• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.131-141
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• 2010

The objective of this study was to propose a development length equation for GFRP bars. A total of 104 modified pullout tests were completed while the test variables were embedment length (15, 30, $45d_b$), net cover thickness ($0.5{\sim}2.0d_b$), top-cast bar effect, different GFRP bar types (K2KR, K3KR and AsUS), and bar diameters (10, 13, 16 mm). Average bond stresses were determined based on modified pullout test results. Two variable linear regression analysis was performed of the average bond stresses. Utilizing 5% fractile concept, a conservative development length design equation was derived. The design equation derived in this study was compared to the ACI 440 committee equation. The cross-comparison revealed that the current equation resulted in shorter development lengths than those determined by the ACI 440 equation when the net cover thickness was large (greater than $1.0d_b$). On the other hand, when the net cover thickness was small (equal to or less than $1.0d_b$), the development lengths required by the current equation were larger than those by the ACI equation. The bond stresses were significantly influenced by the cover thicknesses. The current equation results in development lengths that are more economical when the cover thickness is large, and more conservative lengths when the cover thickness is small than the ACI 440 committee equation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.4
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• pp.567-573
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• 2003

Surimi yields from acid and alkaline processing of 5 fishes were compared to those from conventional processing Effect of sarcoplasmic protein and NaCl on heating gel from acid and alkaline surimi were also investigated by punch test and color. Yield of alkaline surimi was higher than that of conventional surimi. However, the breaking force, deformation and whiteness of heating gel from alkaline surimi were lower than those of heating gel from conventional surimi. The sarcoplasmic protein increased a breaking force and a deformation of gel. A breaking force was decreased, but deformation not significantly with NaCl concentration. Myosin heavy chain (MHC) and actin were greatly degraded in acid processing. Alkaline process for surimi is a valuable way of increasing the utilization of frozen and pelagic fishes, and making kamaboko-type products.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.173-181
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• 2021

Reinforced concrete structures are exposed to various environments, resulting in reinforcement corrosion due to moisture and ions penetration. Reinforced concrete corrosion causes a decrease in the durability performance of reinforced concrete structures. One solution to mitigate such issues is using FRP rebars, which offer several advantages such as high tensile strength, corrosion resistance, and light-weight than conventional rebars, in reinforced concrete instead of conventional steel rebars. The FRP rebar used should be examined at the limit state because FRP reinforced concrete has linear behavior until its fracture and can generate excessive deflection due to the low elastic modulus. It should be considered while designing FRP reinforced concrete for flexure. In the ultimate limit state, the flexural strength of FRP reinforced concrete as per ACI 440.1R is significantly lower than the flexural strength by applying both the environmental reduction and strength reduction factors accounting for the material uncertainty of FRP rebar. Therefore, in this study, the experimental results were compared with the deflection of the proposed effective moment of inertia referring to the local and international standards. The experimental results of GFRP and BFRP reinforced concrete were compared with the flexural strength as determined by ACI 440.1R and Fib bulletin 40. The flexural strength obtained by the experimental results was more similar to that obtained by Fib bulletin 40 than ACI 440.1R. The flexural strength of ACI 440.1R was conservatively evaluated in the tension-controlled section.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.323-326
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• 2009

콘크리트의 보강재로 높은 인장 강도와 비부식성, 비자기성, 비전기성 등의 장점을 갖는 FRP의 사용에 대한 연구가 활발히 진행되고 있다. 하지만 FRP가 갖는 낮은 탄성계수와 취성적 성질로 인해 기존 설계방법을 적용하기에는 문제가 있다. 본 연구에서는 보강비 변화에 따른 AFRP 보강 콘크리트 보의 구조 실험을 수행하여 FRP 보강근을 사용한 콘크리트 부재의 휨 성능 연구에 대한 기초적 자료를 제공하고자 하였다. 각 실험체의 결과 데이터를 비교 분석한 결과 균형보강비를 기준으로 저보강 실험체는 FRP의 파단에 의해 급격한 파괴양상을 보인 반면에, 과보강 실험체는 콘크리트가 압괴하는 파괴 징후를 보이며 파괴에 도달하였다. FRP 보강근을 사용한 보 부재의 설계에 균형보강 이상의 설계가 요구되며, 과보강의 경우 고강도 콘크리트의 사용이 요구되는 것으로 분석되었다.

• Clinics in Shoulder and Elbow
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• v.11 no.2
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• pp.82-89
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• 2008

Ideal rotator cuff repair is to maintain high fixation strength and minimize gap formation for optimizing the environment of biologic healing of tendon to bone. Among the current repair techniques, the suture bridge technique is superior to single- or double-row repair in ultimate load to failure, gap formation, restoring anatomical footprint and achieving pressurized contact area. The suture bridge technique also minimizes gap formation and has rotational and torsional resistances allowing early rehabilitation. However, despite superior biomechanical characteristics of the suture bridge technique, there is no evidence that these mechanical advantages result in better clinical outcomes. Furthermore, there is no difference in failure rates between the double-row repair and suture bridge techniques. An appropriate repair technique should be determined based on tear size and pattern and tendon quality.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.81-90
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• 2022

In this study, for one-way concrete slabs, the flexural strength, deflection, and crack width according to the amount of reinforcing bars were compared for the cases of using steel reinforcing bars and CFRP reinforcing bars. Critical performance dominating the flexural design was investigated and how to design the CFRP-reinforced concrete slab with efficiency was also discussed. It was found that CFRP-reinforced concrete slabs could achieve greater design flexural strength with the same amount of reinforcing bars compared to those using steel rebar, while deflection and crack width were relatively much larger. In concrete slabs using CFRP reinforcing bars, it was confirmed that the maximum crack width acts as a dominant factor in the design. For more efficient flexural design, it is necessary to mitigate the allowable crack width to 0.7 mm and to apply smaller diameter reinforcing bars to control the crack width.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.47-54
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• 2023

In this study, the tensile behavior of concrete specimens reinforced with GFRP (Glass Fiber Reinforced Polymer), BFRP (Basalt Fiber Reinforced Polymer), and CFRP (Carbon Fiber Reinforced Polymer) bars was experimentally analyzed. The tensile strength of the FRP bars is appeared to be similar to the design strength, but the elastic modulus was somewhat lower. Additionally, the specimens for tension stiffening effect were manufacured using OPC (Ordinary Portland Cement) and SFRC (Steel Fiber Reinforced Concrete), with dimensions of 150(W)×150(B)×1000(H) mm. The crack spacing of specimens was most significant for GFRP reinforcement bars, which have a lower elastic modulus and a smoother surface, while BFRP and CFRP bars, with somewhat rougher surfaces and higher elastic moduli, showed similar crack spacings. In the load-strain relationship, GFRP bars exhibited a relatively abrupt behavior after cracking, whereas BFRP and CFRP bars showed a more stable behavior after the cracking phase, maintaining a certain level of tension stiffening effect. The tension stiffening index was somewhat smaller as the diameter increased, and GFRP, compared to BFRP, showed a higher tension stiffening index.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.519-525
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• 2010

Data from beam-based bond tests for FRP bars in the literature were collected and regression analyses were conducted for the data of splitting failure. Average bond strengths obtained from splice tests were found to be lower and more affected by C/$d_b$ values than average bond strengths from anchorage tests, indicating needs of new design equation for the splice length of FRP bars based on the data of splice tests only. In addition, the variation of bond strengths was greater than that of tensile strengths of FRP bars and, therefore, a new safety factor should be involved for the design equation. Five percent fractile coefficients were used to develop the design equations based on the assumption that load and resistance factors for FRP reinforced concrete structures are same to the factors for steel reinforced concrete structures. The proposed design equations give economical and reliable lengths for development and splice of FRP bars. The proposed equation for splice provides shorter lengths than the ACI 440 equation in case of C/$d_b$ of 3.0 or greater. Because FRP bars are expected to be used in slabs and walls exposed to weather with thick cover and large spacing between bars, the proposed equation gives optimal splice lengths.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.413-420
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• 2011

The test results of high-strength concrete beam specimens, which have various combinations of different types of flexural reinforcement and short fibers, were compared with the prediction results of codes, guidelines and models proposed by researchers. The theoretical calculation based on the ultimate strength method of the KCI and ACI Code underestimated the ultimate moments of FRP bar-reinforced beams without fibers. The models proposed by ACI 544.4R and Campione predicted the ultimate moment capacities inaccurately for the FRP bar-reinforced beam with steel fibers, because these models do not consider the increased ultimate compressive strain of fiber reinforced concrete. Bischoff's deflection model predicted the service load deflections reasonably well, while the deflection model of ACI Committee 440 underestimated the deflection of FRP bar-reinforced beams. Because the ACI 440 expression, used to predict member deflection, cannot directly apply to the beams reinforced with different types of reinforcing bars, an alternative method to estimate the deflections of beams with different types of reinforcing bars using the ACI 440 expression was proposed. In addition, Bischoff's approach for computing deflection was extended to include deflection after yielding of the steel reinforcement in the beams reinforced with steel and FRP bars simultaneously.

• Journal of the KSME
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• v.28 no.4
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• pp.408-414
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• 1988

근년에 항공 산업이 많은 관심을 불러일으키고 있음에 즈음하여 독자적인 항공기 구조개발시 구조적 안전성 확보를 위해서는 구조시험 기술의 확보가 필수적이다. 또한 구조시험 관련기술은 다른 기계 구조물의 초기 설계단계에서 구조 강도 및 피로 강도의 확인을 위해서도 응력될 수 있어 구조물의 설계 및 제작공정 결정에 큰 도움이 될 수 있으므로 기업체나 연구소에서도 충 분히 응용할 수 있도록 노력을 기울여야 할 분야이다.