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Publication Number: FHWA-HRT-06-115
Date: August 2006

Index, Structural Behavior of Ultra-High Performance Concrete Prestressed I-Girders

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FOREWORD

We currently are experiencing the initial stages of a significant advancement in the use of structural concrete. Historically, structural forms composed of concrete have relied on the modest compressive strength of concrete to carry compressive loads and internal steel reinforcement to carry tensile forces. Recent advances in concrete technology have allowed for the development of very high compressive strength concretes that also exhibit significant tensile strength and tensile toughness through the use of steel fiber reinforcement. The Federal Highway Administration's Ultra-High Performance Concrete Research Program has been investigating the use of these types of concrete in the highway infrastructure. This report discusses a series of tests that were completed on prestressed concrete I-girders composed of ultra-high performance concrete (UHPC). Although not structurally optimized to take advantage of the high compressive strength of UHPC, these girders did make use of UHPC's significant tensile capacity through the elimination of all mild steel reinforcement. The results contained herein show that UHPC can carry all shear forces normally demanded of a prestressed I-girder and also can significantly enhance the flexural capacity of the girder. These results should aid bridge owners in their initial foray into the use of UHPC within the bridge inventory.

Gary L. Henderson

Director, Office of Infrastructure

Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No.

FHWA-HRT-06-115

2. Government Accession No. 3 Recipient's Catalog No.
4. Title and Subtitle

Structural Behavior of Ultra-High Performance Concrete Prestressed I-Girders

5. Report Date

August 2006

6. Performing Organization Code
7. Author(s)

Benjamin A. Graybeal

8. Performing Organization Report No.

 

9. Performing Organization Name and Address

PSI, Inc.
2930 Eskridge Road
Fairfax, VA 22031

10. Work Unit No. (TRAIS)

11. Contract or Grant No.
12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report, March 2001–May 2005

14. Sponsoring Agency Code

 

15. Supplementary Notes

Additional FHWA Contacts—Joseph Hartmann (Technical Advisor), William Wright (COTR)

16. Abstract

In the past decade significant advances have been made in the field of high performance concretes (HPC). The next generation of concrete, ultra-high performance concrete (UHPC), exhibits exceptional tensile and compressive strength characteristics that make it well suited for use in highway bridge structures. Prestressed highway bridge girders were cast from this material and tested under flexure and shear loadings. These American Association of State Highway and Transportation Officials (AASHTO) Type II girders contained no mild steel reinforcement, forcing the UHPC and its internal passive fiber reinforcement to carry all secondary tensile forces within the girder. These tests demonstrated that UHPC can carry all shear forces normally demanded of a prestressed I-girder and can also significantly enhance the flexural capacity of the girder. Based on this research, a basic structural design philosophy for bridge I-girder design is proposed.

17. Key Words

UHPC, ultra-high performance concrete, fiber-reinforced concrete, AASHTO Type II girder, I-girder, flexure, shear, design philosophy

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.

19. Security Classification
(of this report)

Unclassified

20. Security Classification
(of this page)

Unclassified

21. No. of Pages

104

22. Price
Form DOT F 1700.7 Reproduction of completed page authorized

SI (Modern Metric) Conversion Factors

TABLE OF CONTENTS

  1. INTRODUCTION
  2. BACKGROUND AND PREVIOUS RESEARCH
  3. GIRDER MATERIAL PROPERTIES
  4. GIRDER FABRICATION AND EXPERIMENTAL METHODS
  5. UHPC GIRDER TEST RESULTS
  6. DISCUSSION OF RESULTS
  7. DESIGN PHILOSOPHY FOR UHPC BRIDGE GIRDERS
  8. CONCLUSIONS AND FUTURE RESEARCH

REFERENCES

LIST OF FIGURES

  1. Graph. Sample tensile stress-strain response for steel fiber reinforcement.
  2. Graph. Third-point loading response of a 2-inch by 2-inch prism on a 9-inch.
  3. Illustration. Origin of the four girder specimens, with the south elevation of the tested configuration shown.
  4. Illustration. AASHTO Type II cross section and strand pattern.
  5. Illustration. Instrumentation plan for Girder 80F.
  6. Illustration. Instrumentation plan for Girder 28S.
  7. Illustration. Instrumentation plan for Girder 24S.
  8. Illustration. Instrumentation plan for Girder 14S.
  9. Graph. Load versus midspan deflection response of girder 80F.
  10. Graph. Load-rotation response of Girder 80F.
  11. Graph. Deflected shape of Girder 80F at selected load levels.
  12. Graph. Moment-curvature response of Girder 80F.
  13. Graph. Midspan neutral axis depth from the top of Girder 80F.
  14. Graph. Principal strains in the web near the west support of Girder 80F.
  15. Graph. Principal strain angles in the web near the west support of Girder 80F.
  16. Photo. Crack spacing on the bottom flange of Girder 80F at 305 mm midspan overall girder deflection.
  17. Photo. Girder 80F after approximately 430 mm (17 inches) of deflection.
  18. Photo. Girder 80F immediately after failure.
  19. Photo. Failure surface of Girder 80F including (a) overall west failure surface and (b) closeup of west failure surface showing pulled-out fibers and necked strands.
  20. Graph. Load-deflection response of Girder 28S.
  21. Graph. Bearing rotation response of Girder 28S.
  22. Graph. Deflected shape of Girder 28S.
  23. Graph. Strand slip in Girder 28S.
  24. Graph. Principal tensile strain in the web of Girder 28S.
  25. Graph. Principal tensile strain angle in the web of Girder 28S.
  26. Graph. Principal compressive strain in the web of Girder 28S.
  27. Graph. Principal compressive strain angle in the web of Girder 28S.
  28. Photo. Crack at south base of Girder 28S web at a load of 2,000 kN (450 kips).
  29. Photo. Tension failure of top flange and crushing of web at conclusion of test.
  30. Illustration. Crack pattern at failure in Girder 28S.
  31. Graph. Load-deflection response of Girder 24S.
  32. Graph. Bearing rotation of Girder 24S.
  33. Graph. Deflected shape of Girder 24S.
  34. Graph. Principal tensile strain in the web of Girder 24S.
  35. Graph. Principal tensile strain angle in the web of Girder 24S.
  36. Graph. Principal compressive strain in the web of Girder 24S.
  37. Graph. Principal compressive strain angle in the web of Girder 24S.
  38. Photo. Failure of Girder 24S (a) 1/15 second before failure, (b) 1/30 second before failure, (c) at failure, and (d) 1/30 second after failure.
  39. Photo. Failed Girder 24S (a) south elevation and (b) bottom flange near bearing.
  40. Illustration. Crack pattern at failure in Girder 24S.
  41. Graph. Load-deflection response for Girder 14S.
  42. Graph. Bearing rotation for Girder 14S.
  43. Graph. Deflected shape for Girder 14S.
  44. Graph. Strand slip in Girder 14S.
  45. Graph. Principal tensile strain in the web of Girder 14S.
  46. Graph. Principal tensile strain angle in the web of Girder 14S.
  47. Graph. Principal compressive strain in the web of Girder 14S.
  48. Graph. Principal compressive strain angle in the web of Girder 14S.
  49. Photo. Girder 14S at (a) peak load and (b) postpeak load of 2,650 kN (595 kips).
  50. Illustration. Crack pattern at failure in Girder 14S.
  51. Graph. Predicted behavior of girders tested in the configuration of Girder 80F.
  52. Graph. Girder 80F midspan bottom flange strain throughout testing.
  53. Graph. Flexural crack spacing observed on the bottom flange of Girder 80F at a total applied load of 690 kN (155 kips).
  54. Graph. Flexural crack spacing related to tensile strain.
  55. Equation. Crack spacing as a function of strain.
  56. Graph. Tensile strain related to flexural crack spacing.
  57. Equation. Strain as a function of crack spacing.
  58. Equation. Relationship between the midspan vertical deflection of a girder and its effective moment of inertia.
  59. Equation. Relationship between the vertical deflection of a girder and its effective moment of inertia.
  60. Graph. Effective moment of inertia of Girder 80F.
  61. Equation. Virtual work relationship between applied moment and deflection.
  62. Equation. Cross-sectional flexural stiffness as a function of applied moment.
  63. Graph. Flexural stiffness of an AASHTO Type II girder.
  64. Graph. Ratio of predicted deflections and rotations to experimental results.
  65. Graph. Predicted and observed midspan deflection results.
  66. Graph. Predicted and observed load point deflection results.
  67. Graph. Predicted and observed quarter point deflection results.
  68. Graph. Predicted and observed end rotation results.
  69. Graph. Experimental strain profile results for midspan of Girder 80F.
  70. Graph. Analytically derived uniaxial stress-strain behavior of UHPC.
  71. Graph. Summation of forces on cross section during loading steps.
  72. Graph. External and internal moments on midspan cross section.
  73. Graph. Internally and externally determined moment of inertia.
  74. Equation. Shear capacity as a function of concrete strength.
  75. Equation. Fiber contribution to shear strength.
  76. Illustration. Truss model for failure of Girder 28S.
  77. Graph. Sample uniaxial stress-strain behavior for I-girder flexural design.

LIST OF TABLES

  1. Typical UHPC composition.
  2. Average steam-treated UHPC material properties from associated material characterization study.
  3. Chemical composition of steel fibers.
  4. Compression test results.
  5. Prism flexure test results.
  6. Test matrix.

 

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