• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.10 s.181
• /
• pp.2461-2468
• /
• 2000

In this paper, single fiber pull-out test is used to measure the interfacial bonding shear strength of $Ti_{50}-Ni_{50}$ shape memory alloy composite with temperature. Fiber and matrix of $Ti_{50}-Ni_{50}$ shape memory alloy composite are respectively $Ti_{50}-Ni_{50}$ shape memory alloy and epoxy resin. To strengthen the interfacial bonding shear stress, various surface treatments are used. They are the hand-sanded surface treatment, the acid etched surface treatment and the silane coupled surface treatment etc.. The interfacial bonding shear strength of surface treated shape memory alloy fiber is greater than that of surface untreated shape memory alloy fiber by from 10% to 16%. It is assured that the hand-sanded surface treatment and the acid etched surface treatment are the best way to strengthen the interfacial bonding shear strength of $Ti_{50}-Ni_{50}$ shape memory composite. The best treatment condition of surface is 10% HNO$_3$ solution in the etching method to strengthen the interfacial bonding shear strength of $Ti_{50}-Ni_{50}$ shape memory alloy composite.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.58 no.2
• /
• pp.45-52
• /
• 2016

The object of this paper was to evaulate modified proposed design equation in model test result in order to estimate uplift-resistance of timber pile of reclaimed land greenhouse foundation. Uplift resistance result of model test was increased to according to increased of contact area. Uplift-resistance result of field test tend to lineary increased to according to increased of embedment depth and contact area. Results of field uplift-resistance was evaluate compare with modified proposed design equation results of model test and Effective stress method. As the Effective stress method tend to underestimate, modified proposed design equation results of model test tend to similar type. As the contact area increase, difference between field uplift-resistance results and modified proposed design equation results of model test was considered uplift-speed.

• Geotechnical Engineering
• /
• v.8 no.3
• /
• pp.13-22
• /
• 1992

Model pile tests using calibration chamber are performed in !his paper in order to clarify the effect of the fundamental differences between the newly developed SPLT(Simple Pile Loading Test)and the conventional pile loading test on the pile bearing capacity. They are : (1) the direction of the applied load to mobilize the skin friction ; and (2) the use of reduced sifted sliding core. The conclusions obtained from the model pile tests are as follows : (1) The skin friction in tension loading is found to be somewhat smaller than that in compression loading. The average ration is 0.73 with the coefficient of variation (COV) of 0.18. (2) The ratio of the tip resistance rosin연 the reduced sized sliding core to that using the whole shoe shows wide scattering ; its average is 0.99 and the COV is 0.28. The aver - age of 0.99 means that there is no considerable difference in the tip resistance whether the reduced sized sliding core or the whole shoe is used, on condition that penetration depth ratio is larger than 4 : if the boundary effect of the chamber test is considered, the resistance of the whole shoe might be even larger.

• Geotechnical Engineering
• /
• v.11 no.4
• /
• pp.99-110
• /
• 1995

In this study, friction angles on the surface of vertical rigid ground anchor in normally consolidated dry sand were measured by model pullout tests in laboratory. Friction angles were obtained from the normal and shear stresses measured along depth of the anchor stir face by attaching several 2-dimensional load cells. Model tests were conducted under the plane strain state and axial symmetric state. From the results of tests, it was concluded that the maximum friction angle on the anchor surface coincides nearly with the maximum angle of stress obliquity on the plane of zero-extension direction obtained by plane strain compression test. This result was made with regard to the strength anisotropy and stress dependency of sand. It showed that when angle of shear resistance of the sand is applied to the friction angle of the anchor surface, the design capacity could be less than the applied force, thus making the anchor unsafe.

• Journal of the Korean Wood Science and Technology
• /
• v.39 no.1
• /
• pp.8-14
• /
• 2011

Japanese larch glulam was used as structural members to develop a modern engineered wood jointing system using traditional post and beam structure. For the connections comprised of traditional joining and drift-pins, structural members are processed at a pre-cut factory. As a basic study to examine and increase the whole shear performance of portal frame, pin withdrawal test and moment resistance tests were conducted on each connection. The post and beam members with specified connectors showed good bearing performance in the wood members' joining system, column-base and beam-end. Moment rigidity was a bit better in a joint with higher slenderness ratio of drift-pin, but moment resistance performances, yield moment and maximum moment, were excellent in smaller one.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.4
• /
• pp.125-135
• /
• 2011

The bond properties between polypropylene fiber reinforced cement composites and structural synthetic fiber have been investigated. in this paper. Three levels of polypropylene fibers volume fraction were used, 0.10%, 0.15%, and 0.20% in a series of Dog-bone pull out tests. The bond strength between structural synthetic fiber and polypropylene fiber reinforced cement composites increases with the volume fraction of polypropylene fiber, but the bond strength decreases above the amount of 0.20% by volume of polypropylene fiber reinforced cement composites. Also, the addition of polypropylene fiber a significant improved the interface toughness and the frictional resistance, The microstructure of structural synthetic fiber surface was investigated after the pullout test. The scratched of structural synthetic fiber increased with the polypropylene fiber volume fraction.

• Journal of the Korean Geosynthetics Society
• /
• v.2 no.1
• /
• pp.27-37
• /
• 2003

The factors affecting shear strength and friction characteristics of the fiber-mixed soil can be classified into engineering properties of soil; particle-size, distribution, and particle shape, physical and mechanical properties of fiber; shape, length, diameter, tensile strength, elastic modulus, friction coefficient, and mixed ratio and external factors; confined stress and compaction condition. In this study, a series of shear friction tests and pull-out tests were performed to evaluate the friction properties of fiber-mixed soil according to soil type, fiber type, fiber mixed ratio and compaction degree. The materials and test conditions used in this study are as follows. Soils: SM and ML; mixing fibers: three types of polypropylene fibers(net type 38mm and 60mm, and line type 60mm); reinforcement: geogrid; mixing ratio: 0.2% and 0.3%; degree of compaction : 85% and 95%.

• Journal of the Korean Geosynthetics Society
• /
• v.13 no.2
• /
• pp.21-29
• /
• 2014

The use of filling material based on cement paste is inefficient at field construction because it needs a lot of the charging mass. In addition, it has environmental problem according to the large amount of cement use because its strength is also larger than criterion. The excavated soil with stabilizer can be used as the filling materials when the bored pile is constructed. Therefore, this paper describes field application of solidified soil for economical efficiency and environment-friendly. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. As results, the flowability, segregation and bleeding, and bond strength of filling materials was a good performance than that of the existing cement paste. But the skin friction of pile by PDA was slightly decreased than that of the existing cement paste. However, as pile filling materials, and in terms of economics and environment, the applicability of filling material is considered very effective.

• Composites Research
• /
• v.35 no.2
• /
• pp.80-85
• /
• 2022

This work presents an experiment study to evaluate the nanoparticle adhesion and surface hydrophobicity characteristics of Teflon-polyurethane top coat depending on the number of multi-wall carbon nanotube (MWCNT) coatings, which is a carbon-based hydrophobic particle. In order to measure the adhesion between the nanoparticles and the top coat, adhesion pull-off test was performed with different MWCNT oxidation times. Static contact angle and roughness measurements were carried out to characterize the surface hydrophobic behavior. Through the roughness evaluation, it was confirmed that the carbon nanotubes were wetted in the Teflon-polyurethane top coat, and the degree carbon nanotube wetting was confirmed through a USB-microscope. As a result, it was found that the larger the degree of wetting, the better the adhesion. From the experimental results, as the hydrophobicity of Teflon-polyurethane increased, the adhesive propertydecreased with the number of coatings. It was possible to improve the adhesive force and determine the number of coatings of carbon nanotubes with optimized hydrophobicity.

• Journal of the Korean Geosynthetics Society
• /
• v.21 no.3
• /
• pp.61-69
• /
• 2022

In this study, a large-scale direct shear test was performed to evaluate the shear characteristics of the pile-soil interface according to the fines content and confining pressure conditions as a reasonable evaluation method of the pullout resistance performance of pile considering the soil conditions. It was found that the shear stress was greatly generated under the conditions of high normal stress and low fines content. In addition, the maximum shear stress was found to be rather large under the conditions of the same normal stress and fines content, when pile surface had high roughness. The internal friction angle decreased at the pile-soil interface, when the fines content in the ground increased. On the other hand, the cohesion decreased under the condition of high fines content. And the internal friction angle and cohesion were large regardless of the fines content in the model ground, when the roughness of the pile surface was high.