• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.152-153
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• 2022

In this study, the mechanical properties of PHC Pile were investigated using α-calcium sulfate hemihydrate, an industrial by-product with excellent expansion performance. As a result, the compressive strength of PHC pile showed a tendency to be higher than that of general Portland cement (OPC).

• 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.

• Korean Journal of Construction Engineering and Management
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• v.6 no.4 s.26
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• pp.142-151
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• 2005

Several advanced countries have been continually developed PHC pile cutting automation machines for improving productivity, safety and quality of the conventional PHC pile cutting work. However, the target work of the previously developed PHC pile cutting automation machines is only crushing the head of PHC pile. Dangerous grinding work is still performed by workers with seven inch hand grinder. In domestic construction industry, the PHC pile cutting work is usually performed by a crusher and three to four skilled workers. Recent analysis results of the PHC pile cutting work reveal that it frequently makes a lot of cracks which significantly reduce the strength of the pile and is labor-intensive work. The primary objective of this study is to propose the end-effector which can effectively break PHC pile without any longitudinal cracks and to develop an automated pile cutting machine having unified grinder and crusher parts through a wide variety of laboratory and field tests. It is anticipated that the development of the automated pile cutting machine would be able to bring improvements in safety, productivity, quality as well as cost saving.

• Journal of the Korean Geotechnical Society
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• v.35 no.9
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• pp.29-36
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• 2019

Axial compressive failure loads ($P_n$) of diameter 500 mm and diameter 600 mm A type PHC pile were calculated as 7.7 MN and 10.6 MN, respectively. In the static pile load tests, the maximum axial compressive loads of the above 2 kinds of A type pile were measured as 6.9 MN and 8.8 MN respectively, therefore these measured maximum loads were at the level of 90% and 83% of $P_n$ respectively. Long-term allowable axial compressive loads ($P_a$) of the above 2 kinds of A type pile were 1.7 MN and 2.3 MN respectively. From the bi-directional pile load test data on the prebored PHC piles, it was confirmed that the allowable axial compressive bearing resistance was estimated as 131% of the long-term allowable compressive load of the PHC pile and showed higher than the allowable bearing capacity calculated by the current design method. Therefore, it has been verified that the PHC pile can be used up to the maximum long-term allowable compressive load, and it is suggested that the ultimate pile capacity formula used in the current design for prebored PHC piles should be improved to accommodate the actual capacity.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.71-78
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• 2012

In order to improve the shear strength of conventional pre-tensioned spun high strength concrete (PHC) pile, concrete-infilled composite PHC (ICP) pile, a PHC pile reinforced by means of shear reinforcement and infilled concrete, is proposed. Two types of specimens were cast and tested according to KS (Korean Standards) to verify the shear strength enhancement of ICP pile. Based on the test results, it was found that the KS method was not suitable due to causing shear failure of ICP pile. However, shear strength enhancement was clearly verified. The obtained shear strength of the ICP pile was more than twice that of conventional PHC pile. In addition, the shear strength of ICP pile reinforced with longitudinal reinforcement was estimated to be more than 2.5 times greater than that of conventional PHC pile. The allowable shear force of ICP pile, which was determined by the allowable stress design process, indicated a large safety factor of more than 2.9 compared to the test results.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.37-51
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• 2013

An energy pile encases heat exchange pipes to exchange thermal energy with the surrounding ground formation by circulating working fluid through the pipes. An energy pile has many advantages in terms of economic feasibility and constructability over conventional Ground Heat Exchangers (GHEXs). In this paper, a coil-type PHC energy pile was constructed in a test bed and its thermal performance was experimentally and numerically evaluated to make a preliminary design. An in-situ thermal response test (TRT) was performed on the coil-type PHC energy pile and its results were compared with the solid cylinder source model presented by Man et al. (2010). In addition, a CFD numerical analysis using FLUNET was carried out to back-analyze the thermal conductivity of the ground formation from the Ttype PHC energy RT result. To study effects of a coil pitch of the coil-type heat exchange pipe, a thermal interference between the heat exchange pipes in PHC energy piles was parametrically studied by performing the CFD numerical analysis, then the effect of the coil pitch on thermal performance and efficiency of heat exchange were evaluated. Finally, an equivalent heat exchange efficiency factor for the coil-type PHC energy pile in comparison with a common multiple U-type PHC energy pile was obtained to facilitate a preliminary design method for the coil-type PHC energy pile by adopting the PILESIM2 program.

• Journal of the Korea Institute of Building Construction
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• v.18 no.5
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• pp.439-446
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• 2018

The PHC pile has been increasingly used due to its implementation of the top-base method, which is advantageous in high penetration rate and bearing capacity reinforcement. Typically, when a PHC pile is manufactured, high-strength mixed materials are mainly used to enhance the compressive strength. However, recent studies have been conducted to utilize ground granulated blast-furnace slag (GGBS) in terms of economic efficiency. For this reason, this study manufactured PHC pile considering the replacement ratio and curing conditions of GGBS instead of high-strength mixed materials, and further investigated the engineering properties of the PHC pile. According to the experimental results, the compressive strength of GGBS-replaced PHC pile increased by steam curing, and particularly, PHC pile with 20% replacement of GGBS under $80^{\circ}C$ steam curing condition showed a compressive strength of approximately 84MPa. Furthermore, the experimental results confirmed that more hydration products were generated under the $80^{\circ}C$ steam curing condition than that under the $20^{\circ}C$ steam curing condition, which would affect the higher density of the PHC pile as well as the increase in the compressive strength.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.115-131
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• 2018

Extension plate attached PHC piles and bolts spliced PHC piles were installed in field test site. Pile integrities were checked during installation with dynamic pile test and the actual pile conditions after installation were compared with integrity index (${\beta}$ index) by PDA test. Theoretically the break in near pile end or pile end (especially extension plate itself) was very difficult to access by integrity index (${\beta}$ index) and also require a high level of knowledge and field experience on PDA test. First actual wave equation of bolts spliced PHC piles due to bolts spliced equipment can be different with welding spliced. Second wave length of the stress wave from installing can be longer than the height of bolts spliced equipment (about 100 mm). Third Beta processing in PDA analysis function is very difficult to access without a high level of knowledge and field experience on wave equation. Above-mentioned three reasons can make conclusion that traditional PDA test in domestic site can not access the integrity of bolts spliced equipment in bolts spliced PHC piles.

• Journal of the Korea Convergence Society
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• v.6 no.6
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• pp.163-169
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• 2015

This study was intended to suggest a new-concept construction method of permanent basement wall combined with earth retaining wall by using PHC piles to overcome the disadvantages of conventional CIP methods or the like which have been used just for earth retaining walls during field construction, and to determine its applicability. PHC piles are characterized by the reliable quality attributed to prefabrication (shop fabrication) as well as superior concrete strength and prestressing steel strength to that of CIP in the aspect of materials, and also higher bending moment than that of CIP in the aspect of structure.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.2
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• pp.37-44
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• 2019

The primary objective of this study is to develop a prototype of all-in-one attachment-based PHC pile head cutting robot that improves the conventional work in safety, productivity, and quality. For this, the following research works are conducted sequentially; 1)literature review, 2)development of an all-in-one attachment-based PHC pile head cutting robot prototype, 3)performance evaluation of each device, 4)economic analysis of an automated method. As a result, PHC pile cutting level sensing device, PHC pile cutting device, PHC pile handling device are developed. Futhermore, working process of an automated method is developed based on result of performance evaluation. According to the economic analysis result, the cost of the automated method was 21.37% less than that of the conventional method, and the economic efficiency was also superior(ROR 215.44%, Break-even Point 5.52month). It is expected that conclusions for future improvements are used in the development of the all-in-one attachment-based PHC pile head cutting robot to practical use.