• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.249-257
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• 2017

The purpose of this study was to contribute to the field application cost effectively and reasonably by developing the functional piles that make up for the defects of PHC piles. CFP (Concrete Filled Pretensioned Spun High Strength Concrete Pile with Ring type Composite shear connectors) piles developed in this study increases the compressive stress through enlarged cross section by rearranging composite shear connectors and filling the hollow part of PHC pile with concrete. And it improved shear and bending performance placing the rebar (H13-8ea) within the PHC pile and the hollow part of PHC pile of rebar (H19-8ea). In addition, the composite shear connectors were placed for the composite behavior between PHC pile and filled concrete. Placing Rebars (H13-8ea) of PHC pile into composite shear connector holes are sleeve-type mechanical coupling method that filling the concrete to the gap of the two members. Nonlinear finite element analyzes were performed to verify the performance of shear and bending moments and it deduced the spacing of the composite shear connectors. Through a various interpretation of CFP piles, it's proved that the CFP pile can increase the shear and bending stiffness of the PHC pile effectively. Therefore, this can be utilized usefully on the construction sites.

• Journal of the Korean Wood Science and Technology
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• v.32 no.5
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• pp.29-38
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• 2004

In this study, we investigated the thermal properties of corn-starch filled polybutylene succinate-adipate (PBS-AD) bio-composites. Thermal analysis (TA) is used to describe the analytical method for measuring the chemical property and weight loss of composite materials as a function of temperature. The thermal stability of corn-starch was lower than that of pure PBS-AD. As corn-starch loading increased, the thermal stability and degradation temperature of the bio-composites decreased and the ash content increased. It can be seen that the degree of compatibility and interfacial adhesion of the bio-composites decreased because of the increasing mixing ratio of the corn-starch. As the content of corn-starch increased, there was no significant change in the glass transition temperature (T_g) and the melting temperature (T_m) for the bio-composites. The storage modulus (E') and loss modulus (E") of the corn-starch flour filled PBS-AD bio-composites were higher than those of PBS-AD, because of the incorporation of corn-starch increased the stiffness of the bio-composites. At higher temperatures, the decreased storage modulus (E') of bio-composites was due to the increased polymer chain mobility of the matrix polymer. From these results, we can expect that corn-starch has potential as a reinforcing filler for bio-composites. Furthermore, we recommend using a coupling agent to improve the interfacial adhesion between corn-starch and biodegradable polymer.

• Journal of the Korean Geotechnical Society
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• v.22 no.12
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• pp.67-76
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• 2006

The reasonable assessment of the shear stiffness of a dredged soft ground and soft clay is difficult due to the soil disturbance. This study addresses the development and application of a new in-situ shear wave measuring apparatus (field velocity probe: FVP), which overcomes several of the limitations of conventional methods. Design concerns of this new apparatus include the disturbance of soils, cross-talking between transducers, electromagnetic coupling between cables, self acoustic insulation, the constant travel distance of S-wave, the rotation of the transducer, directly transmitted wave through a frame from transducer to transducer, and protection of the transducer and the cable. These concerns are effectively eliminated by continuous improvements through performing field and laboratory tests. The shear wave velocity of the FVP is simply calculated, without any inversion process, by using the travel distance and the first arrival time. The developed FVP Is tested in soil up to 30m in depth. The experimental results show that the FVP can produce every detailed shear wave velocity profiles in sand and clay layers. In addition, the shear wave velocity at the tested site correlates well with the cone tip resistance. This study suggests that the FVP may be an effective technique for measuring the shear wave velocity in the field to assess dynamic soil properties in soft ground.