• 한국농공학회지
• /
• 제44권3호
• /
• pp.73-84
• /
• 2002

Nominal shear strength of concrete beam is the combined strength of concrete shear strength and steel shear strength in current design code. But Torsional moment strength of concrete is neglected in calculation of the nominal torsional moment strength of reinforced concrete beam in current revised code. Tensile stress of concrete strut between cracks is still in effect due to tension stiffening effect. But the tensile stresses of concrete after cracking are neglected in bending and torsion in design. The torsional behavior is similar to the shear behavior in mechanics. Therefore the torsional moment strength of concrete should be concluded to the nominal torsional moment strength of reinforced concrete beam. To verify the validity of the proposed model, the nominal torsional moment strengths according to CEB, two ACI codes(89, 99) and proposed model are compared to experimental torsional strengths of 55 test specimens found in literature. The nominal torsional moment strengths by the proposed model show the best results.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.53-56
• /
• 2005

This paper investigates the effect of ductile deformation behavior of high performance hybrid fiber-reinforced cement composites (HPHFRCCs) on the shear behavior of coupling beams to lateral load reversals. The matrix ductility and the reinforcement layout were the main variables of the tests. Three short coupling beams with two different reinforcement arrangements and matrixes were tested. They were subjected to cyclic loading by a suitable experimental setup. All specimens were characterized by a shear span-depth ratio of 1.0. The reinforcement layouts consisted of a classical scheme and diagonal scheme without confining ties. The effects of matrix ductility on deflections, strains, crack widths, crack patterns, failure modes, and ultimate shear load of coupling beams have been examined. The combination of a ductile cementitious matrix and steel reinforcement is found to result in improved energy dissipation capacity, simplification of reinforcement details, and damage-tolerant inelastic deformation behavior. Test results showed that the HPFRCC coupling beams behaved better than normal reinforced concrete control beams. These results were produced by HPHFRCC's tensile deformation capacity, damage tolerance and tensile strength.

• 한국공작기계학회논문집
• /
• 제16권2호
• /
• pp.14-22
• /
• 2007

In this paper, the acoustic emission(AE) behaviors were investigated with single-and 2-spot resistance spot welded SPCC specimens. Test specimens were welded horizontally and/or vertically according to the rolling direction of base netal in 2-spot welding. In the case of 2-spot welding, when tensile-shear test has below amplitudes: crack initiation $50{\sim}60dB;$ tear fracture $40{\sim}50dB$. And when cross tensile test has below amplitudes: early stage $75{\sim}85dB;$ yielding point $65{\sim}75dB;$ post yielding $40{\sim}60dB;$ plug fracture $70{\sim}80dB\;or\;90{\sim}100dB$. Also, from the b-value that is slope of AE amplitude, we knew that there are lots of low amplitudes if b-value is big(i.e., tensile-shear $specimen{\rightarrow}tear$ fracture or shear fracture), and there are lots of high amplitudes if b-value is small(i.e.. cross tensile $specimen{\rightarrow}plug$ fracture). As the results of fiacture mechanism analyses through AE amplitude distributions, change of the b-value represented fracture patterns of materials. Correspondingly, low amplitude signals appeared in crack initiation, and high amplitude signals appeared in base metal fracture. We confirmed that these amplitude distributions represented the change or degradation of materials.

• Journal of Welding and Joining
• /
• 제25권6호
• /
• pp.53-58
• /
• 2007

The present study examined the mechanical properties of the friction welding of shaft made of SKH51 and SM45C, of which the diameter is 12mm. Friction welding was done at welding conditions of 2,000rpm, friction pressure of 104MPa, upset pressure of 134MPa, friction time of 0.5sec to 2.5sec by increasing 0.5sec, upset time of 2 seconds. Under these conditions, a tensile test, a bending test, a shear test, a hardness test and a microstructure of weld interface were studied. When the friction time was 1.0 second under the conditions, the maximum tensile strength of the friction weld observed to be 963MPa, which is 89% the tensile strength of SKH51 base metal and 101% of the tensile strength of SM45C base metal. When the friction time was 1.0 seconds under the conditions, the maximum bending strength of the friction weld happened to be 1,647MPa, which is 78% the bending strength of SKH51 base metal(2,113MPa) and 87% of the bending strength of SM45C base metal(1,889MPa). When the friction time was 1.0 seconds under conditions, the maximum shear strength of the friction weld was observed to be 755MPa, which is 92% the shear strength of SKH51 base metal and 122% of the shear strength of SM45C base metal. According to the hardness test, the hardness distribution of the weld interface varied from Hv282 to Hv327. HAZ was formed from the weld interface to 1.2mm of SKH51 and 1.6mm of SM45C. Upon examination it was found that the microstructure became finer along with increase of friction revolution radius.

• Journal of the Korean Wood Science and Technology
• /
• 제43권5호
• /
• pp.661-671
• /
• 2015

To evaluate the shear performance of the textile glass fiber and the sheet glass fiber reinforced glulam bolted connections, a tension type shear test was conducted. The average yield shear strength of the bolted connection of reinforced glulam was increased by 12% ~ 31% compared to the non-reinforced glulam. It was confirmed that the shear performance of 5D end distance of the glass fiber reinforced glulam connection corresponds to that of 7D of the non-reinforced glulam connection proposed in building design requirements in various countries. Compared to the non-reinforced glulam, the average shear strength of textile glass fiber reinforced glulam was markedly increased. The non-reinforced glulam and the GFRP reinforced glulam underwent a momentary splitting fracture. However, the failure mode of textile glass fiber reinforced glulam showed a good ductility.

• 콘크리트학회논문집
• /
• 제19권4호
• /
• pp.441-448
• /
• 2007

지진하중을 받는 철근콘크리트 접합부의 거동은 전단과 부착 메커니즘에 의해 결정된다. 하지만 전단과 부착은 반복하중에 매우 취약하기 때문에 접합부는 항상 탄성 영역 내에 있어야 한다. 내진 설계 기준에서는 보에 소성힌지를 발생시켜 기둥과 접합부는 탄성 상태를 유지하면서 보에서 에너지소산이 이루어지도록 하는 것을 원칙으로 한다. 하지만 접합부와 인접한 보에 소성힌지가 발생할 경우, 보에서 발생한 소성힌지에서의 철근 변형률이 접합부 철근의 변형에 영향을 미쳐 결국 접합부의 전단 및 부착강도를 떨어뜨리는 결과를 가져오게 된다. 본 논문에서는 보 인장 철근량을 변수로 한 다섯 개의 철근콘크리트 보-기둥 접합부를 제작하고 보에 소성힌지를 발생시킨 후 그 결과를 분석하였다. 실험 결과, 보 인장철근량이 적을수록 접합부의 연성은 증가하였다. 또한 소성힌지 영역의 철근이 항복함에 따라 접합부의 연성률이 증가하고 접합부의 보 부재축 방향 인장변형률도 증가하였다.

• 동력기계공학회지
• /
• 제17권4호
• /
• pp.115-119
• /
• 2013

The resistance spot welding of high strength steel degrades the weldability because of its high strength with rich chemical composition and coating layer to protect from corrosion. And the weld Expulsion is prone to occur and severely affect the nugget guality when the initial gap between automatic borrowing galvanied steel sheets(SGARC35) and Zn-coateel trip steels(GA580TRIP and GA980 TRIP) exist in resistance spot welding(RSW). RSW is one of the most popular welding processes used to join sheet metals. but weld guality sometimes do creases due to welding condition. in this paper to verity tue weldability using spot welding with the hemispherically concaved electrode, tensile shear strength and cross-tensile strength were measured by a universal test machine. in addition, the nugget size on cross-sectional area of the weld was observed by optical and electron microscopy. As a result, the nugget size of this specimen is increased with increasing welding current and Max load of tensile-shear strength is increased with welding current is increasing.

• 콘크리트학회논문집
• /
• 제13권2호
• /
• pp.168-174
• /
• 2001

탄소섬유쉬트는 고강도, 경량 및 고 내구성 등의 우수한 재료적 성질을 가지고 있어 철근콘크리트 건축물의 보수 .보강재료 장범위하게 사용되어져 왔다. 탄소섬유쉬트와 콘크리트 사이의 부착강도 즉, 부착거동은 탄소섬유쉬트에 의해 보수.보강되는 철근콘크리트 부재의 보강성능을 좌우하는 매우 중요한 요소이다. 따라서, 탄소섬유쉬트와 콘크리트의 접합면에서 발생되는 부착파괴의 메카니즘은 명확히 구명될 필요가 있다. 본 연구에서는 양생온도, 콘크리트의 표면상태 및 함수율 등의 환경요소변화에 따른 탄소섬유쉬트와 콘크리트의 인발접착강도을 파악함으로써 환경요소의 영향을 평가하였으며 아울러, 탄소섬유쉬트와 콘크리트와의 부착성능을 결정하는 유효부착길이 및 평균부착응력도를 평가하였다. 연구결과, 인발접착강도에 미치는 환경요소에서 양생온도가 가장 중요한 영향인자로 나타났으며, 인장전단부착 실험으로부터 얻어진 유효부착길이 및 평균부착응력도는 각각 15 cm 및 9.78~11.88kgf/$\textrm{cm}^2$ 내외라고 사료된다.

• Structural Engineering and Mechanics
• /
• 제73권2호
• /
• pp.123-132
• /
• 2020

Steel spherical hinged bearings have high loading capacity, reliable load transfer, flexible rotation with universal hinge and allowance of large displacement and rotation angle. However, bearings are in complex forced states subject to various load combinations, which lead to the significant influence on integral structural safety. Taking the large-tonnage complex steel spherical hinged bearings of Terminal 2 of Guangzhou Baiyun International Airport as an example, full-scale rotation and shear behaviour tests of the bearings subject to axial tensile load are carried out, and the corresponding finite element simulation analyses are conducted. The results of experiments and finite element simulations are in good agreement with the coincident development tendency of stress and deformation. In addition, the measured rotational moment is less than the calculated moment prescriptive by the code, and the relationship between horizontal displacement and horizontal shear force is linear. Finally, based on these results, the rotation and shear stiffness models of bearings subject to axial tensile load are proposed for the refinement analysis of integral structure.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2000년도 추계학술대회 논문집
• /
• pp.47-52
• /
• 2000

F.R.P specimens were made by mixture CM(chopped mat) 450-104 matrix & RC(roving clothes)570-100 Roving, the mixture ratio Resin: hardener (92:8) for tensile test. It was also made of plates by hand lay-up method and was been cured for 24 hours and then was cut tensile specimens in accordance with ASTM D638 Type 3. Knowing exact behavior of bonded area's stress and strain when the tensile test was going on, the test specimens were made of 2 plies laminae of F.R.P in each for supporting cut part in middle of specimen length. And in middle part also were covered of F.R.P plies of 1/2, 2/3 length of specimen in each as well. Also we consider shear stress in adhered area. This study reveals that as plys length is more longer, rupture stress grows remarkably larger.