PSI - Issue 64

Mohamed Elkafrawy et al. / Procedia Structural Integrity 64 (2024) 436–444 Author name / Structural Integrity Procedia 00 (2024) 000–000

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0% (0 MPa) and 50% (350 MPa) pre-stressing levels (recovery stress) in Groups II and III, respectively. Beam IDs in groups are structured to specify the size of the opening and diameter of Fe-SMA reinforcement. For example, B-200 2T25-50% indicates that the beam has 200 mm square openings strengthened with 2T25 mm Fe-SMA bars at a 50% pre-stressing level. Table 1 summarizes the characteristics of the studied beams. 3. Experimental Verification The verification of FEM models is essential to ensure the accuracy and reliability of the results (Alhamaydeh, Barakat and Abed, 2013; Assaleh, AlHamaydeh and Choudhary, 2015; Sawires et al. , 2019; Saleh et al. , 2022). Verification was carried out in a previous publication, comparing the behavior of RC beams strengthened with Fe SMA bars from experimental results with numerical results (Elkafrawy et al. , 2023). The behavior of beams under flexure represented by load-deflection relationships from FEM models correlated well with those from experimental data, with some variations due to numerical modeling limitations. For more details, please refer to the previous authors’ work (Elkafrawy et al. , 2023).

Fig. 2. Geometry and reinforcement details of specimens

Table 1. Parameters of the study Groups

Opening dimensions

Reinforcement around openings

Pre-stressing level (%)

Beam ID Control B-100

a (mm)

b (mm)

Type

Diameter (mm)

Control

-

-

- - - -

- - - -

- - - -

100 150 200 100 150 200 100 150 200

100 150 200 100 150 200 100 150 200

Group I

B-150 B-200

B-100-2T25-0% B-150-2T25-0% B-200-2T25-0% B-100-2T25-50% B-150-2T25-50% B-200-2T25-50%

Fe-SMA Fe-SMA Fe-SMA Fe-SMA Fe-SMA Fe-SMA

2T25 2T25 2T25 2T25 2T25 2T25

0% 0% 0%

Group II

50% 50% 50%

Group III

4. Results and Discussion 3.1 Effect of Opening Size

RC beams fail primarily in shear due to openings within the shear span (Nie et al. , 2020b). Openings disrupt the stress transfer mechanism in beams, causing fracture localization and early crack formation. Fig. 3 compares RC beams’ cracking pattern at ultimate load with different opening sizes of 100 mm, 150 mm, and 200 mm to the control beam. Results showed that B-200 experienced the most prominent diagonal cracks around its 200 mm × 200 mm openings, followed by B-150 and then B-100. RC beams with openings in the shear span have lower load-carrying capacity than solid beams. Openings induce stresses in the beam, leading to diagonal cracks forming. As the number of cracks increases, the ability of beams to carry loads and resist deformations reduces significantly (Tiberti et al. , 2017). Fig. 4 shows the load-deflection response of beams with varying opening sizes of 100 mm, 150 mm, and 200 mm. RC beams with openings experienced a gradual increase in the load-deflection curve until reaching the peak load, followed by a drop. However, the control beam underwent greater deflection before failure. This is mainly due to the uniform stress distribution along the cross-