

• Structural Engineering and Mechanics
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• 제32권4호
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• pp.477-488
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• 2009

A slip critical joint has various values to adopt the proper slip coefficient in various conditions of faying surfaces in the following codes: AISC, AIJ and Eurocode 3. However, the Korean Building Code still regulates the unique slip coefficient, 0.45, regardless of the diverse faying conditions. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The faying surfaces were comprised of a clean mill, rust, red lead paint, zinc primer, and shot blast treatment. The candidates for high strength bolts were torque-shear bolts, torque-shear bolts with zinc coating, and ASTM A490 bolts. Based on the test results, the specimens with a shot blasted surface and rusted surface exhibited $k_s$, 0.61, and 0.5, respectively. It is recommended that the specimens with zinc primer exhibit $k_s{\geq}0.40$. The clean mill treated surface had prominently lower values, 0.27. For red lead painted treatment, the thickness of the coating affects the determinant of slip coefficient, so it is necessary to establish a minimum $k_s$ of 0.2, with a coating thickness of 65 ${\mu}m$. During 1,000 hours of relaxation, the uncoated surfaces exhibited the loss of clamping force behind 3%, while the coated surfaces within a certain limited thickness exhibited the loss of clamping within a range of 4.71% and 8.37%.

• 한국운동역학회지
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• 제23권4호
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• pp.377-385
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• 2013

Fall is very fatal accident causes death to older people. Shoe may affect to fall. Shoe influences risk of slips, trips, and falls by altering somatosensory feedback to the foot. The purpose of this study was to investigate the analysis of non-slip shoes for older people and influence on older people's lower extremity. For this study twenty three healthy older people were recruited. Each subjects walked over slippery surfaces (COF 0.08). Four pairs of non-slip shoes (shoe A had the greatest COF, 0.23 while shoe B, C, and D had smaller COF relatively) for older people were selected and tested mechanical and biomechanical experiment. For data collection motion capture and ground reaction forces were synchronized. There were statistically significant differences for slip-displacement, coefficient of friction, braking force, propulsion force, knee range of motion and knee joint stiffness by shoes. It was concluded that shoe A was the best for non-slip function because of the lowest slip displacement, the highest braking and propulsion forces, and the highest mechanical and biomechanical coefficient of friction where as shoe B, C, D were identified as a negative effect on the knee joint than shoe A. To prevent fall and slip, older people have to take a appropriate non-slip shoes such as shoe A.

• Steel and Composite Structures
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• 제26권1호
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• pp.45-53
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• 2018

Experimental investigations have revealed significant mismatches between analytical estimates and experimentally measured deflections of transmission towers. These are attributed to bolt slip and joint flexibility. This study focuses on effects of joint flexibility on tower deflections and proposes criterions for permissible deflection limits based on the stresses in joints. The objective has been framed given that guidelines are not available in the codes of practices for transmission towers with regard to the permissible limits of deflection. The analysis procedure is geometric and material nonlinear with consideration of joint flexibility in the form of extension or contraction of the cover plates. The deflections due to bolt slip are included in the study by scaling up the deflections obtained from analysis by a factor. Using the results of the analysis, deflection limits for the towers are proposed by limiting the stresses in the joints. The obtained limits are then applied to a new full scale tower to demonstrate the application of the current study.