PSI - Issue 64

Muhammad Ishfaq et al. / Procedia Structural Integrity 64 (2024) 1540–1548 Ishfaq et al./ Structural Integrity Procedia 00 (2019) 000 – 000

1542

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100 x 200 mm) and with Grade-60 steel bars having measured yield strength of 483 MPa. For external strengthening, a 740 g/m 2 unidirectional CFRP fabric having a cured composite thickness of 1.02 mm was utilized for both flexural CFRP sheets and U-wraps. Uniaxial tensile tests performed, per ASTM D3039 (ASTM, 2017), on coupons fabricated from the CFRP laminate indicated a measured average tensile strength of 1345 ± 14 MPa, tensile modulus of 102 ± 4 GPa, and rupture strain of 1.3 ± 0.05%. However, the manufacturer reported tensile properties (based on a five percent fractile approach per ACI 440.2) for strength, modulus, and rupture strain were 880 MPa, 98 GPa, and 0.9%, respectively. All specimens were designed following the procedures of ACI 318-19 (ACI, 2019) and the CFRP strengthening was designed based on the guidance of ACI PRC 440.2.

Elevation View

P/2

P/2

Section View

1.52 m

1.22 m

1.52 m

610 mm

102 mm

2#6

2-ply Longitudinal CFRP

102 mm Wide U-wrap

204 mm Typ.

4.27 m

350 mm

Strain Gauge

4#9

Plan View (Tension Face)

U-wrap

408mm Typ.

U-wrap

2-ply Longitudinal CFRP

306 mm

2-ply Longitudinal CFRP

254

mm

Fig. 2. Typical strengthened beam with strain gauge locations shown.

2.2. Test Matrix Specimens were divided into three groups based on the cross-sectional area of internal steel shear reinforcement provided: Group A (no stirrups; =0 ) , B (#2@200 mm; =0.001 ) and C (#4@200 mm; =0.004 ), as listed in Table 1. Table 1. Specimen details and summary of test variables

Test variables (%) (mm 2 ) (mm 2 ) 0 0 0

CFRP Strengthening

Expected Failure mode

Group

S.No.

Specimen

1 2 3 4 5 6 7 8 9

Control

None

0U (no stirrups) 1U (no stirrups) 2U (no stirrups) 0U (#2@200) 1U (#2@200) 2U (#2@200) 0U (#4@200) 1U (#4@200) 2U (#4@200) Control Control

0 0 0

518 518 518 518 518 518 518 518 518 0 0

0

Flexural

Shear

A

207 414

Flexural+U-wraps Flexural+U-wraps

None

0.1 0.1 0.1 0.1 0.4 0.4 0.4 0.4

0 0

Flexural

B

Shear

Flexural+U-wraps Flexural+U-wraps

207 414

None

0 0

10 11 12

Flexural

C

Flexure

Flexural+U-wraps Flexural+U-wraps

207 414

= steel shear reinforcement ratio; = cross-sectional area of longitudinal CFRP sheet; = cross-sectional area of each CFRP U-wrap Each group of four specimens had an unstrengthened control beam (i.e., no longitudinal flexural CFRP or U