U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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This report is an archived publication and may contain dated technical, contact, and link information |
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Publication Number: FHWA-HRT-05-058
Date: October 2006 |
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Optimized Sections for High-Strength Concrete Bridge Girders--Effect of Deck Concrete StrengthPDF Version (751 KB)
PDF files can be viewed with the Acrobat® Reader® FOREWORDFor more than 25 years, concretes with compressive strengths in excess of 41 megapascals (MPa) (6,000 pounds per square inch (psi)) have been used in the construction of columns of highrise buildings. While the availability of high-strength concretes was limited initially to a few geographic locations, opportunities to use these concretes at more locations across the United States have arisen. Although the technology to produce higher-strength concretes has developed primarily within the ready-mix concrete industry for use in buildings, the same technology can be applied in the use of concretes for bridge girders and bridge decks. The durability of concrete bridge decks has been a concern for many years, and numerous strategies to improve the performance of bridge decks have been undertaken.Many of the factors that enable a durable concrete to be produced also result in a high-strength concrete. Consequently, if a concrete for a bridge deck to be durable, it will probably also have a high compressive strength.This report contains an evaluation of the effect of high-performance concrete on the cost and structural performance of bridges constructed with high-performance concrete bridge decks and high-strength concrete girders. Several areas with the potential for improved structural performance through the use of high-performance concretes are investigated. This report should also assist designers and owners in recognizing that the use of high-performance concrete in bridges has advantages beyond those of improving durability. Gary 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
SI (Modern Metric) Conversion Factors PREFACEFor over 25 years, concretes with specified compressive strengths in excess of 41 MPa (6,000 psi) have been used in the construction of columns of highbrows. While the availability of the high-strength concretes was limited initially to a few geographic locations, opportunities have developed to use these concretes at more locations across the United States. As these opportunities have developed,material producers and contractors have accepted the challenge to produce concretes with higher compressive strengths. In the precast, prestressed concrete bridge field, a specified compressive strength of 41 MPa (6,000 psi) for bridge girders has been used for many years. However,strengths at release have often controlled the concrete mix design so that actual strengths at 28 days were often in excess of 41 MPa (6,000 psi). It is only in recent years that a strong interest in the utilization of concrete with higher compressive strengths has emerged. This interest has developed at a few geographic locations for specific projects in a manner similar to the development in the building industry. In parallel with an increased interest in the use of high-strength concretes in bridge girders,the use of high-performance concretes in bridge decks has also been receiving increased attention as a means of improving durability. High-performance concretes provide higher resistance to chloride penetration, higher resistance to deicer scaling, less damage from freezing and thawing, higher wear resistance, and less cracking. Many of the methods used to increase the durability of concrete result in a concrete that has a higher compressive strength. However, the higher concrete strength is rarely considered because the design of prestressed girders is controlled by service load stresses caused by dead load, live load, and impact. This report contains an evaluation of the effect of high-performance concrete on the cost and structural performance of bridges constructed with high-performance concrete bridge decks and high-strength concrete girders. Several areas with the potential for improved structural performance through the use of high-performance concretes are investigated. This report should assist designers and owners in recognizing that the use of high-performance concrete in bridges has advantages beyond those of improving durability. The research described in this report was sponsored by the Federal Highway Administration as part of their program to encourage the greater use of high-performance concretes in bridges. The program includes analytical and experimental research as well as showcase projects. The authors believe that high-performance concrete represents a technology with great potential for improving the infrastructure of the highway system. Table of ContentsOPTIMIZED CROSS SECTIONS FOR BRIDGE GIRDERS HIGH-PERFORMANCE CONCRETE IN BRIDGE DECKS EFFECT OF HIGH-STRENGTH CONCRETE ON PRESTRESS LOSSES CHAPTER 2. TASK 1: COST ANALYSES OF HIGH-PERFORMANCE CONCRETE IN BRIDGE DECKS EFFECTS OF CONCRETE STRENGTH ONLY CHAPTER 3. TASK 2: ANALYSES OF FLEXURAL STRENGTH AND DUCTILITY MOMENT-CURVATURE RELATIONSHIPS CHAPTER 4. TASK 3: ANALYSES OF PRESTRESS LOSSES AND LONG-TERM DEFLECTIONS CHAPTER 5. CONCLUSIONS AND RECOMMENDATIONS List of FiguresFigure 3. Cost chart for a BT-72, 41 MPa. Figure 4. Optimum cost curves for a BT-72, 41 MPa. Figure 5. Optimum cost curves for a BT-72, 83 MPa. Figure 6. Optimum cost curves for a BT-72, 55 MPa. Figure 7. Optimum cost curves for a BT-72, 69 MPa. Figure 8. Comparison of optimum cost curves for a BT-72 with varying concrete strengths. Figure 9. Comparison of optimum cost curves for a FL BT-72 with varying concrete strengths. Figure 10. Optimum cost curves for a BT-72, 41 MPa with cost premium. Figure 11. Optimum cost curves for a BT-72, 55 MPa with cost premium. Figure 12. Optimum cost curves for a BT-72, 69 MPa with cost premium. Figure 13. Optimum cost curves for a BT-72, 83 MPa with cost premium. Figure 14. Optimum cost curves for a FL BT-72, 41 MPa with cost premium. Figure 15. Optimum cost curves for a FL BT-72, 83 MPa with cost premium. Figure 17. Stress–strain curves for concrete used in BEAM BUSTER analysis. Figure 18. Stress–strain curve for prestressing strand used in BEAM BUSTER analysis. Figure 19. Moment–curvature relationships for BT-72, 41 MPa at a span of 24.4 m. Figure 20. Moment-curvature relationships for BT-72, 83 MPa at a span of 24.4 m. Figure 21. Moment-curvature relationships for BT-72, 41 MPa at a span of 44.5 m. Figure 22. Moment-curvature relationships for BT-72, 83 MPa at a span of 53.3 m. Figure 24. Variation of specific creep with compressive strength as published. Figure 25. Variation of ultimate specific creep with compressive strength. List of TablesTable 1. Task 1 variables (SI units). Table 2. Task 1 variables (English units). Table 3. Deck design (English units). Table 4. Deck design (SI units). Table 5. Ratios for high-strength concrete. Table 6. In-place costs as per ACI Committee 363. Table 7. Selected ratios for cost index per unit area to premium costs. Table 8. Relative premium costs of high-strength concretes. Table 9. Task 2 variables (SI units). Table 10. Task 2 variables (English units). Table 11. Calculated values of modulus of elasticity. Table 12. Calculated stresses and strains at maximum moment (SI units). Table 13. Calculated stresses and strains at maximum moment (English units). Table 14. Calculated flexural strengths (SI units) Table 16. Task 3 variables (SI units). Table 17. Task 3 variables (English units). Table 18. Values of creep used in PBEAM.
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