PSI - Issue 28

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Haya H. Mhanna et al. / Procedia Structural Integrity 28 (2020) 811–819 Mhanna et al. / Structural Integrity Procedia 00 (2020) 000–000

817

increases (from 16 to 20 mm) the pullout capacity of the CFRP anchors decreases. Overall, the results of this study show the effectiveness of CFRP anchors as a promising anchorage system in enhancing the capacity, ductility, and delaying debonding failure. In addition, for an embedment depth of 85 mm, 14 mm diameter anchors are considered optimum.

400

300

200

100 Load (kN)

0

0

5

10

15

20

25

30

35

Mid‐span Deflection (mm)

C

BSU

BSD 12

BSD 14

BSD 16

Fig. 7. Load versus mid-span deflection curves.

Table 1. Summary of test results.

P y (kN)

δ y (mm)

P u (kN)

δ u (mm)

P f (kN)

δ f (mm)

Specimen

ε frp (με)

Failure Mode

P u /P u(C)

P u /P u(BSU)

C

148.07 298.77

3.25 7.04

146.69 317.49

3.85 8.35

103.52 287.61

4.22 9.72

-

- -

-

Diagonal shear crack

BSU

2.16

2847.33

Debonding of CFRP laminates Debonding of CFRP laminates + fan-to-sheet debonding Debonding of CFRP laminates Debonding of CFRP laminates

BSD12

322.11

8.30

331.73 13.96 192.56

19.51

2.26

1.04

4142.36

BSD14 BSD16

333.30 318.98

6.99 7.48

365.92 24.73 342.43 22.00

89.37 68.82

30.92 30.13

2.49 2.33

1.15 1.08

4642.60 5160.58

4.3. Strain in the CFRP laminates CFRP strain values ( ε frp ) shown in Table 1 represent the maximum strain recorded in the CFRP laminates at ultimate state. It is clear from Table 1 that the strain attained in the unanchored U-wraps is 2874.33 με utilizing only 20% of the laminate’s ultimate strain. On the other hand, anchoring the laminates with CFRP anchors attained higher strain levels and utilized more of the CFRP strain. Anchored specimens BSD12, BSD14 and BSD16 utilized 30, 33, and 37% of CFRP ultimate strain, respectively. According to the ACI440.2R-17 design provisions, the maximum strain allowed in the well-anchored FRP laminates is 0.004 to prevent loss of aggregate interlock. All anchored specimens in this study attained higher strain values than the code’s limit, thus indicating that it is safe to design anchored CFRP U-wrapped laminates with CFRP splay anchors using the code effective strain value of 0.004. 4.4. Ductility The ductility of all specimens was measured by calculating the ductility index ( µ ) at ultimate load and at failure load by Eqs. (1) and (2), respectively. Table 2 summarizes the ductility results in terms of ductility index at ultimate state ( µ Δ u ) and at failure load ( µ Δ f ). In addition, to assess the ductility of the anchored specimens, the ratio of µ with