• The Journal of the Acoustical Society of Korea
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• v.21 no.1E
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• pp.25-30
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• 2002

We report on the development of a fiber optic hydrophone consists of a sensing Michelson interferometer and a compensating Mach-Zehnder interferometer for optical path length compensation. The double interferometer configuration has the following advantages: the hydrophone can be made more small; a laser source with a relatively short coherence length can be used; and the compensating interferometer can be located near the signal processing electronics, far away from the sensing interferometer and noise introduced by reference arm can be greatly reduced. The performance of the hydrophone is evaluated experimentally by immersing the sensing interferometer in a water tank to detect underwater acoustic signals generated by an acoustic wave projector. Experimental results show that over the frequency range of 1 to 4 kHz, the hydrophone has an almost flat response with an average normalized sensitivity of -302 dB re 1/ μ Pa.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.99-100
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• 2018

Because of the congestion problems, the high-strength reinforcements are expected to be used in nuclear power plant structures in the near future. According to ACI 349-13, it is permitted to use the high-strength(550MPa) hooked bars in design of development length, but there is no special equation for high-strength bars. In order to reflect the anchorage capacity and behavior properties of high-strength bars with large-diameter(43 & 57mm), it is necessary to develope the new development length equation for large-size and high-strength bars.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.110-111
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• 2018

Because of the congestion problems, the high-strength reinforcements are expected to be used in nuclear power plant structures in the near future. According to ACI 349-13, it is permitted to use the high-strength(550MPa) straight bars in design of development length, but there is no special equation for high-strength bars. In order to reflect the anchorage capacity and behavior properties of high-strength straight bars with large-diameter(43 & 57mm), it is necessary to find the modified factor or develop the new development length equation for large-size and high-strength bars.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.4
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• pp.290-299
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• 2011

Field tests were carried out with five different mesh sizes (86.6, 101.0, 121.2, 137.7, 151.5mm) to study the relative efficiency of monofilament and multifilament gill net for Marbled sole, Pleuronectes yokohamae, in the western sea of Korea, 2007-2009. The relative efficiency was analyzed by length distribution, catch in number, catch in weight and weight per individual for Marbled sole. Statistical T-test was done to verify the efficiency between two gears. In the field tests, the total body length range, catch in number and weight of Marbled sole was 15.8-48.2cm, 728 and 254,939g, respectively. During the field tests, Marbled sole less than 15cm length which is prohibition size of fishing was not caught, but the caught number of Marbled sole less than 19.5cm length which is first maturity length was 13 (1.8%) and the caught number of Marbled sole more than 19.5cm was 715 (98.2%). Catches of monofilament gill net was average 1.4 times more efficient than multifilament gill net. The weight per individual and total length by mesh sizes in the two gears tended to gradually increase according to mesh size increasing. But there was little difference of weight per individual and total length by mesh sizes between two gears.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.303-310
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• 2009

CFRP(carbon fiber reinforced polymer) tendons can be used as an alternative to solve the corrosion problem of steel tendons. Material properties of CFRP tendons such as bond strength, transfer length, and development length should be determined in order to apply to concrete structures. First of all, in case of application for pretension concrete members with CFRP tendons, transfer length is an important factor. A total of 9 beams have been cast to determine transfer length and development length of domestic CFRP tendon in this paper. Test results revealed that transfer length of the prestressing 25% and 50% are 34D, 55D respectively. Also, transfer length has increased as the prestressing force has increased. A change was observed in transfer length of developed CFRP tendon after 9 weeks. ${\alpha}_t$ of developed CFRP tendon was 2.3 similar to the steel strand.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.421-426
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• 1998

Current code provisions for the development of positive moment reinforcement is reviewed and criticized in this paper. Both the flexural bond and development length concepts are neccesary to consider anchorage requirement of reinforcement at beam ends. The curent design codes show unconservatism for the detailing of reinforcement at the beam ends. This study proposes a new design formula for the development of positive moment reinforcement.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.753-761
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• 2009

This paper presents the test results of total 24 beam-end specimens to investigate the effect of high-strength concrete and cover thickness on the development resistance capacity in tensile lap splice length regions. Based on bond characteristics that an increase in concrete strength results in higher bond stress and shortening of the transfer length, cracking behavior that thin cover thickness induced a splitting crack easily and brittle crack propagation, current design code that development length provisions as uniform bond stress assumption was investigated apply as it. The results showed that as higher strength concrete was employed, not only development resistance capacity was influenced by cover thickness, but also more sufficient safety factor reserved shorter than the lap splice length provision in current design code. From experimental research results, high-strength concrete development length was not inverse ratio of $\sqrt{f_{ck}}$ but directly inverse of $f_{ck}$, and it is also said that there is a certain limit length of the embedded steel over which the assumption of uniform bond stress distribution is valid specially for high-strength concrete not having a same embed length such as normal-strength concrete in current design criteria hypothesis.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.331-334
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• 2005

The nature of bond of untensioned prestressed strand in concrete differs from that of plain or deformed reinforcing bar as well as tensioned prestressed strand. There is a very limited amount of published research information regarding bonding of this type reinforcing. In order to use and design untensioned strand as reinforcing, relationships defining the load transfer characteristics of the strand are necessary. A program based upon pullout tests was designed to develop data relating the critical parameters for determining load transfer behavior of the untensioned strand. The purpose of this study is to investigate the characteristics of bond and development length between untensioned strand and concrete. The test variables include diameter of strands (9.3mm, 12.7mm) and development lengths. The maximum bond stress at the 9.3mm and 12.7mm strands decreases with the increase of the rate of development length. The untensioned prestressed strands displayed bond performance when secure development length more than 80$\%$ according to the development of deformed bars equation.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.393-398
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• 1999

The main objective of this project is to define the ultimate bond performance of domestic prestressing strands in the precast prestensioned concrete beams. Eight specimens from four different companies were fabricated and tested in this study. Four-point loading tests were performed on the beams of domestic strands with an arbitrary anchorage length. The research has shown, that all seven specimens except one failed in bond are capable of developing their full flexural capacity and the strands within them are fully anchored even with the sudden transfer of frame cutting. Following results are summarized from the tests conducted. 1) All of the specimens are tested at an embedment lengths much shorter than those required by the ACI code, failed in flexure except one failed in bond. 2) It seems that the beam depth can not be an effective variable to estimate the bond length within these sections and length of specimens on this tests. 3) The development length with the stirrup space which are considered for correction factors in the equations of Russel and Paulsgrove, is fully accurate to determine the required length for the beam tested in this research.

• KCI Concrete Journal
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• v.12 no.2
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• pp.31-43
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• 2000

The extensive usage of pretensioned prestressed concrete component in modem construe- tion as structural members mandates precise understanding of its mechanism. Especially, an adequate transfer of prestressing force from steel tendons to concrete around the end regions of the member is a critical issue. Due to the importance of the topic, several investigators have formulated equations modeling the transfer bond length based on various bonding mechanism between steel and concrete. However, the existing models are still inadequate in predicting the bond development in pretensioned prestressed concrete members. Therefore, this study presents a model of transfer bond length based on rational theory that can simulate experimental results. The model is developed into solid mechanics based structural analysis computer program. The program is validated by comparing the analysis results with experimental results of bond stress distribution, concrete strain profiles, and transfer length in pretensioned prestressed concrete members. The proposed analytical procedure in this study can be utilized as a useful tool for realistic evaluation of transfer length in pretensioned prestressed concrete members.