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Figure 1. Photos. Degradation of conventional piles (Iskander and Hassan 1998). The figure consists of three color photographs representing examples of deteriorated piles. The first photo (A) shows corroded steel piles in a water environment. The second photo (B) shows a degraded concrete pile also in a water environment. The third photograph (C) shows deteriorated timber piles.

Figure 2. Illustration. Common types of composite piles. Shown in this figure are line-drawing cross sections of the three types of composite pile products that are well suited for load-bearing applications. The first type (A) has a steel pipe core surrounded by recycled plastic material. The second type (B) has an inner core of recycled plastic matrix, surrounded by a cage of rebar (FRP or steel). The third type of pile product (C) has an FRP shell filled with nonreinforced concrete.

Figure 3. Graph and Photos. Confinement effect of FRP tube on concrete (Fam and Rizkalla 2001 A, B). This figure presents typical stress-strain curves for (A) the composite stub, (B) the unconfined concrete core, and (C) the FRP shell. An arrow relates each of these curves to a color photograph of the respective materials. The X-axis is strain in units of meter per meter (0.002 to 0.012) and the Y-axis is load in kilonewtons (0 to 700). The chart illustrates the confinement effect of an FRP tube on the concrete core of a composite pile. The graph shows that the capacity of the FRP-concrete composite stub significantly exceeds the summed load-sharing capacity of the FRP and the concrete core. The load strain curve begins to depart from the curve of the unconfined concrete in the vicinity of the unconfined concrete strength. The conversion factors are 1 meter equals 3.28 feet and 1 kilonewton equals 225 poundforce.

Figure 4. Graph. Experimental versus predicted load-strain behavior using Fam and Rizkalla's model. This figure compares the load-strain response predicted by the Fam and Rizkalla variable confinement model with the experimental results obtained for Test Stub Number 1. The X-axis is strain in units of microstrain (positive 15 to negative 20). The Y-axis shows load in kilonewtons (0 to 2500). The chart illustrates that, overall, there is good agreement between the model predictions and experimental data for both lateral or hoop strain and axial or compression strain. At loads below about 1800 kilonewtons, predicted and experimental hoop strain are nearly identical. At loads greater than 1800 kilonewtons, experimentally derived hoop strain is slightly greater than model predictions. Both predicted and experimental axial strain data are nearly identical throughout the entire load range. The conversion factor is 1 kilonewton equals 225 poundforce.

Figure 5. Illustration. Strip elements for sectional analysis (Mirmiran and Shahawy 1996). This figure illustrates the basic concept of the Mirmiran and Shahawy strain compatibility/equilibrium model for predicting short-term flexural capacity. It consists of a simple line drawing representing a cross section of a composite pile. The cross section is divided into a series of strip elements, each containing an FRP element and a concrete element, which are used to integrate the normal stresses over the cross-sectional area. Alongside the cross section is a strain diagram with the following undescribed items listed from top to bottom: epsilon subscript top, epsilon subscript CU, C, Neutral Axis, D subscript core, epsilon subscript bottom, and T subscript FRP.

Figure 6. Graphs. Experimental versus analytical moment-curvature response (adapted from Fam and Rizkalla 2002). This figure consists of two graphs comparing, for Beams 4 and 13, the load-curvature response predicted by the Mirmiran and Shahawy (and Fam) train compatibility/equilibrium model with the experimental load-strain results from Fam and Rizkalla (2002). The X-axis on both charts is curvature in units of the product of 1 over meters times 10 to the minus 3 (0 to 160 and 0 to 30 for Beams 4 and 13, respectively). The Y-axis on both charts is moment in kilonewton-meters (0 to 25 and 0 to 2000 for Beams 4 and 13, respectively). The charts show that there is good agreement between the model predictions (analysis) and the experimental data, particularly with respect to tension stiffening. Specifications for Beams 4 and 13 are included alongside the two charts. The conversion factors are 1 meter equals 3.28 feet and 1 kilonewton-meter equals 737.6 poundforce-feet.

Figure 7. Graph. Interaction diagrams, concrete-filled FRP tubes (Mirmiran 1999). This figure shows the results of a study of combined axial and flexural loads on concrete-filled FRP tubes representing both over reinforcement and under reinforcement. The X-axis is moment measured in kips-inches (0 to 5000) and the Y-axis is axial load measured in kips (0 to 1000), kips being 1000 pound-force (lbf). At similar axial loads of about 100 kips, the moment for the overreinforced specimen (about 4000 kips-inches) is higher than the moment for the underreinforced specimen (about 2000 kips-inches). Conversion factors are 1 kip equals 1,000 poundforce equals 4.45 kilonewtons, and 1 kip-inch equals 0.11303 kilonewton-meter.

Figure 8. Graphs. Moisture absorption-related durability model. This figure presents two graphs that schematically illustrate: (A) the effect of time and temperature on absorption of moisture by FRP composite piles; and (B) the effect of moisture content or time on property values of the FRP composite piles. Increases in both time and temperature contribute to increases in moisture content of the composite pile. Moisture content of the composite pile increases most rapidly during the initial time periods and at the highest temperatures. As time increases, moisture content of the pile levels out. The property value decreases inversely with moisture content of the composite pile or with time.

Figure 9. Images. SEM images showing FRP damage (McBagonluri, et al., 2000). This figure consists of two scanning electron microscope images showing water-related damage to submerged FRP composites. The first image, at times 1020 magnification, and the second image, at times 3000 magnification, each show fiber damage and formation of cracks at the fiber-matrix interface.

Figure 10. Illustration. Influence of soil-pile interface friction on pile capacity. This figure presents a line drawing and two graphs that schematically show the effects of the soil-pile interface on the capacity of the pile. The pile capacity, shaft capacity, and tip capacity are labeled on a simple line drawing of a submerged pile. The ultimate pile capacity is represented as the sum of the shaft capacity and tip capacity. Alongside this drawing are two graphs showing that the soil-pile interface and the friction angle are important factors in determining the ultimate capacity and load transfer characteristics of the pile. The top graph is labeled soil-pile interface shear tests. Its X-axis is labeled capital delta, and its Y-axis is labeled tau. The graph has three lines that rise from left to right to a peak and then level off. The bottom line is labeled sigma subscript N1, the middle line is sigma subscript N2, and the top line is sigma subscript N3. The bottom graph is labeled interface friction angle, small delta. Its X-axis is labeled sigma subscript N and has increments labeled sigma subscript N1, sigma subscript N2, and sigma subscript N3. The Y-axis is labeled tau. Two straight lines begin at the origin and rise from left to right. A horizontal line intersects the uppermost line near the uppermost line's right end; the resulting angle is labeled small delta subscript peak. A second horizontal line intersects the lower line near the lower line's right end; the resulting angle is labeled small delta subscript CV.

Figure 11. Graph. Grain size curves of test sands. This figure is a particle size distribution chart showing grain size properties of the Density and Model test sands. The X-axis is a logarithmic scale and is particle diameter in millimeters (10 to 0.001) (0.39 to 0.000039 inches) and the Y-axis is percentage finer (0 to 100). The grain size of the Density sand ranges from 0.2 to 0.9 millimeters (0.0078 to 0.035 inches) and contains no fines. The Model sand grain size ranges from 0.1 to 2 millimeters (0.0039 to 0.078 inches) and contains about 5 percent fines.

Figure 12. Photos. Microscopic views of the test sands. This figure consists of two photomicrographs of the test sand particles. Each photo includes a 0.5-millimeter (0.02-inch) scale. The first photomicrograph (A) is of the Density sand showing the subrounded to rounded shapes of the grains. The second photomicrograph (B) is of the Model sand showing the subangular to angular shapes of the particles.

Figure 13. Graphs. Direct shear test results for Density sand (average D subscript R equals 70 percent). This figure presents the results of the displacement-controlled direct shear tests. The figure consists of two graphs displaying shear stress-displacement curves (A) and shear stress envelopes (B) for the Density test sand at 70-percent relative density. For the shear stress displacement graph (A), the X-axis is horizontal displacement in millimeters (0 to 14) and the Y-axis is shear stress in kilopascals (0 to 150). At the four normal stresses tested, the sand generally showed peak shear stresses followed by a reduction toward a residual shear stress. The highest peak shear stress, about 140 kilopascals, was observed when the highest normal pressure of 202.3 kilopascals was applied. At the lowest normal pressure of 23.7 kilopascals, the peak shear stress, about 20 kilopascals, was the smallest increase and only slightly above the residual stress. For the shear envelope chart (B), the X-axis is normal stress in kilopascals (0 to 250) and the Y-axis is shear stress in kilopascals (0 to 150). Two solid straight lines and one dashed straight line rise from left to right. The bottom solid line is labeled phi prime subscript CV, the whole term equaling 29.8 degrees. The top solid line is labeled phi prime subscript peak, the whole term equaling 34.7 degrees. The dashed line is labeled nonlinear envelope: phi subscript 0 equals 35.95 degrees, delta phi equals 6.2 degrees. Conversion factors are 1 millimeter equals 0.039 inch and 1 kilopascal equals 0.145 poundforce per square inch.

Figure 14. Graphs. Direct shear test results for Density sand (average D subscript R equals 100 percent). This figure presents the results of the displacement-controlled direct shear tests. The figure consists of two graphs displaying shear stress-displacement curves (A) and shear stress envelopes (B) for the Density test sand at 100-percent relative density. For the shear stress displacement graph (A), the X-axis is horizontal displacement in millimeters (0 to 14) and the Y-axis is shear stress in kilopascals (0 to 175). At the four normal stresses tested, the sand generally showed peak shear stresses followed by a reduction toward a residual shear stress. The highest peak shear stress, about 165 kilopascals, was observed when the highest normal pressure of 202.3 kilopascals was applied. At the lowest normal pressure of 24.8 kilopascals, the peak shear stress, about 22 kilopascals, was the smallest increase and only slightly above the residual stress. For the shear envelope chart (B), the X-axis is normal stress in kilopascals (0 to 250) and the Y-axis is shear stress in kilopascals (0 to 175). Two solid straight lines and one dashed straight line rise from left to right. The bottom solid line is labeled phi prime subscript CV, the whole term equaling 29 degrees. The top solid line is labeled phi prime subscript peak, the whole term equaling 39.3 degrees. The dashed line is labeled nonlinear envelope: phi subscript 0 equals 41.05 degrees, delta phi equals 4.6 degrees. Conversion factors are 1 millimeter equals 0.039 inch and 1 kilopascal equals 0.145 poundforce per square inch.

Figure 15. Graphs. Direct shear test results for Model sand (average D subscript R equals 75 percent). This figure presents the results of the displacement-controlled direct shear tests. The figure consists of two graphs displaying shear stress-displacement curves (A) and shear stress envelopes (B) for the Model test sand at 75-percent relative density. For the shear stress displacement graph (A), the X-axis is horizontal displacement in millimeters (0 to 14) and the Y-axis is shear stress in kilopascals (0 to 150). At the four normal stresses tested, the sand generally showed peak shear stresses followed by a reduction toward a residual shear stress. The highest peak shear stress, about 145 kilopascals, was observed when the highest normal pressure of 156.3 kilopascals was applied. At the lowest normal pressure of 23.7 kilopascals, the peak shear stress, about 30 kilopascals, was the smallest increase and only slightly above the residual stress. For the shear envelope chart (B), the X-axis is normal stress in kilopascals (0 to 200) and the Y-axis is shear stress in kilopascals (0 to 150). Two solid straight lines and one dashed straight line rise from left to right. The bottom solid line is labeled phi prime subscript CV, the whole term equaling 36.2 degrees. The top solid line is labeled phi prime subscript peak, the whole term equaling 43.4 degrees. The dashed line is labeled nonlinear envelope: phi subscript 0 equals 44.6 degrees, delta phi equals 9.8 degrees. Conversion factors are 1 millimeter equals 0.039 inch and 1 kilopascal equals 0.145 poundforce per square inch.

Figure 16. Illustration. Stylus profilometer sketch (Johnson 2000). This figure is a schematic of the profilometer used to measure the surface topography of pile material. From left to right, the figure shows the stylus tip on a sample, the pickup, a drive shaft, a motor drive unit, and a cable to the signal processor.

Figure 17. Chart. Graphical representation of roughness parameters R subscript T, S subscript M, and R subscript A. This figure is a sample tracing of a roughness profile. It consists of peaks and valleys, and illustrates the three roughness parameters typically used to characterize surface topography. The X-axis illustrates the peak widths, identified as capital S subscript small I, and includes four sample lengths (capital S subscript 1 through capital S subscript 4). The Y-axis is capital R subscript small T, defined as the maximum height of the profile or the height of the peak plus the height of the valley. Also shown in red are the reference mean line, small X, and the vertical mean height, small Z. The maximum peak and the maximum valley are each identified on the profile trace. Two formulas are shown below the trace. The mean spacing parameter, capital S subscript small M, is the average width of a peak over the evaluation length. The average roughness, capital R subscript small A, is the quotient of the integral of the absolute value of the roughness profile height divided by the evaluation length, the integral also being the area between the roughness profile and its mean line.

Figure 18. Photo and Graph. Surface characteristics of Lancaster FRP composite pile. This figure consists of a photograph of the Lancaster FRP pile surface and a graph of its corresponding surface roughness profile. The photograph reveals a diagonally linear surface texture, shown with a scale of 5 millimeters (0.2 inches). The X-axis of the surface roughness profile is distance in millimeters (0 to 30) (0 to 1.2 inches) and the Y-axis is height in millimeters (negative 0.25 to positive 0.25) (negative 0.01 inches to positive 0.01 inches). Peaks' heights varied narrowly between negative 0.05 millimeters (0.002 inches) and positive 0.05 millimeters (0.002 inches).

Figure 19. Photo and Graph. Surface characteristics of Hardcore FRP composite pile. This figure consists of a photograph of the Hardcore FRP pile surface and a graph of its corresponding surface roughness profile. The photograph reveals an irregular and bumpy surface texture, shown with a scale of 5 millimeters (0.2 inches). The X-axis of the surface roughness profile is distance in millimeters (0 to 30) (0 to 1.2 inches) and the Y-axis is height in millimeters (negative 0.25 to positive 0.25) (negative 0.01 inches to positive 0.01 inches). Peaks' heights varied between negative 0.1 millimeter (0.0039 inches) and about positive 0.07 millimeters (0.0027 inches).

Figure 20. Photo and Graph. Surface characteristics of Hardcore FRP plate. This figure consists of a photograph of the Hardcore FRP plate surface and a graph of its corresponding surface roughness profile. The photograph reveals a faint zigzag surface texture, shown with a scale of 5 millimeters (0.2 inches). The X-axis of the surface roughness profile is distance in millimeters (0 to 30) (0 to 1.2 inches) and the Y-axis is height in millimeters (negative 0.25 to positive 0.25) (negative 0.01 inches to positive 0.01 inches). Peaks' heights varied narrowly between negative 0.06 millimeters (0.0023 inches) and about positive 0.06 millimeters (0.0023 inches).

Figure 21. Photo and Graph. Surface characteristics of Hardcore surface-treated FRP plate. This figure consists of a photograph of the Hardcore surface-treated FRP plate surface and a graph of its corresponding surface roughness profile. The photograph reveals a regularly bumpy surface texture, shown with a scale of 5 millimeters (0.2 inches). The X-axis of the surface roughness profile is distance in millimeters (0 to 30) (0 to 1.2 inches) and the Y-axis is height in millimeters (negative 0.25 to positive 0.25) (negative 0.01 inches to positive 0.01 inches). Peaks' heights varied widely between negative 0.17 millimeters (0.0066 inches) and about positive 0.18 millimeters (0.007 inches).

Figure 22. Photo and Graph. Surface characteristics of Plastic Piling plastic composite pile. This figure consists of a photograph of the Plastic composite pile surface and a graph of its corresponding surface roughness profile. The photograph reveals a regularly swirling surface texture, shown with a scale of 5 millimeters (0.2 inches). The X-axis of the surface roughness profile is distance in millimeters (0 to 30) (0 to 1.2 inches) and the Y-axis is height in millimeters (negative 0.25 to positive 0.25) (negative 0.01 inches to positive 0.01 inches). Peaks' heights varied widely between negative 0.22 millimeters (0.0086 inches) and positive 0.08 millimeters (0.0031 inches).

Figure 23. Photo and Graph. Surface characteristics of prestressed concrete pile. This figure consists of a photograph of the prestressed concrete pile surface and a graph of its corresponding surface roughness profile. The photograph reveals a regularly bumpy surface texture, shown with a scale of 5 millimeters (0.2 inches). The X-axis of the surface roughness profile is distance in millimeters (0 to 30) (0 to 1.2 inches) and the Y-axis is height in millimeters (negative 0.25 to positive 0.25) (negative 0.01 inches to positive 0.01 inches). Peaks' heights varied widely between negative 0.22 and positive 0.09 millimeters (negative 0.0087 and positive 0.0035 inches).

Figure 24. Photo and Graph. Surface characteristics of steel sheet pile. This figure consists of a photograph of the steel sheet pile surface and a graph of its corresponding surface roughness profile. The photograph reveals a slightly bumpy surface texture, shown with a scale of 5 millimeters (0.2 inches). The X-axis of the surface roughness profile is distance in millimeters (0 to 30) (0 to 1.2 inches), and the Y-axis is height in millimeters (negative 0.25 to positive 0.25) (negative 0.01 inches to positive 0.01 inches). Peaks' heights vary narrowly between negative 0.025 millimeters (0.001 inches) and about positive 0.02 millimeters (0.0008 inches).

Figure 25. Illustration. Sketch of modified interface shear test setup. This figure contains schematics of a modified shear box used to accommodate curved surface materials for interface shear testing. The side (left) and end (right) views both identify the locations of the normal load at the top, the shear load at the sides, the test soil contained within the box, and the FRP shell section. The side view also shows a rigid stratum below the FRP shell. The end view shows the curvature in the top half of the shear box that conforms to the curved pile section.

Figure 26. Graphs. Typical interface shear test results for Density sand (sigma prime subscript N approximately equal to 100 kilopascals). This figure consists of two graphs that present the results of the interface shear tests for the composite (A) and conventional (B) pile test materials using a 60- to 66-percent relative Density sand at a normal stress of about 100 kilopascals. On both graphs, the X-axis is interface displacement in millimeters (0 to 12) and the Y-axis is interface shear stress in kilopascals (0 to 90). Among the composite materials (A), the FRP plate with bonded sand showed the highest peak interface shear stress of about 63 kilopascals. The untreated FRP plate, the Hardcore 24-4 FRP shell, and the PPI plastic showed similar peak interface stress values between 55 and 58 kilopascals. A minimal peak interface stress of about 40 kilopascals was recorded for the Lancaster CP40 FRP shell material. Of the two conventional materials (B), the highest peak interface stress, at about 68 kilopascals, was recorded for the prestressed concrete pile material. Peak interface stress for the steel sheet pile material was about 59 kilopascals. Conversion factors are 1 millimeter equals 0.039 inch and 1 kilopascal equals 0.145 poundforce per square inch.

Figure 27. Graphs. Typical interface shear test results for Model sand (sigma prime subscript N approximately equal to 100 kilopascals). This figure consists of two graphs that present the results of the interface shear tests for the composite (A) and conventional (B) pile test materials using a 60- to 65-percent relative density Model sand at a normal stress of about 100 kilopascals. On both graphs, the X-axis is interface displacement in millimeters (0 to 12) and the Y-axis is interface shear stress in kilopascals (0 to 90). Among the composite materials (A), the FRP plate with bonded sand showed the highest peak interface shear stress of about 80 kilopascals, followed by the PPI plastic at 75 kilopascals, and the untreated FRP plate at about 65 kilopascals. Similar results, 50 to 55 kilopascals, were obtained for the Lancaster CP40 FRP shell material and the Hardcore 24-4 FRP shell material. Of the two conventional materials (B), the highest peak interface stress, at about 72 kilopascals, was recorded for the prestressed concrete pile material. Peak interface stress for the steel sheet pile material was about 63 kilopascals. Conversion factors are 1 millimeter equals 0.039 inch and 1 kilopascal equals 0.145 poundforce per square inch.

Figure 28. Graph. Interface shear strength envelopes for Lancaster Composite FRP shell. The X-axis of this graph is effective normal stress in kilopascals (0 to 200). The Y-axis is interface shear stress in kilopascals (0 to 150). The graph has four straight lines rising from the origin on the left to a range between 50 and 110 kilopascals on the right. Two of the lines are solid and indicate peak envelope. The remaining two lines are dashed and indicate constant volume (residual) envelope. The upper solid line is for Model sand and is labeled delta subscript P equals 27.3 degrees. The upper dashed line is for Model sand and is labeled delta subscript CV equals 26 degrees. The lower solid line is for Density sand and is labeled delta subscript P equals 19.7 degrees. The lower dashed line is for Density sand and is labeled delta subscript CV equals 16.6 degrees. The conversion factor is 1 kilopascal equals 0.145 poundforce per square inch.

Figure 29. Graph. Interface shear strength envelopes for Hardcore Composite FRP shell. The X-axis of this graph is effective normal stress in kilopascals (0 to 200). The Y-axis is interface shear stress in kilopascals (0 to 150). The graph has four straight lines rising from the origin on the left to a narrow range between 100 and 110 kilopascals on the right. Two of the lines are solid and indicate peak envelope. The remaining two lines are dashed and indicate constant volume (residual) envelope. The upper solid line is for Model sand and is labeled delta subscript p equals 29.5 degrees. The upper dashed line is for Model sand and is labeled delta subscript CV equals 29.3 degrees. The lower solid line is for Density sand and is labeled delta subscript p equals 29.2 degrees. The lower dashed line is for Density sand and is labeled delta subscript CV equals 27.3 degrees. The conversion factor is 1 kilopascal equals 0.145 poundforce per square inch.

Figure 30. Graph. Interface shear strength envelopes for untreated Hardcore FRP plate. The X-axis of this graph is effective normal stress in kilopascals (0 to 200). The Y-axis is interface shear stress in kilopascals (0 to 150). The graph has four straight lines rising from the origin on the left to a range between 90 and 130 kilopascals on the right. Two of the lines are solid and indicate peak envelope. The remaining two lines are dashed and indicate constant volume (residual) envelope. The upper solid line is for Model sand and is labeled delta subscript P equals 31.7 degrees. The upper dashed line is for Model sand and is labeled delta subscript CV equals 28 degrees. The lower solid line is for Density sand and is labeled delta subscript P equals 28.4 degrees. The lower dashed line is for Density sand and is labeled delta subscript CV equals 25.7 degrees. The conversion factor is 1 kilopascal equals 0.145 poundforce per square inch.

Figure 31. Graph. Interface shear strength envelopes for treated Hardcore FRP plate. The X-axis of this graph is effective normal stress in kilopascals (0 to 200). The Y-axis is interface shear stress in kilopascals (0 to 150). The graph has four straight lines rising from the origin on the left to a range between 110 and 150 kilopascals on the right. Two of the lines are solid and indicate peak envelope. The remaining two lines are dashed and indicate constant volume (residual) envelope. The upper solid line is for Model sand and is labeled delta subscript P equals 37.3 degrees. The upper dashed line is for Model sand and is labeled delta subscript CV equals 32.6 degrees. The lower solid line is for Density sand and is labeled delta subscript P equals 31.9 degrees. The lower dashed line is for Density sand and is labeled delta subscript CV equals 27.8 degrees. The conversion factor is 1 kilopascal equals 0.145 poundforce per square inch.

Figure 32. Graph. Interface shear strength envelopes for PPI plastic. The X-axis of this graph is effective normal stress in kilopascals (0 to 200). The Y-axis is interface shear stress in kilopascals (0 to 150). The graph has four straight lines rising from the origin on the left to a range between 90 and 140 kilopascals on the right. Two of the lines are solid and indicate peak envelope. The remaining two lines are dashed and indicate constant volume (residual) envelope. The upper solid line is for Model sand and is labeled delta subscript P equals 33.4 degrees. The upper dashed line is for Model sand and is labeled delta subscript CV equals 28.8 degrees. The lower solid line is for Density sand and is labeled delta subscript P equals 27.6 degrees. The lower dashed line is for Density sand and is labeled delta subscript CV equals 24.9 degrees. The conversion factor is 1 kilopascal equals 0.145 poundforce per square inch.

Figure 33. Graph. Interface shear strength envelopes for concrete. The X-axis of this graph is effective normal stress in kilopascals (0 to 200). The Y-axis is interface shear stress in kilopascals (0 to 150). The graph has four straight lines rising from the origin on the left to a range between 110 and 150 kilopascals on the right. Two of the lines are solid and indicate peak envelope. The remaining two lines are dashed and indicate constant volume (residual) envelope. The upper solid line is for Model sand and is labeled delta subscript P equals 34.3 degrees. The upper dashed line is for Model sand and is labeled delta subscript CV equals 28.0 degrees. The lower solid line is for Density sand and is labeled delta subscript P equals 33 degrees. The lower dashed line is for Density sand and is labeled delta subscript CV equals 27.7 degrees. The conversion factor is 1 kilopascal equals 0.145 poundforce per square inch.

Figure 34. Graph. Interface shear strength envelopes for steel. The X-axis of this graph is effective normal stress in kilopascals (0 to 200). The Y-axis is interface shear stress in kilopascals (0 to 150). The graph has four straight lines rising from the origin on the left to a range between 90 and 130 kilopascals on the right. Two of the lines are solid and indicate peak envelope. The remaining two lines are dashed and indicate constant volume (residual) envelope. The upper solid line is for Model sand and is labeled delta subscript p equals 31.2 degrees. The upper dashed line is for Model sand and is labeled delta subscript CV equals 28.6 degrees. The lower solid line is for Density sand and is labeled delta subscript P equals 28.2 degrees. The lower dashed line is for Density sand and is labeled delta subscript CV equals 25.1 degrees. The conversion factor is 1 kilopascal equals 0.145 poundforce per square inch.

Figure 35. Graph. Multiple linear regression on Density sand tan (delta subscript peak) values. The X-axis of this graph is tan (delta subscript peak) from multiple linear regression and ranges from 0.3 to 0.8. The Y-axis is measured tan (delta subscript peak) and ranges from 0.3 to 0.8. The trend line stretches from the origin in the lower left corner to the upper right corner. One of the seven data points is located on the trend line, three are located below it, and three are located above. The coefficient of determination, or R squared, for this fit was 0.662.

Figure 36. Graph. Multiple linear regression on Density sand tan (delta subscript CV) values. The X-axis of this graph is tan (delta subscript CV) from multiple linear regression and ranges from 0.3 to 0.7. The Y-axis is measured tan (delta subscript CV) and ranges from 0.3 to 0.7. The trend line stretches from the origin in the lower left corner to the upper right corner. Three of the seven data points touch the trend line, two are located below it, and two are located above. The coefficient of determination, or R squared, for this fit was 0.581.

Figure 37. Graph. Multiple linear regression on Model sand tan (delta subscript peak) values. The X-axis of this graph is tan (delta subscript peak) from multiple linear regression and ranges from 0.3 to 0.8. The Y-axis is measured tan (delta subscript peak) and ranges from 0.3 to 0.8. The trend line stretches from the origin in the lower left corner to the upper right corner. Four of the seven data points touch the trend line, one is located below it, and two are located above. The coefficient of determination, or R squared, for this fit was 0.892.

Figure 38. Graph. Multiple linear regression on Model sand tan (delta subscript CV) values. The X-axis of this graph is tan (delta subscript CV) from multiple linear regression and ranges from 0.3 to 0.8. The Y-axis is measured tan (delta subscript CV) and ranges from 0.3 to 0.8. The trend line stretches from the origin in the lower left corner to the upper right corner. Two of the seven data points touch the trend line, three are located below it, and two are located above. The coefficient of determination, or R squared, for this fit was 0.474.

Figure 39. Photos. Burnoff testing. This figure consists of two color photographs. The left photograph (A) is the furnace oven used for burnoff testing conducted in this study. The oven is cylindrical in shape and appears to be a laboratory bench-top size. The right photograph (B) is an FRP coupon sample after the resin matrix is burned off in the oven. The photograph shows the diagonal orientation of the fibers and the direction of the longitudinal axis.

Figure 40. Photo. Typical tension test setup. This figure is a color photograph of the setup used to conduct the axial tension tests to evaluate tension properties of the composite materials. The setup consists of a floor-model INSTRON^®test frame, and shows the vertical alignment of the test grips and the load cell.

Figure 41. Photos. Typical split disk test setup. This figure consists of two color photographs of custom-made split disk fixtures used to conduct the hoop tension tests on precision-cut ring specimens of the composite materials. The left photograph (A) shows a closeup of the 61-centimeter (24-inch) split disk fixture containing a sample. The right photograph (B) shows the 30.5-centimeter (12-inch) split disk fixture containing a sample and mounted in the INSTRON^®test frame.

Figure 42. Photo. Freeze-thaw chamber. This figure is a color photograph of the programmable freeze-thaw chamber used to conduct a series of freeze-thaw tests on the composite materials. The figure shows the chamber with the door opened, revealing the stainless steel interior, shelf, and specimen fixture.

Figure 43. Photo and Illustration. Freeze-thaw fixture. This left side (A) of this figure is a color photograph of the freeze-thaw specimen fixture. The fixture is shown with the Lancaster 61-centimeter (24-inch) samples loaded in 4-point bending. On the right side (B) of the figure is a line drawing illustrating, in a cross-section view, 4-point bending of the sample. It shows a slightly bent sample subjected to the fixed 4-point surface strain.

Figure 44. Graph. Average freeze-thaw cycle undergone by FRP samples. This figure illustrates a typical freeze-thaw cycle. The X-axis is time in hours (0 to 3) and the Y-axis is sample temperature in degrees centigrade (negative 20 to positive 10) (negative 4 degrees Fahrenheit to positive 50 degrees Fahrenheit). The figure shows the temperature of the sample, beginning at 0 degrees centigrade (32 degrees Fahrenheit), climbing rapidly to about 6 degrees centigrade (43 degrees Fahrenheit) in 0.3 hours, declining to about negative 17 degrees centigrade (1.4 degrees Fahrenheit) by 2 hours, and rising again to 0 degrees centigrade (32 degrees Fahrenheit) at 2.4 hours, the time for one complete freeze-thaw cycle. Corresponding text on the chart indicates a minimum temperature of negative 17 degrees centigrade (1 degree Fahrenheit) and a maximum temperature of 5.6 degrees centigrade (42 degrees Fahrenheit). One complete cycle consists of a 20-percent thaw and an 80-percent freeze component.

Figure 45. Graph. Representative baseline longitudinal tension stress-strain curves. The figure presents baseline typical axial tension stress-strain curves for the 30.5-centimeter (12-inch) and 61-centimeter (24-inch) Lancaster FRP, and for the 30.5-centimeter (12-inch) and 61-centimeter (24-inch) Hardcore FRP. The X-axis is strain in percent (0 to 2) and the Y-axis is tensile stress in megapascals (0 to 600). The graph indicates that the 30.5-centimeter (12-inch) Hardcore FRP tube exhibited the highest tensile stress, rising to approximately 475 megapascals at a strain of 1.8 percent. The 61-centimeter (24-inch) Lancaster FRP showed the lowest tensile stress, rising to approximately 100 megapascals at a strain of 1 percent. The 61-centimeter (24-inch) Hardcore FRP rose to approximately 425 megapascals at a strain of 1.8 percent, and the 30.5-centimeter (12-inch) Lancaster FRP rose to a peak of approximately 250 megapascals at a strain of 1.5 percent. One megapascal equals 145 pounds-force per square inch.

Figure 46. Graph. Representative baseline hoop tension stress-strain curves. The figure presents baseline hoop tension stress-strain curves for the composite materials determined by the split disk tests. Measurements were made on circular samples of the 30.5-centimeter (12-inch) and 61-centimeter (24-inch) Lancaster FRP and on the 30.5-centimeter (12-inch) Hardcore FRP materials. The X-axis is strain in percent (0 to 1.6) and the Y-axis is tensile stress in megapascals (0 to 250). The chart indicates that the 30.5-centimeter (12-inch) Lancaster FRP material exhibited the highest hoop tensile stress, rising to approximately 190 megapascals at a strain of just under 1.4 percent. The 30.5-centimeter (12-inch) Hardcore FRP material had the lowest tensile stress, rising to approximately 90 megapascals at a strain of just over 1.2 percent. The tensile stress of the 61-centimeter (24-inch) Lancaster FRP materials rose to approximately 120 megapascals at a strain of just under 1.4 percent.

Figure 47. Graph. Absorption curves for Lancaster 12-inch FRP tube. This figure presents the changes over time in the moisture absorption by samples of the 30.5-centimeter (12-inch)Lancaster FRP material at six different water temperatures. The X-axis is the square root of time, time being measured in hours; thus the X-axis is hours to the one-half power (0 to 140). The Y-axis is moisture content in percent (0 to 1.2). The water temperatures of the tests are 22, 35, 45, 55, 65, and 80 degrees centigrade (72, 95, 113, 131, 149, and 176 degrees Fahrenheit). Six curves, one for each water temperature, are shown on the graph. Except for the sample immersed in 80-degree-centigrade (176-degree-Fahrenheit) water, the moisture content of the samples increases rapidly near the beginning of the tests and generally stabilizes. At all five test temperatures, except the highest, the maximum moisture content of the samples is near or below 0.4 percent after 577 days. For the test conducted at 80 degrees centigrade (176 degrees Fahrenheit), maximum moisture content of the sample increases dramatically to about 1 percent at 100 square root hours. In general, the results indicate that moisture absorption by the 30.5-centimeter (12-inch)Lancaster samples increases as the water temperature increases.

Figure 48. Absorption curves for Lancaster 24-inch FRP tube. Chart. This figure presents the changes over time in the moisture absorption by samples of the 61-centimeter (24-inch)Lancaster FRP material at six different water temperatures. The X-axis is the square root of time, time being measured in hours; thus the X-axis is hours to the one-half power (0 to 160). The Y-axis is moisture content in percent (0 to 1.6). The water temperatures of the tests are 22, 35, 45, 55, 65, and 80 degrees centigrade (72, 95, 113, 131, 149, and 176 degrees Fahrenheit). Six curves, one for each water temperature, are shown on the graph. The moisture content of the samples at the four lowest temperatures increases rapidly near the beginning of the tests and generally stabilizes near the maximum. After 819 days, the moisture content of the samples at these four lowest temperatures is below about 0.6 percent. For the test conducted at 65 degrees centigrade (149 degrees Fahrenheit), maximum moisture content of the sample increases dramatically to a maximum of almost 1.2 percent and does not appear to level off. Moisture content of the sample tested at 80 degrees centigrade (176 degrees Fahrenheit) increases rapidly, peaks at about 1.5 percent at approximately 60 square root hours, and then sharply decreases to nearly zero.

Figure 49. Graph. Absorption curves for Hardcore 12-inch FRP tube. This figure presents the changes over time in the moisture absorption by samples of the 30.5-centimeter (12-inch) Hardcore FRP material at six different water temperatures. The X-axis is the square root of time, time being measured in hours; thus the X-axis is hours to the one-half power (0 to 140). The Y-axis is moisture content in percent (0 to 1.8). The water temperatures of the tests are 22, 35, 45, 55, 65, and 80 degrees centigrade (72, 95, 113, 131, 149, and 176 degrees Fahrenheit). Six curves, one for each water temperature, are shown on the graph. For the five lowest temperature, the moisture content of the samples increases rapidly near the beginning of the tests and generally stabilizes near the maximum. At these five test temperatures, the maximum moisture content of the samples is near or below about 0.25 percent after 578 days. For the test conducted at 80 degrees centigrade (176 degrees Fahrenheit), moisture content of the Hardcore sample increases dramatically to a maximum of about 1.7 percent and shows no sign of leveling off..

Figure 50. Graph. Absorption curves for Hardcore 24-inch FRP tube. This figure presents the changes over time in the moisture absorption by samples of the 61-centimeter (24-inch) Hardcore FRP material at six different water temperatures. The X-axis is the square root of time, time being measured in hours; thus the X-axis is hours to the one-half power (0 to 160). The Y-axis is moisture content in percent (0 to 0.5). The water temperatures of the tests are 22, 35, 45, 55, 65, and 80 degrees centigrade (72, 95, 113, 131, 149, and 176 degrees Fahrenheit). Six curves, one for each water temperature, are shown on the graph. The absorption curves are similar for the samples tested at the five lowest water temperatures. The moisture content for these five groups of samples increases rapidly near the beginning of the tests and generally stabilizes. The moisture content of the samples immersed at these temperatures is between 0.2 and 0.3 percent after 681 days. The moisture content of the sample immersed in 80-degree-centigrade (176-degree-Fahrenheit) water reaches a maximum of about 0.45 percent and shows no sign of leveling off.

Figure 51. Graphs. Selected diffusion analyses for Lancaster 12-inch FRP samples. This figure consists of three graphs, each representing a unique test temperature and two curve fits of the experimentally obtained absorption data for the Lancaster 30.5-centimeter (12-inch) FRP samples using both the Fickian diffusion model and the Langmuirian diffusion model. The top graph (A) presents data for the 22-degree-centigrade (72-degree-Fahrenheit) water; the middle graph (B) presents the 45-degree-centigrade (113-degree-Fahrenheit) water test results; and the bottom graph (C) shows the 65-degree-centigrade (149-degree-Fahrenheit) data. On all graphs, the X-axis is the square root of time, time being measured in hours; thus the X-axis is hours to the one-half power (0 to 140). The Y-axis is moisture content in percent (0 to 0.4 or 0.5). The experimental data fit both models well in the initial absorption period and near the maximum absorption at the end of the test. For moisture absorption during the middle of the test period, all three graphs show that the Langmuirian model tracks the experimental absorption data more closely than the Fickian model.

Figure 52. Graphs. Selected diffusion analyses for Lancaster 24-inch FRP samples. This figure consists of three graphs, each representing a unique test temperature and two curve fits of the experimentally obtained absorption data for the Lancaster 61-centimeter (24-inch) FRP samples using both the Fickian diffusion model and the Langmuirian diffusion model. The top graph (A) presents data for the 22-degree-centigrade (72-degree-Fahrenheit) water; the middle graph (B) presents the 45-degree-centigrade (113-degree-Fahrenheit) water test results; and the bottom graph (C) shows the 65-degree-centigrade (149-degree-Fahrenheit) data. On all graphs, the X-axis is the square root of time, time being measured in hours; thus the X-axis is hours to the one-half power (0 to 160; 0 to 160; and 0 to 180). The Y-axis is moisture content in percent (0 to 0.6; 0 to 0.5; and 0 to 1.4). For the 22-degree-centigrade (72-degree-Fahrenheit) test (graph A) and the 45-degree-centigrade (113-degree-Fahrenheit) test (graph B), the experimental data fit both models well in the initial absorption period and near the maximum absorption at the end of the test. For moisture absorption during the middle of the test period, graph A and graph B show that the Langmuirian model tracks the experimental absorption data more closely than the Fickian model. The 65-degree-centigrade (149-degree-Fahrenheit) test data (graph C) appears to be tracked more closely by the Langmuirian model during the duration of the test.

Figure 53. Graphs. Selected diffusion analyses for Hardcore 12-inch FRP samples. This figure consists of three graphs, each representing a unique test temperature and two curve fits of the experimentally obtained absorption data for the Hardcore 30.5-centimeter (12-inch) FRP samples using both the Fickian diffusion model and the Langmuirian diffusion model. The top graph (A) presents data for the 22-degree-centigrade (72-degree-Fahrenheit) water; the middle graph (B) presents the 45-degree-centigrade (113-degree-Fahrenheit) water test results; and the bottom graph (C) shows the 65-degree-centigrade (149-degree-Fahrenheit) data. On all graphs, the X-axis is the square root of time, time being measured in hours; thus the X-axis is hours to the one-half power (0 to 140). The Y-axis is moisture content in percent (0 to 0.25 or 0.30). The curves from the Langmuirian and Fickian models are very similar in the three charts, and both models track the experimental data fairly well and fairly similarly, although the 45-degree-centigrade (113-degree-Fahrenheit) data (graph B) are slightly more aligned with the Langmuirian model curve.

Figure 54. Graphs. Selected diffusion analyses for Hardcore 24-inch FRP samples. This figure consists of three graphs, each representing a unique test temperature and two curve fits of the experimentally obtained absorption data for the Hardcore 61-centimeter (24-inch) FRP samples using both the Fickian diffusion model and the Langmuirian diffusion model. The top graph (A) presents data for the 22-degree-centigrade (72-degrees Fahrenheit) water; the middle graph (B) presents the 45-degree-centigrade (113-degree-Fahrenheit) water test results; and the bottom graph (C) shows the 65-degree-centigrade (149-degree-Fahrenheit) data. On all graphs, the X-axis is the square root of time, time being measured in hours; thus the X-axis is hours to the one-half power (0 to 140). The Y-axis is moisture content in percent (0 to 0.3 or 0.25). The experimental data fit both models well in the initial absorption period and near the maximum absorption at the end of the test. For moisture absorption during the middle of the test period, all three graphs show that the Langmuirian model tracks the experimental absorption data more closely than the Fickian model.

Figure 55. Graph. Longitudinal tensile properties versus submergence time for Lancaster 24-inch FRP tube. This figure is a bar graph presenting the variations in three longitudinal tensile properties of the 61-centimeter (24-inch) Lancaster FRP sample with time submerged in the water. The X-axis is submergence time in days (0, 4, 10, 26, 66, 185, 444, and 787) and the Y-axis is the normalized value of the tensile property (0 to 1.4). For each of the eight submergence times, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is considerable scatter in the data sets. Based on the longitudinal tensile property data obtained over the period of submergence, no significant degradation is indicated.

Figure 56. Graph. Hoop tensile properties versus submergence time for Lancaster 24-inch FRP tube. This figure is a bar graph presenting the variations in three hoop tensile properties of the 61-centimeter (24-inch) Lancaster FRP sample with time submerged in the water. The X-axis is submergence time in days (0, 55, 127, 252, 391, and 525) and the Y-axis is the normalized value of the tensile property (0 to 1.4). For each of the six submergence times, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is considerable scatter in the data sets. Over the 525-day period of submergence, the hoop tensile strength showed the least change, decreasing by only 8 percent. Initial stiffness and strain to failure revealed greater degradation, but not to a significant extent.

Figure 57. Graph. Longitudinal tensile properties versus submergence time for Lancaster 12-inch FRP tube. This figure is a bar graph presenting the variations in three longitudinal tensile properties of the 30.5-centimeter (12-inch) Lancaster FRP sample with time submerged in the water. The X-axis is submergence time in days (0, 56, 116, 253, and 399) and the Y-axis is the normalized value of the tensile property (0 to 1.4). For each of the five submergence times, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is some scatter in the data sets, but less than that observed for the 61-centimeter (24-inch)Lancaster samples. After nearly 400 days of submergence, the longitudinal tensile property showing the greatest degradation is the strain to failure, which decreased nearly 20 percent in the 30.5-centimeter (12-inch)Lancaster sample. The data indicate a smaller decline in tensile strength over the same time period. Little variation in the initial stiffness parameter is shown.

Figure 58. Graph. Hoop tensile properties versus submergence time for Lancaster 12-inch FRP tube. This figure is a bar graph presenting the variations in three hoop tensile properties of the 30.5-centimeter (12-inch) Lancaster FRP sample with time submerged in the water. The X-axis is submergence time in days (0, 102, 254, 384, and 453) and the Y-axis is the normalized value of the tensile property (0 to 1.4). For each of the five submergence times, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is some scatter in the data sets. Over the 453-day period of submergence, the hoop tensile strength and initial stiffness both decreased by about 18 percent, significantly more than observed for the 61-centimeter (24-inch)Lancaster sample. The strain-to-failure parameter revealed the least amount of variation, remaining relatively constant over time.

Figure 59. Charts. Longitudinal tensile properties versus moisture content for Lancaster 12-inch FRP tube. This figure consists of two scatter charts illustrating the effect of moisture content on longitudinal tensile strength and stiffness of the 30.5-centimeter (12-inch) Lancaster FRP sample. The top chart (A) presents the variation in tensile strength with increases in moisture content and the bottom chart (B) presents the variation in stiffness with increases in moisture content. The X-axis on both charts is moisture content in percent (0 to 0.6), and the Y-axis is the normalized value of each parameter (0 to 1.2 and 0 to 1.4). Individual data points, representing normalized values for each parameter, are shown primarily for moisture contents between 0.2 and 0.5 percent, corresponding to about 26 and 420 days submergence, respectively. Chart A indicates that longitudinal tensile strength of the 30.5-centimeter (12-inch) Lancaster FRP sample declines gradually as the moisture content increases, but at the higher end of the moisture scale, the tensile strength stabilizes. Chart B indicates that this trend is not evident for the longitudinal stiffness parameter. Between 0.2 and 0.5 percent moisture, stiffness data points are scattered irregularly around the baseline value of 1.

Figure 60. Charts. Hoop tensile properties versus moisture content for Lancaster 12-inch FRP tube. This figure consists of two scatter charts illustrating the effect of moisture content on hoop tensile strength and stiffness of the 30.5-centimeter (12-inch) Lancaster FRP sample. The top chart (A) presents the variation in tensile strength with increases in moisture content and the bottom chart (B) presents the variation in stiffness with increases in moisture content. The X-axis on both charts is moisture content in percent (0 to 0.8), and the Y-axis is the normalized value of each parameter (0 to 1.2 and 0 to 1.4). Individual data points, representing normalized values for each parameter, are shown across the full moisture content scale. Chart A indicates that hoop tensile strength of the 30.5-centimeter (12-inch) Lancaster FRP sample declines gradually as the moisture content increases, but at the higher end of the moisture scale (0.6 to 0.8 percent), this decline appears to stabilize. The data points on chart B indicate a similar behavior, showing a gradual decline in the stiffness with increased moisture content. At moisture levels greater than about 0.4 percent, stiffness values for the 30.5-centimeter (12-inch)Lancaster sample appear to stabilize.

Figure 61. Graph. Longitudinal tensile properties versus submergence time for Hardcore 24-inch FRP tube. This figure is a bar graph presenting the variations in three longitudinal tensile properties of the 61-centimeter (24-inch) Hardcore FRP sample with time submerged in the water. The X-axis is submergence time in days (0, 71, 111, 161, and 636), and the Y-axis is the normalized value of the tensile property (0 to 1.4). For each of the five submergence times, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is considerable scatter in the initial stiffness and the strain to failure data sets. The bar graph indicates that, after 636 days of submergence, the longitudinal tensile strength declined by about 13 percent and the strain-to-failure parameter decreased by about 20 percent. No trend for initial stiffness is apparent.

Figure 62. Charts. Longitudinal tensile properties versus moisture content for Hardcore 24-inch FRP tube. This figure consists of two scatter charts illustrating the effect of moisture content on longitudinal tensile strength and initial stiffness of the 61-centimeter (24-inch) Hardcore FRP sample. The top chart (A) presents the variation in tensile strength with increases in moisture content and the bottom chart (B) presents the variation in stiffness with increases in moisture content. The X-axis on both charts is moisture content in percent (0 to 0.3), and the Y-axis is the normalized value of each parameter (0 to 1.4 and 0 to 1.6). Individual data points, representing normalized values for each parameter, are shown primarily for moisture contents between 0.1 and 0.3 percent. Chart A indicates that longitudinal tensile strength of the 61-centimeter (24-inch) Hardcore FRP sample declines gradually as the moisture content increases. The data show a 16-percent decline in longitudinal tensile strength at the highest moisture content of 0.33 percent. The stiffness data points on chart B are widely scattered around the baseline and do not suggest any obvious trends.

Figure 63. Graph. Longitudinal tensile properties versus submergence time for Hardcore 12-inch FRP tube. This figure is a bar graph presenting the variations in three longitudinal tensile properties of the 30.5-centimeter (12-inch) Hardcore FRP sample with time submerged in the water. The X-axis is submergence time in days (0, 42, 115, 252, and 398) and the Y-axis is the normalized value of the tensile property (0 to 1.6). For each of the five submergence times, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is considerable scatter in the data sets. After nearly 400 days of submergence, the longitudinal tensile strength and the strain to failure parameters for the 30.5-centimeter (12-inch) Hardcore sample each declined by approximately 25 percent. Over the same time period, the initial stiffness increased by about 10 percent.

Figure 64. Graph. Hoop tensile properties versus submergence time for Hardcore 12-inch FRP tube. This figure is a bar graph presenting the variations in three hoop tensile properties of the 30.5-centimeter (12-inch) Hardcore FRP sample with time submerged in the water. The X-axis is submergence time in days (0, 118, 265, 401, and 464) and the Y-axis is the normalized value of the tensile property (0 to 2). For each of the five submergence times, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. Over the 464-day period of submergence, the data indicate that the hoop tensile strength decreased by about 20 percent. The error bars reveal relatively high scatter among the data sets for initial stiffness and strain to failure, hindering the identification of any trends over time.

Figure 65. Charts. Longitudinal tensile properties versus moisture content for Hardcore 12-inch FRP tube. This figure consists of two scatter charts illustrating the effect of moisture content on longitudinal tensile strength and stiffness of the 30.5-centimeter (12-inch) Hardcore FRP sample. The top chart (A) presents the variation in tensile strength with increases in moisture content and the bottom chart (B) presents the variation in stiffness with increases in moisture content. The X-axis on both charts is moisture content in percent (0 to 0.35) and the Y-axis is the normalized value of each parameter (0 to 1.2 and 0 to 1.8). Individual data points, representing normalized values for each parameter, are shown primarily for moisture contents between 0.1 and 0.3 percent. Chart A indicates that longitudinal tensile strength of the 30.5-centimeter (12-inch) Hardcore FRP sample declines as the moisture content increases. A 25-percent maximum degradation in tensile strength occurs at a moisture content of about 0.25 percent. The stiffness data points on chart B are widely scattered primarily above the baseline and do not suggest any obvious trends.

Figure 66. Charts. Hoop tensile properties versus moisture content for Hardcore 12-inch FRP tube. This figure consists of two scatter charts illustrating the effect of moisture content on hoop tensile strength and stiffness of the 30.5-centimeter (12-inch) Hardcore FRP sample. The top chart (A) presents the variation in tensile strength with increases in moisture content and the bottom chart (B) presents the variation in stiffness with increases in moisture content. The X-axis on both charts is moisture content in percent (0 to 0.8) and the Y-axis is the normalized value of each parameter (0 to 1.4). Individual data points, representing normalized values for each parameter, are shown primarily for moisture contents between 0.2 and 0.7 percent. The widely scattered data sets for hoop tensile strength and stiffness shown in charts A and B, respectively, preclude identification of any trends.

Figure 67. Graph. Influence of freeze-thaw cycling on the longitudinal tensile properties for the Lancaster 24-inch FRP tube. This figure is a bar graph presenting variations in three longitudinal tensile properties of the 61-centimeter (24-inch) Lancaster FRP sample with freeze-thaw cycles. The X-axis is the number of freeze-thaw cycles (0, 100, 300, and 500) and the Y-axis is the normalized value of the tensile property (0 to 1.5). For each of the four freeze-thaw cycles, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is some scatter in the data sets. The most notable change after 500 freeze-thaw cycles is the longitudinal tensile strength, which declined by about 25 percent. Taking the standard deviations into account, the variation in the initial stiffness and the strain to failure parameters is minor.

Figure 68. Graph. Influence of freeze-thaw cycling on the longitudinal tensile properties for the Lancaster 12-inch FRP tube. This figure is a bar graph presenting variations in three longitudinal tensile properties of the 30.5-centimeter (12-inch) Lancaster FRP sample with freeze-thaw cycles. The X-axis is the number of freeze-thaw cycles (0, 100, 300, and 500) and the Y-axis is the normalized value of the tensile property (0 to 1.75). For each of the four freeze-thaw cycles, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is significant scatter in the data sets. Taking the data scatter into account, the variations in the three tensile properties over 500 freeze-thaw cycles appear to be minor.

Figure 69. Graph. Influence of freeze-thaw cycling on the longitudinal tensile properties for the Hardcore 24-inch FRP tube. This figure is a bar graph presenting variations in three longitudinal tensile properties of the 61-centimeter (24-inch) Hardcore FRP sample with freeze-thaw cycles. The X-axis is the number of freeze-thaw cycles (0, 100, 300, and 500) and the Y-axis is the normalized value of the tensile property (0 to 1.5). For each of the four freeze-thaw cycles, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is some scatter in the data sets. Taking the data scatter into account, the variations in the three tensile properties over 500 freeze-thaw cycles appear to be minor.

Figure 70. Graph. Influence of freeze-thaw cycling on the longitudinal tensile properties for the Hardcore 12-inch FRP tube. This figure is a bar graph presenting variations in three longitudinal tensile properties of the 30.5-centimeter (12-inch) Hardcore FRP sample with freeze-thaw cycles. The X-axis is the number of freeze-thaw cycles (0 and 500) and the Y-axis is the normalized value of the tensile property (0 to 1.5). For each of the two freeze-thaw cycles, three normalized vertical property bars are given: one for strength, one for initial stiffness, and one for strain to failure. Error bars for plus and minus one standard deviation are shown on each of the property bars. The error bar brackets reveal that there is some scatter, primarily in the strain-to-failure data set. The bar chart does not show degradation in any of the three longitudinal tensile properties of the 30.5-centimeter (12-inch) Hardcore sample after 500 freeze-thaw cycles.

Figure 71. Photo. SEM images of Lancaster 24-inch FRP tube. This figure consists of three black-and-white scanning electron micrographs of the 61-centimeter (24-inch) Lancaster FRP material. The first micrograph (A) on the left is the material in the original condition it was received. The center micrograph (B) is a sample at moisture saturation, and the sample shown on the right (C) is after freeze-thaw cycling. All micrographs are magnified times 1000. In the condition received, as shown in micrograph A, the micrograph shows densely packed circular components with entire margins. At moisture saturation (B), the micrograph shows circular components with some fraying at the margins. After freeze-thaw cycles (C), the micrograph appears similar to that of the original condition and consists of circular components showing no sign of fraying at the margins.

Figure 72. Photo. SEM images of Lancaster 12-inch FRP tube. This figure consists of three black-and-white scanning electron micrographs of the 30.5-centimeter (12-inch) Lancaster FRP material. The first micrograph (A) on the left is the material in the original condition it was received. The center micrograph (B) is a sample at moisture saturation, and the sample shown on the right (C) is after freeze-thaw cycling. All micrographs are magnified times 1000. In the condition received (A), the micrograph shows densely packed circular components with entire margins and some variation in size. At moisture saturation (B), the micrograph is similar to that of the original condition with no evidence of damage. After the freeze-thaw cycles (C), the micrograph appears similar to the original and consists of densely packed circular components of varying size. No evidence of damage is visible.

Figure 73. Photo. SEM images of Hardcore 24-inch FRP tube. This figure consists of three black-and-white scanning electron micrographs of the 61-centimeter (24-inch) Hardcore FRP material. The first micrograph (A) on the left is the material in the original condition it was received. The center micrograph (B) is a sample at moisture saturation, and the sample shown on the right (C) is after freeze-thaw cycling. All micrographs are magnified times 1000. In the condition received (A), the micrograph shows circular components with entire margins and some variation in size. At moisture saturation (B), the micrograph consists of circular components with some evidence of fraying at the margins. After the freeze-thaw cycles (C), the micrograph appears similar to that of the original material and consists of densely packed circular components of varying size. No evidence of damage is visible.

Figure 74. Photo. SEM images of Hardcore 12-inch FRP tube. This figure consists of three black-and-white scanning electron micrographs of the 30.5-centimeter (12-inch) Hardcore FRP material. The first micrograph (A) on the left is the material in the original condition it was received. The center micrograph (B) is a sample at moisture saturation, and the sample shown on the right (C) is after freeze-thaw cycling. All micrographs are magnified times 1000. In the condition received (A), the micrograph consists of circular components with entire margins and some variation in size. Also shown are longitudinally oriented fibers. At moisture saturation (B), the micrograph consists of circular components, many with evidence of fraying at the margins. After the freeze-thaw cycles (C), the micrograph is similar to that of the original and consists of densely packed circular components of varying size. No evidence of damage is visible.

Figure 75. Graph. Estimated long-term axial capacity of the 12-inch Lancaster pile. This figure presents the axial load-strain response curve for a 30.5-centimeter (12-inch)Lancaster pile. The X-axis is axial strain in units of microstrain (0 to 16) and the Y-axis is axial load in kilonewtons (0 to 5000). Two curves are shown originating from zero. A solid line represents a typical axial load-strain response curve determined from the Fam and Rizkalla model and based on the hoop properties of the original 30.5-centimeter (12-inch) Lancaster FRP material as it was received. Between an axial strain of 0 and 1 microstrains, the axial load increases rapidly to 1500 kilonewtons. Thereafter, the slope of the line is less steep. At approximately 14 microstrains, the line reaches 4500 kilonewtons. Paralleling this load-strain response curve is a second dotted-line long-term load-strain curve that represents a 5-percent reduction in axial structural capacity. This second curve suggests that the impact of degradation of the FRP mechanical properties on the long-term axial structural capacity of the concrete-filled FRP composite pile is small due to the fact that the majority of the capacity contribution is from the concrete infill. The conversion factor for kilonewtons is 1 kilonewton equals 225 poundforce.

Figure 76. Graph. Estimated long-term flexural capacity of the 12-inch Lancaster pile. This figure presents the moment-curvature response for a 30.5-centimeter (12-inch)Lancaster pile. The X-axis is curvature in units of the product of 1 over meters times 10 to the minus 3 (0 to 140) and the Y-axis is moment in kilonewton-meters (0 to 250). Two curves are shown originating from zero. A solid line represents the short-term moment-curvature response determined from the Fam and Rizkalla model and based on the longitudinal properties of the original 30.5-centimeter (12-inch) Lancaster FRP material as it was received. The moment-curvature relationship is somewhat linear, reaching a moment of 200 kilonewton-meters at a curvature of about 110. A second similar moment-curvature response, representing a 24-percent reduction in long-term structural flexural capacity, is shown below the short-term response solid line as a dashed line. This second curve suggests that the impact of degradation of the FRP mechanical properties is significant for the flexural capacity because the FRP shell contributes most of the capacity on the tension side of the pile in flexion. The conversion factor for kilonewton-meters is 1 kilonewton meter equals 737.57 poundforce-feet.

Figure 77. Map. Location map of the Route 40 Bridge project in Sussex County, Virginia (Fam, et al., 2003). This figure consists of two small maps. On the left is a map of the State of Virginia showing several interstate highways and the general location of the bridge project in Sussex County in the southeastern part of the State. On the right is an area map of Sussex County showing the Nottoway River and its tributaries, Interstate 95, State Route 40, State Route 657, the Town of Stony Creek near the junction of Routes 657 and 40, and the location of the Route 40 Bridge.

Figure 78. Photo. Former Route 40 Bridge. The figure is a color photograph of the old Route 40 Bridge across the Nottoway River. The photograph shows the steel truss that is supported by concrete piers.

Figure 79. Photos. Signs of deterioration of the former Route 40 Bridge (Fam, et al., 2003). This figure consists of three color photographs demonstrating cracks and deterioration in the supports. The first photograph (A) is a concrete column of the bridge pier, revealing full-height vertical cracks. Photograph (B) is a closeup of a concrete bearing seat, revealing primarily vertical cracks and spalling. The third photograph (C) shows map cracking horizontally along an abutment bearing seat.

Figure 80. Illustration. Schematic of the new Route 40 Bridge. This figure consists of two simple line drawings illustrating the schematic plans of the new bridge in elevation view and in plan view. The first illustration is an elevation view of the bridge, identifying its overall length of 85.34 meters (280 feet), and a 5-span concrete slab supported by 4 piers and 2 end abutments. The illustration also shows the positions of the battered piles alongside the reinforced concrete beam-type pile structure. The reinforced concrete pile cap is shown joining the piers to the concrete slab. The plan view shows the four piers and the spaced distance between them. From left to right, pier number 1 is located 11.25 meters (37 feet) from the left end abutment. Pier number 2 is located 18.52 meters (61 feet) from pier number 1. Pier number 3 is located 18.52 meters (61 feet) from pier number 2. Pier number 4 is located 18.52 meters (61 feet) from pier number 3 and 18.55 meters (61 feet) from the right end abutment. The plan view also shows the structural components of each pier. Piers number 1, 3, and 4 each consist of 10 prestressed solid square-column concrete piles. Pier number 2 consists of 10 concrete-filled FRP circular tubes for support. The test pile area is shown between piers number 1 and 2.

Figure 81. Photo and Illustration. Concrete-filled tubular piles. This figure consists of two color photographs of the concrete-filled FRP tubes (A) and a simple line drawing of the laminate structure of the composite piles (B). The first photograph depicts four of the tubular composite piles as they are being installed at pier number 2 of the new bridge. The second photograph is a view of the tubular composite piles from below the pier structure, showing 6 of the 10 supporting piles. The line drawing (B) below the photographs illustrates the laminate structure of the composite pile. The composite consists of 5 FRP layers, each 1.13 millimeters (0.044 inches) thick and together comprising the structural wall thickness of the FRP tube. From left to right, in the longitudinal direction, the angles of the fibers in each layer, top to bottom, are identified as positive 35 degrees, negative 35 degrees, positive 85 degrees, positive 35 degrees, and negative 35 degrees. Below these five layers is a 1.68-millimeter- (0.066-inch-) thick inner liner.

Figure 82. Graph. Stress-strain response of concrete used in the composite pile. This figure is a stress-strain graph for the concrete mix used to fill the FRP tube. The X-axis consists of tension strain and compression strain, both in meters per meter. The tension strain is shown between negative 0.002 and 0 meters per meter. Compression strain is shown between 0 and 0.005 meters per meter. The Y-axis is stress in megapascals (negative 10 to positive 70). Data tracings displayed on the chart are from the concrete model and two experimental compression tests on concrete core samples from the composite test pile. The three tracings rise from 0 megapascals at 0.000 meters per meter to approximately 60 megapascals at a compression strain of approximately 0.004 meters per meter. Just to the left of 0.000 meters per meter, the concrete model tracing dips to approximately minus 4 megapascals and then rising abruptly to just below 0 megapascals. At this point, the tracing is labeled "residual tensile strength due to tension stiffening." The tensile strength of the concrete mix, based on Brazilian tensions tests, is 4.35 megapascals.

Figure 83. Illustration. Reinforcement details of prestressed concrete pile. This figure consists of two simple line drawings showing details of the prestressed concrete pile. The first drawing is a cross section of the 508-millimeter- (20-inch-) square concrete pile showing the 14 seven-wire strands arranged evenly around and 75 millimeters (2.9 inches) in from the perimeter of the pile. Each seven-wire strand is approximately 13 millimeters (0.5 inches) in diameter. The second figure is a horizontal view of the concrete pile showing the overall length of 13.1 meters (43 feet), and the locations of the wire spiral turns along the length of the pile. The wire ties are identified as number 16M (number 5) gage spiral wire. At both ends of the column, the wire is shown with approximately 5 turns in 25 millimeters (0.98 inches). The next segments toward the middle show approximately 16 turns in 75 millimeters (2.9 inches).

Figure 84. Illustration. Simplified soil stratigraphy near test pile area. This figure consists of an illustrated soil column, identifying general soil layers below the surface, and an adjacent chart displaying standard penetration test blow counts versus depth. The soil column depicts five defined layers that correspond to the adjacent chart of blow counts. From top to bottom, they are (1) between the surface and 3.5 meters (11.5 feet) depth, a brown medium-fine loose sand with some fine gravel and traces of silt; the blow count average is about 5 per 0.3 meters (about 1 foot); (2) between about 3.5 meters (11.5 feet) and 6 meters (19.7 feet), a brown fine-grained medium-dense sand, silty with some gravel; the blow count is about 16 per 0.3 meters (1 foot); (3) between 6 meters (19.7 feet) and 8 meters (26.2 feet), a gray fine-grained medium-dense sand, silty with some gravel; the blow count average is about 21 per 0.3 meters (1 foot); (4) between 8 meters (26.2 feet) and about 10 meters (33 feet), a green very stiff to hard clay, with a trace of silt; the blow count is about 40 per 0.3 meters (1 foot); and (5) from about 10 meters (33 feet) to the lower limit of 16 meters (52 feet), a green hard silty clay layer; the blow count varies between 60 and 88.

Figure 85. Photo. Fabrication of prestressed concrete pile. This figure is a color photograph of a standard prestressed concrete pile being fabricated at the precasting plant. It shows the pile form, wire strands and spiral ties of the pile, and construction workers pouring concrete into the pile form.

Figure 86. Photos. Fabrication of concrete-filled FRP piles. This figure consists of three color photographs illustrating the fabrication of concrete-filled FRP piles. The top photograph (A) shows an FRP tube, supported by a steel beam along the entire length of the tube, held in an inclined position while the tube is being filled with the concrete mix. Photograph B shows a different view of the same scene shown in photograph A. Seven tubes are lying on the ground. The end of each is sealed with a wooden plug held in place by three metal straps attached to the tube. Photograph C shows an eight-point lifting device lifting a filled tube.

Figure 87. Photos. Driving of test piles. This figure consists of two color photographs depicting the composite pile and the prestressed pile being driven into the ground by a hydraulic impact hammer. Photograph A on the left shows the tubular composite pile vertically attached to a crane-supported hydraulic hammer and partially embedded in the soil. On the right side, photograph B shows the prestressed square pile vertically attached to a hydraulic hammer and partially embedded in the soil. In the foreground of photograph B, a tubular composite pile is shown fully embedded in the ground.

Figure 88. Graph. Driving records for test piles. This figure compares the driving records of the composite pile and the prestressed concrete pile. The X-axis is number of blows per 0.25 meters (9.8 inches). The Y-axis is the depth in meters below the driving template. At the end of driving, approximately 10.5 meters (34.4 feet) below the driving template, the composite pile required 60 blows per 0.25 meters (9.8 inches). The prestressed pile required about 32 blows per 0.25 meters (9.8 inches) to reach approximately the same depth. The chart indicates that, overall, compared to the prestressed pile, more blows are required to drive the composite pile.

Figure 89. Graphs. End-of-driving PDA recordings. This figure consists of two graphs presenting the end-of-initial-driving records from the pile driving analyzer (PDA) for the composite pile (A) and for the prestressed pile (B). The X-axis on both charts is time in milliseconds (0 to 51.2). The left Y-axis is force in kips (to 3000) and the right Y-axis is velocity in feet per second (0 to 16.6 for the composite pile and 0 to 17.8 for the prestressed pile). Graphs A and B suggest that both types of piles have similar dynamic behavior. Each graph reveals two distinct force peaks and a velocity peak.

Figure 90. Illustration. Test pile instrumentation. This figure shows the locations of instrumentation fitted to the prestressed and the composite test piles. It consists of a vertically oriented generic test pile and two cross sections representing each type of test pile. The vertical pile shows the locations of six strain gages oriented in the axial direction at three depths along the 13.1-meter- (43-foot-) long pile. Three pair of strain gages, each set positioned at opposite sides of the pile, are located at 3.87 meters (12.7 feet), 6.95 meters (22.8 feet), and 11.58 meters (38 feet) down the length of the pile. A string of eight lateral motion sensors is shown running through the center of the test pile. The upper six sensors are located 1 meter (3.3 feet) apart and the lower two are located 2 meters (6.56 feet) apart. An embedded accelerometer is shown installed 0.3 meters (0.98 feet) above the bottom of the test pile. A second illustration is a circular cross-sectional view of the composite pile, shown with the lateral motion sensor located in the center, and the pair of axially oriented strain gages, each positioned 150 millimeters (5.9 inches) in from the exterior of the pile. The final illustration is a square cross-sectional view of the prestressed pile showing the location of the lateral motion sensor in the center, and a pair of axially oriented strain gages, each positioned 75 millimeters (2.9 inches) in from the exterior of the pile.

Figure 91. Photo. Axial load test setup using the Statnamic device. This figure is a color photograph of the Statnamic Testing System used to conduct axial load tests on the composite and prestressed test piles in the field. The photograph shows the reaction mass; the pressure chamber directly below the reaction mass; the load cell below the pressure chamber; and the test composite pile, directly below the load cell. A laser-beam device, mounted in position to measure the test pile head displacement, is also shown in the photograph.

Figure 92. Graph. Pile head displacement versus equivalent axial static load. This graph depicts the equivalent static load versus the pile head axial displacement for the three axial load testing cycles conducted on the prestressed and composite test piles. The X-axis is equivalent static load in kilonewtons (0 to 5000) and the Y-axis is pile head axial displacement measured in millimeters (0 to negative 20) (0 to negative 0.79 inches). The data tracing for the composite pile shows an ultimate load capacity of about 4300 kilonewtons at a head displacement of about 18 millimeters (0.71 inches). A maximum load capacity of about 4190 kilonewtons applied to the prestressed pile corresponds to a pile head displacement of about 13 millimeters (0.51 inches). For both test piles, a rapid increase in the pile displacement near the end of the third cycle axial load testing suggests that the geotechnical capacity of the piles was fully mobilized.

Figure 93. Graph. Axial load-axial strain behavior of test piles. This graph presents the relationship between axial static load and axial strain for each of the two test piles. The X-axis is axial strain times 10 to the minus six (0 to 800). The Y-axis is equivalent axial static load in units of kilonewtons (0 to 5000). Data for both the composite pile and the prestressed pile reveal a linear relationship between axial strain and axial load. At a maximum load of about 4300 kilonewtons, the axial strain of the composite round-column pile is around 600 times 10 to the minus six. For the prestressed square-column pile, a maximum axial load of about 4200 kilonewtons results in an axial strain of about 675 times 10 to the minus six. The behavior of both piles is generally similar, but the composite pile exhibits more stiffness than the prestressed pile. The chart also shows the design load as a broken horizontal line at 667 kilonewtons.

Figure 94. Illustration and Graph. Variation of axial strain along pile length for three Statnamic loads. This figure shows the locations of the axial strain gages along the length of a test pile and includes a graph relating these gages to their strain measurements for three test cycles. The X-axis is axial strain times 10 to the minus six (0 to 800) and the Y-axis is distance from the tip of the pile (0 to 12 meters) (0 to 39 feet). The variations in axial strain along the length of the composite and prestressed test piles are shown for three test cycles. The measured strain along the length of the pile is similar for both the composite and prestressed materials, and the strain for both types decreases with increasing depth of the pile.

Figure 95. Photos. Lateral Statnamic setup at the Route 40 project. This figure consists of two color photographs of the Statnamic Testing System used to conduct lateral load tests on the composite and prestressed test piles in the field. The first photograph shows the horizontally mounted system in place at the bridge site. It shows the pressure chamber between the composite pile and the reaction mass. The second photograph shows the reaction mass being connected to the pressure chamber.

Figure 96. Graphs. Displacement time histories at the loading point for both piles (Pando, et al., 2004). This figure consists of two graphs presenting the displacement measurements versus time for the prestressed pile (A) and the composite pile (B). The X-axis in both charts is time in seconds (0 to 1) and the Y-axis is displacement in meters (negative 0.2 to positive 0.2) (negative 0.66 feet to positive 0.66 feet). Data tracings are included for the four load cycles applied to each of the test piles. For both test piles, the graphs indicate that the period of oscillation increases with increasing displacement amplitude. Compared to the data tracing for the prestressed pile shown in chart A, the larger displacement amplitude and longer period shown in chart B suggest a less stiff lateral response for the composite pile.

Figure 97. Graphs. Peak lateral displacement profiles for both test piles at different cycles of Statnamic load. This figure consists of two graphs presenting peak lateral displacement profiles for the four Statnamic load test cycles applied to the two test piles. The X-axis is peak lateral deflection in meters (0 to 0.4) (0 to 1.3 feet) and the Y-axis is depth below the load point in meters (positive 1 to negative 10) (positive 3.3 to negative 33 feet). The variations in peak lateral deflection are shown for each of the four load cycles and for each type of pile. The data in these two charts indicate that both test piles appear to form a hinge at about 5 meters (16 feet) below the point of loading. Maximum lateral deflection shown for the prestressed concrete pile is 0.3 meters (0.98 feet) and for the composite pile it is 0.35 meters (1.15 feet). For both types of piles, the deflection profile along the depth of the piles is nearly bilinear for load cycles 3 and 4, with a change in slope detected at a depth of about 4.8 meters (16 feet) below the loading point.

Figure 98. Graph. Calculated static and dynamic (static plus damping) resistances for both test piles. This figure presents the peak static soil resistance and the peak dynamic soil resistance calculated for the each of the four lateral load cycles applied to the prestressed pile and to the composite pile. The X-axis is displacement in meters (0 to 0.4) (0 to 1.3 feet) and the Y-axis is load in kilonewtons (0 to 200) (0 to 45,000 poundforce). For both types of piles, a comparison of the static soil resistance with the total (static plus damping) soil resistance indicates that damping accounts for only a small amount of the total resistance. The graph also indicates that, at a lateral load of about 50 kilonewtons (11,250 poundforce), there is a significant change in the slope of the load versus the deflection curve for the composite pile. For the prestressed pile, the change in slope of the load versus the deflection curve occurs at a lateral load of about 125 kilonewtons (28,125 poundforce).

Figure 99. Graph. Moment-curvature responses for composite and prestressed concrete piles. This figure presents the calculated and experimentally derived moment-curvature responses for the prestressed and composite test piles. The X-axis is curvature in radians per kilometer (0 to 40) and the Y-axis is moment measured in kilonewton-meters (0 to 700). For a study performed by Fam (2000), the chart reveals that there is good agreement between the calculated and experimental data. The moment-curvature data, calculated for the composite pile used in this study, are displayed as mostly linear and the response is stiff until a moment of about 110 kilonewton-meters is reached. Beyond this value, the composite pile exhibits less stiffness. The moment curvature response for the prestressed pile, derived from modeling predictions, is somewhat logarithmic. The curve achieves a nearly flat moment of 500 kilonewton-meters at a curvature of approximately 15 radians per kilometer.

Figure 100. Graph. Computed and measured lateral load-displacement response for both test piles (Pando, et al., 2004). This figure compares the predicted and measured lateral load-displacement responses for the prestressed and composite piles. The X-axis is displacement in meters (0 to 0.4) (0 to 1.3 feet) and the Y-axis is applied load in kilonewtons (0 to 200) (0 to 45,000 poundforce). The data show that the predicted and measured responses for the composite pile track very well, with a lateral load of about 120 kilonewtons (27,000 poundforce) resulting in a displacement of 0.3 meters (0.98 feet). For the prestressed pile, the predicted and measured responses agree well initially, although the calculated minimum load is less than the measured maximum load, but after a load of about 100 kilonewtons (22,500 poundforce), the measured response is significantly higher than the predicted response.

Figure 101. Illustration. Details of pile head showing the bars used to connect the pile to cap beam. This figure consists of two sets of drawings, each representing the pile head and a cross section of the top end of each of the two types of test piles, the square-column prestressed pile and the circular-tube composite pile. The cross-sectional views illustrate the positions of the eight 25.4-millimeter- (1-inch-) diameter holes drilled parallel to the longitudinal axis and to a depth of 460 millimeters (18 inches). In the prestressed pile, the 8 holes are shown equally spaced along a 330-by-330-millimeter- (13-by-13-inch-) square perimeter within the 508-by-508-millimeter (20-by-20-inch) square top of the pile. In the composite pile, the 8 drilled holes are shown equally spaced along a 447-millimeter- (17.6-inch-) diameter circle within the 625-millimeter- (24.6-inch-) diameter composite pile. The longitudinal views show the positions of the 1219-millimeter- (48-inch-) long Number-7 steel rebars inserted into the eight holes. In both the prestressed and composite piles, the rebars are shown embedded in the pile to a depth of 457 millimeters (18 inches).

Figure 102. Illustration. Connection of composite piles to cap beam at Pier Number 2. This figure consists of two drawings depicting (A) the elevation of Pier Number 2, and (B) the longitudinal section of the pier at a location where the composite pile is connected to the cap beam. The first illustration (A) shows Pier Number 2, consisting of the horizontal cap beam supported by 10 vertical composite piles. The drawing also indicates the location enlarged in the longitudinal section shown in (B). The next drawing (B) is a longitudinal section through a point in the cap beam where a composite pile is attached. This illustration shows the Number-7 steel rebars embedded in the cap beam. The section of the cap beam shown is 1 meter (39.4 inches) wide and 1 meter (39.4 inches) high. Drawing (B) also shows rebars throughout the cap beam.

Figure 103. Photos. Pier Number 2 including the composite piles and reinforced concrete cap beam. This figure consists of two color photographs showing the reinforced concrete cap beam of Pier Number 2 and a closeup view of the cap beam joined to a composite pile.

Figure 104. Photo. The new Route 40 Bridge over the Nottoway River in Virginia. This figure is a color photograph of the new Route 40 Bridge, showing 8 of the 10 composite piles of Pier Number 2. Two other bridge piers, constructed of the square-column prestressed concrete piles, are also visible in the photograph.

Figure 105. Map. Location map of the Route 351 Bridge in Hampton, Virginia. This figure consists of two small maps. On the left is a map of the State of Virginia showing the major interstate highways and the general location of the bridge project in Hampton, located in the southeastern part of the State. On the right is an enlarged view of the project area showing the Hampton Roads Bridge-Tunnel, and Interstate 64 and State Route 351 where they cross the Hampton River.

Figure 106. Photo. Aerial view of the Route 351 Bridge in Hampton, Virginia. This figure is a Globexplorer color aerial photograph of the original Route 351 Bridge over the Hampton River. The photograph shows the bridge located beneath and at an angle (southwest to northeast) opposite to the Interstate-64 overpass (northwest to southeast).

Figure 107. Photos. Wide-angle views of the original Route 351 Bridge. This figure consists of two color wide-angle photographs of the original Route 351 Bridge, taken from the north side. Both photographs show most of the length of the bridge and its position beneath the Interstate-64 overpass. The first photograph also clearly shows the piers being supported by three piles. The second photograph is a closer view of the bridge showing the same features.

Figure 108. Photo. Signs of deterioration of the original Route 351 Bridge. This figure is a color photograph of the Route 351 Bridge, taken from the south side, showing deterioration of the pier pilings and also in the superstructure. Dotted lines show the areas of deterioration.

Figure 109. Illustration. Schematic of the new Route 351 Bridge. This figure consists of two simple line drawings illustrating the new Route 351 Bridge in elevation view and in plan view. The first illustration is an elevation view of the proposed bridge, showing the superstructure supported by 12 piers and 2 end abutments. The illustration shows the first four spans on the west side of the bridge supported by steel plate girder spans and the remaining bridge deck supported by prestressed concrete beams. The plan view shows the 12 piers, the 2 end abutments, their orientation, and the distance between each pier. Each pier, except number 2, is shown supported by seven prestressed concrete piles. The orientation of each of the 1-to-4 battered piles is also indicated by arrows on the pier schematics. From west to east, pier number 1 is located 15.2 meters (49.9 feet) from the west end abutment. Pier number 2 is located 26.6 meters (87.3 feet) from pier number 1. Pier number 3 is located 25.4 meters (83.3 feet) from pier number 2. Pier number 4 is located 21.29 meters (69.8 feet) from pier number 3. Piers 5 through 12 are each located 15.49 meters (50.8 feet) apart and pier 12 is also 15.49 meters (50.8 feet) from the right end abutment. The plan view also shows the location of an instrumented prestressed concrete pile in the center of pier number 10 and an instrumented FRP composite pile in the center of pier number 11.

Figure 110. Illustration. Test pile cross section details. This figure consists of three drawings comparing cross sections of the prestressed concrete pile (A), the FRP pile (B), and the plastic pile (C). The cross section of the prestressed concrete pile (A) illustrates the arrangement of the 12.7-millimeter- (0.5-inch-) diameter steel strands. The 16 steel wire strands are shown equally spaced along a 432-millimeter- (16.8-inch-) square perimeter within the 610-millimeter- (24-inch-) square pile column. Text below the illustration states that the strands are tied to a Number 15M-gage-wire external spiral with a 0.15-meter (5.9-inch) pitch. The cross section of the 622-millimeter- (24.5-inch-) diameter composite pile (B) shows the 10.7-millimeter- (0.42-inch-) thick outer FRP shell and the inner concrete core reinforced with steel rebar. The reinforcement consists of 14 Number 25M steel bars equally spaced along a 506-millimeter- (19.7-inch-) diameter circle within the concrete core. Text below the illustration states that the rebar is tied to a Number 9M-gage-wire external spiral with a 0.15-meter (5.9-inch) pitch. The cross section of the 592-millimeter- (23.3-inch-) diameter plastic pile (C) illustrates the recycled MDPE plastic matrix reinforced with 24 Number 25M steel bars. The bars are shown equally spaced along a 506-millimeter- (19.7-inch-) diameter circle within the plastic matrix. Text below the illustration states that the rebar is welded to a Number 9M-gage-wire internal spiral with a 0.23-meter (9-inch) pitch.

Figure 111. Graphs. Test pile material properties. This figure consists of seven graphs summarizing material properties of the three types of test piles. Part A of this figure includes two stress-strain charts for the prestressed concrete test pile. The X-axis of the chart for the concrete is strain in meters per meter (0 to 0.003) (0 to 0.010 feet) and the Y-axis is compressive stress in megapascals (0 to 60). The concrete stress-strain diagram shows two results of nearly linear relationships to a stress of about 50 megapascals at a strain of about 0.00225 meters per meter (0.074 feet), at which point there are indications of leveling off. For the steel component of the prestressed concrete pile, the X-axis is strain in meters per meter (0 to 0.05) (0 to 0.16 feet) and the Y-axis is tensile stress in megapascals (0 to 2,000). The curve for the prestressed steel strand consists of two components: a linear relationship to a tensile stress of about 1,750 megapascals at a strain of 0.01 meters per meter (0.033 feet); and a horizontal component at a tensile stress of about 1,800 megapascals between a strain of 0.01 and 0.04 meters per meter (0.033 and 0.13 feet). Text associated with this chart states that the diagram represents a 7-wire strand, 12.7 millimeters (0.5 inches) in diameter, with a low relaxation and a yield of 1,850 megapascals. Part B of this figure includes two stress-strain charts for the FRP test pile. The X-axis of the chart for the concrete fill is strain in meters per meter (0 to 0.002) (0 to 0.0066 feet) and the Y-axis is compressive stress in megapascals (0 to 40). The diagram shows a nearly linear relationship to a stress of about 35 megapascals at a strain of about 0.0014 meters per meter (0.0046 feet). For the FRP shell, the stress-strain relationship is compared to that for Grade 420 steel. The X-axis for this chart is strain in meters per meter (0 to 0.02) (0 to 0.066 feet) and the Y-axis is tensile stress in megapascals (0 to 500). The diagram for the FRP shell is a nearly perfect linear relationship between tensile stress and strain. The diagram for Grade 420 steel, included for comparison, is again a two-part curve, similar to that of the steel strands in the prestressed concrete pile (A). Part C of this figure consists of three charts showing two stress-strain diagrams for recycled plastic and one for Grade 420 steel. The X-axis of the two charts for plastic is strain in meters per meter (0 to 0.10) (0 to 0.33 feet) and the Y-axis is compressive strength in megapascals (0 to 12). The relationships in both charts appear to be somewhat logarithmic in shape. At a stress between 9 and 10 megapascals, the strain is between 0.08 and 0.09 meters per meter (0.26 and 0.29 feet). The final chart in part C shows the stress-strain relationship for the Grade 420 steel reinforcements). The X-axis is strain in meters per meter (0 to 0.01) (0 to 0.33 feet) and the Y-axis is tensile stress in megapascals (0 to 500). The diagram consists of a two-part curve and is very similar to the stress-strain relationship shown for Grade 420 steel in part B of this figure. The conversion factor for megapascals is 1 megapascal equals 145 poundforce per square inch.

Figure 112. Graph. Axial load-axial strain behavior of test piles. This figure presents the axial load-axial strain relationships for the three types of test piles. The X-axis is axial strain in meters per meter (0 to 0.002) (0 to 0.0066 feet) and the Y-axis shows axial load in units of kilonewtons (0 to 18,000). All three piles exhibit linear strain-load relationships. The line for the plastic pile has the smallest slope, the line for the prestressed concrete has the largest slope, and the line for the FRP composite pile is just below that of the concrete pile. The prestressed concrete pile exhibits the highest axial stiffness (EA) at 8.2 times 10 to the 6 kilonewtons. The lowest axial stiffness, 3.2 times 10 to the 6 kilonewtons, is associated with the plastic pile. The axial stiffness of the FRP composite pile is 7.36 times 10 to the 6 kilonewtons. The conversion factor for kilonewtons is 1 kilonewton equals 225 poundforce.

Figure 113. Graphs. Flexural characteristics for the three test piles. This figure consists of two graphs presenting the moment-curvature response (A) and the flexural stiffness as a function of applied moment (B) for the prestressed concrete pile, the FRP composite pile, and the plastic pile. The X-axis of the first chart (A) is curvature in radians per kilometer (0 to 30) and the Y-axis is moment measured in kilonewton-meters (0 to 1,200). The shape of the moment-curvature response for the prestressed concrete pile appears logarithmic, with a maximum moment at about 700 kilonewton-meters between 5 and 25 radians per kilometer. For the plastic pile, a two-part curve is shown. The initial part is linear to a curvature of about 10 radians per kilometer at a moment of about 625 kilonewton-meters. Between a curvature of about 10 and 30 radians per kilometer, the moment-curvature response for the plastic pile then levels out between 625 and about 800 kilonewton-meters. The response for the FRP composite pile appears similar to the response for the plastic pile but, rather than leveling out, continues a gradual increase to about 1100 kilonewton-meters at 25 radians per kilometer. Part B of this figure presents flexural stiffness as a function of applied moment. The X-axis is moment in kilonewton-meters (0 to 1,200) and the Y-axis is flexural stiffness (EI) in kilonewton-meters squared (0 to 400,000). A two-part curve is shown for the prestressed concrete pile. Between a moment of 0 and about 350 kilonewton-meters, the response curve for the prestressed concrete pile is essentially flat at a flexural stiffness of about 36,000 kilonewton-meters squared. Between about 350 and 725 kilonewton-meters, the curve decreases linearly to about 4,000 kilonewton-meters squared. For the FRP composite pile, the flexural stiffness curve is flat at about 185,000 kilonewton-meters squared between a moment of 0 and about 200 kilonewton-meters. It then declines linearly to a moment of 250 kilonewton-meters and a flexural stiffness of about 140,000 kilonewton-meters squared. Thereafter, the curve declines very gradually to a moment of around 1,150 kilonewton-meters and a flexural stiffness of 5,000 kilonewton-meters squared. The flexural stiffness curve for the plastic pile is essentially flat at about 7,500 kilonewton-meters squared between a moment of 0 and about 700 kilonewton-meters. Between 700 and 800 kilonewton-meters, the flexural stiffness declines to about 2,000 kilonewton-meters squared. The conversion factors are: 1 kilonewton-meter equals 737.57 poundforce-feet; 1 radian per kilometer equals 0.621 radian per mile; and 1 kilonewton-meter squared equals 2,421 poundforce-feet squared.

Figure 114. Map. Location of test pile site at the Route 351 Bridge. This figure is a color map showing the location of the test pile area in the vicinity of the Hampton River in the City of Hampton, Virginia. The test pile area is shown on a spit of land extending into the Hampton River just south of the existing Route 351 Bridge. Also shown crossing the Hampton River are Interstate-64 and Route 351.

Figure 115. Charts. Simplified soil stratigraphy near test pile area. This figure consists of a simplified soil column showing depth and stratigraphy, and three charts showing boring and probe test results with depth. Depth is shown on the left from 0 at the top to 30 meters (98 feet) at the bottom. Between the surface and about 1 meter (3.3 feet), the soil material is described as fill and silty fine sand (SM). Between 1 meter (3.3 feet) and about 13 meters (42.6 feet), the material is primarily fine-grained medium-dense silty sand, with shell fragments, and either brown or gray in color (SM). From about 13 meters (42.6 feet) to 16 meters (52.5 feet), the soil consists of sandy stiff clay, gray in color, with traces of shell fragments (CL). Below this layer, between 16 and 19 meters (52.5 and 62.3 feet), the soil is characterized by medium dense fine-grained gray silty sand (SM). Between 19 and about 23 meters (62.3 and 75.5 feet), the soil layer is described as medium dense clayey to silty sand, with traces of shell fragments and gray in color (SM-SC). In the layer between 23 and 30 meters (75.5 and 98 feet), the material is medium-dense to dense fine-grained silty sand, gray in color, with shell fragments. Adjacent to the soil stratigraphy is a chart of standard penetration test N-values. The X-axis is the N-value (0 to 30) and the Y-axis is depth in meters (0 to 30) (0 to 98 feet), corresponding to the soil stratigraphy depths. The results for two field tests are shown in a scatter plot. The lowest values, between about 3 and 15 are shown corresponding to the upper 8 meters (26 feet). Below that depth, the field N-values range from about 10 to 30 and are somewhat scattered between 8 and 15 meters (26 and 49 feet). At the lower depths, from about 15 to 30 meters (49 to 98 feet), the field N-values range more narrowly between about 20 and 30, with very good agreement between the two tests. Adjacent to the SPT chart is a depth profile of the tip resistance and another profile showing the sleeve resistance, both obtained from cone penetrometer tests. The X-axis of the tip resistance chart is bars (0 to 400) and the X-axis of the sleeve friction profile is also bars (0 to 4). The tip resistance data include the results of four tests, all in very good agreement. The tip resistance appears to be greatest between 23 and 30 meters (75.5 and 98 feet). The results of the four sleeve friction tests are more inconsistent and do not show an obvious trend.

Figure 116. Illustration. Pile load test layout. This figure is a diagram of the layout of the borings and probe used to conduct load tests on the three test piles. The scale shown is 4 centimeters (1.6 inches) equal 5 meters (16.4 feet). The test piles, boring locations, and probe locations are shown in vertical alignment. The arrangement of the three test piles along this vertical axis, from top (north) to bottom (south), consists of the hardcore composite pile, the PPI recycled plastic pile, and the prestressed concrete pile. Directly north of and adjacent to the hardcore composite test pile is the location of a cone penetrometer test probe (CPT034). On the same vertical axis and about 5 meters (16.4 feet) north of the hardcore composite test pile is the location of a standard penetration test boring (SPT-1). The SPT-1 boring site is approximately in the center of a quadrangle formed by four HP 14-by-89 reaction piles. The reaction pile in the southwest corner is located approximately 2.85 meters (9.35 feet) northeast of the hardcore composite pile. Approximately 3 meters (9.8 feet) south of the hardcore composite test pile is another cone penetrometer test probe (CPT-1) location, also in the approximate center of four HP 14-by-89 reaction piles. On the vertical axis about 8 meters (26 feet) south of the hardcore composite test pile is the location of the PPI recycled plastic test pile. Four meters (13 feet) below the plastic pile is the location of another standard penetration test boring (SPT-2), which is located in the approximate center of four HP 14-by-89 reaction piles. Four meters (13 feet) south of the SPT-2 boring and 2.85 meters (9.35 feet) southeast of the southwest corner reaction pile is the location of the prestressed concrete test pile. Immediately below and adjacent to the concrete test pile is the location of a cone penetrometer test probe (CPT033). A DMT probe (DMT-1) is located about 3 meters (9.8 feet) on the vertical axis south of the prestressed concrete test pile. Another cone penetrometer test probe (CPT-2) is approximately 1 meter (3.3 feet) south of the DMT probe location. The DMT-1 and the CPT-2 are approximately centered in a quadrangle of four HP 14-by-89 reaction piles.

Figure 117. Illustration. Instrumentation layout for prestressed concrete test pile. This figure consists of two illustrations depicting the vertical layout and a cross section of the instrument-fitted prestressed concrete test pile. The vertical diagram shows the locations of 16 "sister-bar" strain gages along the 18-meter- (59-foot-) long test pile. A pair of "sister bars," on opposite sides of the pile, is located at 6 intervals along the pile. Two additional gages are shown at the top and also at the bottom of the test pile. Four sister bars (SB-1) are located at a depth of 1.12 meters (3.7 feet) from the top of the pile. Two "sister bars" (SB-2) are shown 3.25 meters (10.5 feet) below SB-1. Two "sister bars" (SB-3) are shown at a depth of 3.05 meters (10 feet) below SB-2. A pair of "sister bars" (SB-4) is located 2.97 meters (9.7 feet) below SB-3. Three meters (9.8 feet) below SB-4 is another pair of "sister bars" (SB-5). The last set of four "sister bars" (SB-6) is located 4.01 meters (13 feet) below SB-5. The vertical diagram of the instrumented test pile also shows a 17.06-meter- (56-foot-) long inclinometer casing through the center of the pile. The cross section diagram of the instrumented test pile shows the inclinometer casing through the center of the square-column pile, and a pair of "sister bars," each mounted 95 millimeters (3.74 inches) in from the outer wall and on opposite sides of the pile.

Figure 118. Illustration. Instrumentation layout for FRP composite test pile. This figure consists of three illustrations depicting two vertical layouts and a cross section of the instrument-fitted FRP composite test pile. One vertical diagram shows the locations of instruments embedded in the concrete infill and a second vertical diagram presents the locations of the instruments embedded in or bonded to the outer FRP tube. Embedded in the concrete are 16 "sister-bar" strain gages at six intervals along the 18.3-meter- (60-foot-) long test pile. One pair of "sister bars," on opposite sides of the pile, is located at six intervals along the pile. Two additional gages are shown at the top and also at the bottom of the test pile. Four sister bars (SB-1) are located at a depth of 1.22 meters (4 feet) from the top of the composite pile. Two "sister bars" (SB-2) are shown 3.51 meters (11.5 feet) below SB-1. Two "sister bars" (SB-3) are shown at a depth of 4.32 meters (14.2 feet) below SB-2. A pair of "sister bars" (SB-4) is located 3.15 meters (10.3 feet) below SB-3. About 2.9 meters (9.5 feet) below SB-4 is another pair of "sister bars" (SB-5). The last set of four "sister bars" (SB-6) is located 2.44 meters (8 feet) below SB-5. The vertical diagram of the concrete embedded instrumented test pile also shows a 16.76-meter- (60-foot-) long inclinometer casing through the center of the pile. A second diagram of the vertical pile illustrates the locations of instruments embedded in or bonded to the FRP shell. This diagram reveals the locations of 18 foil strain gages, mounted on opposite sides of the pile and bonded to the internal wall of the FRP tube, and 10 fiber optic sensors, mounted on opposite sides of the pile and embedded in the FRP tube. The two fiber optic cables, on opposite sides of the pile, are shown exiting the pile at 1.14 meters (3.74 feet) from the top of the pile. The first pair of foil strain gages (IG-1) is located at a depth of 0.81 meters (2.7 feet) below the fiber optic cable exits. The next set of foil gages (IG-2) is mounted 0.94 meters (3.1 feet) below IG-1 and at the same depth on the pile as the first pair of fiber optic sensors (FO-1). Approximately 1.83 meters (6 feet) below IG-2 is the location of another set of foil gages (IG-3). A pair of fiber optic sensors (FO-2) is mounted at 1.68 meters (5.5 feet) below the location of IG-3. A set of foil strain gages (IG-4) is located 1.78 meters (5.8 feet) below the location of the FO-2 soil gages. A pair of fiber optic sensors (FO-3) and a pair of foil strain gages (IG-5) are mounted 0.86 meters (2.8 feet) below IG-4. Approximately 1.75 meters (5.7 feet) below the location of the IG-5 gages, another pair of foil strain gages (IG-6) is bonded to the FRP tube. A set of fiber optic sensors (FO-4) is embedded in the FPR tube about 1.22 meters (4 feet) below the location of IG-6. A set of foil gages (IG-7) is attached at a depth of 2.01 meters (6.6 feet) below FO-4. Another set of foil strain gages (IG-8) and a set of fiber optic sensors (FO-5) are located at a depth of 1.07 meters (3.5 feet) below IG-7. The final set of foil gages (IG-9) is located 1.8 meters (5.9 feet) below IG-8 and 1.41 meters (4.6 feet) above the bottom of the test pile. The cross section diagram of the instrumented test pile shows the inclinometer casing through the center of the tubular pile, and a pair of "sister bars," each mounted 58 millimeters (2.28 inches) in from the FRP outer wall and on opposite sides of the pile.

Figure 119. Illustration. Instrumentation layout for plastic composite test pile. This figure consists of two illustrations depicting the vertical layout and a cross section of the instrument-fitted plastic composite test pile. The vertical diagram shows the locations of 16 "sister-bar" strain gages along the 18.3-meter- (60-foot-) long test pile. A pair of "sister bars," on opposite sides of the pile, is located at six intervals along the pile. Two additional gages are shown at the top and also at the bottom of the test pile. Four sister bars (SB-1) are located at a depth of 1.09 meters (3.6 feet) from the top of the pile. Two "sister bars" (SB-2) are shown 3.51 meters (11.5 feet) below SB-1. Two "sister bars" (SB-3) are shown at a depth of 3.01 meters (9.9 feet) below SB-2. A pair of "sister bars" (SB-4) is located 3.11 meters (10.2 feet) below SB-3. About 2.74 meters (9 feet) below SB-4 is another pair of "sister bars" (SB-5). The last set of four "sister bars" (SB-6) is located 4.25 meters (14 feet) below SB-5. The vertical diagram of the instrumented test pile also shows an 18-meter- (59-foot-) long inclinometer casing through the center of the pile. The cross section diagram of the instrumented test pile shows the inclinometer casing through the center of the tubular pile, and a pair of "sister bars," each mounted 65 millimeters (2.6 inches) in from the outer wall and on opposite sides of the pile. The inclinometer casing is shown inside a steel pipe with an outer diameter of 141 millimeters (5.5 inches) and a wall diameter of 6.35 millimeters (0.25 inches).

Figure 120. Photos. Fabrication of prestressed concrete test pile. This figure consists of two color photographs documenting the fabrication of the prestressed concrete test pile. The first photograph, taken at the casting yard, shows the pile partially filled with concrete. In the unfinished section, the form containing the prestressed steel bars can be seen, along with the inclinometer casing in the center and one of the "sister-bar" strain gages. The second photograph shows the finished square-column prestressed concrete test pile wrapped and ready for transport.

Figure 121. Photos. Fabrication of concrete-filled FRP piles. This figure consists of three color photographs of the concrete-filled FRP test pile. The first photograph (A) shows two FRP shells, one for the test pile and one for the production pile, on the lawn at the casting yard. The second photograph (B) is a view inside the tubular FRP shell showing the foil strain gages installed in the walls of the tube. The third photograph depicts the instrumented rebar cage on a dolly and partially inserted into the FRP shell.

Figure 122. Photos. Setup used for concrete filling of FRP composite piles. This figure consists of four color photographs documenting the steps to fill the reinforced and instrumented FRP tubes with concrete. The first photograph (A) shows the prepared FRP tube attached to a crane and being raised in a vertical position alongside a steel supporting structure. The next photograph (B) shows the two prepared FRP tubes in a vertical position and secured in the steel brace. The third photograph (C) is a closeup of the L-shaped steel angle bars securing the base of the FRP piles to a concrete slab. The last photograph (D) shows the hopper and the elephant trunk that are used to pour the concrete into the FRP tubes.

Figure 123. Photos. Concrete filling of FRP composite piles. This figure consists of a series of four color photographs documenting the steps to fill the FRP tubes with concrete. The first photograph (A) shows the 2-cubic-yard bucket being filled with concrete. Photograph (B) shows the concrete-filled bucket being hoisted by a crane into position above the vertically mounted FRP tubes. The next photograph (C) is a view from below the concrete-filled bucket, showing that operators, located in an adjacent manhold lift, control the position of the bucket over the FRP shell and the filling process. Photograph (D) is a closeup of the top of the concrete-filled FRP production pile, specifically showing the sleeves used to insert the steel dowels that connect the pile to the pile cap.

Figure 124. Photos. Rebar cage of the plastic composite test pile. This figure consists of two color photographs of the tubular rebar cage for the plastic composite test pile. The first photograph is an end view showing the steel pipe used to install the inclinometer casing in the center of the cage. The second photograph is a closeup of the side of the rebar cage showing the longitudinal steel bars and spiral ties welded to the bars.

Figure 125. Photos. Manufacturing process for the plastic composite test pile. This figure consists of five color photographs depicting steps in the manufacturing of the plastic composite test pile. The first photograph (A) shows two workers loading the instrumented rebar cage into a tubular steel injection mold. The next photograph (B) is a view of the bottom end of the steel mold loaded with the rebar cage and the center steel pipe used to install the inclinometer. Photograph (C) shows the injected steel mold being submerged horizontally into a water-cooling tank. The next photograph (D) is the manufactured pile still inside the steel mold. As shown in photograph (E), the finished product is the extruded plastic test pile.

Figure 126. Graph. Driving records for test piles. This figure presents the pile driving records for the prestressed concrete pile, the plastic pile, and the FRP composite pile. The X-axis is number of pile blows (0 to 60) per 0.25 meters (0.82 feet). The Y-axis is depth below the ground surface in meters (0 to 20) (0 to 66 feet). The shapes of the three curves are somewhat inversely proportional, indicating that more blows are required to drive the pile at greater depths. To reach a depth of about 17 meters (56 feet), about 18 blows per 0.25 meters (0.82 feet) were needed for the plastic pile. On the other hand, to reach approximately the same depth, about 50 blows per 0.25 meters (0.82 feet) were required for the prestressed concrete pile. The FRP composite pile required about 22 blows per 0.25 meters (0.82 feet) to reach a depth of about 17 meters (56 feet).

Figure 127. Photos. Installation of prestressed concrete test pile. This figure consists of three color photographs documenting the installation of the prestressed concrete test pile. The first photograph (A) shows the concrete pile below the pile driver at the bridge site. The next photograph (B) depicts the pile after the completion of driving. It shows the compressed driving cushion at the top of the pile as well as instrumentation wires exiting the pile near the top. Photograph (C) is a closeup depicting restrike of the prestressed pile.

Figure 128. Photos. Installation of FRP composite test pile. This figure consists of three color photographs documenting the installation of the FRP composite test pile. The first photograph (A) shows the FRP pile below the pile driver at the bridge site. The next photograph (B) depicts the pile after the completion of driving. It shows the top of the pile as well as instrumentation wires exiting the pile near the top. Photograph (C) also depicts the pile after completion of driving, and shows th