• International Journal of Naval Architecture and Ocean Engineering
• /
• v.8 no.2
• /
• pp.177-187
• /
• 2016

To evaluate the tractive performance of tracked trencher on seafloor surface, a new shear stress-displacement empirical model was proposed for saturated soft-plastic soil (SSP model). To validate the SSP model, a test platform, where track segment shear test can be performed in seafloor soil simulacrum (bentonite water mixture), was built. Series shear tests were carried out. Test results indicate that the SSP model can describe the mechanical behavior of track segment with good approximation in seafloor soil simulacrum. Through analyzing the main external forces applied to seafloor tracked trencher during the uniform linear trenching process, a drawbar pull prediction model was deduced with the SSP model. A tracked walking mechanism of the seafloor tracked trencher prototype was built, and verification tests were carried out. Test results indicate that this prediction model was feasible and effective; moreover, from another side, this conclusion also proved that the SSP model was effective.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.55 no.3
• /
• pp.113-121
• /
• 2013

Recently, it has been studied for the application of nano-materials in the concrete. Applied a small amount of nano-materials can achieve the goal of high strength, high performance and high durability. The small addition of nano clay improves strength, thermal stability, and durability of concrete because of the excellent dispersion. The present study has investigated the effectiveness, when varying with the contents of nano clay, influencing the pull-out behavior of macro synthetic fibers in nano materials cement mortar. Pullout tests conducted in accordance with the Japan Concrete Institute (JCI) SF-8 standard for fiber-reinforced concrete test methods were used to evaluate the pullout performance of the different nano clay. Nano clay was added to the 0, 1, 2, 3, 4 and 5 % of cement weight. The experimental results demonstrated that the addition of nano clay led to improve the pull-out properties as of the load-displacement curve in the precracked and debonded zone. Also, the compressive strength, flexural strength and pullout performance and of Mix No. 1 and No. 2 increased up to the point when nano clay used increased by 2 and 3 % contents, respectively, but decreased when the exceeded 3 and 4 %, respectively. It was proved by verifying increase of the scratching phenomenon in macro synthetic fiber surface through the microstructure analysis on the surface of macro synthetic fiber.

• Tunnel and Underground Space
• /
• v.21 no.5
• /
• pp.377-385
• /
• 2011

In order to prove the applicability of rock bolts with compressible spacers, laboratory model tests and large scale model tests were conducted. Laboratory model tests were performed in various distance of compressible spacers to determine the optimal distance of compressible spacers. The optimal distance of compressible spacers was found that is 1/4 of rock bolts unit length. Large scale model tests that the size was 0.6 m (diameter) ${\times}$ 4.45 m (length) were conducted. Test results showed that pull out resistance could be increased up to 15% larger than that of unused case by using compressible spacers.

• Composites Research
• /
• v.34 no.1
• /
• pp.30-34
• /
• 2021

This paper present a three-dimensional unit cell finite element analysis to predict the pull-out behavior of a single stitch in a composite laminate. The stitching process used for this study correspond to the I-fiber stitching method that has been studied by the Composite Structures Lab (CSL) as a new through-thickness reinforced method. A total of six cases were analyzed, which were divided in two groups by the stitching yarn used, 6k and 12k. Each group of cases have three different thickness according to the amount of plies; 16 plies, 32 plies and 64 plies. The finite element analysis used the cohesive zone method to characterize the single stitch reinforcement in the interface. Due to the complexity of the load vs displacement curves taken from the experimental results, a bilinear and trilinear bridging laws were implemented in the models. The cohesive parameters used for each case showed a good agreement with the experimental data and can be used for future studies.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.35 no.4
• /
• pp.421-427
• /
• 1999

The critical fracture energy and failure mechanisms of GF/PP composites are investigated in the temperatures range of the ambient temperature to $-50^{\circ}C$ The critical fracture energy increase as fiber volume fraction ratio increased The critical fracture energy shows a maximum at ambient temperature and it tends to decrease as temperature goes up. Major failure mechanisms can be classfied such as fiber matrix debonding, fiber pull-out and/or delamination and matrix deformation.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.647-652
• /
• 1999

The purpose of this study is to find the bond properties of deformed bars in hign-strength concrete by experimental and analytical method. In this study the following variables were adopted, i.e. (1) the compressive strength of concrete : 270, 400 and 600kg/$\textrm{cm}^2$ (2) the corrosion the bars : corroded and normal bars (3) the mixing ratio of natural and smashed fine aggregate : 7 : 3 and 5 : 5 (natural sand : smashed sand) For analytical method, the finite element analysis is performed. And the Pull-out test is performed as the experimental method.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.11a
• /
• pp.132-135
• /
• 2003

Mechanical anchorage can substitute a standard hook. To enhance the workability and economical benefit of mechanical anchorage, the size of anchor plate should be optimized. In this paper, the pull-out behaviors such as strength, failure mode, and crack patterns of mechanically anchored reinforcement in concrete are investigated using nonlinear finite element analysis. The nonlinear finite element analysis results are consistent with the experimental results. These results show that the optimal anchor plates can be designed using the nonlinear finite element analysis.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.5
• /
• pp.149-156
• /
• 2021

FRP has been proposed to replace the steel as a reinforcement in the concrete structures for addressing the corrosion issue. However, FRP-Rebar does not behave in the same manner as steel because the properties of FRP are different. For example, FRP-Rebar has a high tensile strength, low stiffness, and linear elastic behavior which results in a difference bonding mechanism to transfer the load between the reinforcement and the surrounding concrete. Therefore, bonding behavior between FRP-Rebar and concrete has to be investigated using the bonding test. So, Pull-out test has been used to estimate bond behavior because it is simple. However, the results of pull-out test have a difference with flexural-boding behavior of FRP-Rebar concrete member. So, it is needed to evaluate the real fleuxral-bonding behavior. In this study, the evaluation method to flexural-bonding behavior of FRP-Rebar concrete member was reviewed and compared. It was found that the most accurate evaluation method for the fleuxral-bonding behavior of FRP-Rebar concrete member was splice beam test, however, the size and length of specimen have to increase than other test method and the design and analysis of splice beam is complex. Meanwhile, characteristics of concrete could be reflected by using arched beam test, unlike hinged beam test which is based on the ignored change of moment arm length in equilibrium equation. However, the possibility of shear failure exists before the flexural-bonding failure occur.

• Geotechnical Engineering
• /
• v.5 no.3
• /
• pp.51-62
• /
• 1989

Prior to the centrifugal model experiments of reinforced earth retaining walls, frictional tests were performed to investigate the frictional behavior between the sand and the reinforcements. Coefficient of friction between the soil and the reinforcements was evaluated using different reinforcements, their lengths and testing methods. Two different testing methods, the direct shear and the pull-out tests, were adopted and their testing results were compared to determine which. method better represented the actual behavior In the field.

• Journal of the Korean Ceramic Society
• /
• v.28 no.10
• /
• pp.785-792
• /
• 1991

An investigation of the crack propagation behavior of Al2O3-33Vol.% SiCw at 140$0^{\circ}C$ was conducted with various loading frequencies. Higher crack propagation was observed in lower frequency and higher load ratios. Interface sliding fracture due to glassy phase from the oxidation of SiCw and cavitation along grain boundary of diffusional creep appeared to be the main mechanism of fatigue fracture in slower crack propagation while interface sliding and whisker pull out aided by glassy phase formation played main role of fatigue fracture for higher crack growth condition. The frequency effect on deformation behavior was discussed with a Maxwell model.