Journal of the Korean Geosynthetics Society (한국지반신소재학회논문집)

Korean Geosynthetics Society (한국지반신소재학회)
권호 표지
DOI QR코드

DOI QR Code

A Study on the Calculation of Load Resistance Factor of over Tension Anchors by Optimization Design

최적화 설계를 통한 과긴장 앵커의 하중-저항계수 산정 연구

  • Soung-Kyu Lee (Dept. of Civil and Environment Engineering, Daejin Univ.) ;
  • Yeong-Jin Lee (Dept. of Civil and Environment Engineering, Daejin Univ.) ;
  • Yong-Jae Song (Dept. of Civil and Environment Engineering, Daejin Univ.) ;
  • Tae-Jun Cho (Dept. of Smart Construction and Environmental Engineering, Daejin Univ.) ;
  • Kang-Il Lee (Dept. of Smart Construction and Environmental Engineering, Daejin Univ.)
  • Received : 2023.10.10
  • Accepted : 2023.12.11
  • Published : 2023.12.30
Download PDF
⟨ Previous Next ⟩

Abstract

To consider the risk of damage and fracture of P.C strands, the existing post-maintenance system alone has the limitations, hence it is necessary to quantitatively evaluate and predict the deterioration, durability and safety of facilities and establish a reasonable maintenance system considering the asset value of facilities. Therefore, it is worth considering a preventive maintenance plan that allows proactive measures to be taken before a major defect occurs in the temporary anchor. This study devised a preventive over tension method, reviewed its effectiveness through design and field tests, by calculating the resistance factors by performing a reliability-based optimization design. At this time, the over tension anchor method was evaluated using the ratio of the residual tension force after the fracture of P.C strands to the effective tension force before the fracture of P.C strand, followed by the resistance factor calculated by the optimal solution for each random variables using Excel solver and applying it to the limit state equations. As a result of the study, if the over tension ratio is 125% to 130%, the remaining strands showed a high resistance effect even after the fracture of P.C strand. As a result of the optimization design, it was found that it is appropriate to apply the load factor (γ) of 1.25, and the resistance factors of Φ1, Φ2, Φ3 as 0.7, 0.5, 0.6.

강연선의 손상 및 파단위험에 대하여 적극적으로 대처하기 위해서는 기존의 사후 유지관리 체계만으로는 한계가 있으며 시설물의 내구성, 안전성 저하를 정량적으로 평가 및 예측하고 시설물의 자산가치를 고려한 합리적인 유지관리 체계의 구축이 요구된다. 따라서 가설앵커에 큰 결함이 발생하기 전 사전조치가 이루어지도록 하는 선제적 유지관리 방안을 고려해볼 가치가 있다. 이를 위해 본 연구에서는 선제적 과긴장 공법을 고안하여 설계 및 현장시험을 통해 그 효과를 검토하고 신뢰성 기반 최적화 설계를 수행하여 저항계수를 산정하였다. 이때 과긴장 앵커의 흙막이 가시설 지지효과는 강연선 파단전 유효긴장력에 대한 강연선 파단후 잔존긴장력의 비를 이용하여 평가하였으며 저항계수는 각 확률변수에 대한 최적해를 Excel solver를 이용하여 구하고 이를 한계상태식에 적용하여 산정하였다. 연구결과 과긴장률이 125%~130%인 경우 강연선 파단 후에도 높은 흙막이 가시설 지지효과를 보였으며 최적화 설계결과 하중계수(γ)는 1.25, 저항계수 Φ1, Φ2, Φ3은 0.7, 0.5, 0.6을 적용함이 적절한 것으로 나타났다.

Keywords

References

  1. Benamara, Z. F., Rouaiguia, A. and Bencheikh, M. (2020), Stability of Anchored retaining Walls under Seismic Loading Conditions to Obtain Minimal Anchor Lengths Using the Improves Failure Model, Civil and Environmental Engineering Reports, Vol.30, No.3 pp.214-233. https://doi.org/10.2478/ceer-2020-0041
  2. British Standard Institution (1989), British Standard Code of Practice of Ground Anchorages, BS. 8081.
  3. Cha, A. R., Chang, B. S., You, D. W., Kim, B. H. and Kim, T. H. (2009), Proposal for the maintenance and inspection of ground anchor, KGS Spring National Conference, pp.1032-1041.
  4. Cho, H. N., Lim, J. G., Choi, Y. M. and Park, K. H. (2008), Life Cycle Cost Analysis of Infrastructure, Goomibook, p.6.
  5. Choi, T. S., Yun, J. M., Kim, Y. S., You, S. K. and Lee, K. I. (2021), "Stability Evaluation of Anchors Using Lift-off Field Test", Proceedings of the The Korean Society of Disaster Information, Vol.17, No.1, pp.128-142.
  6. Deutsches Norm (1990), Ground Anchorages Design, Construction and Testing, DIN-4125.
  7. Han, J. M., Kim, G. H., Woo, J. T. and Lee, K. I. (2017), "Evaluation of Pullout Capacity of Anchors by Bonded Length through Model Test", Journal of Korean Geosynthetics Society, Vol.16, No.3, pp.11-19.
  8. Japan Anchor Association (2009), Inspection and Maintenance Manual for Ground Anchor, CIR.
  9. KICT (2019), Development of Preventive Management System for Road Facilities based on Big-data considering Preemptive Countermeasures and Renewal, KICT 2019-025.
  10. Meyerhof, G. G. (1970), "Safety factors in soil mechanics", Canadian Geotechnical Journal, Vol.7, pp.349-355. https://doi.org/10.1139/t70-047
  11. Muller, A., Marquez, A. and Iung, B. (2008), "On the Concept of E-maintenance: Review and Current Research", Reliability Engineering and System Safety, Vol.93, No.8, pp.1165-1187. https://doi.org/10.1016/j.ress.2007.08.006
  12. Public Works Research Institute (2008), Inspection and Maintenance Manual for Ground Anchors, Japan anchor association.
  13. Sabatini, P. J., Pas, D. G. and Bachus, R. C. (1999), Geotechnical Engineering Circular No.4 Ground Anchors and Anchored Systems, FHWA-SA-99-015, Office of Bridge Technology Federal Highway Administartion, Washington, D.C.
  14. Tang, W., Woodford, D. and Pelletier, J. (1990), "Performance reliability of offshore piles", Proceedings of the 22nd Annual Off-shore Technology Conference, Houston, TX, Paper No.OTC 6379, Offshore Technology Conference, Richardson, TX, Vol.3, pp.299-308.
  15. Whitlow, R. B. (1995), Asic soil mechanics, Wesley Longman, Editor received the manuscript.
  16. Wu, T., Tang, W., Sangrey, D. and Baecher, G. (1989), Reliability of offshore foundations-state of the art, Journal of Geotechnical Engineering, Vol.115, No.2, pp.157-178. https://doi.org/10.1061/(ASCE)0733-9410(1989)115:2(157)