PSI - Issue 37

Jamal A. Abdalla et al. / Procedia Structural Integrity 37 (2022) 652–659 Abdalla et al./ Structural Integrity Procedia 00 (2019) 000 – 000

656

5

3. Results and Discussions Table 5 shows a summary of the ultimate attained load values, deflection at yield, deflection at ultimate, and deflection at failure. It also shows the percentage changes of these values with respect to that of the control beam. The flexural capacity of beams strengthened with AA plate increased by 18.53%-40.34% compared to that of the control beam. The beam strengthened with AA plate that was anchored by two layers of CFRP (B3W2) sheets developed the highest flexural strength. It can also be deduced from Table 5 that the deflection at yield of the three strengthened beams (B1W0, B2W1, B2W2) decreased by 17.52%-20.51% compared to the deflection at yield of the control beam. Similarly, the deflection at ultimate load and the deflection at failure of the strengthened beams with anchored CFRP U-wraps (B2W1, B3W2), also decreased by 7.54%-23.92% and 8.65%-13.66%, respectively. However, for the beam strengthened with unanchored AA plate, both its deflection at ultimate load and its deflection at failure increased by 9.77% and 28.01%, respectively. It is clear that, beams strengthened with anchored AA plate, although they are stiffer and showed less deflection compared with the control beam, however, they preserved around 80% of it accompanied by increase in flexural capacity up to 40.34% as previously indicated.

Table 5 Summary of ultimate load and deflections Specimen P u (kN) % P u Increase over CB1

δ y (mm)

% δ y Change over CB

δ u (mm) 32.74 35.94 30.27 24.91

% δ u Change over CB

δ f (mm) 33.75 43.23 30.83 29.14

% δ f Change over CB

CB

58.78 69.67 70.13 82.49

-

9.36 7.72 7.45 7.44

-

-

-

B1W0 B2W1 B3W2

18.53 19.31 40.34

-17.52 -20.41 -20.51

9.77 -7.54

28.08 -8.65 -13.66

-23.92

Table 6 shows the yield ductility, the ultimate ductility (define..) and the failure ductility (define ..)of the tested beams and their changes with respect to that of the control beam. The percentage difference to the control beam of the calculated ductility indices are also provided in Table 6. It can be deduced from Table 6 that the ultimate ductility of the three strengthened beams (B1W0, B2W1, B2W2) changed by -5.0%-33.00% compared to the ultimate ductility of the control beam. Similarly, the failure ductility of all strengthened beams increased by 8%-55%, where the beam without CFRP U-wrap showed the maximum increase in ultimate and failure ductility, 33% and 55%, respectively. Furthermore, the beam strengthened with AA plate that were anchored with two layers of CFRP U-wrap showed the least ultimate ductility and failure ductility, -5% and 8%, respectively compared to the control beam. It can be concluded that using AA plates as externally strengthening material will increase both the strength and ductility of RC beams compared to the control beam, while ductility of RC beams strengthened with CFRP sheets or plates deceases compared to the ductility of the unstrengthened RC beams. Table 6 Summary of ductility indices at ultimate and failure loads Specimen δ y (mm) δ u (mm) δ f (mm) µ  , ultimate ( δ u / δ y) % µ  , ultimate over CB µ  , failure ( δ f / δ y) % µ  , fail over CB

3.50 4.66 4.07 3.35

1.00 1.33 1.16 0.95

3.61 5.60 4.14 3.92

1.00 1.55 1.15 1.08

CB

9.36 7.72 7.45 7.44

32.74 35.94 30.27 24.91

33.75 43.23 30.83 29.14

B1W0 B2W1 B3W2

4. Load-Deflection Relationships and Failure Modes Figure 4 shows the load-deflection response curves of all tested beams. The load-deflection curves of the beams were relatively matching until the first yield. After that the beam with two layers of U-Wrap anchors (B3W2) showed larger stiffness compared to the other beams and larger ultimate attained load, however with the lowest deflection. The beam with one layer of U-Wrap anchors (B2W1) mimicked the beam with two layers of U-Wrap anchors in trends however with smaller values in load and deflection. Furthermore, the load-deflection curve of this beam (B2W1) coincided with that of the beam without anchorage (B1W0) for most of its trajectory and both has very comparable yield and