Strengthening a Concrete Slab Bridge Using Carbon Fiber Reinforced Polymer (CFRP) Composites Presentation to: NJDOT Design Summit 2009 By: Thomas G. Zink, P.E.
Structurally Deficient What Does it Mean? Deck, Superstructure, or Substructure with a Condition Rating 4 Advanced deterioration Loss of capacity Low Inventory Rating Not necessarily unsafe Requires immediate attention/repair
Case Study - 19 th Ave. Bridge over Salt River Canal Typical Concrete Slab Bridge Constructed 1940 s Widened 1960 s Three spans Five lanes ADT = 30,000 Deficient Load Capacity Should be Posted Original Concept Full Replacement $3.5 - $4.5 million 10-12 months
Innovative Solution: Strengthen using CFRP Material Rapid solution was desired Truesdell/Gannett Fleming Design-Build Team proposes CFRP alternative Why CFRP materials? High strength Low density Corrosion resistance Easily fabricated/shipped Jobsite handling Green alternative Speed of installation Cost benefit
A Two Part Solution Positive Moment Regions Surface bonded CFRP sheets SikaWrap Hex 103C Two layers of 1 x 15 strips Spaced at 3 centers High strength adhesive Negative Moment Regions Near Surface Mount solution 1 x ¾ grooves in slab CFRP bars grouted in grooves Aslan 200 Bar 0.5 diameter (13 long) 63 bars at 10 centers ¾ thick polymer overlay
Design Approach Inspection Determine in-situ material properties NDT (including GPR) Supplemental mild destructive tests Coring Determine existing live load capacity Compute additional capacity needed ACI 440.2R-08: Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures
Load Rating Comparison Vehicle Before Retrofit After Retrofit RF Tons RF Tons HS-20 - IR 0.43 15.6 1.0 36 HS-20 - OR 0.72 26 1.67 60 Rating Factors 1.0 Load Posting Not Required CFRP wraps increased (+) flexural capacity by 140% CFRP rods increased (-) flexural capacity by 80%
Construction and Instrumentation Surface preparation key Remove deteriorated concrete Patch spalls & fill cracks Air blast Vibration control during 48 hr cure Smart Structure Instrumentation Strain gauge sensors Benchmark tests Solar powered wireless data transmission
Load Test Verification City owned trucks Placed to produce maximum bending Concrete strain reduction observed Testing verified the successful participation of the CFRP components in resisting live load.
Bridge Ratings Cost Savings Inventory HS-9 (16 tons) Inventory HS-20 (36 tons) Before Operating HS-14 (26 tons) $ Millions After 2 Operating HS-33 (60 tons) 5 4 3 1 0 CFRP Replace Advantages of CRFP Strengthening Alternative: Construction time: 3 weeks Minimal disruption to traffic Green Solution Substantial cost savings
CFRP Strengthening Opportunities in New Jersey 6,447 bridges in the State Average age: 50 years 693 (11%) are Structurally Deficient 1,504 (23%) are Functionally Obsolete Deterioration continues Much work; limited funding Fix-it-First approach Other potential CFRP applications include: Pier strengthening Culvert strengthening Seismic hardening Concrete pavement repair
Thank You! Any questions, please contact: Tom Zink (856) 802-9930