Calibration of AASHTO LRFD for Filled Grid Decks

Calibration of AASHTO LRFD for Filled Grid Decks Based on Historical Performance Christopher Higgins and O. Tugrul Turan School of Civil and Construction Engineering Oregon State University and Mark Kaczinski and Phil Gase Bridge Grid Flooring Manufacturing Association International Bridge Conference June 8, 2011

Introduction & Background • Widely used in practice • Light weight compared to conventionally reinforced decks • Two way bending (orthotropic behavior) Source: www. bgfma. org Main Bars (Strong Direction) Cross Bars (Weak Direction)

Introduction & Background • Orthotropic Thin Plate Theory • Non-homogenous biharmonic equation. • Stiffnesses can be determined experimentally

Introduction & Background

Introduction & Background D=∞ D=0 D=2 • • D = 0, plate acts like a one –way slab or beam. D = ∞, plate behaves like a collection of separate strips.

Introduction & Background AASHTO-LRFD (2004) section 4. 6. 2. 1. 8 Higgins 2003, Higgins 2004 , ,

Introduction & Background • One-way slab, (Prior to AASHTO-LRFD, 1994) • Orthotropic Thin Plate Theory (AASHTOLRFD, 1994) , Single patch at the center • Orthotropic Thin Plate Theory (AASHTOLRFD, 2004), Tandem axle and multiple patches, Fatigue Limit State Deflection equations

Introduction & Background C=0. 8 C=1. 0

Introduction & Background • Many of the decks were constructed more than 30 years ago and AASHTO-LRFD(2004) not calibrated against historically successful performance • BGFMA selected 26 decks, design details and supporting information provided • Min. 10; max. 51 years in service.

Comparison of AASHTO LRFD 2004 and AASHTO LRFD 1994 Strength Limit State Comparison Moment main bars transverse to traffic Region generally used in practice

Comparison of AASHTO LRFD 2004 and AASHTO LRFD 1994 Strength Limit State Comparison Moment main bars parallel to traffic Region generally used in practice

Comparison of AASHTO LRFD 2004, AASHTO LRFD 1994 and Table A 4 AASHTO-LRFD (2004), AASHTO-LRFD (1994) moment values for D=1. 0 and C=0. 8, and AASHTO-LRFD (2004) deck slab design table positive moment values (A 4)

Comparison of AASHTO LRFD 2004, AASHTO LRFD 1994 and Table A 4 AASHTO-LRFD (2004), AASHTO-LRFD (1994) moment values for D=1. 0 and C=0. 8, and AASHTO-LRFD (2004) deck slab design table negative moment values (A 4).

Comparison of AASHTO LRFD 2004 and AASHTO LRFD 1994 Strength Limit State Comparison, 26 Decks Demands somewhat higher now.

Comparison of AASHTO LRFD Design Demands with Available Resistance Strength Limit State (Positive Moment) Max= 2. 32 Min=1. 27 Mean=1. 64 58% above 1. 5 M+ “Capacity” is adequate

Comparison of AASHTO LRFD Design Demands with Available Resistance Strength Limit State (Negative Moment) Max= 2. 77 Min=1. 08 Mean=1. 48 35% above 1. 5 M- “Capacity” is adequate

Strength Limit State with FEA: Superstructure and Distributed Stiffness D (pos. ) D (neg. ) Number of Spans Supports Case 1 Cracked NA Single Rigid Case 2 Uncracked NA Single Rigid Case 3 Cracked 3 Span Rigid Case 4 Uncracked 3 Span Rigid Case 5 Cracked Uncracked 3 Span Rigid Case 6 Uncracked Cracked 3 Span Rigid Case 7 Cracked NA Single Flexible Case 8 Uncracked NA Single Flexible Case 9 Cracked 3 Span Flexible Case 10 Uncracked 3 Span Flexible Case 11 Cracked Uncracked 3 Span Flexible Case 12 Uncracked Cracked 3 Span Flexible Super structure flexibility: Slightly reduced negative moments, slightly increased positive moments for strength. Distributed stiffness due to cracking not significant.

Deflection Criteria

Fatigue Limit State (Positive Moment) SR<5 ksi Inf. Life

Fatigue Limit State (Negative Moment)

Fatigue Limit State, 26 Decks Bridge # Name ADTT Y. in ser. N occurred C=0. 8 SR neg. (ksi) Fat. L. (Years) 7. 5 10. 9 17, 054, 625 6. 3 26. 0 NA 12. 2 NA 1 Green Island 890 27 26, 312, 850 2 Quincy Memorial 623 25 3 Country Road 18 NA 16 4 Meadowcroft Bridge 5 Gold Star Bridge 6 7 3 10 19, 710 11. 2 >75 years 6958 34 259, 046, 340 12. 4 0. 3 Mackinac Bridge 830 51 46, 351, 350 10. 1 4. 7 Interstate 55 7014 28 215, 049, 240 12. 2 0. 3 8 Pennsylvania Turnpike 7020 22 169, 111, 800 12. 1 0. 3 9 Tarentum Bridge 1855 21 42, 655, 725 12. 2 10 US Route 6 220 20 4, 818, 000 11. 5 12. 0 11 Jerome Street Bridge 1007 19 20, 950, 635 11. 9 2. 4 12 Ohio State Route 360 17 6, 701, 400 11. 5 7. 3 13 Crown Point Bridge (Per. ) 296 17 5, 510, 040 15. 2 3. 9 14 North Main Street 625 15 10, 265, 625 11. 7 4. 0 15 Crown Point Bridge (Par. ) 296 17 5, 510, 040 13. 6 5. 3 16 Tobin Bridge 9000 28 275, 940, 000 8. 5 0. 7 17 WB I-70 7700 29 244, 513, 500 14. 7 0. 2 18 Cairo Bridge 40 29 1, 270, 200 8. 4 >75 years 19 Gypsy Bridge NA 28 NA 9. 7 NA 20 US 219 204 25 5, 584, 500 8. 8 21 Daybrook Bridge NA 23 NA 10. 8 NA 22 State Route 601 1348 16 23, 616, 960 12. 4 1. 6 23 West Street 595 15 9, 772, 875 11. 2 4. 8 24 Westbound GA 1265 15 20, 777, 625 13. 8 1. 2 25 Upper Buckeye Bridge NA 14 NA 11. 7 NA 26 Smithfield Bridge 1140 13 16, 227, 900 14. 5 1. 1

Fatigue Limit State

Fatigue Limit State Elkins and Higgins, 2006

Fatigue Limit State Elkins and Higgins, 2006

Fatigue Limit State : Transverse M • SR/2 (transverse) N= 2 Big 1 Small Rainflow counting! N = 4 Moderate 1 Small Rainflow counting!

Fatigue Limit State: Parallel M • SR/2. 5 (parallel) N = 4 Big 2 Small Rainflow counting N = 2 Moderate 6 Small Rainflow counting

Fatigue Limit State: Parallel M • SR/2. 5 (parallel)

Fatigue Limit State : Design Section M 2=0. 9 x. M 1 Normalized negative moment (from Table A 4 -1 AASHTO-LRFD)).

Fatigue Limit State, 26 Decks C=0. 8 Bridge # Name 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Green Island Quincy Memorial Country Road 18 Meadowcroft Bridge Gold Star Bridge Mackinac Bridge Interstate 55 Pennsylvania Turnpike Tarentum Bridge US Route 6 Jerome Street Bridge Ohio State Route Crown Point Bridge (Per. ) North Main Street Crown Point Bridge (Par. ) Tobin Bridge WB I-70 Cairo Bridge Gypsy Bridge US 219 Daybrook Bridge State Route 601 West Street Westbound GA Upper Buckeye Bridge Smithfield Bridge ADTT 890 623 NA 3 6958 830 7014 7020 1855 220 1007 360 296 625 296 9000 7700 40 NA 204 NA 1348 595 1265 NA 1140 Inst. Y. Y. in ser. 1981 1983 1992 2002 1974 1957 1980 1986 1987 1988 1989 1991 1993 1991 1980 1979 1980 1983 1985 1992 1993 1994 1995 27 25 16 6 34 51 28 22 21 20 19 17 17 15 17 28 29 29 28 25 23 16 15 15 14 13 n N occurred 5 8 5 5 5 5 5 7 8 5 5 5 43, 854, 750 45479000 NA 32, 850 431, 743, 900 123, 600 358, 415, 400 281, 853, 000 71, 092, 875 8, 030, 000 34, 917, 725 11, 169, 000 9, 183, 400 17, 109, 375 12, 856, 760 735, 840, 000 407, 522, 500 2, 117, 000 NA 14, 892, 000 NA 39, 361, 600 16, 288, 125 34, 629, 375 NA 27, 046, 500 SR neg. (ksi) Fat. L. (Years) 3. 4 2. 2 5. 5 5. 0 5. 6 3. 6 5. 5 5. 2 5. 3 5. 2 6. 8 5. 3 4. 88 3. 1 6. 6 3. 8 4. 4 3. 2 4. 9 5. 6 5. 0 6. 2 5. 3 6. 5 Inf. life NA Inf. life 2. 0 Inf. life 2. 1 7. 9 >75 years 15. 7 48. 1 25. 5 26. 3 Inf. life 1. 1 Inf. life 10. 4 Inf. life 8. 0 NA 7. 6 • SR/2 (transverse) • SR/2. 5 (parallel) • 3 in. away from the CL of the support (SRx 0. 9) • 9/26 less than years in service

Fatigue Limit State If: Fatigue cracking over the supports Fatigue Limit State C=0. 8 All the main bars cracked over the continuous supports Strength Limit State C=1. 0 • Negative fatigue moment could be ignored

Limits on Possible Span Lengths Limiting Span Lengths for different limit states Bridge # Actual Span (ft) Strength (ft) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 10. 17 4. 83 8. 17 10. 00 6. 67 5. 00 6. 50 6. 42 6. 50 6. 33 6. 12 6. 33 6. 37 6. 38 8. 00 6. 46 7. 13 4. 50 6. 17 4. 25 5. 25 4. 67 5. 50 4. 33 8. 25 6. 00 12. 88 10. 78 23. 72 30. 97 7. 03 7. 33 11. 77 24. 39 11. 77 24. 28 7. 18 17. 97 10. 25 8. 02 7. 84 8. 09 7. 26 7. 06 4. 83 5. 73 4. 70 14. 20 6. 88 Deflection L/800 (ft) Fatigue M+ (ft) 8. 05 5. 76 8. 35 9. 12 5. 55 4. 96 5. 89 5. 87 5. 89 7. 01 5. 77 7. 01 5. 49 6. 52 6. 12 6. 00 6. 18 5. 40 6. 00 5. 10 5. 55 5. 08 5. 50 4. 90 7. 48 5. 73 209. 81 90. 63 30. 01 61. 02 137. 39 99. 56 99. 37 205. 52 99. 32 204. 66 181. 62 2681. 26 33. 05 96. 84 2941. 20 260. 69 106. 54 298. 96 93. 03 45. 89 147. 92 47. 87 1215. 49 Theoretical spans were determined • Strength: C=1. 0; M+ only with first yeild limit • Deflection: AASHTO-LRFD Prescribed deflection • Fatigue: C=1. 0; AASHTO-LRFD Prescribed fatigue SR (Strength/3) to limit of 5 ksi • L/800 was the most conservative • New service level stresses were determined for L/800

Conclusions and Recommendations • Current AASHTO-LRFD moment provisions are not substantially higher than those specified for RC decks in traditional design • Suite of decks not controlled by the strength or positive fatigue moment • All 26 decks are limited by negative fatigue moment • Negative fatigue moment can be reduced by a factor of 2. 2 (for design say 2) for transverse to traffic and 2. 8 (for design say 2. 5) for parallel to traffic cases • Additional analyses and/or tests around the negative moment region may help identify additional load distribution that may reduce stress range over the support for fatigue design • Design approach would be: use the current design for Strength I with C=1. 0, detail to obtain infinite life for positive fatigue moment, and limit the service level deflections to L/800