MODELING AND CHARACTERIZATION OF HOLLOW AND CONCRETEFILLED FRP PILES

Traditional piling systems for marine applications have been constructed of steel,
timber, and reinforced concrete. These systems have well-known, predictable material
properties. The major shortfall of the traditional materials in this application is their
susceptibility to corrosion and environmental degradation. The use of composite
materials to construct the piles is an option that can extend the service life of marine
piling structures. Several companies in the U.S. have recognized the benefits of
composites in this application and are producing fiber reinforced polymer (FRP),
cylindrical, tubular piles that can be installed as hollow members, or can be filled with
concrete to improve the structural properties.
One major hurdle for widespread acceptance of FRP piles is the lack of
established and accepted design methodology. Contractors and engineers are
uncomfortable designing structural systems with these piles because of the new, and
relatively unfamiliar, procedures used to characterize the piles. A structural design
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methodology describing the appropriate analytical procedures to design piles is needed to
encourage growth in this new industry.
Review of literature on the subject has revealed several models that have been
developed to predict pile behavior, including numerical models for bending and
compression of FRP tubes filled with concrete. These analytical methods include both
simplified analysis methods, and a nonlinear moment-curvature model. In this project,
the numerical methods developed by past research are combined to analyze hollow and
concrete-filled FRP piles in four-point bending. These model results are compared to
full-scale flexural test results of piles fabricated at Harbor Technologies in Maine. The
test matrix included four-point bending tests on 24 hollow piles and 16 concrete-filled
piles. The objective of the testing program is to verify the validity of the proposed
numerical models for predicting the flexural strength and stiffness of hollow and
concrete-filled FRP piles, and to propose a workable design methodology for both hollow
and concrete-filled FRP piles.