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Flexural Behavior of SFRC: Testing and Modeling

Flexural Behavior of SFRC: Testing and Modeling. By: J.A.O. Barros and J.A. Figueiras Presented by: Jared Weisman. Scope. Contribution to ongoing research to model SFRC structures Experimental Investigation Layered model for analysis of SFRC cross sections Model and thin slab testing.

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Flexural Behavior of SFRC: Testing and Modeling

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  1. Flexural Behavior of SFRC: Testing and Modeling By: J.A.O. Barros and J.A. Figueiras Presented by: Jared Weisman

  2. Scope • Contribution to ongoing research to model SFRC structures • Experimental Investigation • Layered model for analysis of SFRC cross sections • Model and thin slab testing

  3. Introduction • SFRC – Steel Fiber Reinforced Concrete • Act as crack “arrestors” • Used in: pavements, overlays, floors, hydraulic and marine structures, and repair and rehabilitation • Properties of steel fibers in general

  4. Test Backgrounds • ASTM C1018 • JSCE-SF4 • Tensile Strain-Softening Law • Fracture Energy, Gf • 3 point bending tests with notched beams

  5. Mix Proportioning Main Variables: w/c ratio, fiber percentage, fiber aspect ratio (L to Φ ratio) S3 and S4 – Compression behavior S2 – Slab strips Fiber types: ZP30/.50 and ZX60/.80

  6. Mixing • Water, cement, aggregates, and sand were mixed for 2 minutes, then fibers slowly added • Internal vibration was used for the compaction of cylinder and prismatic specimens • Slabs used external vibration • Covered with wet cloths • Kept at 65% humidity

  7. Compression Behavior • Main Goal: to define a σ-ε relationship to simulate complete behavior of SFRC to be analyzed • Test: standard compressive testing machine, specimens tested in a displacement controlled condition • Normal stress-strain law doesn’t sufficiently take into account postpeak response of SFRC. One using experimental data which takes into account things like fiber geometry, volume fraction, and fiber shape was needed.

  8. Compression Results

  9. More Compression Graphs

  10. Tensile Behavior Three-point bending tests were performed on notched beams Measurement of Fracture Energy Placed in a ‘Japanese yoke’ to prevent extraneous deformations, middle point deflections were measured by LVDTs.

  11. Tensile Results and Graphs Model relates force and deformation

  12. Flexural Model For tensile postcracking behavior, a few things need derived: tensile strength (fctm), width of fracture-process zone (lb), fracture energy (Gf), and the shape of the softening diagram. fctm- from CEB-FIP Model Code lb – taken as the average crack spacing, or ~3 times the maximum aggregate size Gf – evaluated from tensile model previously presented Using FEM of the three-point bending tests on notched beams, they found the softening law could be modeled with accuracy. Tension-softening The proposed stress-strain relationship from before is used to determine the states of concrete layers. When concrete cracks, the stress in the layer depends on the state, either tension softening or tension stiffening. Tension-stiffening

  13. Flexural Results • New Model takes into account fracture properties and reinforcement characteristics • Compared to experimental data and FEA

  14. Model Appraisal

  15. Conclusion • Compression Tests σ-ε relationship  Numerical models for analyzing SFRC structures • Tension Tests  post-peak tensile behavior of SFRC was assessed using fracture energy concepts • Flexural model  evaluates flexural resistance and ductility  increase in fibers improve load-carrying capacity and decreased crack opening and spacing  complete moment-curvature relationship of SFRC for use in FEMs

  16. Thank You

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