FRP FOR SUSTAINABLE PRECAST CONCRETE STRUCTURES Sami Rizkalla - - PowerPoint PPT Presentation

FRP FOR SUSTAINABLE PRECAST CONCRETE STRUCTURES

Sami Rizkalla North Carolina State University October 21-22, 2009

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Underground Precast Utility Tanks

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First Bulb-Tee bridge girder pre- tensioned with CFRP tendons

1993 Beddington Trail Bridge

No signs of degradation when tested in July 2008, after 15 years of service

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Instrumentation of the girder before casting First AASHTO Girder prestressed and Reinforced with CFRP CFRP stirrups

1997 Taylor Bridge

Route 40 Bridge, Virginia

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Bending Resistance

CFFT Piles

Confinement effect

+

100 200 300 400 500 600 700 2 4 6 8 10 12 strain (µε) load (kN)

Axial Resistance

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5.8 t 12 t

Power line poles

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Recent Innovation for Precast Concrete Products

• Double-Tee beams
• Wall Panels

– Composite – Non-composite

• Architectural Cladding

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“Corrosion Free” Double-Tee

Thin flange susceptible to chloride penetration CFRP Grid replacement for WWF conventional steel

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Carbon Fiber Grids

Carbon grids are manufactured in an automated process: – High production volume – High quality control

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Pre-topped Double Tees

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Pre-topped Double Tees

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Carbon Fiber Installation

• Embedment and finishing

machine to place the grid

• More precisely for optimum

performance

• More consistent; less opportunity

for human error

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Research and Development at NC State

Uniformly distributed applied load Experimental Program

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Testing Program

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Testing Program

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Testing Program

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Testing Program

Initial Cracking: DT1 DT2

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Results

Failure Mode DT1 2” thick flange

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Results

Failure Mode DT1 2” thick flange

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Results

“Failure” Mode DT2 3.5” thick flange

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Results

2” thick flange – Midspan

• 0.1

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 2 4 6 8 10 12 Distance along DT Profile (ft.) Measured Vertical Deflection (in.) Ultimate Service Factored 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2 4 6 8 10 12 Distance along DT Profile (ft.) Measured Vertical Deflection (in.) Ultimate Service Factored

3.5” thick flange – Midspan

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Concentrated Load Test

Failure load = 11,300 lbs

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Summary

• C-GRID is effective transverse flange

reinforcement for precast concrete Double-Tees.

• The concentrated load carrying capacity

satisfies PCI requirement.

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• Double-Tee beams
• Wall Panels

– Composite – Non-composite

• Architectural Cladding

Recent Innovation for Precast Concrete Products

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Prestressed Concrete Sandwich Load Bearing Panels

• Resist vertical and lateral loads
• Provide building envelope
• Consists of two concrete wythes

and a layer of rigid foam.

• Composite action achieved by shear

connectors

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Composite Action & Shear Connection

Available FRP shear connectors

Discrete Continuous

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– Orthogonal CFRP Grid – Cut at a 45-degree angle to develop truss action – Structurally and thermally efficient

Insulated Sandwich Panel

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Insulated Sandwich Panel

Carbon fiber grid shear connectors:

• Provide composite action

between wythes

• Increase insulation value

due to low thermal conductivity of the connector

Typical Cross Section

Exterior Interior Carbon Fiber Shear Connector Wythe Reinforcement Pilaster

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Experimental Program At NCSU

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5000 10000 15000 20000 25000 0.0 0.5 1.0 1.5 2.0 2.5 Lateral Deflection (in) Lateral Load (lbs) 22 44 67 89 111 0.00 1.27 2.54 3.81 5.08 6.35 Lateral Deflection (cm) Lateral Load (kN) Representative EPS Panel Service Load Ultimate Load Composite Non-composite

Overall Panel Behavior

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Degree of Shear Connection

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1.2D+0.5Lr+1.6W150 EPS 2

Experimental Results

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Flexural-shear failure

Failure Modes

Panel Separation

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42 foot panel tests

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Analysis

• Theoretical composite and non-

composite load-deflection relationships were calculated following PCI guidelines.

100 (%)

exp x nc c nc

∆ − ∆ ∆ − ∆ = κ

g cr a cr g a cr eff

I I M M I M M I ≤                 − +         =

3 3

1

g g cr a cr cr eff

I I I M M I I ≤         −         − = 1 1

2

ACI 318-08

Valid only for Ig/Icr < 3.0

Bischoff and Scanlon (2007)

Calculation of Ieff for non-composite behavior

• Percent composite action was

determined based on deflections as follows:

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Partial Interaction Theory

Z F M M M

O I u

+ + =

100 (%) x F F

action compsoite full the At curvature given the At

= κ

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CFRP grid 5.5 in. (140 mm) spacing

CFRP grid 3.5 in. (89 mm) spacing

Finite Element Analysis

8-Node solid elements for foam and concrete Truss elements for C-Grid

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2 4 6 8

• 500
• 300
• 100

100 300 500 Strain x 106

Experimental Rational model FEA

Panel Thickness (mm) 50.8 101.6 152.4 203.2 Panel Thickness (in)

Inner wythe

Outer wythe

Tension Compression

Outer wythe

Results

Strain distribution for EPS2 Panel at service load

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Extreme Events

Fire testing

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GFRP Truss Connector

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GFRP Truss Connector

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Summary

• FRP can provide shear transfer mechanism without

thermal breaks in precast prestressed concrete sandwich panels.

• Simple rational design approach can be used to

determine degree of composite action

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• Double-Tee beams
• Wall Panels

– Composite – Non-composite

• Architectural Cladding

Recent Innovation for Precast Concrete Products

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FRP Connector:

Non-Composite Sandwich Panel

Composite Panel Non-composite Panel

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Thermo graphic image showing:

NO thermal bridging Thermal bridging

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• Double-Tee beams
• Wall Panels

– Composite – Non-composite

• Architectural Cladding

Recent Innovation for Precast Concrete Products

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Insulated Architectural Panel

Vertical Back Ribs Intermediate ribs attached to architectural façade with CFRP grid to avoid discoloration or ‘shadowing’

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Insulated Architectural Panel

Horizontal Back Ribs

Intermediate ribs attached to architectural façade with CFRP grid to avoid discoloration or ‘shadowing’

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Panel Configuration

Primary vertical rib Secondary vertical rib Carbon fiber grid in the panel face for crack control

6” Typical

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Manufacturing Process

Placement of CFRP grid reinforcement for architectural facade

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Foam rib forms Steel reinforcing of structural frame

Manufacturing Process

FRP shear grid between frame and facade

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Full-scale testing under reversed cyclic uniform pressure loading representing extreme high-wind loads

Full-scale experimental validation

B3 B4 D C

• 7

DC-10 Line B Line C

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Inward pressure (suction) Outward pressure

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Closing Remarks

Innovative use of FRP with careful analysis techniques will lead to significant advancements in design, construction and sustainability of precast concrete structures and bridges.

Questions?

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