Precast, Prestress Bridge Girder Design Example

1 precast , Prestress Bridge Girder Design Example PGSuper Training Richard Brice, PE. WSDOT Bridge and Structures Office precast , Prestressed Girder Design Example PGSuper Training (2/4/2020). Table of Contents 1 1. Sign Convention .. 1. 2 Bridge Description .. 1. Site Conditions .. 1. Roadway .. 1. Bridge Layout .. 2. 3 Design Preliminaries .. 4. Construction 4. Girder Length .. 4. Section Properties .. 5. Effective Flange Width .. 5. Composite Girder 6. First Moment of Area of deck slab, .. 7. Section Property Summary .. 7. Structural Analysis .. 8.

2 Girder Construction (Casting Yard) .. 8. Erected Girder .. 9. Analysis Results Summary .. 12. Limit State Responses .. 12. Live Load Distribution Factors .. 13. 4 Flexure Design .. 15. Step 1 Design for Final Service Conditions .. 16. Stresses due to loads on non-composite 16. Stresses due to loads on the composite section .. 17. Check Estimate of Final Concrete Strength .. 19. Step 2 - Design for Lifting without Temporary Top Strands .. 20. Proportion Strands .. 20. Prestress losses .. 20. Check Girder stability .. 22. Determine Concrete Strength at Lifting.

3 28. Step 3 - Design for Shipping .. 28. Estimate Prestress Losses at Shipping .. 28. Check Girder Stability .. 30. Check concrete strength .. 39. Step 4 - Design for Lifting with Temporary Top Strands .. 39. Step 5 Check Erection Stresses .. 40. i precast , Prestressed Girder Design Example PGSuper Training (2/4/2020). Losses between Transfer to Deck Placement .. 40. Stresses .. 41. Step 6 Check Final 42. Losses from Deck Placement to Final .. 42. Stresses .. 44. Moment Capacity .. 46. Check Splitting Resistance .. 50. Check Confinement Zone Reinforcement.

4 51. 5 Shear Design .. 51. Locate Critical Section for Shear .. 51. Check Ultimate Shear Capacity .. 52. Compute Nominal Shear Resistance .. 52. Check Requirement for Transverse Reinforcement .. 54. Check Minimum Transverse Reinforcement .. 54. Check Maximum Spacing of Transverse 55. Longitudinal Reinforcement for 55. Check Horizontal Interface Shear .. 55. Check Nominal Capacity .. 56. Check Minimum Reinforcement .. 57. 6 Check Haunch Dimension .. 57. Slab and Fillet .. 57. Profile Effect .. 58. Vertical Curve .. 59. Horizontal Curve .. 59. Profile Effect.

5 60. Girder Orientation Effect .. 60. Excess Camber .. 60. Compute Creep Coefficients .. 62. Compute Deflections .. 62. Check Required Haunch .. 63. Compute Lower Bound Camber at 40 days .. 63. Creep Coefficients .. 63. Compute Deflections .. 63. Check for Possible Girder Sag .. 63. 7 Bearing Seat Elevations .. 64. 8 Design Summary .. 64. 9 Load Rating .. 64. ii precast , Prestressed Girder Design Example PGSuper Training (2/4/2020). Inventory Rating .. 64. Moment .. 64. Shear .. 65. Bending Stress Service III limit state .. 65. Operating Rating.

6 66. Moment .. 66. Shear .. 66. Legal 66. Moment .. 67. Shear .. 67. Bending Stress Service III limit state .. 68. Permit Loads .. 68. 10 Software .. 69. 11 69. iii precast , Prestressed Girder Design Example PGSuper Training (2/4/2020). List of Figures Figure 2-1: Bridge Section at Station 7+65 .. 2. Figure 2-2: Girder Dimensions .. 2. Figure 2-3: Slab Detail .. 3. Figure 3-1 Assumed Construction Sequence .. 4. Figure 3-2 Connection Geometry .. 5. Figure 3-3 Effective Flange Width .. 5. Figure 3-4 Centroid of Non-composte and Composite Section .. 7.

7 Figure 3-5: Slab Haunch .. 10. Figure 3-6: HL93 Live Load Model .. 12. Figure 3-7: eg Detail .. 13. Figure 4-1: Optimized Fabrication Girder Design Procedure .. 16. Figure 4-2: Optimum Strand Arrangement .. 20. Figure 4-3: Equilibrium of Hanging Girder .. 22. Figure 4-4: Girder Self-Weight Deflection during 22. Figure 4-5: Offset Factor .. 24. Figure 4-6: Equilibrium during Hauling .. 30. Figure 4-7: Prestress induced Deflection based on Storage Datum .. 31. Figure 4-8: Discretized Girder Section for Strain Compatibility Analysis .. 48. Figure 4-9: Graphical method to Determine Critical Section Location.

8 51. Figure 5-1: Slab + Fillet Effect .. 58. Figure 5-2: General Method for Profile Effect .. 58. Figure 5-3: Vertical Curve Effect .. 59. Figure 5-4: Horizontal Curve Effect .. 60. Figure 5-5: Top Flange Effect .. 60. Figure 5-6: Camber Effect .. 61. Figure 5-7: Camber Diagram .. 61. iv precast , Prestressed Girder Design Example PGSuper Training (2/4/2020). 1 Introduction The purpose of this document is to illustrate how the PGSuper computer program performs its computations. PGSuper is a computer program for the Design , analysis, and load rating of precast , prestressed concrete Girder bridges.

9 A Design Example followed by a load rating analysis illustrates the engineering computations performed by PGSuper. PGSuper uses a state-of-the-art iterative Design algorithm and other iterative computational procedures. Only the final iterative steps are of interest. To avoid lengthy iterations in this document, trial variables are guessed based on the final iterations produced by the software. PGSuper uses 16 decimals of precision. There will be minor differences between these hand calculations and numbers reported by PGSuper. When noted, these calculations adopt numeric values reported by PGSuper.

10 Sign Convention This document and PGSuper use the following sign convention. Item Value Compression <0. Tension >0. Upward Deflection >0. Downward Deflection <0. Top Section Modulus <0. Bottom Section Modulus >0. Strand Eccentricity above Centroid <0. Strand Eccentricity below Centroid >0. 2 Bridge Description Site Conditions Normal Exposure Average Ambient Relative Humidity: 75%. Roadway Alignment PI Station Back Tangent Delta Radius 10+00 N 34 45' 32 W 12 34' 15 L 6000 ft Profile PVI Station PVI Elevation Grade in ( ) Grade out ( ) Length 9+00 -2% 600 ft Superelevations Left Right.