Structural Strengthening of Concrete with FRP CompositesC
onst
ruct
ion
Presented at a meeting of the Thermoset Resin Formulators Association in Chicago, IL on September 16, 2008
David White, P.E.Sika Corporation
Lyndhurst, NJ
Why Do Structures Need Strengthening?
Insufficient reinforcement
Corrosion damage Change in use Structural damage Seismic upgrade
1950’s 2000’s
What are Composites?
Fiber reinforced polymers (FRP)• Fibers (carbon or glass)• Resins (epoxy matrix)
Reinforced concrete• Concrete (matrix)• Steel (reinforcement)
Composites are a combination of two or more distinct materials
Structures
Additional loads
Earthquake Ductility
FRP in Construction
Bridge Decks
Rebar
© U. Maryland
© U. Wisconsin
Material Properties
Grade 60 Rebar
E-Glass
Carbon
Type 270 PT Strand
0
100
200
300
400
500
600
0% 1% 2% 3% 4%
Tensile Strain (%)
Tens
ile S
tres
s (k
si)
Typical ApplicationsBridges
Girder Strengthening Column Wrapping Pier Upgrades Deck Stiffening
Typical Applications
Buildings
Modifications Change in use Wall
strengthening Seismic
upgrades
Typical ApplicationsParking Structures
Shear Strengthening
Corbel Upgrades Corrosion Damage Negative moment
strengthening
Epoxy Resins Pre-packaged kits (A/B) Mix with low speed drill Uniformly blended Different viscosities for various applications
liquid paste
Saturating the Fabric
FabricResin
Fabric Application
Damaged Girders
© NCHRP Panel 10-59
CFRP Laminate
Tensile Strength 406 ksi Modulus of elasticity 23.9 x 106 psi Elongation at break 1.7%
Designing with FRP
Provides supplemental reinforcement
Must comply with local building and fire codes
Concrete BeamLoad
Path of tension on beam
Shear crack
Negative moment cracks
Flexural cracks
Combination flexural and shear crack
CFRP Design SpreadsheetSample of Design Spreadsheet in English
User input in white areas
Confirmation it WORKS!
Number of Strips or Number of Fabric Layers
Available Documents ACI 440
• State-of-the-Art– Published 1996
• ACI 440.2R-08 (Design Guide)
CarboDur Design Software
Blast Hardening Embassy work Gov’t buildings Chemical & Industrial Plants Airports
©Baker Engineering
Case Studies
Sunshine Skyway Bridge
Con
stru
ctio
n
Sika Corporation
Ohio State University Stadium
Conclusions
Composites are now considered a viable means of strengthening existing structures
Thousands of projects have already been successfully strengthened with FRP materials
National guidelines are available to assist Engineers in design (i.e. ACI 440, ICRI, NCHRP, etc.)
Thank you
Con
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