FRP FOR SUSTAINABLE PRECAST CONCRETE STRUCTURES Sami Rizkalla North Carolina State University October 21-22, 2009 1
Underground Precast Utility Tanks 2
1993 Beddington Trail Bridge First Bulb-Tee bridge girder pretensioned with CFRP tendons 3 No signs of degradation when tested in July 2008, after 15 years of service
1997 Taylor Bridge First AASHTO Girder prestressed and Reinforced with CFRP CFRP stirrups 4 Instrumentation of the girder before casting Route 40 Bridge, Virginia
CFFT Piles 700 load (kn) 600 500 400 300 200 Confinement effect + Bending Resistance 100 0 0 2 4 6 8 10 12 strain (me) Axial Resistance 5
Power line poles 5.8 t 12 t 6
Recent Innovation for Precast Concrete Products Double-Tee beams Wall Panels Composite Non-composite Architectural Cladding 7
Corrosion Free Double-Tee Thin flange susceptible to chloride penetration CFRP Grid replacement for WWF conventional steel 8
Carbon Fiber Grids Carbon grids are manufactured in an automated process: High production volume High quality control 9
Pre-topped Double Tees 10 10
Pre-topped Double Tees 11
Carbon Fiber Installation - Embedment and finishing machine to place the grid - More precisely for optimum performance - More consistent; less opportunity for human error 12
Research and Development at NC State Uniformly distributed applied load Experimental Program 13
Testing Program 14
Testing Program 15
Testing Program 16
Testing Program Initial Cracking: 17 DT1 DT2
Results Failure Mode DT1 2 thick flange 18
Results Failure Mode DT1 2 thick flange 19
Results Failure Mode DT2 3.5 thick flange 20
Results 2 thick flange Midspan 0 2 4 6 8 10 12 Measured Vertical Deflection (in.) 21-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Distance along DT Profile (ft.) 3.5 thick flange Midspan Measured Vertical Deflection (in.) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Ultimate Service Factored 0 2 4 6 8 10 12 Distance along DT Profile (ft.) Ultimate Service Factored
Concentrated Load Test 22 Failure load = 11,300 lbs
Summary C-GRID is effective transverse flange reinforcement for precast concrete Double-Tees. The concentrated load carrying capacity satisfies PCI requirement. 23
Recent Innovation for Precast Concrete Products Double-Tee beams Wall Panels Composite Non-composite Architectural Cladding 24
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 25
Composite Action & Shear Connection Available FRP shear connectors Discrete 26 Continuous
Insulated Sandwich Panel Orthogonal CFRP Grid Cut at a 45-degree angle to develop truss action Structurally and thermally efficient 27
Insulated Sandwich Panel Wythe Reinforcement Exterior Interior Pilaster Typical Cross Section Carbon Fiber Shear Connector Carbon fiber grid shear connectors: - Provide composite action between wythes - Increase insulation value due to low thermal conductivity of the connector 28 28
Experimental Program At NCSU 29
Overall Panel Behavior 0.00 1.27 2.54 3.81 5.08 6.35 25000 111 Composite Lateral Deflection (cm) 20000 89 Lateral Load (lbs) 15000 10000 Ultimate Load Representative EPS Panel 67 44 Lateral Load (kn) 5000 Service Load 22 Non-composite 0 0 0.0 0.5 1.0 1.5 2.0 2.5 30 Lateral Deflection (in)
Degree of Shear Connection 31
Experimental Results EPS 2 32 1.2D+0.5L r +1.6W 150
Failure Modes Flexural-shear failure Panel Separation 33
42 foot panel tests 34
Analysis Theoretical composite and noncomposite load-deflection relationships were calculated following PCI guidelines. Percent composite action was determined based on deflections as follows: Calculation of I eff for non-composite behavior ACI 318-08 I eff M = M cr a 3 I g M + 1 M cr a 3 I Valid only for I g /I cr < 3.0 cr I g 35 κ (%) = nc c exp x nc 100 Bischoff and Scanlon (2007) I eff = M 1 M cr a I cr 2 1 I I cr g I g
Partial Interaction Theory κ FAt the given curvature (%) = x100 F At the full compsoite action M u = M I + M O + F Z 36
Finite Element Analysis CFRP grid 5.5 in. (140 mm) spacing CFRP grid 3.5 in. (89 mm) spacing 8-Node solid elements for foam and concrete 37 Truss elements for C-Grid
Results Strain distribution for EPS2 Panel at service load 8 203.2 6 152.4 Inner wythe Compression Panel Thickness (in) 4 101.6 Panel Thickness (mm) Tension Experimental Rational model FEA 2 50.8 Outer wythe Outer wythe 38 0-500 -300-100 100 300 500 Strain x 10 6
Extreme Events 39 Fire testing
GFRP Truss Connector 40
GFRP Truss Connector 41
42
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 43
Recent Innovation for Precast Concrete Products Double-Tee beams Wall Panels Composite Non-composite Architectural Cladding 44
Non-Composite Sandwich Panel FRP Connector: 45 Composite Panel Non-composite Panel
Thermo graphic image showing: 46 Thermal bridging NO thermal bridging
Recent Innovation for Precast Concrete Products Double-Tee beams Wall Panels Composite Non-composite Architectural Cladding 47
Insulated Architectural Panel Vertical Back Ribs 48 Intermediate ribs attached to architectural façade with CFRP grid to avoid discoloration or shadowing
Insulated Architectural Panel Horizontal Back Ribs 49 Intermediate ribs attached to architectural façade with CFRP grid to avoid discoloration or shadowing
Panel Configuration Primary vertical rib 50 Secondary vertical rib 6 Typical Carbon fiber grid in the panel face for crack control
Manufacturing Process 51 Placement of CFRP grid reinforcement for architectural facade
Manufacturing Process Foam rib forms 52 FRP shear grid between frame and facade Steel reinforcing of structural frame
Full-scale experimental validation DC-7 Line C B3 DC-10 Line B B4 53 Full-scale testing under reversed cyclic uniform pressure loading representing extreme high-wind loads
Inward pressure (suction) Outward pressure 54
Closing Remarks 55 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?