An Analytical Approach to Determine Point-of-Fixity of Deep Foundation Utilizing Nonlinear Response from p-y Analysis
Publication: Geo-Congress 2024
ABSTRACT
The design of deep foundation systems often warrants a simplified approach for analysis by structural engineers. The point-of-fixity method is widely used as a common design practice where the complex interaction between soil and deep foundation under lateral load is sought to be replaced by an equivalent, fixed-based cantilever model. Recent studies attempted to propose more robust procedures to calculate depth-to-fixity, depending on various factors affecting the nonlinear lateral response of the soil-foundation system, as opposed to using empirical equations from design codes. This study proposes a simple method to determine depth-to-fixity, based on an analytical solution to the equivalent cantilever model. Following the recommendations from past research, the new method utilizes numerical lateral response obtained from the finite-difference program, NVShaft, to effectively translate the complex nonlinear soil model into a simplified equivalent cantilever analysis. Case studies of three lateral load test programs were considered to evaluate the proposed method and preceding point-of-fixity models based on design codes and recent literature.
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REFERENCES
AASHTO. (2020). AASHTO LRFD Bridge Design Specifications. AASHTO, Washington, D.C.
Abdelaziz, A. Y., El Naggar, M. H., and Ouda, M. (2021). “Determination of depth-of-fixity point for laterally loaded vertical offshore piles: A new approach.” Ocean Engineering, 232, 109113.
Bhuiyan, F. M., Siddharthan, R. V., and Motamed, R. (2023). “Evaluation of a semi-empirical p-y model for caliche material based on numerical simulations of field load tests in cemented soils.” Geo-Congress 2023, Los Angeles, California, March 26-29 2023, pp.163–174.
Bhuiyan, F. M., Siddharthan, R. V., and Motamed, R. (2022a). “Evaluation of existing p-y models for caliche based on numerical analysis of Raiders Stadium lateral load tests.” DFI 47th Annual Conference on Deep Foundations, National Harbor, Maryland, October 4-7, 297–309.
Bhuiyan, F. M., Motamed, R., Siddharthan, R. V., and Sanders, D. H. (2022b). “Evaluation of a unified p-y method for lateral analysis of large-diameter drilled shafts using NVShaft.” Transportation Geotechnics, 36, 100813.
Bhuiyan, F. M., Siddharthan, R. V., Motamed, R., and Sanders, D. H. (2020). “Evaluation of a new p-y analysis tool for lateral analysis of drilled shafts using load tests in Nevada.” DFI 45th Annual Conference on Deep Foundations, October 13-16, 303–312.
Bhuiyan, F. M., Toth, J., Siddharthan, R. V., and Motamed, R. (2021). “Evaluation of existing t-z models for caliche based on numerical analysis of bi-directional load tests using NVShaft.” DFI 46th Annual Conference on Deep Foundations, Las Vegas, Nevada, October 12-15, 21–31.
Chai, Y. H., and Hutchinson, T. C. (2002). “Flexural strength and ductility of extended pile-shafts. II: Experimental study.” Journal of structural engineering, 128(5), 595–602.
Davisson, M. T., and Robinson, K. E. (1965). “Bending and buckling of partially embedded piles.” Proc. Sixth Int. Conf. Soil Mechanics and Foundation Engineering, University of Toronto Press, Montreal, 243–246.
Fiorelli, D., Zorne, J., Siegel, T., and Faust, P. (2018). “Value engineering – design risk and reward at major sport arena projects.” DFI 43rd Annual Conference on Deep Foundations, Anaheim, California.
Heidari, M., and Hesham El Naggar, M. (2018). “Analytical approach for seismic performance of extended pile-shafts.” Journal of Bridge Engineering, 23(10), 04018069.
Hetényi, M., and Hetbenyi, M. I. (1946). Beams on elastic foundation: theory with applications in the fields of civil and mechanical engineering (Vol. 16). Ann Arbor, MI: University of Michigan press.
Jeong, S., and Kim, Y. (2020). “Analysis for laterally loaded offshore piles in marine clay.” Geotechnical Engineering, 51(2), 166–171.
Jeong, S., Kim, Y., Kim, J., and Shin, S. (2007). “Cyclic lateral load tests of offshore large diameter piles of Incheon Bridge in marine clay.” In The Seventeenth International Offshore and Polar Engineering Conference. OnePetro.
Robinson, B., Suarez, V., Robalino, P., Kowalsky, M., and Gabr, M. (2006). “Pile bent design criteria.”, 19.
Robinson, B., Suarez, V., Robalino, P., Kowalsky, M., and Gabr, M. (2007). “A point of fixity model for pile and shaft bents.” Contemporary Issues in Deep Foundations, 1–11. https://doi.org/10.1061/40902(221)16.
Robinson, B., Suarez, V., Gabr, M. A., and Kowalsky, M. (2011). “Simplified lateral analysis of deep foundation supported bridge bents: driven pile case studies.” Journal of Bridge Engineering, 16(4), 558–569. https://doi.org/10.1061/(ASCE)BE.1943-5592.0000182.
Suarez, V., and Kowalsky, M. J. (2007). “Displacement-based seismic design of drilled shaft bents with soil-structure interaction.” Journal of earthquake engineering, 11(6), 1010–1030.
Yang, Y., and Bakalovic, S. (2010). “Bridge substructure point of fixity and horizontal force distribution.” In 2010 Concrete Bridge Conference: Achieving Safe, Smart & Sustainable Bridges.
Zafir, Z., and Vanderpool, W. (1998). “Lateral response of large diameter drilled shafts: I-15/US 95 load test program.” Proc., 33rd Engineering Geology and Geotechnical Engineering Symp, 161–176.
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Geo-Congress 2024
Pages: 87 - 96
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Published online: Feb 22, 2024
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