• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.4
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• pp.72-80
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• 2020

The purpose of this study is to secure the same or more structural performance and constructability for the details of hooks cross-constructed at 135 degrees used as external-ties standard detail in RC columns, therefore, to the purpose of improving constructability, the clip-type binding implement was suggested and A total of 28 pull-out specimens were prepared with the parameters of concrete compressive strength and clip-embeded length, clip installation location to examine the anchorage behavior of the clip-type binding implement. The experiment was carried out. The results of the experiment confirmed that the anchorage strength of the clip-type binding implement was higher than the details of hooks cross-constructed at 135-degree regardless of the diameter of tie and concrete strength, embeded clip length, clip installation. and The 90-degree end hook with clip-type binding implement was showed a similar an anchorage behavior of 135-degree end-hooked transverse reinforcement, consequently, The 90-degree end hooked with clip-type binding implement is evaluated to be the same anchorage behavior and performance as standard 135-degree end hook detail.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.249-263
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• 2017

The expansion behavior of inflatable steel pipe rockbolt shows geometric nonlinearity due to its ${\Omega}-shaped$ section. Previous studies on the anchoring behavior of inflatable steel pipe rockbolt were mainly performed using theoretical method. However, those studies oversimplified the actual behavior by assuming isotropic expansion of inflatable steel pipe rockbolt. In this study, the anchoring behavior of the inflatable steel pipe rockbolt were investigated by the numerical method considering the irregularity of pipe expansion and other influencing factors. The expansion of inflatable steel pipe rockbolt, the contact stress distribution and the change of the average contact stress and the contact area during installation were analyzed. The contact stresses were developed differently depending on the constitutive behavior of rocks. Small contact stresses occurred in steel pipes installed in elasto-plastic rock compared to steel pipes installed in elastic rock. Also, the anchoring behaviors of the inflatable steel pipe rockbolt were different according to the stiffness of the rock. The steel pipe was completely unfolded in the case of the stiffness smaller than 0.5 GPa, but it was not fully unfolded in the case of the stiffness larger than 0.5 GPa for the given analysis condition. When the steel pipe is completely unfolded, the contact stress increases as the rock stiffness increases. However, the contact stress decreases as the rock stiffness increases when the steel pipe is not fully expanded.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.102-110
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• 2006

This paper examines experimentally the ultimate behavior of I-type steel beam strengthened with external tendon and cylindrical anchorage and analyzes the strengthening effect on the parameters such as initial tendon force, eccentricity, number of strands, and strand areas. The experiment demonstrated that increasing the number of strands, strand areas and eccentricity is more effective than increasing initial tendon force. The proposed cylindrical anchorage system has advantages in applying these parameters. The results showed that the cylindrical anchorage system is efficient and applicable to strengthen steel beam.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.157-164
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• 1997

최근 손상된 구조물에 탄소섬유쉬트 보강공법이 많이 사용되고 있다. 탄소섬유쉬트 보강에 따른 휨내력의 증진이 이루어지기 위해서는 보와 탄소섬유쉬트의 일체거동이 이루어져야 하며, 쉬트단부에서 부착파괴가 발생하지 않아야 한다. 따라서 이번 실험에서는 탄소섬유쉬트의 보강매수에 따른 부착파괴의 거동을 살펴보았다. 전시험체에서 부착파괴가 발생하였으며 부착파괴가 발생한 하중의 크기는 보강매수에 관계없이 비슷하였다. 부착파괴의 거동은 순수부착파괴와 피복박리파괴로 구분될 수 있었으며 부착응력은 단부에서 집중현상이 나타났고 집중된 응력의 크기는 15.39~41.42kg/$\textrm{cm}^2$로 나타났다. 정착길이내의 평균부착응력은 6.85~8.99kg/$\textrm{cm}^2$으로서 평균 7.38kg/$\textrm{cm}^2$이고 이 값은 이론치인 6.19kg/$\textrm{cm}^2$보다 약간 높으며 설계부착응력인 6kg/$\textrm{cm}^2$에 부합되는 것으로 나타났다. 따라서 설계부착응력 6kg/$\textrm{cm}^2$은 정착길이의 설계시 합리적 값으로 평가되었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.93-98
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• 2017

The fixing behaviors of raw silk yarns treated with melamine and formaldehyde at a molar ratio of 1:3 for trimethylolmelamine were investigated. Sericin was fixed during the fixing process, but a part of sericin I was removed simultaneously by hot water. The weight losses by fixing and the degumming losses by degumming greatly decreased with increasing concentrations of melamine and formaldehyde. The silk yarns fixed with 0.011 M melamine and 0.033M formaldehyde were significantly degummed due to the insufficient fixation of sericin and the alkaline hydrolysis of sericin by sodium carbonate during the degumming process. On the other hand, the silk yarns fixed with 0.055M melamine and 0.165M formaldehyde were degummed slightly (the degumming losses of 3-8%) due to the strong fixation of sericin, which might result from the many cross-linkages between the sericin I molecules, which were formed by trimethylolmelamine. Those fixed with the fixing solution containing 15% owf softener showed the lowest weight and degumming losses because under the condition of 15% owf softener, the cation of the softener can effectively form ionic bonds with the negatively charged side chain of aspartic acid in sericin. In addition, van der Waals' forces may be also formed between the hydrophobic tail of the softener and the hydrophobic region of sericin, which may help inhibit the removal of sericin I.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2797-2803
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• 2012

This paper presents the pull-out behaviors of headed glass fiber reinforced polymer (GFRP) rebar embedded in mortar under tension loading. Five specimens with headed GFRP rebars that were anchored in the center of mortar bases were constructed and the pull-out test was conducted. To verify the test results, the finite element analysis was conducted and the results were compared with the FE analysis using ANSYS software package. Based on the test results it was indicated that the CCD(concrete capacity design) failure theory should be adopted and not to use the 45o cone failure theory as the breakout capacity in the headed GFRP rebar embedded in mortar.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.217-224
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• 2013

Design provisions for the development length of headed bars in ACI 318-08 include concrete compressive strength and yield strength of headed bars as design parameters but do not consider the effects of transvers reinforcement. In addition, they have very strict limitation for clear spacing and material strengths because these provisions were developed based on limited tests. In this study, splice tests using SD600 headed bars with $2d_b$ clear spacing and transverse reinforcement were conducted. Test results show that unconfined specimens failed due to prying action and bottom cover concrete prematurely spalled. The contribution of head bearing on the anchorage strength is only 15% on average implying that unconfined specimens failed before the head bearing was not sufficiently developed. Confined specimens with stirrups placed along whole splice length have enhanced strengths in bearing as well as bond because the stirrups prevented prying action and improved bond capacity. Bond failure occurred in locally confined specimens where stirrups were placed only at the ends of splice length. The stirrups at ends of splice lengths can prevent prying action but the bond capacity did not increase. From regression analysis of test results, an equation to predict anchorage strength of headed bars was developed. The proposed equation consists of bond and bearing contributions and includes transverse reinforcement index. The average ratio of tests to predictions is 1.0 with coefficient of variation of 6%.

• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.209-218
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• 1996

The purpose of the present study is to explore the effects of local reinforced type and to suggest reliable failure mechanism and the design criteria on the anchorage zones of the precast prestressed concrete bridges. To accomplish these objectives, a comprehensive experimental and analytical study has been conducted. From this study, the cracking and ultimate load capacities for spirally reinforced anchorage zone are found to be larger than those for orthogonal reinforced anchorage zone. This indicate the effectiveness of spiral reinforcement in controlling the cracking. And realistic failure mechanism and design criteria of prestressed anchorage zones based on the present study are suggested.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.65-73
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• 2007

Recently, large-scale underground cavern such as underground hydraulic-power plant tend to be constructed very largely, so long-length rock bolt are generally used to support the huge plastic zone. However, problems fur bend-ing shape of the long-length steel bar and the bonding effects of anchoring systems are caused during the construction of the long-length rock bolt. In this study, field pull-out test for long-length rock bolt are carried out to estimate the most efficient anchoring system among the saw-toothed shape, grooved shape and smoothed shape with each 6 shells for 5.0m, 7.5m, 10.0m, 15.0m length. The axial load and axial displacement are measured with each load stage and than test results are analyzed to evaluate the behavior characteristics for each anchoring systems of long-length rock bolt. Also, the improvements of anchoring systems are proposed and discussed in this paper.

• Journal of the Korean Geotechnical Society
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• v.33 no.10
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• pp.59-69
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• 2017

The tension load of the ground anchor inserted in the ground gradually changes over time. In this regard the change of the initial tension load is primarily decreased by the fixation condition of the fixing head and the mechanical characteristics of the tensile material. The subsequent additional tension load is a time-dependent loss mostly due to the fixing conditions of the bonded length and the surrounding ground properties of the field. In this paper, therefore, a measurement system using a relative displacement detector that can relatively easily measure the change of tension load is discussed. As a result of the review, it was confirmed that the results using the relative displacement detector are similar to those of the real scale model test, and it was also confirmed that similar results were obtained with the result of the pull-out test conducted on the ground anchors fixed to weathered rocks condition. In addition, a pull-out test was conducted on the test anchors whose initial tension load loss was relatively large and through this test pull-out behavior of the tension type ground anchors was verified.