PSI - Issue 54

Jamal A. Abdalla et al. / Procedia Structural Integrity 54 (2024) 609–616 Abdalla et al./ Structural Integrity Procedia 00 (2019) 000 – 000

614

6

(c) NS-90 and RS-90

(d) NCU and RCU

(E) NU-45 and RU-45 Fig. 3: Failure modes of the tested beams

3.2. Summary of test results and load-deflection curves The experimental results in terms of the maximum attained load ( ), maximum shear force ( ), mid-span deflection at the maximum shear ( ), maximum strain in CFRP laminates ( ), shear in concrete ( ), CFRP contribution to shear ( ), percentage increase in , and the observed failure modes, are presented in Table 2. In addition, the load deflection curves for the tested beams are shown in Figs. 4 and 5, respectively. In Fig. 5, a comparison is illustrated between the NAC and RAC beams with different schemes of CFRP wrapping. Fig. 4-a shows that the load-deflection behavior exhibited by the control (unstrengthened) specimens was almost identical. This trend is also noticed in Fig. 4-d, where both specimens having a continuous wrapping showed a similar behavior.

Table 2: Mechanical properties of CFRP sheets and laminates

Ꜫ max ( strain)

Beam Designation

Percentage increase in Vn (%)

Failure modes

Pn (kN)

Vn (kN)

Δmax (mm)

Vf (kN)

Vc (kN)

CN

60.0

30.0

8.90

-

-

30.0

-

SC

CR

54.4

27.2

8.60

-

-

27.2

-

SC

RU-90

86.8

43.4

10.2

2347.0

16.2

27.2

59.6

SC & D

NU-90 RS-90 NS-90

81.6 76.8 90.5

40.8 38.4 45.3

17.8

2230.2 867.1 3343.1 2275.4 4632.4 2454.7 2372.49

10.8 11.2 15.3 22.9 19.4 27.1 15.0

30

36.0 84.2 51.0 84.2 64.7 99.6 50.0

SC & D SC & D SC & D FC & CC FC & CC FC & CC

7.4 9.6

27.2

30

RCU

100.1

50.05

21.4

27.2

NCU

98.8

49.4 54.3

22.9 12.6 17.6

30

RU-45 NU-45

108.6

27.2

90.0

45

30

PF

SC: Shear Crack at 45°; D: Debonding of CFRP laminates; FC: Flexure Cracking; CC: Concrete Crushing; PBF: Premature Failure

Overall, it can be seen that the ultimate shear force attained by the RAC beams and the load-deflection behavior were comparable to the NAC beams. In fact, specimen RU-45, which had a recycled aggregate concrete composition and was strengthened by U-wraps at 45 ⸰ angle, showed a higher shear capacity than its counterpart beam with normal aggregate concrete. Thus, it can be deduced that the full substitution of normal aggregates with recycled aggregates did not adversely affect the shear behavior of strengthened and unstrengthened specimens. Fig. 5 compares the load deflection behavior with respect to the strengthening configuration within the same group (NAC or RAC). It can be