Journal of the Korean GEO-environmental Society (한국지반환경공학회 논문집)

Korean Geo-Environmental Society (한국지반환경공학회)
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Estimation of Vertical Load Capacity of PCFT Hybrid Composite Piles Using Dynamic Load Tests

동재하시험을 통한 긴장력이 도입된 콘크리트 충전 강관말뚝을 사용한 복합말뚝의 연직지지력 평가

  • Park, Nowon (Department of Civil Engineering, University of Seoul) ;
  • Paik, Kyuho (Department of Civil Engineering, Catholic Kwandong University)
  • Received : 2018.12.13
  • Accepted : 2019.02.19
  • Published : 2019.03.01
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Abstract

To determine the optimum dynamic load test analysis for PCFT (Prestressed Concrete Filled steel Tube) hybrid composite piles that PCFT piles are connected to the top of PHC piles, the dynamic load tests and CAPWAP analyses were performed on two hybrid composite piles with steel pipe and PCFT piles as upper piles. The results of the dynamic load tests and CAPWAP analyses showed that the particle velocity measured in PCFT hybrid composite piles was equal to the wave speed of PHC piles when the strain gauges and accelerometers are attached to the surface of inner composite PHC pile after removing the steel pipe in the upper PCFT pile. In addition, when assuming that the material of that upper PCFT pile was the same as that of the lower PHC pile and the cross-sectional area of the steel pipe in upper PCFT pile was converted to that for concrete through the pile model (PM) in CAPWAP analysis, the accuracy of the CAPWAP analysis result for PCFT hybrid composite piles was very high.

PCFT말뚝의 하부에 PHC말뚝을 연결한 PCFT 복합말뚝에 대한 최적의 동재하시험 분석 방법을 도출하기 위하여 동일 현장에 시공된 강관 복합말뚝과 PCFT 복합말뚝에 대해 동재하시험을 실시한 후 CAPWAP분석 결과를 비교하였다. 그 결과 PCFT 복합말뚝에 대한 동재하시험 수행 시 변형률계와 가속도계는 상부 PCFT말뚝에서 강관을 제거한 후 내부 합성 PHC말뚝에 부착하는 것이 바람직하고, 이렇게 측정된 PCFT 복합말뚝의 입자 변위속도는 PHC말뚝 고유의 변형파 속도인 4,000m/sec과 동일하였다. 그리고 CAPWAP분석 시 PM과정을 통해 상부 PCFT말뚝의 재질을 PHC말뚝과 동일하게 하고 말뚝 단면적으로 콘크리트로 환산한 단면적을 사용했을 때 CAPWAP분석의 정확도가 가장 높은 것으로 나타났다.

Keywords

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Fig. 1. Schematic diagram of dynamic load tests (Park, 2017)

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Fig. 2. Screen for pile model

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Fig. 3. Structural detail and picture of PCFT piles

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Fig. 4. Concrete pouring inside steel pipe using tremie pipe

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Fig. 5. Hybrid composite piles using PCFT piles

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Fig. 7. PCFT hybrid composite piles connected by bolting joint

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Fig. 8. Dynamic load test for PCFT hybrid composite piles

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Fig. 9. Force wave up-time curves for test piles

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Fig. 10. CAPWAP analysis for PCFT hybrid composite pile when ignoring PM

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Fig. 11. CAPWAP analysis for PCFT hybrid composite pile when applying change of pile impedance

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Fig. 12. CAPWAP analysis for PCFT hybrid composite pile when applying only PM

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Fig. 13. CAPWAP analysis for HCP when applying only PM

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Fig. 6. Boring log and SPT results at test site

Table 1. Variation of allowable base load capacity and MQ with CAPWAP analysis condition

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References

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