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Publication Number: FHWA-HRT-04-107
Date: August 2006

Behavior of Fiber-Reinforced Polymer Composite Piles Under Vertical Loads

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Chapter 5. Conclusions and Recommendations

The main purpose of this project was to address the need for a feasibility assessment of FRP composite-bearing piles for highway and related facilities substructures, replacing traditional materials such as timber, concrete, or steel, specifically in the construction of waterfront structures in hostile marine environments. The engineering use of FRP composite-bearing piles raised the need to investigate their field performance and to develop and evaluate reliable testing procedures and design methods to assess:

This project report summarizes the results of the full-scale experiment conducted at Port Elizabeth, NJ, and the companion laboratory tests. The main conclusions are summarized below.

Mechanical Short-Term Behavior of FRP composite materials under axial compression loads

Chapter 2 presented an engineering analysis approach for establishing the equivalent mechanical properties of the composite material, including elastic modulus for the initial loading quasilinear phase, axial compression strength, inertia moment, and critical buckling load. The conclusions of this chapter were as follows:

Behavior of FRP Composite Piles Under Vertical Loads

The testing program included four SLTs on instrumented piles, which were driven in the selected site at Port Elizabeth, NJ. In chapter 3, the experimental results were compared with the methods commonly used for evaluating the ultimate capacity, end bearing capacity, and shaft frictional resistance along the piles. This engineering analysis led to the following conclusions:

Evaluation of FRP Composite Piling Capacity, Drivability, and Constructability

In chapter 4, the authors described the full-scale experiment, the dynamic pile testing results, and the engineering analysis of the SLTs on the FRP piles. The main objectives of this demonstration project were to:

The engineering analysis of the dynamic pile testing results and the SLTs led to several conclusions.

Drivability and Integrity During Driving

Evaluation of Dynamic Testing Methods

CAPWAP Analysis

Correlations Between CAPWAP Analysis and Static Load Tests

Design Criteria and Allowable Stresses

R&D Needs Assessment

The dynamic and static loading tests on instrumented FRP piles conducted in this project demonstrated that these piles can be used as an alternative engineering solution for deep foundations. However, their widespread use will require further site testing and full-scale experiments to establish a relevant performance database to develop and evaluate reliable testing procedures and design methods.

The time-dependent stress-deformation behavior of composite recycled plastic materials is of concern, because the FRP piles may undergo an excessive deformation due to an applied sustained loading. The engineering use of FRP piles on a widespread basis requires developing and evaluating reliable testing procedures and design methods to determine the long-term behavior of these composite piles.

Further, research is now required to evaluate the effect of environmental conditions (i.e., soil confinement, groundwater, etc.) on the long-term behavior of recycled plastic composite materials as well as the combined effects of chemical and mechanical degradation processes. Both laboratory and full-scale loading tests are required to provide a relevant database to develop and evaluate the assessment of the long-term performance of composite, time-dependent FRP piles and to determine the limit creep load for their engineering use in waterfront and highway structures.


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