Presentation in support of

Transcription

1 Presentation in support of Proposed Acceptance Criteria For Continuous or Semi- Continuous Fiber-Reinforced Grid Connectors used in combination with Rigid Insulation in Concrete Sandwich Panel Construction Dr. Sami Rizkalla February 3, 2010

2 Carbon Fiber Grids Carbon grids are manufactured in an automated process: High production volume High quality control Typical Nomenclature: Individual Strand Strength 4.45 kn Young's Modulus GPa

3 Grids are Engineered to provide the right amount of strength in each direction. Carbon Grid Types

4 Carbon-Fiber Grid Installation For Prestressed Concrete Double Tee Beams

5 Carbon-Fiber Grid Installation Embedment and finishing machine to place the grid More precise placement for optimum performance More consistent; less opportunity for human error

6 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 6

7 Composite Action & Shear Connection Typical mechanisms include: Steel truss connectors Thermally inefficient Steel tie connectors Thermally and structurally inefficient Discrete FRP connectors Non-composite Action Concrete solid zones Thermally inefficient

8 Insulated Sandwich Panel Orthogonal CFRP Grid Cut at a 45-degree angle to develop truss action Structurally and thermally efficient 8

9 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 9 9

10 Research At NCSU Evaluate behavior of wall panels reinforced with CFRP grids. Determine effectiveness of grid as shear mechanism. Calculate the degree of composite action achieved. Model behavior and develop design guidelines.

11 Experimental

12 Test Setup Teflon Pads Neoprene Pads Simulated loading due to lateral wind pressure

13 Flexural-shear failure Failure Modes

14 Lateral Load (lbs) Lateral Load (kn) Overall Panel Behavior Lateral Deflection (cm) Composite Representative EPS Panel Ultimate Load Service Load Non-composite Lateral Deflection (in)

15 Degree of Shear Connection

16 Experimental Results EPS D+0.5L r +1.6W 150

17 42 foot panel tests 17

18 Extreme Events 18 Fire testing

19 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 19 Truss elements for C-Grid

20 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 I eff M M cr a 3 I g 1 M M Valid only for I g /I cr < 3.0 cr a 3 I cr I g 20 (%) nc c exp x nc 100 Bischoff and Scanlon (2007) I eff 1 M M cr a I cr 2 1 I I cr g I g

21 Partial Interaction Theory M u M I M O F Z FAt the given curvature (%) x100 F At the full compsoiteaction 21

22 Panel Thickness (in) Panel Thickness (mm) Results Strain distribution for EPS2 Panel at service load Inner wythe Compression Tension Experimental Rational model FEA Outer wythe Outer wythe Strain x 10 6

23 Insulated Architectural Cladding Steel-reinforced precast rib CFRP shear grid (thermal break) Insulating Foam CFRP grid secondary reinforcing Thin brick finish

24 Insulated Architectural Panel Vertical Back Ribs 24 Intermediate ribs attached to architectural façade with CFRP grid to avoid discoloration or shadowing

25 Insulated Architectural Panel Horizontal Back Ribs 25 Intermediate ribs attached to architectural façade with CFRP grid to avoid discoloration or shadowing

26 Panel Configuration Primary vertical rib 26 Secondary vertical rib 6 Typical Carbon fiber grid in the panel face for crack control

27 Manufacturing Process 27 Placement of CFRP grid reinforcement for architectural facade

28 Manufacturing Process Foam rib forms 28 FRP shear grid between frame and facade Steel reinforcing of structural frame

29 Full-scale experimental validation DC-7 Line C B3 DC-10 Line B B4 29 Full-scale testing under reversed cyclic uniform pressure loading representing extreme high-wind loads

30 Inward pressure (suction) Outward pressure 30

31 Full-Scale Experimental Validation ± 1.2 kpa cyclic loading 2.5 kpa static loading

32 Technical Papers Hassan, T. and Rizkalla, S., Analysis and Design Guidelines of Precast/Prestressed Composite Load Bearing Sandwich Wall Panels, Accepted for Publication, PCI Journal, Frankl, B., Lucier, G., Hassan, T. and Rizkalla, S., Behavior of Insulated Precast, Prestressed Concrete Sandwich Wall Panels Reinforced with CFRP Grid, Accepted for publication, PCI Journal, Rizkalla, S., Hassan, T. and Lucier, G., FRP Shear Transfer Mechanism for Precast, Prestressed Concrete Sandwich Load Bearing Panels, Accepted for Publication, ACI Special Publication 31, November 2009

33 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 Any ESR related to AC422 for the shear flow and shear modulus will be given for a specific properties of the insulation material,insulation thickness,material properties of concrete,spacing of the grid strips, orientation and strength of the grid. 33

34 Closing Remarks 34 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?