## Behavior of Fiber-Reinforced Polymer (FRP) Composite Piles under Vertical Loads

**Publication No. FHWA-HRT-04-107**

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**FOREWORD**

A full-scale experiment on fiber-reinforced polymer (FRP) piles, including static and dynamic load tests, was conducted at a site provided by the Port Authority of New York and New Jersey at its Port of Elizabeth facility in New Jersey, with the cooperation and support of its engineering department and the New York State Department of Transportation. The engineering use of FRP-bearing piles required field performance assessment and development and evaluation of reliable testing procedures and design methods to assess short-term composite material properties, load-settlement response and axial-bearing capacity, drivability and constructability of composite piling, soil-pile interaction and load transfer along the installed piling, and creep behavior of FRP composite piles under vertical loads.

Gary L. Henderson

Director, Office of Infrastructure

Research and Development

## NOTICE

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

## QUALITY ASSURANCE STATEMENT

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

**Technical Report Documentation Page**
**1. Report No.**
FHWA-HRT-04-107 |
**2. Government Accession No.** |
**3. Recipient's Catalog No.** |

**4. Title and Subtitle**
BEHAVIOR OF FIBER-REINFORCED POLYMER (FRP) COMPOSITE PILES UNDER VERTICAL LOADS |
**5. Report Date**
August 2006 |

**6. Performing Organization Code** |

**7. Author(s)**
Ilan Juran and Uri Komornik |
**8. Performing Organization Report No.** |

**9. Performing Organization Name and Address**
Urban Utility Center
Polytechnic University
6 Metrotech Center
Brooklyn, NY 11201 |
**10. Work Unit No.** |

**11. Contract or Grant No.**
DTFH61-99-X-00024 |

**12. Sponsoring Agency Name and Address**
Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296 |
**13. Type of Report and Period Covered**
Final Report 2000-2003 |

**14. Sponsoring Agency Code** |

**15. Supplementary Notes**
Contracting Officer's Technical Representative (COTR): Carl Ealy, HRDI-06 |

**16. Abstract**
Composite piles have been used primarily for fender piles, waterfront barriers, and bearing piles for light structures. In 1998, the Empire State Development Corporation (ESDC) undertook a waterfront rehabilitation project known as Hudson River Park. The project is expected to involve replacing up to 100,000 bearing piles for lightweight structures. The corrosion of steel, deterioration of concrete, and vulnerability of timber piles has led ESDC to consider composite materials, such as fiber-reinforced polymers (FRP), as a replacement for piling made of timber, concrete, or steel. Concurrently, the Federal Highway Administration (FHWA) initiated a research project on the use of FRP composite piles as vertical load-bearing piles.
A full-scale experiment, including dynamic and static load tests (SLT) on FRP piles was conducted at a site provided by the Port Authority of New York and New Jersey (PANY&NJ) at its Port of Elizabeth facility in New Jersey, with the cooperation and support of its engineering department and the New York State Department of Transportation (NYSDOT). The engineering use of FRP-bearing piles required field performance assessment and development and evaluation of reliable testing procedures and design methods to assess short-term composite material properties, load-settlement response and axial-bearing capacity, drivability and constructability of composite piling, soil-pile interaction and load transfer along the installed piling, and creep behavior of FRP composite piles under vertical loads.
This project includes:
- Development and experimental evaluation of an engineering analysis approach to establish the equivalent mechanical properties of the composite material. The properties include elastic modulus for the initial loading quasilinear phase, axial compression strength, inertia moment, and critical buckling load. The composite material used in this study consisted of recycled plastic reinforced by fiberglass rebar (SEAPILE
^{TM} composite marine piles), recycled plastic reinforced by steel bars, and recycled plastic reinforced with randomly distributed fiberglass (Trimax), manufactured respectively by Seaward International Inc., Plastic Piling, Inc., and U.S. Plastic Lumber.
- Static load tests on instrumented FRP piles. The instrumentation schemes were specifically designed for strain measurements. The experimental results were compared with current design codes as well as with the methods commonly used for evaluating the ultimate capacity, end bearing capacity, and shaft frictional resistance along the piles. As a result, preliminary recommendations for the design of FRP piles are proposed.
- Analysis of Pile Driving Analyzer
^{®} (PDA) and Pile Integrity Tester (PIT) test results using the Case Pile Wave Analysis Program (CAPWAP)^{(1)} and the GRL Wave Equation Analysis of Piles program GRLWEAP^{(2)} to establish the dynamic properties of the FRP piles. The PDA also was used to evaluate the feasibility of installing FRP piles using standard pile driving equipment. Pile bearing capacities were assessed using the CAPWAP program with the dynamic data measured by the PDA, and the calculated pile capacities were compared to the results of static load tests performed on the four FRP piles.
The dynamic and static loading test on instrumented FRP piles conducted in this project demonstrated that these piles can be used as an alternative engineering solution for deep foundations. The engineering analysis of the laboratory and field test results provided initial data basis for evaluating testing methods to establish the dynamic properties of FRP piles and evaluating their integrity and drivability. Design criteria for allowable compression and tension stresses in the FRP piles were developed considering the equation of the axial force equilibrium for the composite material and assuming no delamination between its basic components. However, the widespread engineering use of FRP piles will require further site testing and full-scale experiment to establish a relevant performance database for the development and evaluation of reliable testing procedure and design methods. |

**17. Key Words **Piles, fiber-reinforced polymers, static load tests, dynamic load tests |
**18. Distribution Statement**
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161. |

**19. Security Classif. (of this report)**
Unclassified |
**20. Security Classif. (of this page)**
Unclassified |
**21. No. of Pages**
97 |
**22. Price** |

Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized

**SI* (Modern Metric) Conversion Factors**

### TABLE OF CONTENTS

**CHAPTER 1. INTRODUCTION**

CURRENT STATE OF PRACTICE

Mechanical Behavior of FRP Piles

Field Observations Use and Experimental Demonstration Projects

RESEARCH AND DEVELOPMENT NEEDS

**CHAPTER 2. MECHANICAL SHORT-TERM BEHAVIOR OF FRP COMPOSITE MATERIALS UNDER AXIAL COMPRESSION LOADS**

SEAPILE COMPOSITE FRP MATERIAL

MECHANICAL PROPERTIES OF THE FRP COMPOSITE AND THE COMPONENT MATERIALS

ENGINEERING ANALYSIS OF THE AXIAL COMPRESSION TEST ON THE COMPOSITE PILE SAMPLE

Elastic Modulus and Compressive Strength

Moment of Inertia

Critical Buckling Force

PPI PILES

TRIMAX STRUCTURAL PLASTIC MATERIAL

Axial Compression Tests on the Trimax Pile Recycled Plastic

**CHAPTER 3. BEHAVIOR OF FRP COMPOSITE PILES UNDER VERTICAL LOADS**

PILE MANUFACTURING AND INSTRUMENTATION

Lancaster Composite, Inc.

PPI

SEAPILE Piles

FIELD TESTING PROGRAM

Full-Scale Experiment

GEOTECHNICAL SITE CONDITIONS

STATIC LOAD TEST PROCEDURE

ENGINEERING ANALYSIS OF STATIC LOAD TEST RESULTS

Ultimate Capacities of FRP Piles

Analysis of the End Bearing and Shaft Friction Distribution

Correlations With Standard Penetration Test (SPT) Data

Comparison Between Various Analysis Methods and Test Results

**CHAPTER 4. EVALUATION OF FRP COMPOSITE PILING CAPACITY USING WAVE EQUATION ANALYSIS**

TESTING PROGRAM AND SITE OBSERVATIONS

Test Piles and Dynamic Instrumentation

Site Observations on Drivability and Durability During Pile Installation

DYNAMIC PROPERTIES OF THE FRP COMPOSITE PILE MATERIALS

Methods for Evaluating Dynamic Properties

Dynamic Properties—Test Results

DYNAMIC PILE TESTING DATA ANALYSIS

Case Method Analysis (PDA)

CAPWAP Analysis

GRLWEAP Analysis

STATIC LOAD TEST RESULTS—CORRELATIONS WITH CAPWAP ANALYSIS

Pile Capacity and Setup

Correlations of CAPWAP Analysis With Static Load Test Results

Pile Tension and Tensile Stress During Driving

**CHAPTER 5. CONCLUSIONS AND RECOMMENDATIONS**

MECHANICAL SHORT-TERM BEHAVIOR OF FRP COMPOSITE MATERIALS UNDER AXIAL COMPRESSION LOADS

BEHAVIOR OF FRP COMPOSITE PILES UNDER VERTICAL LOADS

EVALUATION OF FRP COMPOSITE PILING CAPACITY, DRIVABILITY, AND CONSTRUCTABILITY

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

**REFERENCES**

**BIBLIOGRAPHY**

### LIST OF FIGURES

Figure 1. Photo. Marine borers (Limnoria) attacking untreated timber piles that support many of New York's highways and harbor piers

Figure 2. Photo. Complete corrosion of steel H piles supporting a harbor pier (recently installed retrofit channels are already corroding)

Figure 3. Photo. Fender piles in the U.S. Naval Submarine Base, San Diego, CA

Figure 4. Photo. Fendering system in the U.S. Navy Pier 10, San Diego, CA

Figure 5. Photo. Fendering system, Nashville Avenue Marine Terminal, Port of New Orleans, LA

Figure 6. Photo. Floating dock project

Figure 7. Photo. Port of Elizabeth demonstration site

Figure 8. Illustration. Locations of pile manufacturers

Figure 9. Photo. SEAPILE composite marine piles

Figure 10. Graph. Stress-strain relationship of 4.4-cm (1.75-inch) fiberglass bars

Figure 11. Photo. Fiberglass bar before axial compression test and disintegrated fiberglass parts

Figure 12. Graph. Stress-vertical strain relationship of SEAPILE pile recycled plastic

Figure 13. Graph. Stress-radial strain relationship of SEAPILE pile recycled plastic; rate 0.33 percent/min

Figure 14. Graph. Force-vertical strain relationship of SEAPILE pile sample. 13

Figure 15. Graph. SEAPILE pile sample after axial compression test

Figure 16. Equation. Applied load F

Figure 17. Equation. Young's modulus E

Figure 18. Equation. σ_{c}/σ_{b}

Figure 19. Equation. E_{c}/E_{b}

Figure 20. Equation. G_{c}

Figure 21. Equation. R_{c}/R_{b}

Figure 22. Equation. FLF

Figure 23. Equation. Bending moment M

Figure 24. Equation. Moment of inertia I_{c}(1)

Figure 25. Equation. Moment of inertia I_{c}(2)

Figure 26. Equation. Relative inertia moment coefficient λ

Figure 27. Equation. I_{c}/ΣI_{b}

Figure 28. Equation. Critical buckling force P_{cr}

Figure 29. Equation. P_{cr} of an axially loaded bar

Figure 30. Equation. Equivalent critical buckling load for composite material

Figure 31. Equation. Critical buckling load factor BLF

Figure 32. Equation. Critical buckling load decomposed

Figure 33. Graph. Buckling force versus length for SEAPILE pile sample and fiberglass bars

Figure 34. Photo. PPI pile

Figure 35. Graph. PPI pile—stress-strain relationship

Figure 36. Photo. Trimax pile

Figure 37. Graph. Trimax pile—vertical stress-strain curves at different rates

Figure 38. Graph. Trimax pile—vertical stress-lateral strain curve; strain rate 0.33 percent per minute

Figure 39. Photo. Port of Elizabeth demonstration site

Figure 40. Photo. Equipment used in the in-load tests

Figure 41. Illustration. Schematic of the equipment used in the in-load tests

Figure 42. Illustration. Data acquisition system

Figure 43. Photo. Strain gauges installation in pile of Lancaster Composite, Inc.

Figure 44. Photo. Vibrating and foil strain gauges attached to steel cage in PPI pile

Figure 45. Photo. Vibrating and foil strain gauges attached to SEAPILE composite marine pile

Figure 46. Illustration. Schematic drawing of Port Elizabeth site

Figure 47. Graph. Lancaster pile—settlement-time relationship

Figure 48. Graph. PPI pile—settlement-time relationship

Figure 49. Graph. SEAPILE pile—settlement-time relationship

Figure 50. Graph. American Ecoboard pile—settlement-time relationship

Figure 51. Equation. Settlement, S

Figure 52. Graph. Lancaster Composite pile—Davisson criteria and measured load-settlement curve

Figure 53. Graph. PPI pile—Davisson criteria and measured load-settlement curve

Figure 54. Graph. SEAPILE pile—Davisson criteria and measured load-settlement curve

Figure 55. Graph. American Ecoboard pile—Davisson criteria and measured load-settlement curve

Figure 56. Graph. DeBeer criterion plotted for FRP piles

Figure 57. Chin-Kondner method plotted for FRP piles

Figure 58. Chin-Kondner method plotted for American Ecoboard pile

Figure 59. Equation. Ultimate load capacity P_{uc}

Figure 60. Equation. Ultimate shaft friction in compression f_{s}

Figure 61. Equation. Ultimate end bearing resistance f_{b}

Figure 62. Equation. Relationship between f_{s} and in situ stresses

Figure 63. Equation. Empirical correlations for shaft friction

Figure 64. Equation. Empirical correlation for end bearing resistance

Figure 65. Graph. PPI pile, measured loads versus depth

Figure 66. Graph. SEAPILE pile, measured loads versus depth

Figure 67. Graph. Lancaster Composite, Inc., pile, measured loads versus depth

Figure 68. Photo. PPI pile

Figure 69. Photo. SEAPILE pile

Figure 70. Photo. Lancaster Composite, Inc., pile

Figure 71. Photo. American Ecoboard pile

Figure 72. Equation. Dynamic modulus E

Figure 73. Equation. Pile particle speed v

Figure 74. Graph. American Ecoboard pile—blows per foot versus elastic modulus

Figure 75. Graph. PPI pile—blows per foot versus elastic modulus

Figure 76. Graph. SEAPILE pile—blows per foot versus elastic modulus

Figure 77. Equation. S_{elastic}

Figure 78. Graph. SLT and CAPWAP analysis—Lancaster Composite, Inc., pile

Figure 79. Graph. SLT and CAPWAP analysis—PPI pile

Figure 80. Graph. SLT and CAPWAP analysis—SEAPILE pile

Figure 81. Graph. SLT and CAPWAP analysis—American Ecoboard pile

Figure 82. Equation. Applied axial force F

Figure 83. Equation. Equivalent axial stress σ^{t}

Figure 84. Graph. Stress versus penetration depth for Lancaster Composite, Inc., SLT pile

Figure 85. Graph. Stress versus penetration depth for PPI SLT pile

Figure 86. Graph. Stress versus penetration depth for SEAPILE SLT pile

Figure 87. Graph. Stress versus penetration depth for American Ecoboard splice SLT pile

### LIST OF TABLES

Table 1. Material properties—test results and model calculations

Table 2. Selected design material properties (published by Lancaster Composite, Inc.)

Table 3. Compression strength testing of the concrete

Table 4. Testing program details, Port Elizabeth site

Table 5. Soil profile and soil properties at Port Elizabeth site

Table 6. Comparison of measured and calculated ultimate loads

Table 7. Total stress analysis approaches for estimating f_{s}.^{(34)}

Table 8. Effective stress analysis approaches for estimating ultimate shaft friction

Table 9. Factor C_{N} for base resistance.^{(43)}

Table 10. Comparison between SLT results and several analysis methods and design codes

Table 11. Elastic modulus of FRP piles estimated from PIT and PDA tests

Table 12. PDA results

Table 13. CAPWAP program calculation results

Table 14. Quake and damping values recommended by GRL

Table 15. Comparison of GRLWEAP results with measured elastic modulus, number of blows, and energy

Table 16. Comparison, static and dynamic elastic modulus of SEAPILE, PPI, and steel piles

Table 17. Comparison between CAPWAP analysis and static load test results

Table 18. Measured and allowable stresses for FRP piles