Seismic Stability of Marine Piers Built With Prestressed Concrete Piles

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Title: Seismic Stability of Marine Piers Built With Prestressed Concrete Piles

Author(s): Stuart Stringer and Robert Harn

Publication: Special Publication

Volume: 295

Issue:

Appears on pages(s): 1-22

Keywords: Prestressed Concrete Piles, Seismic Stability, Marine Piers.

Date: 10/4/2013

Abstract:
This study was conducted to examine the seismic behavior of piers built on prestressed concrete piles founded in dense sand with grouted dowel bar connections. The following key observations were made. (1) The ground motions that caused collapse typically had a displacement pulse or fling in the record. These characteristics were particularly harmful to longer period, more flexible piers. (2) In general connection and in-ground steel demands were low; with few cases experiencing steel strains larger than 0.03. This indicates that sway instability due to P-Δ effects is the most common cause of collapse for piers. (3) A stability index limit of 0.25 provides sufficient protection against dynamic collapse when P-Δ effects are ignored in the analysis for piers supported on prestressed concrete pile, while a stability index limit of 0.1 will protect against significant P-Δ displacement amplification variability when increased analytical accuracy is desired. (4) For typical pile lengths and axial loading the P-Δ sensitive behavior is expected and the stability index limit will likely control the displacement capacities over material strain limits. Finally a simple procedure was proposed to help identify when a pier is potentially at risk from instability due to dowel bar fracture.