Guide Specification for Service Life Design of Highway Bridges

NCHRP 12-108 Guide Specification for Service Life Design of Highway Bridges AASHTO Webinar NCHRP NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule DISCLAIMER: This investigation is sponsored by TRB under the NCHRP Program. Data reported is work in progress. The contents of this presentation has not been reviewed by the project panel or NCHRP, nor do they constitute a standard, specification, or regulation. 2 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Presentation Outline Research Project Overview Survey Results Guide Specification Outline Methodology Review of Guide Specification Sections Case Studies 3 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Research Team Firm POC Email Modjeski and Masters, Inc. Thomas Murphy Ed Wasserman Maria Lopez Travis Hopper TPMmurphy@modjeski.com Independent Consultant John Kulicki JMKulicki@modjeski.com Rutgers University-CAIT Frank Moon Nick Romano franklin.moon@rutgers.edu COWI Anne-Marie Langlois amln@cowi.com NCS GeoResources Naresh Samtani naresh@ncsgeoresources.com 4 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Project Objectives Develop an AASHTO Guide Specification for Service Life Design of Highway Bridges Develop Case Studies to demonstrate the application of the proposed Guide 5 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Overview of Guide Specification Section 1 – Introduction Section 2 – Classification Section 3 – General Design Guidelines Philosophy, approach, etc. Service life category, environmental exposure classes General design guidance Section 4 – Concrete Structures Section 5 – Steel Structures Section 6 – Foundations and Retaining Walls Section 7 – Renewable Elements Major organization by material, then component Guidance on deterioration mechanisms, protective measures, detailing, and construction within each section Section 8 – LCCA Overview of bridge LCCA Appendix A – Probabilistic Framework fib 34 full probabilistic method Appendix B – Case Studies Demonstrations of guide spec implementation 6 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Methodology What is the definition of service life? The period of time that the bridge is expected to be in operation – AASHTO LRFD (2014) The actual period of time during which a structure performs its design function without unforeseen costs for maintenance and repair – CSA S6-14 A period over which a structure or structural element is intended to perform its function without major maintenance or repair – AS 5100.5 Assumed period for which a structure or part of it is to be used for its intended purpose with anticipated maintenance, but without major repair being necessary – ISO 16204 and EN 1990 Research Team Definition: The assumed period of time the bridge is expected to remain in operation, without rehabilitation or significant repair, and with only routine maintenance. This would include replacement of renewable elements. Assumed period for which a structure or part of it is to be used for its intended purpose – fib Bulletin 34 The period of time after installation (or in the case of concrete, placement) during which all the properties exceed the minimum acceptable values when routinely maintained – ACI 365.1R (2000) 7 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Methodology Three tiered approach, separating practice into: Good Better Best Example: Steel protection Good: Unpainted weathering steel Better: Coated steel Best: Metallized A709 Majority of the methodology consists of: Deemed-to-satisfy Avoidance-of-deterioration Supplemented by probabilistically calibrated deemed-to-satisfy provisions where applicable, Chloride-induced corrosion 8 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Target Service Life Categories| Section 2: Classification Renewable Only used for probabilistic calibration Elements designed for replacement Normal Standard practice Enhanced Improvement over standard practice Maximum At or beyond practical designs Category Bridge Component Type Bridge Description Level of Qualitative Practice Target Service Life Renewable Bearings, joints, strip seals, guardrails, barriers, sign structures, coating systems, approach slabs, sleeper slabs, deck overlays All Replaceable - Typical bridges Good 75 Better 100 Best 150 Normal Enhanced All other components Maximum Bridges with high cost, high ADT, social context, etc. Bridges with higher cost, higher ADT, social context, etc. 9 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Exposure Zones| Section 2: Classification Rural/Mild/Non-Aggressive: little to no exposure to airborne or applied salts. Low pollution/humidity/precipitation Industrial/Moderate: occasional exposure to airborne salts or deicing salt runoff. Industrial areas with pollution Marine: coastal areas with exposure to airborne salts or direct contact with sea water/brackish water Deicing: region where de-icing salts are used with low to high application rate Macro Exposure Zones (Atmospheric) Weyers et al (1994) 10 NCHRP 12-108 directly exposed to de-icing salts Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Exposure Zones| Section 2: Classification Micro Exposure Zones not exposed to soil, water, or de-icing salts indirectly exposed to de-icing salt thru roadway splash/spray region above tidal zone subject to splash/spray not permanently submerged in water, subject to wet/dry cycles permanently submerged in water, below tidal zone permanently buried in soil, below the mudline (after consideration of all applicable scour) 11 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Exposure Zones| Section 2: Classification Roadway Splash/Spray Zone Centerline of Roadway Edge of Roadway y (see Note 2) x (see Note 1) Envelope of CSA and Eurocode guidance: CSA: x = 10 meters, y = 3 meters Eurocode: x = 6 meters, y = 6 meters Notes: 1x may be taken as 30 feet in lieu of other guidance 2y may be taken as 20 feet in lieu of other guidance 12 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Exposure Classes| Section 2: Bridge Classification Steel Category Class C1 C2 C3 Corrosion (C)1 C4 C5I C5M Fatigue (F) Notes: 1Adopted from ISO (2017) Condition Very low Low Description Atmospheres with low level of pollution, mostly rural areas Medium Urban and industrial atmospheres, moderate sulphur dioxide pollution, coastal areas with low salinity High Industrial areas and coastal areas with moderate salinity Very High Industrial Industrial areas with high humidity and aggressive atmosphere Very High Marine Offshore areas with high salinity and sub-tropical and tropical atmospheres See Article 6.6 of AASHTO LRFD Bridge Design Specifications 13 NCHRP 12-108 Background Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Exposure Classes| Section 2: Bridge Classification Concrete ACI Fall 2018 – Dennis Mertz Symposium 14 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule 3.2 Design Approach| Section 3: General Design Guidelines Deterioration Experience Drainage Decks Joints and Bearings 15 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule 3.2 Design Approach| Section 3: General Design Guidelines Deterioration Experience Concrete Steel Foundations and Retaining Walls 16 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule 3.2 Design Approach| Section 3: General Design Guidelines Deterioration Experience Utilities and Appurtenances 17 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Development of Cover Table| Section 4: Concrete Structures Two-phase service life model for chloride-induced corrosion Confidence level of 90% used for modeling 18 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Development of Cover Table| Section 4: Concrete Structures Estimate the time to corrosion initiation using Fick’s 2nd Law Chloride Concentration at Reinforcement Apparent Chloride Diffusion Coefficient  Ccrit  C ( x  a, t )  C0  C S ,x  C0  1  erf      a  X   2 Dapp ,C  t  𝐷𝑎𝑝𝑝 ,𝑐 = 𝑘𝑒 𝐷𝑅𝐶𝑀,0 𝐴(𝑡) Environmental Variable   1 1  ke  exp  be      Tref Treal   (Temperature)    Aging Function 𝐴 𝑡 = 𝑡𝑜 𝑡 𝛼 19      Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Development of Cover Table| Section 4: Concrete Structures Exposure Class Class C-M1 C-M2 C-M3 Condition Description Concrete Type2 Examples Any Any Surfaces OPCFA+SF, OPCFA, GGBS+SF, GGBS Marine exposed to OPC Superstructure Atmospheric airborne OPCFA+SF, GGBS chlorides OPCFA GGBS+SF OPC Any OPCFA+SF, OPCFA, GGBS+SF GGBS OPC Surfaces Substructures OPCFA+SF permanently between Marine OPCFA submerged mudline and Submerged with salt water GGBS+SF tidal zone present GGBS OPCFA+SF OPCFA, GGBS+SF GGBS Any OPCFA+SF OPCFA Surfaces in GGBS+SF contact with GGBS Marine - Tidal Substructures salt water OPC or within tidal either in the OPCFA+SF Splash/Spray zone or tidal zone or OPCFA, GGBS+SF Zone splash/spray splash/spray GGBS zone OPCFA+SF OPCFA GGBS+SF Reinforcement Class3 D C B B A A A A D C C C B B B B A A A D C C C C C B B B A A A Service Life Category Normal Enhanced Maximum Cover (in)1,4 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.5 1.5 1.5 1.5 2.0 2.0 2.0 2.5 2.5 1.5 1.5 1.5 2.5 2.5 3.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.5 1.5 2.0 2.5 2.5 1.5 1.5 1.5 1.5 2.0 2.0 2.0 2.0 2.0 2.5 2.5 3.0 2.5 2.5 2.5 3.0 3.0 3.5 4.0 1.0 1.0 1.0 1.5 1.5 1.5 1.5 1.5 2.0 1.5 2.0 2.0 2.0 2.0 2.5 3.5 4.0 2.0 2.0 2.5 2.5 2.5 3.0 3.5 3.5 4.0 3.0 3.0 3.5 3.5 4.0 4.0 3.5 4.0 Max Allowable Chloride Migration Coefficients (m2/s) OPC = 12.5x10-12 OPCFA = 8.0x10-12 OPCFA+SF = 4.7x10-12 GGBS = 5.0x10-12 GGBS+SF = 2.3x10-12 Reinforcement Class A: uncoated reinforcing steel (black bar) B: improved corrosion resistance C: higher corrosion resistance, not to level D D: highly corrosion resistant materials (316LN stainless steel) 20 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Development of Cover Table| Section 4: Concrete Structures Example – Concrete Pier Column Overpass structure – roadway adjacent to piers Target service life category = Enhanced Centerline of Roadway Edge of Roadway y (see Note 2) Notes: 1x may be taken as 30 feet in lieu of other guidance 2y may be taken as 20 feet in lieu of other guidance x (see Note 1) Within the roadway splash/spray zone PennDOT (2016) 21 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Development of Cover Table| Section 4: Concrete Structures Example – Concrete Pier Column Exposure Class Class Condition Description C-D1 C-D2 Surfaces exposed to airborne chlorides Indirect Deicing Salts Surfaces exposed or potentially exposed to drainage water containing deicing salts or roadway spray Reinforcement Class3 Any Any Any OPCFA+SF, GGBS+SF, GGBS OPCFA, OPC Any Any Any OPCFA+SF, GGBS OPCFA GGBS+SF OPC Any Any OPCFA+SF, OPCFA, GGBS+SF GGBS OPC OPCFA+SF OPCFA GGBS+SF D C B A A D C B A A A A D C B B B A A A GGBS A Examples Underside of Deck (Interior Bays) Atmospheric in a deicing salts environment Concrete Type2 All Other Surfaces (abutments, piers, pile caps, girders, underside deck overhang) Surfaces below expansion joints or drains, deck fascia, substructure surfaces near a roadway Service Life Category Normal Enhanced Maximum Cover (in)1,4 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.5 1.5 1.5 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.5 1.5 1.5 2.0 2.0 2.0 1.0 1.0 1.5 2.0 2.0 2.5 1.0 1.0 1.0 1.0 1.0 1.0 1.5 1.5 1.5 2.0 2.0 2.0 3.0 3.5 3.5 2.0 2.0 2.5 2.5 2.5 2.5 2.5 2.5 3.0 3.0 3.5 4.0 22 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Model Limitations| Section 4: Concrete Structures Concrete oriented in the vertical position Uncracked concrete • i.e., not bridge decks This is currently the best model we have to work with How to address horizontal concrete members (i.e., bridge decks)? • Crack width should be kept below a characteristic value – fib Bulletin 34 • Research shows cracking increases chloride diffusion, but magnitude of effect is not clear due to the number of influencing factors How do you design for cracking? At this time, must assume uncracked concrete or cracks are sufficiently small to prevent chloride ingress Promotion of quality materials and workmanship is key to preventing earlyage cracking 23 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Other Protection Strategies| Section 4: Concrete Structures Detailing Reinforcement Post-tensioning Drainage Decks Sealers and Overlays Waterproofing Membranes Concrete Curing FDOT (2017) PennDOT (2016) Corven and Morenten (2013) 24 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Deterioration Mechanisms| Section 5: Steel Structures Corrosion is the primary influencer on steel service life Fatigue should not be forgotten 25 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Protection Strategies| Section 5: Steel Structures Deemed-to-satisfy provisions by exposure class Service Life Category Mild (C2) Environmental Exposure Class Moderate (C3) Severe (C5-I) Normal Uncoated Weathering Grades Uncoated Weathering Grades Coated Non-weathering Grades Enhanced Uncoated Weathering Grades Uncoated Weathering Grades Metallized / Galvanized Non-weathering grades Maximum Uncoated Weathering Grades Coated Non-weathering Grades Uncoated Gr 50CR or Duplex Coated Non-weathering Grades Seacoast (C5-M) Coated or Metallized / Galvanized Non-weathering Grades Uncoated Gr 50CR or Duplex Coated Non-weathering Grades Duplex Coated Non-weathering Grades Notes: 1Where ASTM A709 Grades 50W or 70W are referenced, utilize HPS 50W or 70W for members in tension. 2When specifying metallization for main members, cross frames should be specified as galvanized. 26 Past Work Guide Spec Outline Methodology NCHRP 12-108 Guide Spec Sections Future Work Schedule Detailing| Section 5: Steel Structures Guidance on member detailing for corrosion, fatigue, and drainage McDad et al. (2000) Albrecht et al. (1989) FDOT (2017) 27 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule Overarching Considerations| Section 6: Foundations and Retaining Walls • There are many types of foundations and retaining walls • Each foundation or retaining wall type has an established design protocol that is often guided by specific industry groups • • Examples: PDCA (Pile Driving Contractors Association), ADSC (The International Association of Foundation Drilling), AMSE (Association of Mechanically Stabilized Earth), etc. Because of the large differences in established practices for different foundations and retaining walls, the 3-tiered concept of “Good-Better-Best” is not uniformly applicable and difficult to apply • An alternative 3-tiered approach has been developed using the concept of Protection Index, PI, based on the deterioration environment, consequences of adverse performance, location, and the type of facility supported • The PI approach (a) permits a uniform approach for all foundations and retaining walls (b) allows incorporation of past efforts and best practices to the greatest extent possible, and (c) provides flexibility to the owner based on local past successful practices. 28 NCHRP 12-108 Past Work Guide Spec Outline Methodology Guide Spec Sections Future Work Schedule NCHRP 12-108 Guide Specification for Service Life Design of Highway Bridges Questions? 29