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Pile Design for Downdrag: Examples and Supporting Materials (2024)

Chapter: Appendix B: Statistical Analyses of t-z and q-z Curve Models

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Page 70
Suggested Citation:"Appendix B: Statistical Analyses of t-z and q-z Curve Models." National Academies of Sciences, Engineering, and Medicine. 2024. Pile Design for Downdrag: Examples and Supporting Materials. Washington, DC: The National Academies Press. doi: 10.17226/27864.
×

APPENDIX B

Statistical Analyses of t-z and q-z Curve Models

The statistical output for analysis of t-z relationships is included herein. These analyses provide a measurement of validation of the different models that were used to develop t-z curves.

Table B.1. Statistical output for Bohn et al. (2017) Cubic Root relationship.

Averages
Bohn et al. (2017) Cubic Root Mean Bias COV Bias NRMSE
A Steel Plastic 0.97 29.84 16.7%
Granular 1.02 33.50 23.8%
Concrete Plastic 0.99 34.86 20.2%
Granular 1.00 34.55 18.1%
B Steel Plastic 1.00 30.46 21.9%
Granular 1.03 33.34 21.1%
Concrete Plastic 1.06 27.05 20.3%
Granular 1.01 31.89 19.4%

Table B.2. Statistical output for Vijayvergiya (1977) relationship.

Averages
Vijayvergiya (1977) Mean Bias COV Bias NRMSE
A Steel Plastic 0.78 34.70 23.7%
Granular 0.80 35.62 27.6%
Concrete Plastic 0.74 38.88 25.8%
Granular 0.74 36.56 24.8%
B Steel Plastic 0.83 36.83 29.2%
Granular 0.80 38.69 28.9%
Concrete Plastic 0.77 30.96 23.0%
Granular 0.76 35.75 24.7%
Page 71
Suggested Citation:"Appendix B: Statistical Analyses of t-z and q-z Curve Models." National Academies of Sciences, Engineering, and Medicine. 2024. Pile Design for Downdrag: Examples and Supporting Materials. Washington, DC: The National Academies Press. doi: 10.17226/27864.
×

Table B.3. Statistical output for Bohn et al. (2017) Hyperbolic relationship.

Averages
Bohn et al. (2017) Hyperbolic Mean Bias COV Bias NRMSE
A Steel Plastic 1.80 44.35 16.4%
Granular 1.31 45.80 24.0%
Concrete Plastic 1.00 38.70 19.1%
Granular 1.10 34.67 18.1%
B Steel Plastic 2.01 48.20 23.3%
Granular 1.56 48.56 23.5%
Concrete Plastic 1.07 25.38 16.6%
Granular 1.18 37.81 17.8%

Table B.4. Statistical output for Mosher (1984) relationship.

Averages
Mosher (1984) Mean Bias COV Bias NRMSE
A Steel Plastic
Granular 2.65 46.66 25.3%
Concrete Plastic
Granular 1.46 39.85 25.5%
B Steel Plastic
Granular 2.01 48.14 29.2%
Concrete Plastic
Granular 1.40 42.98 22.2%

*Plastic soils not considered for Mosher (1984), because it was developed for granular soils.

Table B.5. Statistical output for API (2002) relationship.

Averages
API (2002) Mean Bias COV Bias NRMSE
A Steel Plastic 2.14 52.33 19.5%
Granular 1.05 50.69 31.8%
Concrete Plastic 0.95 45.97 22.7%
Granular 0.81 41.46 28.0%
B Steel Plastic 2.45 56.16 26.4%
Granular 1.14 52.78 32.4%
Concrete Plastic 0.97 29.35 17.7%
Granular 0.85 46.38 28.1%
Page 72
Suggested Citation:"Appendix B: Statistical Analyses of t-z and q-z Curve Models." National Academies of Sciences, Engineering, and Medicine. 2024. Pile Design for Downdrag: Examples and Supporting Materials. Washington, DC: The National Academies Press. doi: 10.17226/27864.
×

Table B.6. Statistical output for Coyle and Reese (1966) relationship.

Averages
Coyle and Reese (1966) Mean Bias COV Bias NRMSE
A Steel Plastic 0.99 43.56 27.8%
Granular
Concrete Plastic 0.82 50.80 31.6%
Granular
B Steel Plastic 1.95 56.18 27.8%
Granular
Concrete Plastic 0.93 41.78 31.3%
Granular

*Granular soils not considered for Coyle and Reese (1966), because it was developed for plastic soils.

References

API (American Petroleum Institute). (2002). API Recommended Practice 2A-WSD - Planning, Designing, and Constructing Fixed Offshore Platforms – Working Stress Design, 21st ed. American Petroleum Institute.

Bohn, C., Lopes dos Santos, A., and Frank, R. (2017). “Development of Axial Pile Load Transfer Curves Based on Instrumented Load Tests.” Journal of Geotechnical and Geoenvironmental Engineering 143 (1): 04016081.

Coyle, H.M., and Reese, L.C. (1966). “Load Transfer for Axially Loaded Piles in Clay.” Journal of the Soil Mechanics and Foundations Division 92 (2).

Mosher, R.L. (1984). Load Transfer Criteria for Numerical Analysis of Axially Loaded Piles in Sand. U. S. Army Waterways Experiment Station, Automatic Data Processing Center, Vicksburg, Mississippi.

Page 70
Suggested Citation:"Appendix B: Statistical Analyses of t-z and q-z Curve Models." National Academies of Sciences, Engineering, and Medicine. 2024. Pile Design for Downdrag: Examples and Supporting Materials. Washington, DC: The National Academies Press. doi: 10.17226/27864.
×
Page 70
Page 71
Suggested Citation:"Appendix B: Statistical Analyses of t-z and q-z Curve Models." National Academies of Sciences, Engineering, and Medicine. 2024. Pile Design for Downdrag: Examples and Supporting Materials. Washington, DC: The National Academies Press. doi: 10.17226/27864.
×
Page 71
Page 72
Suggested Citation:"Appendix B: Statistical Analyses of t-z and q-z Curve Models." National Academies of Sciences, Engineering, and Medicine. 2024. Pile Design for Downdrag: Examples and Supporting Materials. Washington, DC: The National Academies Press. doi: 10.17226/27864.
×
Page 72
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