Replaceable Grouted External Post-Tensioned Tendons 6
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Replaceable Grouted External Post-Tensioned Tendons Publication No. FHWA-HIF-19-067 October 2019 Notice This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) 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. They are included for informational purposes only and are not intended to reflect a preference, approval, or endorsement of any one product or entity. FHWA is the source for all images unless otherwise noted, 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 TECHNICAL REPORT DOCUMENTATION PAGE 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA-HIF-19-067 4. Title and Subtitle 5. Report Date October 2019 Replaceable Grouted External Post-Tensioned Tendons 6. Performing Organization Code: 7. Author(s) 8. Performing Organization Report No. Ledesma, T. 9. Performing Organization Name and Address 10. Work Unit No. 11. Contract or Grant No. WSP USA DTFH61-14-D-00048 One Penn Plaza, 2nd floor, 250 W 34th Street NY 10119 New York United States 12. Sponsoring Agency Name and Address 13. Type of Report and Period 14. Sponsoring Agency Code Federal Highway Administration Office of Infrastructure – Bridges and Structures 1200 New Jersey Ave., SE Washington, DC 20590 15. Supplementary Notes Work funded by task order “Advance Concrete Bridge Technology to Improve Infrastructure Performance” between FHWA and WSP. 16. Abstract Corrosion of prestressing strands has required replacement of external post-tensioning tendons in several existing post-tensioned bridges. External tendons are commonly used in concrete box girder bridges constructed using the span-by-span or balanced cantilever methods. Currently in the US, external tendons are discretely bonded at anchorages and deviator locations. Replacement of these types of tendons is a complex and time-consuming operation with safety concerns for personnel. Under task order 5009, WSP conducted a state-of-the-art review, then developed and presented guidance for fully replaceable grouted external tendons. Specific details included post-tensioning system components, structural design and detailing aspects, and tendon installation and replacement procedures. 17. Key Words 18. Distribution Statement No restrictions. This document is available to the public Post-tensioning, bridge design, box girder, through the National Technical Information Service, replaceable, deviator, diablo, double enveloped Springfield, VA 22161. 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified 47 Free Form DOT F 1700.7 (8-72) Reproduction of completed page authorized. TABLE OF CONTENTS 1.0 INTRODUCTION ---------------------------------------------------------------------------1-1 1.1 Background -------------------------------------------------------------------------------1-1 1.2 Objectives ---------------------------------------------------------------------------------1-1 1.3 Review of Other Replaceable Tendon Concepts --------------------------------1-2 2.0 REPLACEABLE EXTERNAL TENDON CONCEPT ------------------------------2-4 2.1 Current Detailing of External Tendons----------------------------------------------2-4 2.2 Proposed Detailing of External Tendons -------------------------------------------2-7 3.0 DIABOLOS ----------------------------------------------------------------------------------3-1 3.1 Cross Section Shape -------------------------------------------------------------------3-1 3.2 Basic Geometry --------------------------------------------------------------------------3-4 3.3 Diabolo Uses -----------------------------------------------------------------------------3-5 3.4 Half-Shell Cushion Form System ----------------------------------------------------3-8 4.0 POST-TENSIONING ANCHORAGES ------------------------------------------------4-1 5.0 TESTING -------------------------------------------------------------------------------------5-1 5.1 SR 826/ SR 836 Interchange Design-Build Project, Miami, FL ---------------5-1 6.0 DESIGN PARAMETERS -----------------------------------------------------------------6-1 6.1 Tendon Curvature Effects -------------------------------------------------------------6-1 6.2 Diabolo Dimensions---------------------------------------------------------------------6-2 6.3 Deviators with Diabolos ----------------------------------------------------------------6-3 7.0 CONSTRUCTION CONSIDERATIONS ----------------------------------------------7-1 7.1 Diabolo Construction -------------------------------------------------------------------7-1 7.2 Grouting of External PT Tendon -----------------------------------------------------7-3 7.3 De-tensioning an External PT Tendon----------------------------------------------7-4 7.4 Stressing of New External PT Tendon----------------------------------------------7-6 8.0 REFERENCES -----------------------------------------------------------------------------8-1 i LIST OF FIGURES Figure 1-1 Typical External Tendons in a Box Girder ------------------------------------- 1-1 Figure 2-1 Typical External Tendon Details ------------------------------------------------- 2-4 Figure 2-2 Bonded Rigid Steel Pipes in Deviator ------------------------------------------ 2-5 Figure 2-3 Bonded Rigid Steel Pipe in Diaphragm ---------------------------------------- 2-5 Figure 2-4 Cracked Concrete Anchor Block During De-tensioning -------------------- 2-6 Figure 2-5 Rigid Steel Pipe Pull-out Resulting in Spalled Concrete ------------------- 2-6 Figure 2-6 Replaceable External Tendons using the Double Envelope Concept -- 2-7 Figure 3-1 Alternative Diabolo Cross Section Shapes ------------------------------------ 3-2 Figure 3-2 Rendering of Trumpet Shaped Diabolos at a Deviator --------------------- 3-3 Figure 3-3 Rendering of Race Track Shaped Diabolos at a Deviator ----------------- 3-3 Figure 3-4 View of External Tendons at a Deviator --------------------------------------- 3-4 Figure 3-5 Diabolo Form Basic Geometry --------------------------------------------------- 3-5 Figure 3-6 Elevation View of a Span-by-Span Bridge with External Tendons ------ 3-6 Figure 3-7 Type 1 Form at Deviator----------------------------------------------------------- 3-6 Figure 3-8 Type 2 Form at Pier Diaphragm for a Continuous Tendon ---------------- 3-7 Figure 3-9 Type 3 Form near Anchorage ---------------------------------------------------- 3-7 Figure 3-10 Type 4 Form near Anchorage -------------------------------------------------- 3-8 Figure 3-11 DSI PE Deflection Half Shell Systems ---------------------------------------- 3-9 Figure 3-12 DSI Half Shell Inserts in Diaphragm during Installation------------------ 3-10 Figure 3-13 DSI PE Half Shell Inserts ------------------------------------------------------- 3-10 Figure 4-1 DSI External PT Plate Anchorage System ------------------------------------ 4-1 Figure 4-2 VSL Type A Plate Anchorage System ----------------------------------------- 4-2 Figure 4-3 VSL Type GC Anchorage System for External Tendons ------------------ 4-2 Figure 5-1 ETAG 013 Deviator Test Set-up for Static Load Test ---------------------- 5-2 Figure 5-2 Diabolo Test Specimen Prior to Concreting----------------------------------- 5-2 Figure 5-3 Diabolo Testing in Progress ------------------------------------------------------ 5-3 Figure 5-4 Stressing Jack Fully Retracted--------------------------------------------------- 5-3 Figure 5-5 Duct Internal Area Wear after Testing------------------------------------------ 5-4 Figure 6-1 Minimum Tendon Radii and Tangent Length --------------------------------- 6-1 Figure 6-2 Deviator Design --------------------------------------------------------------------- 6-3 Figure 7-1 Diabolo Constructed using Removable Form – During Construction --- 7-1 ii Figure 7-2 Diabolo Constructed using Stay-In-Place Form ------------------------------ 7-2 Figure 7-3 Diabolo Constructed using Removable Form – After Construction ------ 7-2 Figure 7-4 Current Grouting Detail for Tendon at Diaphragm--------------------------- 7-3 Figure 7-5 Proposed Grouting Detail for Tendon at Diaphragm ------------------------ 7-3 Figure 7-6 Proposed Grouting Detail for Tendon at Diaphragm ------------------------ 7-4 Figure 7-7 Tendon De-tensioning Schematic ----------------------------------------------- 7-5 Figure 7-8 U-bolt Clamps around Strands --------------------------------------------------- 7-6 Figure 7-9 Stressing End Clearance Diagram ---------------------------------------------- 7-7 Figure 7-10 Anchorage Clearance at Interior Diaphragm for Span-by-Span Construction ---------------------------------------------------------------------------------------- 7-9 Figure 7-11 Non-Stressing End Anchorage Clearance at End Diaphragm ---------- 7-9 LIST OF TABLES Table 1-1 External Tendon Requirements in Various Countries ----------------------- 1-3 Table 6-1 Minimum