FRP Composite Piles Applications & Durability Considerations

Transcription

1 FRP Composite Piles Applications & Durability Considerations by Miguel A. Pando, Felipe J. Acosta, P.E. UPRM Jack Lesko Virginia Tech Virginia Fiber-Reinforced Composites Showcase Bristol, VA, September 20-21, 2006

2 Outline Case Histories involving use of FRP piles: Route 40 bridge Route 351 bridge Cost comparison Durability Studies Work at Virginia Tech and with NCSU (w/ Amir Fam) Joint work Virginia Tech and UPRM Recommendations for future work Acknowledgments

3 Background Recent work at Virginia Tech (Pando, Lesko, Filz - FHWA project) Investigate the feasibility of using composite piles for load bearing applications such as in bridge substructures. Assessment of driveability, axial capacity, lateral capacity, and long-term durability of composite piles Route 40 project This presentation Route 351 project This presentation Evaluate their long-term durability This presentation

4 Case Histories: - Rte. 40 Bridge - Rte. 351 Bridge

5 Route 40 Bridge N I-64 I-66 Stony Creek 657 Nottoway river I-81 I-77 I-85 Virginia I-95 I-95 40

6 Location of FRP Piles Concrete slab m RC cap beam Battered piles Elevation m m m m m Test pile area Plan view : Prestressed pile : Composite pile

7 Route 40 Bridge

8 a) Photograph of composite piles installed at Pier No. 2 of the Route 40 Bridge Longitudinal direction θ = +35 o (1.13 mm) θ = -35 o (1.13 mm) θ = +85 o (1.13 mm) θ = +35 o (1.13 mm) θ = -35 o (1.13 mm) Inner liner (1.68 mm) Five FRP layers constitute the structural wall thickness of the FRP tube b) FRP tube laminate structure of composite pile

9 0 2 Blows per 0.25 m COMPOSITE PILE (0.62m) PCP PILE (0.51 m) 3000 kips F a) Composite Pile: EA/c = kips-s/ft F V 16.6 ft/s V 4 Sand 6.2 ms b) Prestressed Concrete Pile: 8 10 Clay 3000 kips F EA/c = kips-s/ft F V 17.8 ft/s V 12 Pile m 6.0 ms 51.2 PILE DRIVING RECORDS END-OF-DRIVING PDA

10 PILE HEAD AXIAL DISPLACEMENT (mm) AXIAL STATNAMIC RESULTS Davisson Failure Criteria COMPOSITE PILE PRESTRESSED PILE EQUIVALENT STATIC AXIAL LOAD (kn)

11 LATERAL STATNAMIC RESULTS EQUIVALENT STATIC LATERAL LOAD (kn) COMPOSITE PILE PRESTRESSED PILE PILE HEAD LATERAL DISPLACEMENT (m)

12 The new Route 40 Bridge over the Nottoway river in Virginia Composite Piles

13 Lessons from Route 40 Driveability: No major differences in driving behavior (FRP piles can be installed) Axial Capacity: Both piles performed similarly Composite pile: P ult = 4360 kn ( y =18 mm) PCP pile: P ult = 4190 kn ( y = 13 mm) Lateral Capacity: Both piles appeared to have similar ultimate lateral load capacity Composite pile had lower flexural stiffness after initial concrete cracking which appeared to occur at 50 kn Composite piles were designed as specified for axial load only Use of concrete-filled FRP composite piles for bridge foundations feasible & practical based on this project.

14 Case Histories (continued): - Rte. 40 Bridge - Rte. 351 Bridge

15 Rte. 351 Bridge in Hampton, VA I-64 Existing Rte. 351 bridge

16 Prestressed Pile Composite Pile Recycled Plastic Pile

17 Subsurface conditions 0 Description CPT q c (MPa) of material Fill (SM ) Sand (SM) SPT N field Clay (CL) Sand (SM) 20

18 Pile driving records Depth below ground surface (m) Plastic pile FRP pile Prestressed pile Pile blows per 0.25 m

19 Static Axial Load Tests

20 Static Axial Load Test Results Pile head displacement (mm) A pplied axial load (kn) Prestressed pile FRP pile Plastic pile

21 Load Transfer during Static Load Tests 0 Load (kn) Depth (m) Plastic pile FRP pile Prestressed pile 20

22 Comparison of Axial Load Test Results with LCPC Method Q ult (kn) LCPC (Concrete) Load Test Prestressed concrete pile FRP pile LCPC (Steel) Plastic pile

23 Static Lateral Load Test Results 350 Lateral load (kn) FRP pile Prestressed pile Plastic pile Lateral deflection at ground surface (mm)

24 Lessons Route 351 Penetration resistance during driving increases in order: plastic pile, FRP pile, prestressed concrete pile Pile capacities (Davisson) increase in the same order: Plastic pile, Q ult = 2130 kn (239 tons) FRP pile, Q ult = 2260 kn (254 tons) Prestressed concrete pile, Q ult = 3095 kn (348 tons) Traditional methods FRP pile and prestressed concrete pile exhibit similar stiffnesses in axial loading, plastic pile is not as stiff FRP pile and prestressed concrete pile exhibit similar stiffnesses in lateral loading, plastic pile is not as stiff

25 Cost information at two case studies Initial costs of composite piles were higher than those for prestressed concrete piles 77 % higher at Route 40 bridge project 289% and 337% higher for plastic and FRP piles, respectively, at Route 351 bridge Cost effectiveness of composite piles is expected to improve as production volume increases, and by considering life-cycle costs of low-maintenance composite piles

26 Durability Studies

27 Experimental durability study Assumptions: Moisture is the dominant damage mechanism Homogenized FRP Residual strength is only moisture dependent Moisture diffusion is not stress dependent No chemical processes Creep rupture behavior is not considered FRP-concrete friction is not affected Track FRP moisture content Track FRP residual stiffness/strength FRP Pile strength (Fam & Rizkalla, 2001) Prediction of Residual Pile Life

28 Material characterization Lancaster 12- and 24-inch: Filament wound E-glass fiber 12-inch = epoxy, [-88/+8/-88/+8/-88/+8/-88/+8/-88], t = 6 mm 24-inch = polyester, [+35/-35/+85/+35/-35], t = 7.3 mm Hardcore 12- and 24-inch: VARTM E-glass fiber (multi-axis fabric Quad Q-9100) Vinyl ester 12-inch = 3 plies [0/+45/-45/90], t = 5.7 mm 24-inch = 4 plies [0/+45/-45/90], t = 8.9 mm

29 Evaluation of FRP Shell Properties Axial Hoop Split Disk

30 Testing As received properties Tensile stress (MPa) Axial H H L L Strain (%) Tensile stress (MPa) Hoop L L H Strain (%)

31 Moisture absorption Lancaster 24-inch Hardcore 24-inch Moisture content, m (%) o C Langmiuirian Fickian Square root of time (hours1/2) Moisture content, m (%) days 681 days o C Langmiuirian Fickian Square root of time (hours1/2)

32 Property degradation Normalized strength X T /X o % loss Moisture content (%) Normalized hoop modulus E T /E o % loss Moisture content (%) (Data for Hoop tests on Lancaster 12-inch)

33 SEM Images As received & Aged As-received Aged

34 Hardcore Lancaster

35 Normalized Axial Strength vs. Time 1.00 Normalized Axial Strength Experimental Data Submergence Time (Days)

36 Axial testing of concrete-filled FRP stubs 1,200,000 1,000,000 50% stiffness loss in secondary region 800,000 Load (Lbs) 600, , ,000 Concrete-filled tube (Fresh) Concrete-filled tube (Aged 2 months) Concrete-filled tube (Aged 7 months) Plain concrete core Slight increase in ε f microstrain (Axial)

37 Estimated long-term axial capacity Axial Load (kn) Predictions using Fam and Rizkalla 2002 Assumed % reductions: - 25% hoop stiffness - 40% hoop strength As-received 5 % decrease at strain Initial properties: Concrete f' c = 20 MPa E co = 22.4 GPa 12-inch Lancaster FRP shell OD = 324 mm t = 6.1 mm E hoop-frp = 13 GPa σ hoop-frp = 195 MPa Aged Axial strain (ms)

38 Estimated long-term flexural capacity 250 Moment (kn-m) As-received Assumed % reductions: - 25% axial stiffness - 40% axial strength Curvature (1/m) x (10-3 ) 199 kn-m 24% decrease 147 kn-m Aged

39 Joint Work VT and UPRM Objectives To evaluate the material hygrothermal degradation of CFFRP tubes Constituents level (FRP and concrete) Structural level (CFFRP) Include larger number of replicas using smaller size specimens

40 Experimental Program Aged FRP at three different water temperatures (30 C, 40 C, and 50 C) Axial and hoop direction (Special fixture was designed for hoop tests) Aged CFFRP at 30 C Periodical tests over the course of 2,000 day long study (Near 300 days completion) Work distribution CFFRP tubes and concrete (UPRM) FRP tubes (VT) Concrete subjected to triaxial loads (UPRM)

41 Conclusions Durability study Significant strength and stiffness degradation due to moisture absorption Little degradation effect of exposure to freeze-thaw cycles on longitudinal tensile properties of saturated FRP tubes Small impact of FRP degradation on long term axial capacity Significant impact of FRP degradation on flexural capacity

42 Future work Durability studies Durability studies involving small diameter concretefilled FRP piles to study the durability of axial and flexural structural capacity A durability study that includes exposure to salt water and other aqueous solutions representing other groundwater conditions Other recommended studies degradation due to UV and exposure to high temperatures resistance to fire corrosion of steel cage in PPI piles

43 Future work Structural tests Determine the influence of temperature on structural behavior, and effects of differences in coefficients of thermal expansion of the different pile constituents on pile performance Expand testing under combined axial load and bending to establish the full interaction diagrams of composite piles Behavior under cyclic loading Creep under axial compression Establish design guidelines for design of composite piles (FAM s work is helping with this)

44 Acknowledgments Carl Ealy (FHWA) Mike Hall (VDOT) Dr. Ed Hoppe (VTRC) Drs. George Filz and Jack Lesko (VT) Dr. Amir Fam (Queen s University)