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

Korean Geo-Environmental Society (한국지반환경공학회)
권호 표지

Analyses of Widely Used Design Codes for Pile Foundation Using the t-z Method

t-z 방법을 이용한 말뚝기초 설계기준별 비교분석

  • Published : 2012.10.01
⟨ Previous Next ⟩

Abstract

The efficiency of the current design methods for computing pile resistances is analyzed using field load-settlement tests results. Twelve load-settlement test data for drilled shafts and bored piles were obtained from the literature. These load-test data were fitted using the t-z method. Subsequently, the ultimate resistances were evaluated based upon the failure criteria from following methods: (1) the Davisson's approach and (2) settlement corresponding to 5% or 10% shaft diameter approach. The ultimate resistances for these drilled shafts and bored piles were also predicted using methods based on the design code from North America (United States, Canada), Europe, and Asia (Japan). The pile resistances determined from field load-settlement tests were compared with those calculated using the design codes. The comparisons show that most design codes predict a conservative resistance for drilled shafts and bored piles. However, in the case of drilled shafts, we find that some of the design codes can over-predict the resistance and, therefore, should be applied cautiously. This research also shows that the t-z method can be successfully used to predict the ultimate resistance and the load transfer mechanism for a single pile.

현장재하시험결과를 이용하여 현재 우리나라를 비롯한 많은 나라에서 사용하고 있는 말뚝기초 설계기준에 대한 효율성을 분석하였다. 문헌조사를 통해 12개의 현장타설말뚝 및 매입말뚝 재하시험자료를 수집하였으며 이를 t-z 방법으로 분석하였다. 재하시험결과로부터 각 설계기준에서 제시하고 있는 (1) Davisson 방법, (2) 말뚝직경의 5% 또는 10%의 침하가 발생하는 하중을 이용하여 극한지지력을 평가하였다. 또한, 미국, 캐나다, 유럽, 그리고 일본의 설계기준에서 각각 제시한 방법을 이용하여 현장타설말뚝과 매입말뚝의 극한 지지력을 계산하였다. 재하시험에서 분석된 극한 지지력과 설계기준에 의해 계산된 극한 지지력을 비교한 결과, 대부분의 설계기준은 말뚝기초의 극한지지력을 보수적으로 예측하는 것으로 나타났다. 그러나 일부 설계기준은 현장타설말뚝의 지지력을 과대평가하는 것으로 나타나 일부 설계기준은 적용 시 주의를 요하는 것으로 분석되었다. 또한, 본 연구는 t-z 방법을 이용하여 말뚝기초의 극한 지지력 및 하중전이 관계를 성공적으로 예측할 수 있음을 알 수 있었다.

Keywords

References

  1. AASHTO(2007), AASHTO LRFD Bridge Design Specifications, American Association of State Highway and Transportation Officials, Washington, D. C., pp. 10-1-10-159.
  2. Bowles, J. E.(1996), Foundation Analysis and Design, McGraw -Hill, New York, pp. 867-967.
  3. CGS(2006), Canadian Foundation Engineering Manual, Canadian Geotechnical Society, Richmond, British Columbia, pp. 123-142, pp. 260-302.
  4. FHWA(1998), Design and Construction of Driven Pile Foundations-Workshop Manual Volume II, Federal Highway Administration, Mclean, VA, pp. 19-1.
  5. FHWA(1999), Drilled Shaft: Construction Procedures and Design Methods, Federal Highway Administration, Mclean, VA, pp. 386-422.
  6. Fukui, J., Shirato, M. and Matsui, K.(2005). Performance-based Specifications for Japanese Highway Bridges, ICOSSAR 2005. Millpress, Rotterdam, pp. 3319-3322.
  7. JGS(2006), Principles for Foundation Designs Grounded on a Performance-based Design Concept, Japanese Geotechnical Society, Tokyo, Japan, pp. 13-54.
  8. JRA(2002), Japanese Specifications for Highway Bridge, Japanese Road Association, Maruzen, Japan, pp. 348-433.
  9. Kwak, K., Park, J., Choi, Y. and Huh, J.(2006), Evaluation of the Resistance Bias Factors to Develop LRFD for Driven Steel Pipe Piles, Journal of the Korean Society of Civil Engineering, Vol. 25, No. 5C, pp. 343-350.
  10. Lee, W., Lee, W. J., Lee, S. B. and Salgado, R.(2004), Measurement of Pile Load Transfer using the Fiber Bragg Grating Sensor System, Canadian Geotechnical Journal, Vol. 41, No. 6, pp. 1222-1232. https://doi.org/10.1139/t04-059
  11. Misra, A. and Roberts, L. A.(2006), Probabilistic Analysis of Drilled Shaft Service Limit State Using the "t-z" Method, Canadian Geotechnical Journal, Vol. 43, No. 12, pp. 1324- 1332. https://doi.org/10.1139/t06-074
  12. Misra, A., Roberts, L. A. and Levorson, S.(2007), Reliability Analysis of Drilled Shaft Behavior Using Finite Difference Method and Monte Carlo Simulation, Geotechnical and Geological Engineering, Vol. 25, No. 1, pp. 65-77. https://doi.org/10.1007/s10706-006-0007-2
  13. Orr, T. L. L. and Farrell, E. R.(1999). Geotechnical Design to Eurocode 7, Springer, New York, pp. 1-166.
  14. Park, S. and Misra, A.(2010), Evaluation of Pile Foundation Design Methods Using Load Tests, Proceedings of the 34th Annual Conference on Deep Foundations, Kansas City, MO, pp. 1-10.
  15. Park, S., Roberts, L. A. and Misra, A.(2011), Static Load Test Interpretation using the t-z Model and LRFD Resistance Factors for Auger Cast-in-place(ACIP) and Drilled Displacement(DD) Piles, International Journal of Geotechnical Engineering, Vol. 5, No. 3, pp. 283-295. https://doi.org/10.3328/IJGE.2011.05.03.283-295
  16. Pizzi, J. F.(2007), Case History: Capacity of a Drilled Shaft in the Atlantic Coastal Plain, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 133, No. 5, pp. 522-530. https://doi.org/10.1061/(ASCE)1090-0241(2007)133:5(522)
  17. prEN 1997-1 Eurocode 7(2001), Geotechnical design, Part 1: General rules, European Committee for Standardization(CEN) Brussels, Final draft October 2001, pp. 1-155.
  18. Smith, I.(2006), Smith's Elements of Soil Mechanics, Wiley-Blackwell, Malden, MA, pp. 303-360.