• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.87-93
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• 1997

The bonding strength evaluation of light weight materials for electrical vehicle applications has been performed through single lap joint tests in which the design parameters such as fillet, joint style, adherend, bonding overlap length,bonding thickness, and environmental condition(soaking time in $25^{\circ}C$ water) are considered. It is experimentally oberved that lap shear strength of joint increases for higher fillet height, longer overlap length, and thinner bonding layer thickness. Al-Al adherend combination shows much higher lap shear strength than AL-FRP and FRP-FRP adherend combinations. Riveting at adhesive bonded joint of AL-AL adherend combination makes lap shear strength decrease. Effect of soaking time on lap shear strength is negligible.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.63-71
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• 1999

In evaluating the ultimate strength of a section for a reinforced concrete flexural member, the effect of member length is not usually considered, even though the strength tends to decrease with increase of member length. In this paper the influence of specimen length on flexural compressive strength of concrete was evaluated. For this purpose, a series of C-shaped specimens subjected to axial compression and bending moment were tested using four different length-to-depth ratios (from 1,2,3 and 4) of specimens with compressive strength of 590 kgf/$\textrm{cm}^2$. Results indicate that for the region of h/c <3.0 the reduction in flexural compressive strength with increase of length-to-depth ratios was apparent. A model equation was depth of an equivalent rectangular stress block was larger than that by ACI. It was also founded that the effect of specimen length on ultimate strain was negligible. Finally more general model equation is also suggested.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.107-108
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• 2017

The purpose of this study is to derive the optimum water absorbing curing time. It was found that the cement paste compressive strength was increased with the water absorbing ratio up to 40%, but the compressive strength was slightly lower when the catch level was over 50%. It is considered that the superfluous water did not react and remained in the inside of the specimen, causing microcracks in the inside due to the high temperature curing, resulting in a decrease in strength. Therefore, it is considered that the optimum catcher curing time for improving the strength through catcher curing is when the catcher reaches 40%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.69-72
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• 2011

The purpose of this study is to identify basic property of porous concrete using cooper slag as fine aggregate. The specimens were made with cooper slag with various mixing ratio(10, 20, 30, 50%), porous concrete and porous concrete containing river fine aggregate and crushed fine aggregate, which W/B ratio fixed 0.25. Compressive strength, Flexural strength, coefficient of permeability. From the test results, various fine aggregate mixing ratio improves compressive strength and flexural strength, but cooper slag fine aggregate mixing ratio over 20%, concrete indicates trend to decrease performance of permeability. Concrete containing fine aggregate is improved the performance of permeability and strength compared to other specimen, when age 28days, and cooper slag mixing ratio less than 20% concrete indicates better performance than cooper slag mixing ratio 20% over.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.123-130
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• 2001

The purpose of this study is to suggest the non-destructive equation for the estimation of concrete strength by ultrasonic pulse velocity at the Age of 28day compressive strength of $600{\sim}1000kg/cm^2$. For this purpose, selected test variables were water-hinder ratio, replacement ratio of silica fume, binder content, maximum size of coarse aggregate and sand-aggregate ratio. From the results, the average increase or decrease of ultrasonic pulse velocity is 61m/sec for each 1% of moisture content. And the correlation equation between the ultrasonic pulse velocity and the compressive strength of concrete is as follows. $F_c=896.3V_p-3514$ ($R^2$ = 0.81) where, $F_c$ : compressive strength($kgf/cm^2$), $V_p$ : ultrasonic velocity(km/sec).

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.96-97
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• 2020

In this study, the compressive strength and porosity characteristics of cement mortar mixed with liquid and powder composite water repellent were evaluated. When the liquid water repellent was mixed, the compressive strength at 28 days of age was 42% compared to OPC, and the compressive strength was greatly reduced. However, the 28-day compressive strength of the powder water repellent mixture and P5L1, P6L1 liquid and powder composite water repellent was about 97% compared to OPC, and there was little decrease in compressive strength.

• Journal of the Korea Institute of Building Construction
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• v.7 no.1 s.23
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• pp.71-77
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• 2007

This paper is to investigate the effect of the curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of the compressive strength of the concrete was conducted using the equivalent age equation and the rate constant model proposed by Carino. Correction of Carino model was studied to secure the accuracy of strength development estimation by introducing correction factors regarding rate constant and age. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of BS has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.3 no.1
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• pp.1-12
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• 2005

This study aimed at examining the maximal isometric contraction caused by voluntary exercise and at comparing its aspects of decrease and restoration in their different repeated application, as to the quadriceps muscles of thigh in the subjects composed of patients with spastic hemiplegia and normal adults. Using isokinetic exercise analyser(Biodex Medical Systems Inc., Biodex System 3PRO, U.S.A.), experiment was conducted as to the normal group composed of fifteen adults and the patient group composed of fifteen patients with spastic hemiplegia. As to each group, MVIC(maximal voluntary isometric contraction) of the quadriceps muscle of thigh caused by voluntary exercise and the aspects of decrease and restoration of the isometric contraction were examined with the method to induce isometric exercise, and their SDI(strength decrement index) and SRI(strength recovery index) were also calculated. The results can be summarized as follows: 1. As for decrease of maximal isometric contraction, both groups showed slow decrease in voluntary exercise, but the normal group showed rapid decrease later phase. 2. As for SDI, no significant differences could be observed in comparison between groups. 3. As for restoration of maximal isometric contraction, both groups showed slow restoration in voluntary exercise, but the normal group showed rapid restoration early phase. 4. As for SRI, comparison between groups showed significant differences in voluntary exercise. These results lead us to the conclusions that spastic muscle is characterized by slow decrease and restoration of MVIC in comparison with normal muscle in voluntary exercise.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.75-78
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• 2005

This raper investigates the effect of curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of compressive strength of concrete was conducted using equivalent age equation and rate constant model. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of 35 has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

• International Journal of Highway Engineering
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• v.15 no.4
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• pp.1-9
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• 2013

PURPOSES : Bonded concrete overlay is a favorable maintenance method since the material properties are similar to existing concrete pavements. In addition, bonded concrete overlay has advantage of structural performance since the overlay layer and the existing pavement perform as a monolithic layer. It is important to have suitable bond strength criteria to secure the performance of bonded concrete overlay. This study aimed to investigate the factors influencing bond strength characteristics between existing concrete pavement and overlay material. METHODS: Bond strength between overlay and existing pavement are measured and analyzed for various conditions such as the type of overlay materials, compressive and flexure strength of overlay and existing pavement, and deterioration status of existing pavement. RESULTS: The strength of overlay material does not significantly influence the bond strength. The overlay of ultra-rapid hardening cement generally gives low bond strength. However, ultra rapid hardening polymer modified concrete gives robust bond strength. The deterioration of existing concrete significantly decrease the bond strength. CONCLUSIONS: Bond strength of bonded concrete overlay highly depends on condition of existing concrete pavement rather than overlay material.