Development of Product Design Guides

1. Development of Product Design Guides John J. Lesko & Thomas E. Cousins, Department of Engineering Science & Mechanics Department of Civil and Environmental Engineering, Virginia Tech Blacksburg, VA 24061 Dan E. Witcher & Glenn P. Barefoot Strongwell, Corp Bristol, VA, 24203 2003 Technical Conference on Construction, Corrosion and Infrastructure Las Vegas, NV, 22-25 April 2003

2. Where is Virginia Tech? Hawthorne St. Bridge That Other Univ. Troutville Weigh Station Tom’s Creek Bridge Tangier Island Dickey Creek Bridge Rt. 601 Bridge

3. Administrative Fragmentation of the industry Lack of interdisciplinary training for design engineers Cost (first vs. life cycle) Limited commercial capital for development of new systems Incremental - piecemeal approach to FRP implementation in designs Technical Lack of design specifications Performance vs. Material specification Lack of sufficient long-term data and experience Plethora of new materials, additives & combinations One-for-One material substitution Lack of confidence in adhesive bonding Barriers to Routine use of FRP

4. Administrative Fragmentation of the industry Lack of interdisciplinary training for design engineers Cost (first vs. life cycle) Limited commercial capital for development of new systems Incremental - piecemeal approach to FRP implementation in designs Technical Lack of design specifications Performance vs. Material specification Lack of sufficient long-term data and experience Plethora of new materials, additives & combinations One-for-One material substitution Lack of confidence in adhesive bonding Barriers to Routine use of FRP

5. Administrative Fragmentation of the industry Lack of interdisciplinary training for design engineers Cost (first vs. life cycle) Limited commercial capital for development of new systems Incremental - piecemeal approach to FRP implementation in designs Technical Lack of design specifications Performance vs. Material specification Lack of sufficient long-term data and experience Plethora of new materials, additives & combinations One-for-One material substitution Lack of confidence in adhesive bonding Barriers to Routine use of FRP

6. Administrative Fragmentation of the industry Lack of interdisciplinary training for design engineers Cost (first vs. life cycle) Limited commercial capital for development of new systems Incremental - piecemeal approach to FRP implementation in designs Technical Lack of design specifications Performance vs. Material specification Lack of sufficient long-term data and experience Plethora of new materials, additives & combinations One-for-One material substitution Lack of confidence in adhesive bonding Barriers to Routine use of FRP

7. Mil Handbook 17 Mission Statement Develop world-class engineering handbooks for structural applications of composite materials. These handbooks will include standards for test/characterization methods, statistics and databases, as well as guidelines for processing, design and analysis. http://www.mil17.org/

8. Modified LRFD Approach • 8” & 36” DWB Design Guide • Deflection (A&B Allowables) • Strength (A&B Allowables) • Stability • Bearing • Connections • Fatigue & Long Term Reliability based approach to assessing A & B basis Allowables, as described through Weibull Statistics

9. Extren™ 8” Double Web Beam (DWB) Characteristics Pultruded Hybrid Glass & Carbon/Vinyl Ester Shape Ixx = 129 in4 Iyy = 31.8 in4 Sx = 32.2 in3 Sy = 10.6 in3 rx = 3.07 in ry = 1.52 in A = 13.7 in2 A2 webs = 5.36 in2 A2 flanges = 7.44 in2 Weight/foot = 11lbs/ft

10. Extren™ 36” Double Web Beam (DWB) Characteristics Pultruded Hybrid Glass & Carbon/Vinyl Ester Shape Ixx = 15291 in4 Sx = 849 in3 Iyy = 2626 in4 Sy = 292 in3 rx = 12.9 in ry= 5.37 in A2w = 50.1 in2 Asf = 34.0 in2 Weight/foot = 75 lbs./foot Dimensions in inches

11. Load Resistance Factor Design (LRFD) Resistance, R Load, Q AASHTO (1998) LRFD based design

12. Resistance, R B-Basis A-Basis Level of Risk DWB Design Guide Approach User supplies loads and level of acceptable risk based on change in Resistance Cumulative Probability

13. Design Guide • Material Specification • Weibull Statistics & Reliability • 8” & 36” Deep DWB Design Guide • Deflection (A&B Allowables) • Strength (A&B Allowables) • Stability • Bearing • Connections • Fatigue & Long-term

14. Stiffness & Capacity Unsupported Spans: 8, 14, and 20 feet Instrumentation: S – Shear, B – Bending, D - Deflection

15. 8” DWB 36” DWB Top flange failure due to delamination Support failures at spans shorter than 30’

16. Moment Capacity & Material Moment capacity controlled by carbon/glass interlaminar interface

17. DWB: Strength vs. Span

18. Shear Deformation: 36” DWB B-basis Allowable E = 6.1 Msi

19. Assessing Stiffness Allowables Bending modulus is determined in the constant moment section from axial strains kGzyAv is not independent of Ezz And is therefore determined from deflection under the 4 point loading condition

20. Development of Allowables Using Median Rank and Weibull statistics we develop a and b Establish the blower(5% confidence interval) and the A and B basis allowables based on the desired reliability A Allowable = B Allowable =

21. Resistance, R B-Basis A-Basis Level of Risk FRP Design Allowables Weibull Cumulative Probability Design Stress

22. Weibull Statistics on Modulus, Ezz

23. 8” DWB Hybrid Beam A-basis Allowables Ezz = 5.66 x 106 psi kGzyAV = 1.8 x 106 psi-in2 Mmax = 36.1 kip-ft. Based on a simply supported beam under distributed load Shear Deflection 30% @ 8’ 7% @ 20’

24. 36” DWB Hybrid Beam B-basis Allowables Ezz = 6.10 x 106 psi kGzyAV = 46.2 x 106 psi-in2 Mmax = 1139 kip-ft @30’ Span & 916.7 kip-ft 40-60’ Span Based on a simply supported beam under distributed load Shear Deflection 15% @ 30’ 5% @ 60’

25. Lateral Torsional Buckling 8” DWB Rotation & lateral displacement allowed at mid-span Unsupported Spans Tested: 40, 36, 32, 28, 24, 20 feet To L/90 No LTB observed! Impose Limit L/180

26. Lateral Torsional Buckling 36” DWB Rotation & lateral displacement allowed at mid-span Unsupported Spans Tested: 60 feet To L/180 No LTB observed! Impose Limit L/360

27. Bearing Capacity: Web Buckling Bearing controlled by web buckling Factor of Safety Total allowed bearing load

28. Bolt Bearing in Connections Bolt bearing controlled by ultimate bearing strength of the web material FpCr = 30 ksi Allowable pin bearing load Fastener edge distances: 2 diameters or 1” (25mm) minimum, which ever is greater. Fastener pitch:4 diameters or 3” (76mm) minimum, which ever is greater.

29. So what about durability?

30. Tom’s Creek Bridge Tom’s Creek Bridge

31. Tom’s Creek Bridge, June 1997 Deflection = L/490 Wheel Load Distribution Factor = 0.101 Dynamic Load Allowance = 0.9

32. Beam Removal & Replacement Two beams having seen 15 months (Sept 1998) of service were removed to assess remaining strength and stiffness • After 15 months of service... • No residual creep deflection • No reduction in residual strength and stiffness

33. Dickey Creek Bridge Dickey Creek Bridge

34. Dickey Creek Bridge Deflection = L/1100 Wheel Load Distribution Factor = 0.2 Dynamic Load Allowance = 0.36

35. Resistance, R A, Residual Resistance X-years of service B, Residual Resistance X-years of service Initial Resistance How Does the Resistance Change? FRP Life prediction is required as a function of load and environmental history to assess the changes in Resistance “Emphasis on Combined Environments” CERF/MDA Durability Gap Analysis

36. Estimating Remaining Strength & Stiffness FRP composites durability is best described by nonlinear cumulative damage approaches where residual strength and stiffness are tracked during life Degradation Processes • Cycle dependent damage • Kinetic • Chemical • Thermodynamic Geometry Constitutive Remaining Strength Of Critical Element Initial Strength Stress or Strength Life N Reifsnider et al. (1975- present) Stress on Critical Element

37. Stress or Strength Life Simulation Approach Loads • Develop estimate on resistance based on stress analysis/material • Develop load/environment history based on statistical description (Monte Carlo Simulation) Yes No ? Compute f & Pf Life Prediction • Input material characteristics (S-N curve, stiffness and strength reduction as a function of environment -including statistical description)

38. Engineering Practice: Example Element: FRP Pultruded hybrid vinyl ester structural girder Region: Northeast US (Environmental factors - thermal, moisture & UV) Rn = X moment capacity (Resistance and inherent resistance variation) gQn = Operating Moment based on stress analysis from AASHTO HS20, with ADT 10,000, 30% fully loaded (Load and load variation) Example NOT meant for design

39. Conclusions • FRP design guide • Materials specification • Laboratory testing • Reliability based • Long-term validity of as received design allowables • Durability Modified LRFD for FRP: a possiblymeans to gain acceptance among practicing engineers • Suggest inspection cycle • Phenomenological vs. First Principles • Material Specification? • Is this realistic or just academic???

40. Acknowledgements • FHWA, Innovative Bridge Research & Construction Program • Virginia Dept of Transportation • National Science Foundation • Virginia Center For Innovative Technology • Strongwell, Corp.

41. QUESTIONS?