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EXPERIMENTS ON BOND BEHAVIOR OF GFRP BOLTS

EXPERIMENTS ON BOND BEHAVIOR OF GFRP BOLTS. By JIA Xin Supervisor Prof. YUAN Yong. Contents. I. GFRP bolt II. Experiment program III. Experiment results and discussion IV. Conclusions. I. GFRP bolts. Disadvantages of traditional steel bolts Easy to rust!! Heavy to carry

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EXPERIMENTS ON BOND BEHAVIOR OF GFRP BOLTS

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  1. EXPERIMENTS ON BOND BEHAVIOR OF GFRP BOLTS By JIA Xin Supervisor Prof. YUAN Yong

  2. Contents • I. GFRP bolt • II. Experiment program • III. Experiment results and discussion • IV. Conclusions

  3. I. GFRP bolts • Disadvantages of traditional steel bolts • Easy to rust!! • Heavy to carry • Difficult to install

  4. I. GFRP bolts • What is FRP? • Fiber Reinforced Polymer • Three kinds of FRP: Glass FRP, Carbon FRP, Aramid FRP. • Using GFRP bar as bolts

  5. I. GFRP bolts • Advantage of GFRP bolts • Impervious to chloride ion and low pH chemical attack. • Tension strength is greater than that of steel, about 2~3 times. • 1/4 weight of steel bars. • Non-conductive.

  6. I. GFRP bolts • Advantage of GFRP bolts • Impervious to chloride ion and low pH chemical attack. • Tension strength is greater than that of steel, about 2~3 times. • 1/4 weight of steel bars. • Non-conductive.

  7. I. GFRP bolts • GFRP bars used for experiments • Tensile strength:600~650MPa • Elasticity of modulus( longitudinal direction) : 42.5GPa • Density: 2.0g/cm3

  8. I. GFRP bolts • GFRP bars used for experiments

  9. Experiment program • Objective • Study the bond behaviour of mortar grouted GFRP bolts • Bearing capacity • critical bond length • Average bond strength • Slip – load relationship

  10. Experiment program • Experimental method • Modified pull out test method • The test procedure is following the ASTM D4435-84(Reapproved 1998).

  11. Experiment program • Experimental samples • Quantity: 24 • Bond length: 65mm,130mm,260mm,390mm,900mm • Bar diameter: 10mm,13mm,16mm,25mm(steel comparison with GFRP bar)

  12. Experiment program • Mortar design • 1. High strength mortar: Cement-sand-water proportion=100:100:42 Compressive strength is 55.5MPa • 2. Modified mortar: cement-sand-water proportion =100:100:42 adding the epoxy resin Compressive strength is 41.5MPa

  13. II.Experiment program • Simulation of rock mass • Concrete block simulates rock mass

  14. Experiment program • Loading and data collection equipments • Hollow hydraulic jack 200kN • Force sensor: precision 0.05kN • Dial indicator: precision 0.01mm • Data collection machine: collect data every one minute

  15. Experiment program • Loading and data collection equipments

  16. III. Experiment results and discussion • Failure mode:

  17. III. Experiment results and discussion • Failure mode :

  18. III. Experiment results and discussion • Failure mode :

  19. III. Experiment results and discussion • Critical bond length 20 times diameter of the bar

  20. III. Experiment results and discussion • Bearing capacity

  21. III. Experiment results and discussion • Bearing capacity- with bond length changing

  22. III. Experiment results and discussion • Bearing capacity- with diameter changing

  23. III. Experiment results and discussion • Bearing capacity- with mortar strength changing

  24. III. Experiment results and discussion • Average bond strength - with bond length changing

  25. III. Experiment results and discussion • Average bond strength - with bond length changing

  26. III. Experiment results and discussion • Average bond strength - with mortar strength changing

  27. III. Experiment results and discussion • Load-slip curve

  28. III. Experiment results and discussion • Comparison with steel bolts

  29. IV. Conclusions • GFRP material is suitable for mortar grouted bolts. • Three patterns of failure happen with the bond length varying. When bond length is short, the first failure mode happen; with bond length getting longer, the second failure mode happens; when bond length is long enough, the third failure mode happens.

  30. IV. Conclusions • The critical bond length is about 20 times diameter for GFRP bolt in the condition that the compressive strength of moratr is 55.5MPa, compressive strength of concrete is 57.23MPa, diameter of bar is 13mm. • When bond length is shorter than the critical bond length, the load carrying capacity increases linearitiy with the bond length increasing, but keep the same value after reaching the critical bond length.

  31. IV. Conclusions • The average bond strength are almost the same before the critical bond length, and decreases with the bond length increasing after critical bond length. • The averages of bond strength of GFRP and steel bars are closing. • The slip of GFRP bolt is greater than that of steel bar.

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