• Earthquakes and Structures
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• 제26권5호
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• pp.363-382
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• 2024

In India's north-eastern region, low-strength autoclaved aerated concrete (AAC) blocks are widely used for constructing masonry structures, making them susceptible to lateral forces due to their low tensile and shear strengths and brittleness nature. The absence of earthquake-resistant attributes further compromises their resilience during seismic events. An economically viable solution to enhance the structural integrity of these masonry structures involves integrating steel wire mesh within the masonry mortar joints. This study investigates the in-plane shear behaviour of AAC masonry by employing two approaches: incorporating steel wire mesh within the masonry bed joint "BJ" and the masonry bed and head joint "BHJ". These approaches aim to augment strength and ductility, potentially serving as earthquake-resistant attributes in masonry structures. Three distinct variations of steel wire mesh and three reinforcing arrangements, i.e. (-), (L) and (Z) arrangement were employed to reinforce the two approaches. The test result reveals a significant enhancement in structural performance upon inclusion of steel wire mesh in both reinforcing approaches, with the "BHJ" approach outperforming the "BJ" approach and the unreinforced masonry, along with increase in capacity as the wire mesh size increases. Furthermore, the effectiveness of the reinforcing arrangement is ranked with the (Z) arrangement showing the largest performance, followed by the (L) and (-) arrangement.

• Computers and Concrete
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• 제27권2호
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• pp.99-109
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• 2021

Experimental and discrete element methods were used to investigate the effects of echelon non-persistent joint on the failure behaviour of joint's bridge area under uniaxial compressive test. Concrete samples with dimension of 150 mm×100 mm×50 mm were prepared. Uniaxial compressive strength and tensile strength of concrete were 14 MPa and 1MPa, respectivly. Within the specimen, three echelon non-persistent notches were provided. These joints were distributed on the three diagonal plane. the angle of diagonal plane related to horizontal axis were 15°, 30° and 45°. The angle of joints related to diagonal plane were 30°, 45°, 60°. Totally, 9 different configuration systems were prepared for non-persistent joint. In these configurations, the length of joints were taken as 2 cm. Similar to those for joints configuration systems in the experimental tests, 9 models with different echelon non-persistent joint were prepared in numerical model. The axial load was applied to the model by rate of 0.05 mm/min. the results show that the failure process was mostly governed by both of the non-persistent joint angle and diagonal plane angle. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. It was shown that the shear behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint angle. The strength of samples increase by increasing both of the joint angle and diagonal plane angle. The failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods.

• Advances in concrete construction
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• 제13권 2호
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• pp.199-213
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• 2022

Experimental and discrete element approaches were used to examine the effects of F shape non-persistent joints on the failure behaviour of concrete under uniaxial compressive test. concrete specimens with dimensions of 200 cm×200 cm×50 cm were provided. Within the specimen, F shape non-persistent joint consisting three joints were provided. The large joint length was 6 cm, and the length of two small joints were 2 cm. Vertical distance between two small joints change from 1.5 cm to 4.5 cm with increment of 1.5 cm. In constant joint lengths, the angle of large joint change from 0° to 90° with increments of 30°. Totally 12 different models were tested under compression test. The axial load rate on the model was 0.05 mm/min. Concurrent with experimental tests, numerical simulation (Particle flow code in two dimension) were performed on the models containing F shape non-persistent joint. Distance between small joints and joint angles were similar to experimental one. the results indicated that the failure process was mostly governed by both of the Distance between small joints and joint angles. The axial loading rate on the model was 0.05 mm/min. The compressive strengths of the samples were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore, it was shown that the compressive behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint angle. In the first, there were only a few acoustic emission (AE) hits in the initial stage of loading, and then AE hits rapidly grow before the applied stress reached its peak. Furthermore, a large number of AE hits accompanied every stress drop. Finally, the failure pattern and failure strength are similar in both approaches i.e., the experimental testing and the numerical simulation approaches.

• 한국방재학회 논문집
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• 제4권4호
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• pp.1-6
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• 2004

축방향 인장응력이 작용하는 두께 20-80mm의 SM520-TMC강 맞대기 용접부를 대상으로 피로시험을 수행하였다. 시험 결과를 통계 분석하여 두께의 변화 및 용접방법에 따른 피로 강도를 검토하였다. 공칭응력을 기준으로 한 피로강도는 국내외의 기존 기준을 만족한다. 두께가 작은 경우에는 시험체의 제작오차에 따른 휨응력이 상당히 큰 것으로 나타났다. 측정값을 기준으로 한 피로강도는 공칭응력을 기준으로 한 경우보다 두께가 작은 20mm 경우 크게 증가하였다. 피로강도의 감소는 Gurney의 제안식과 유사한 것으로 나타났다.

• Geomechanics and Engineering
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• 제5권1호
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• pp.71-86
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• 2013

For rock materials, a transversely isotropic failure criterion established through the extended Lade-Duncan failure criterion incorporating an anisotropic state scalar parameter, which is a joint invariant of deviatoric microstructure fabric tensor and normalized deviatoric stress tensor, is verified with the results of triaxial compressive data on Tournemire shale. For torsional shear mode with $0{\leq}b{\leq}0.75$, rock shear strengths decrease with ${\alpha}$ increasing until the rock shear strength approaches minimum value at ${\alpha}{\approx}40^{\circ}$, and after this point, the rock shear strengths increase as ${\alpha}$ increases further. For the torsional shear mode with b > 0.75, rock shear strengths are almost constant for ${\alpha}{\leq}40^{\circ}$, but it increases with increase in ${\alpha}$ afterwards. The rock shear strength variation against ${\alpha}$ agrees with shear strength changing tendency of heavily OCR natural London Clays tested before. Prediction results show that the transversely isotropic failure criterion proposed in the paper is reasonable.

• 한국항공우주학회지
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• 제38권1호
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• pp.29-34
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• 2010

본 연구에서는 새롭게 개발된 "강도 향상 인써트"에 대해 조인트 시편을 제작하여 Pull-out 및 전단시험을 수행하여 보통 인써트의 조인트 강도와 비교하고 그 파손 특성을 조사하였다. 이를 통해 새로운 인써트에 대한 성능을 확인하였다. 시험 결과, 새로운 "강도 향상 인써트"는 기존의 보통 인써트에 비해 Pull-out 강도는 2.1배, 전단강도는 2.04배 향상되는 것을 확인하였다. 따라서 향후 높은 인써트 강도를 요구하는 구조에 유용하게 사용될 수 있을 것이다.

• Journal of Welding and Joining
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• 제31권4호
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• pp.7-12
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• 2013

The dissimilar welding between magnesium alloy and steel sheet was required in automobile industry to increase the strength of the dissimilar joints. Laser brazing is one of the good joining processes for Mgsteel dissimilar joint. In this study, the effect of coating materials was evaluated on the laser brazing for the dissimilar joint between AZ31 and coated steels such as Zn, Sn and Ni. Diode direct laser was used to braze the lap-edge joint with Mg600 filler wire and Superior #21 flux. The wettability was best on Zn coated steel. The interlayer was formed at the interface between brazement and steel for all coating materials. The strengths of brazed specimen were 146.5N/mm, 204.6N/mm and 101.6N/mm for Zn, Sn and Ni coated steel respectively.

• Advances in concrete construction
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• 제14권2호
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• pp.139-151
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• 2022

Filling materials poured into precast member joint are subjected to restraint stress by the precast member and joint reinforcement. The induced stress will likely cause cracks at early ages and performance degradation of the entire structure. To prevent these issues and design reasonable joints, it is very important to analyze and evaluate the restrained shrinkage cracks of filling materials at various restraint conditions. In this study, a new time zero-that defines the shrinkage development time of a filling material-is proposed to calculate the accurate amount of shrinkage. The tensile stresses and strengths at different ages were compared through the ring test (AASHTO PP34) to evaluate the crack potential of the restrained filling materials at various restraint conditions. The mixture which contained an expansive additive and a shrinkage reducing agent exhibited high resistance to shrinkage cracking owing to the high-drying shrinkage compensation effect. The high-performance, fiber-reinforced cement composite, and ultra-high-performance, fiber-reinforced cement composite yielded very high resistance to shrinkage and cracking owing to the pull-out property of steel fibers. To this end, multiple nonlinear regression analyses were conducted based on the test results. Accordingly, a modified tensile stress equation that considered both the geometric shape of the specimen and the intrinsic properties of the material is proposed.

• Smart Structures and Systems
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• 제30권1호
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• pp.49-62
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• 2022

Experimental and discrete element methods were used to investigate the effects of triple joints lengths and triple joint angle on the failure behavior of rock mass under uniaxial compressive test. Concrete samples with dimension of 20 cm × 20 cm × 5 cm were prepared. Within the specimen, three imbedded joint were provided. The joint lengths were 2 cm, 4cm and 6 cm. In constant joint lengths, the angle between middle joint and other joints were 30°, 60°, 90°, 120° and 150°. Totally 15 different models were tested under compression test. The axial load rate on the model was 0.05 mm/min. Concurrent with experimental tests, the models containing triple joints, length and joint angle are similar to the experiments, were numerical by Particle flow code in two dimensions (PFC2D). Loading rate in numerical modelling was 0.05 mm/min. Tensile strength of material was 1 MPa. The results show that the failure behaviors of rock samples containing triple joints were governed by both of the angle and the length of the triple joints. The uniaxial compressive strengths (UCS) of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore, it was shown that the compressive behavior of discontinuities is related to the number of the induced tensile cracks which are increased by decreasing the joint length. Along with the damage failure of the samples, the acoustic emission (AE) activities are excited. There were only a few AE hits in the initial stage of loading, then AE hits rapidly grow before the applied stress reached its peak. In addition, every stress drop was accompanied by a large number of AE hits. Finally, the failure pattern and failure strength are similar in both methods i.e., the experimental testing and the numerical simulation methods.

• Advances in concrete construction
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• 제14권5호
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• pp.317-330
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• 2022

This paper investigated computationally and experimentally the interaction here between a notch as well as a micropore under uniaxial compression. Brazilian tensile strength, uniaxial tensile strength, as well as biaxial tensile strength are used to calibrate PFC2d at first. Then, uniaxial compression test was conducted which they included internal notch and micro pore. Experimental and numerical building of 9 models including notch and micro pore were conducted. Model dimensions of models are 10 cm × 10 cm × 5 cm. Joint length was 2 cm. Joints angles were 30°, 45° and 60°. The position of micro pore for all joint angles was 2cm upper than top of the joint, 2 cm upper than middle of joint and 2 cm upper than the joint lower tip, discreetly. The numerical model's dimensions were 5.4 cm × 10.8 cm. The fractures were 2 cm in length and had angularities of 30, 45, and 60 degrees. The pore had a diameter of 1 cm and was located at the top of the notch, 2 cm above the top, 2 cm above the middle, and 2 cm above the bottom tip of the joint. The uniaxial compression strength of the model material was 10 MPa. The local damping ratio was 0.7. At 0.016 mm per second, it loaded. The results show that failure pattern affects uniaxial compressive strength whereas notch orientation and pore condition impact failure pattern. From the notch tips, a two-wing fracture spreads almost parallel to the usual load until it unites with the sample edge. Additionally, two wing fractures start at the hole. Both of these cracks join the sample edge and one of them joins the notch. The number of wing cracks increased as the joint angle rose. There aren't many AE effects in the early phases of loading, but they quickly build up until the applied stress reaches its maximum. Each stress decrease was also followed by several AE effects. By raising the joint angularities from 30° to 60°, uniaxial strength was reduced. The failure strengths in both the numerical simulation and the actual test are quite similar.