Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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A Study on the Load Distribution Ratio and Axial Stiffness on Existing and Reinforcing-Pile in Vertical Extension Remodeling

수직증축시 기존말뚝과 보강말뚝의 하중분담율 및 축강성 분석

  • 정상섬 (연세대학교 토목환경공학과) ;
  • 조현철 (연세대학교 토목환경공학과)
  • Received : 2018.10.02
  • Accepted : 2018.12.12
  • Published : 2019.01.31
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Abstract

This study presents the application of the numerical and analytical technique to simulate the Load Distribution Ratio (LDR) and to define axial stiffness on reinforcing pile foundation ($K_{vr}$) in vertical extension remodeling structure. The main objective of this study was to investigate the LDR between existing piles and reinforcing piles. Therefore, to analyze the LDR, 3D FEM analysis was performed as variable for elastic modulus, pile end-bearing condition, raft contacts, and relative position of reinforcing pile in a group. Also, using the axial stiffness ($K_{ve}$) of existing piles, the axial stiffness of reinforcing pile was defined by 3D approximate computer-based method, YSPR (Yonsei Piled Raft). In addition $K_{vr}$ was defined by reducing the $K_{ve}$considering the degradation of the existing piles.

본 연구는 3차원 수치해석을 통해 기존말뚝과 보강말뚝의 하중분담율(Load Distribution Ratio)과 근사적 해석 기법으로 보강말뚝의 축방향 강성(Axial Stiffness)을 산정하였다. 시공단계를 고려하여 말뚝기초의 LDR에 영향을 미치는 인자를 파악하기 위해서 1) 말뚝기초의 강성, 2) 말뚝기초의 선단지지조건, 3) 기초판 접촉효과, 4) 보강말뚝의 설치위치에 따라 해석을 수행하여 기존말뚝과 신설말뚝의 하중분담율 거동을 확인하였다. 또한 5) 기존말뚝의 축방향 강성($K_{ve}$)를 사용하여 말뚝지지 전면기초의 3차원 근사적 해석기법(YSPR)으로 보강말뚝의 직경에 따른 강성($K_{vr}$)을 산정하고, 장기간 사용으로 인한 경화를 고려하여 $K_{ve}$를 3단계로 나누어 감소시켜 보강말뚝의 강성 변화의 경향을 살펴보고, 신설 말뚝의 강성 산정방법을 제시하였다.

Keywords

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Fig. 1. Load case along the construction stages of remodeling process

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Fig. 2. Top view of model

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Fig. 3. Front view of model

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Fig. 4. Top view of model

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Fig. 6. Load-settlement curve

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Fig. 5. Front view of model & material properties

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Fig. 7. Variable stiffness of reinforcing pile

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Fig. 8. Pile end-bearing condition

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Fig. 9. Load distribution ratio with Raft

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Fig. 10. Reinforcing pile installation

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Fig. 11. YSPR (Yonsei Piled Raft) (Jeong, 2015)

GJBGC4_2019_v35n1_17_f0012.png 이미지

Fig. 12. Axial stiffness calculation

GJBGC4_2019_v35n1_17_f0013.png 이미지

Fig. 13. Load-settlement curves of different size of reinforcing piles

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Fig. 14. Kυr-settlement curves depending on different Kυe values

Table 1. Physical properties of soil

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Table 2. Properties of piles and raft

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Table 3. Loading level applied on pile foundation

GJBGC4_2019_v35n1_17_t0003.png 이미지

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