Closure to “Comprehensive Load Test on Prestressed Concrete Piles in Alluvial Clays and Marl in Savannah, Georgia” by Yong Tan and Guoming Lin

Abstract

Tan and Lin are commended on presenting a detailed case history of the performance of prestressed concrete piles installed and tested for a liquefied natural gas (LNG) facility in Georgia, United States. The pile testing program was comprehensive and included high-strain dynamic tests, Statnamic tests, and static axial compression and reciprocal lateral load tests. To extract information about the mobilized skin friction (shaft resistance) from the tests, the authors made use of the readings of the strain gauges installed at various levels along the test piles. From the results, the authors concluded, among other findings, that “the potential degradation of pile concrete stiffness attributable to pile driving should be accounted for in pile capacity analysis” (p. 178), a point that this discusser also made in the paper by Lam and Jefferis (2011). However, in this discusser’s opinion, this study would benefit from a fuller discussion of the process involved in the derivation of the pile stiffness (Young’s modulus) values for the various load tests because the chosen values of this important parameter can have a significant effect on the accuracy of the interpretation. Specific discussion points are given subsequently.