Issue 72

M. A. M. Khalil, Fracture and Structural Integrity, 72 (2025) 193-210; DOI: 10.3221/IGF-ESIS.72.14

The yield strength and ultimate strength of smooth steel bars were 304 MPa and 415 MPa for 8 mm stirrups bars, 470 MPa and 636 MPa for 10 mm, and 566 MPa and 764 MPa for 12 mm, respectively. The results of steel bars are summarized in Tab. 2.

a) After installed shear connectors b) Connection at the supports Figure 2: Steel mesh and concrete of composite beam with external GFRP I-section.

No. of samples

Length (mm)

Diameter. (mm)

Tensile strength (Mpa) Elongation (%) y f u f

Specification Elongation

Nominal

Actual 8.15 10.12 11.54

5 5 5

500 500 500

8

304 470 566

415 636 764

61 32 26

≥ 20% ≥ 16% ≥ 16%

10 12

Table 2: Results of Steel bars properties. According to manufacturing date, the tensile strength of GFRP I-section was 336 MPa, and tensile modulus of elasticity 35300 MPa [23] as shown in Tab. 3.

No.

Item

Data

1 2 3 4 5 6 7 8 9

Specific gravity Tensile strength Tensile modulus Flexural strength Flexural modulus

1.85 g/cm 3 336 MPa 35300 MPa 334 MPa 73000 MPa 327 MPa 2385 J/M 52 HRC

Compressive strength Impact strength

Hardness

Water-absorption rate Heat distortion temperature

1.39 % 204 ℃

10

Table 3: GFRP I-section properties.

Test setup and instrumentation The testing frame shown in the lower part of Fig. 3 was fixed to the strong solid floor of the RC laboratory of the Faculty of Engineering at Helwan University. The supporting structure consisted of a horizontal frame made of four steel I-beams. It was supported by four vertical steel I-beam legs fixed to the solid floor and the tested beams were supported on the frame. The loading was achieved by using a cell with a capacity of 1250 kN, which transferred the load to a high stiffness steel plate at two points in the middle of the beams; with a length of the pure bending area was 400 mm, setup as shown in the upper part of Fig. 3.

196