Durability of Post-Tensioning: fib Bulletin 33 and FHWA Scan tour Findings. Presented by Brett Pielstick P.E., F.ASCE

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1 Durability of Post-Tensioning: fib Bulletin 33 and FHWA Scan tour Findings Presented by Brett Pielstick P.E., F.ASCE 1

2 Introduction Early Durability Issues Assessment Concrete Society TR-47 FHWA Scan Tour fib Bulletin 33 Florida Strategies Conclusions

3 Early Durability Issues EU Performance Seg l and Cable Stay FHWA Scan Tour European average 10 years older than US First segmental bridges - from 1960 s First modern cable-stay - c (Swiss) Overall performance is good - Europeans are well satisfied and continue to build them Old-issues c s (e.g. excess creep deflection, etc.) solved by standards and practice introduced in All now O.K.

4 Early Durability Issues Rehab of 1st Generation (pre 1970 s) Chillon Viaduct (Switzerland) Added PT to cantilevers with mid-span hinges No corrosion - good waterproofing / overlay Autobahn Bridges (various - Germany) Cracks at 1/4 span joints with coupled tendons Add external grease and sheath mono-strand Corbeil Bridge (France) Added external longit PT to midspan - with Transverse PT to bottom slab / internal frames

5 Early Durability Issues Chillon Viaduct, Switzerland, built 1967 Continuous Midspan hinges Deflection External PT added Waterproof deck - no corrosion of tendons

6 Early Durability Issues Rehab. of Coupling Joint - Koln, 1999

7 Early Durability Issues Corbeil Bridge Rehabilitation France

8 Early Durability Issues Internal Transverse Frames

9 Early Durability Issues Failures of pc-bridges in Europe due to corrosion of the pt-tendons: 1967: 2 pedestrian bridges (UK) 1985: Ynis-y-Gwas Bridge (UK) 1992: Bridge over the Melle River (B) 1999: San Stefano Bridge (I)

10 Early Durability Issues San Stefano Bridge (I):

11 Early Durability Issues San Stefano Bridge (I):

12 What are the problems? Voids Bleed water Recharge water Failure due to corrosion Material Deficiencies Poor Design Details Poor Construction Practices Assessment US Experience EU Experience

13 Assessment EU Maintenance Policy All EU countries perform regular inspections or condition checks Generally, pro-active repair is implemented as soon as any damage found Bridge Management Systems vary according to country, resources and needs but most are similar to those in the US Maintenance funds may meet half of need (compare to US where only 10 to 20%)

14 Assessment Non-Destructive Evaluation (NDE) EU and US methods for old tendons and stays: gammagraphy x-ray ultra-sonic georadar magnetic perturbation electrical resistance etc all only partially useful = no magic bullet

16 CONCRETE SOCIETY TR 47 Durable post-tensioned concrete bridges Holistic approach, covering:- Materials Design Detailing Construction quality Concept of multi-layer protection to the tendons to the structural elements to the bridge as a whole Scope All bridges in all environments, without preknowledge of design details or construction quality

17 DESIGN DETAILS POST-TENSIONING DURABILITY Exposed Anchorage

18 DESIGN DETAILS Expansion Joint

19 DESIGN DETAILS POST-TENSIONING DURABILITY Buried Anchorage

20 fib Bulletin 33: Durability of post-tensioning tendons Recommendation prepared by Task Group 5.4: Jean Philippe Fuzier Peter Matt Hans Rudolf Ganz

21 fib Bulletin 33: Durability of post-tensioning tendons 1. Design concepts for durable post-tensioning tendons 2. Materials and construction 3. Maintenance, assessment and rehabilitation References Appendix: Maintenance, assessment and Appendix references rehabilitation of post-tensioning tendons in existing structures

22 fib Bulletin 33: Durability of post-tensioning tendons Hazard scenarios for prestressing steel in a typical box girder bridge

23 fib Bulletin 33: Durability of post-tensioning tendons Protection levels for post-tensioning tendons Structural protection layers [Protection provided by structure] High Medium Low High PL3 Aggressivity or Exposure Medium PL2 Low PL1

24 fib Bulletin 33: Durability of post-tensioning tendons Aggressivity of the environment and exposure examples: Based on EN classes Aggressivity level: Class [Description of environment] [Informative examples where exposure classes may occur] 1 No risk of corrosion or attack Low: X0

25 fib Bulletin 33: Durability of post-tensioning tendons Aggressivity of the environment and exposure examples: Based on EN classes Aggressivity level: Class [Description of environment] [Informative examples where exposure classes may occur] 1 No risk of corrosion or attack Low: X0 2 Corrosion induced by carbonation Low: XC1, Medium: XC4

26 fib Bulletin 33: Durability of post-tensioning tendons Aggressivity of the environment and exposure examples: Based on EN classes Aggressivity level: Class [Description of environment] [Informative examples where exposure classes may occur] 1 No risk of corrosion or attack Low: X0 2 Corrosion induced by carbonation Low: XC1, Medium: XC4 3 Corrosion induced by chlorides other than from sea water Medium: XD1, High: XD3 4 Corrosion induced by chlorides from sea water Medium: XS1, High: XS3

27 Aggressivity of the environment and exposure examples: Based on EN classes Aggressivity level: Class [Description of environment] [Informative examples where exposure classes may occur] 1 No risk of corrosion or attack Low: X0 2 Corrosion induced by carbonation Low: XC1, Medium: XC4 3 Corrosion induced by chlorides other than from sea water Medium: XD1, High: XD3 4 Corrosion induced by chlorides from sea water Medium: XS1, High: XS3 5 Freeze / thaw attack with or without de-icing agents Moderate saturation High saturation Medium: XF1 Medium: XF3 [No de-icing agent] High: XF2 High: XF4 [With de-icing agent] 6 Chemical attack Medium: XA1, High: XA3

28 Agressivity level and exposure examples: Based on EN classes Aggressivity level Class Description of environment 1 No risk of corrosion or attack Low X0 For concrete without reinforcement or embedded metal: all exposures except where there is freeze/thaw, abrasion or chemical attack. For concrete with reinforcement or embedded metal: very dry. 2 Corrosion induced by carbonation Informative examples where exposure classes may occur Concrete inside buildings with very low air humidity Low XC1 Dry or permanently wet Concrete inside buildings with very low air humidity Concrete permanently submerged in water XC2 Wet, rarely dry Concrete surfaces subject to long-term water contact Many foundations XC3 Moderate humidity Concrete inside buildings with moderate or high air humidity External concrete sheltered from rain Medium XC4 Cyclic wet and dry Concrete surfaces subject to water contact, not within exposure class XC2

29 fib Bulletin 33: Durability of post-tensioning tendons Protection provided by the structure Recognizes concept of multi-layer protection and related influences: Concrete quality and cover Waterproofing / surface protection systems Drainage system Expansion joints Cracking Construction joints Segment joints Tendon layout Access for inspection & maintenance

30 fib Bulletin 33: Durability of post-tensioning tendons Protection provided by the structure Recognizes concept of multi-layer protection and related influences. Further considerations are: the quality of construction: contractor qualification, specific competence, workmanship certification products availability, quality of materials inspection and maintenance program possibility of tendon replacement

31 fib Bulletin 33: Durability of post-tensioning tendons Tendon system for Protection level 1 PL1 Temporary protection cap Anchor head Prestressing steel Sheet metal duct Cement grout 60mm Anchorage

32 fib Bulletin 33: Durability of post-tensioning tendons Tendon system for Protection level 2 PL2 Permanent protection cap Anchor head Prestressing steel Plastic duct Cement grout 60mm Anchorage

33 fib Bulletin 33: Durability of post-tensioning tendons Tendon system for Protection level 3 PL3 Isolating protection cap Anchor head Prestressing steel Plastic duct Isolating insert Cement grout 60mm Anchorage Electrical connection for the resistance measurement For unbonded tendons, the cement grout is replaced by grease in the above systems, and there should be a permanent cap for all systems.

34 Bulletin 33: Further considerations For the finished works to be durable it is necessary: To make reference international QA & QC standards For good design practice to be matched with good construction practice. For expertise and craftsmanship to be recognised & required in project specifications in order to assure that best practices are followed. That protection Levels (PL) should be established by performance testing rather than by prescriptive solutions.

resistance of tendons (PL3) End caps and electrical

35 fib Bulletin 33: Durability of post-tensioning tendons Instrument for measuring the electrical resistance of tendons (PL3) End caps and electrical junction box for monitoring of electrically isolated tendons (PL3)

36 Bulletin 33: Construction Details

37 Florida Strategies Contents Precast Balanced Cantilever Precast Span-by-Span Spliced I-Girders CIP Balanced Cantilever CIP on Falsework Substructures Transverse Superstructure Condition Inspection & Maint. Load Rating Concrete Segmental Concrete Beam

38 Florida Strategies Objective To Provide Consistency and Uniformity in the Design, Detailing, and Construction of Post- Tensioned Structures in Order to Provide a Higher Quality Product with a Minimum Cost Increase

39 Florida Strategies Objective More Specifically, to Improve the Quality of PT Hardware, Grouting, and Anchor Protection in Order to Reduce the Incidences of Recharge and Corrosion in Post-Tensioned Structures

40 Florida Strategies Post-Tensioning Strategies Enhanced PT Systems Multiple Tendons Paths FDOT PT Strategy Fully Grouted Tendons Watertight Bridges Anchor Protection

41 Florida PT Strategy Florida Strategies Requirements Enhanced PT Systems Fully Grouted Tendons Anchor Protection Watertight Bridges Multiple Tendon Paths Pre-Approved PT Systems Pre-Bagged Grout Requirements Three-Level Continuous Protection Anchorage Plastic Ducts Accessibility with Improved Cell Class Low Positively Point Sealed Injection Requirements Ducts Semi-Standard Permanent Plastic Requirements Drawings Anchor Caps 4 Certified Pressure Levels Grouters of Testing Protection and Inspectors No Dry Joints Semi Controlled Standard Rates Details of Grouting Pre-formed Tapered Holes Anchorages Flow Rate Testing Sealed of at Ejected all Times Material Drip Notches at Anchorages Inspect Voids and Secondary Grout Bottom Slab Drains Requirements Sealed Surfaces of Secondary Pours Wearing Maximize Surfaces Use of Smaller for Ride Tendons not Protection No Permanent Impact Due Tensile to Loss Stresses of Critical Tendon Compensation for Loss Due to Corrosion

42 Florida Strategies Objective Strategy 1 Enhanced Post-Tensioning Systems Sealing Of Grout Ports, Vents and Drains Strategy 2 Fully Grouted Tendons Accessible Anchors Grouting of Tendons / General Procedures

43 Florida Strategies Objective Strategy 3 Multi-Level Anchor Protection Anchors at Expansion Joints / Inside Boxes / Blisters Embedded Anchors Strategy 4 Watertight Bridges: Double Face Epoxy Access, Lifting Holes Drip Notches

44 Florida Strategies Objective Strategy 5 Multiple Tendon Paths Maximize Use of Smaller Tendons Design for Tendon Loss Compensation for Loss Due to Corrosion

45 Florida Strategies Balanced Cantilever Construction

46 Florida Strategies Balanced Cantilever Construction

47 Florida Strategies Critical Nature of Tendons Type of Construction CIP on Falsework CIP Balanced Cantilever P/C Balanced Cantilever P/C Span-By-Span P/C Beam w/ CIP Slab Structural Purpose Superstructure Substructure Construction vs. Permanent Bonded vs. Unbonded Tendon Protection System Mat ls Duct, Anchor, Grout Wet vs. Dry Joints Risk of Exposure Maintainability Access to Inspect Components Applicability of Test Methods Ability to be Replaced Redundancy External # & Distribution of Tendons

48 Florida Strategies Drawing Indices Instructional Notes Post-Tensioning Vertical Profiles Post-Tensioning Anchorage Protection Post-Tensioning Anchorage and Grouting Details

49 Florida Strategies Instructional Notes Designer to Provide Tendon Profile and Anchor Protection Type for Each Type of Tendon Tendon Profile and Anchor Protection Type to be Included in the PT Schedule

50 Florida Strategies Instructional Notes Tendon Profiles may be Amended by the Engineer EOR Responsible for Reviewing the Contractors Grouting Plan (Shop Drawings) Deviations from the Standards shall be Approved by the FDOT

51 Florida Strategies Reminder Details are Great but one Must Always INTEGRATE STRATEGIES INTO THE CONSTRUCTION AND MATERIALS SPECIFICATIONS One gets what he INSPECTS not what he EXPECTS

52 Florida Strategies Post-Tensioning System example items Inspectable Anchors Bar Couplers Permanent Grout Caps Inlets and Outlets Duct Schedule 40 Steel or Plastic Polypropylene Corrugated Duct Polyethylene Smooth Duct (Dr 17) Pressure Testing Components with System

53 Florida Strategies Plastic Duct And Connections example issues All Components Assembled into Pressure Tested Systems Polypropylene Corrugated Duct for Internal Tendons Greater Stiffness with Less Heat Gain Polyethylene Duct Thick Wall with Pressure Pipe Chemistry In-place Testing for Leaks Before Grouting

54 Florida Strategies Where is Florida Now? Revisiting Galvanized Ducts for Beam Bridges Evaluating Pressure Testing of Systems in Field Utilizing New DSI Coupler System on I-95/I-295 North Flyover, Jacksonville, Florida

55 FHWA European Scan - Conclusions In general, segmental and cable-stay bridges in Europe are performing well They comprise important technology and are still being designed and built. The Scan found no new dramatic revelations In general, US and EU head in same direction - thus confirming current practice

56 17st Causeway, Ft Lauderdale, Florida Ernest Lyons, Stuart, Florida Garcon Point, Oriole Beach, Florida Memorial Causeway, Clearwater, Florida Hathaway Bridge, Panama City, Florida

57 Sallingsund, Denmark (opened 1979) Sunnibergbrucke - Switzerland Chillon Viaduct, Switzerland, built 1967 M180, Trent Bridge, UK, (opened 1979)

58 Proper Procedure & Inspection will Yield Enduring Results Acosta Bridge Jacksonville, Florida Seabreeze Bridge Daytona Beach, Florida Broadway Bridge Daytona Beach, Florida

The Hashemite University Department of Civil Engineering. Dr. Hazim Dwairi. Dr. Hazim Dwairi 1

The Hashemite University Department of Civil Engineering. Dr. Hazim Dwairi. Dr. Hazim Dwairi 1 Department of Civil Engineering Lecture 2.1 Methods of Prestressing Advantages of Prestressing Section remains uncracked under service loads Reduction of steel corrosion (increase durability) Full section