Implementation of LRFD Geotechnical Design for Deep Foundations Using Texas Cone Penetrometer (TCP) Test: Fid-Bau Portal

Implementation of LRFD Geotechnical Design for Deep Foundations Using Texas Cone Penetrometer (TCP) Test

H. Seo / R. B. Moghaddam / J. G. Surles / W. D. Lawson

This study provides resistance factors () for design of deep foundations to implement Load and Resistance Factor Design (LRFD) for bridge foundations using Texas Cone Penetrometer (TCP) Test data. Initial efforts were made to determine resistance factors using Davisson’s criterion in Research Project 0-6788: Reliability Based Deep Foundation Design Using Texas Cone Penetrometer (TCP) Test, completed on 8/31/2014. In this study, additional LRFD reliability analyses were performed using 5%, and 10% relative settlement criteria to determine ultimate capacities. The resistance factors obtained using Davisson, 5%, and 10% criteria were 0.30, 0.32, and 0.31, respectively, for total capacity of driven piles in soils with target reliability index ( ) of 3.0. Similarly, the resistance factors obtained using Davisson, 5%, and 10% criteria were 0.38, 0.40, and 0.39, respectively, for total capacity of drilled shafts in soils with  of 3.0. These resistance factors reflect TCP blow counts not corrected for hammer efficiency. Based on the size and scope of the dataset, literature review, and statistical analyses, it is recommended that resistance factors from Davisson and 5% criteria be used for driven piles in soils ( = 0.44 and 0.30 with  of 2.33 and 3.0, respectively) and drilled shafts ( = 0.54 and 0.40 with  of 2.33 and 3.0, respectively) in soils, respectively. It is considered that these values are suitable for implementation for small projects. For large projects, it is recommend consideration of determining ultimate capacity from static or dynamic load tests in accordance with AASHTO policy which will yield higher resistance factors.