Structural Strengthening of Concrete with FRP CompositesC

onst

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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

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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

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