Issue 78

S. A. Mustafa et alii, Fracture and Structural Integrity, 78 (2026) 298-314; DOI: 10.3221/IGF-ESIS.78.18

with concrete pore structure. This observation confirms the importance of adhesive mechanical properties on bonded bars and anchorage systems, where variations in resin composition directly impact bond-slip response and failure mode [19]. Based on this output, (CMB) bonding material was used in nine pull out specimens with a steel bar diameter of 18 mm. the same studied ratios for the hole diameter of (1.125 ϕ , 1.25 ϕ and 1.375 ϕ ). Three specimens were tested for each hole diameter. The average bond stress per unit length was plotted against the hole diameter, to obtain the best size of the hole diameter to be used later in the shear wall specimens. As can be seen from Fig. 10, using 1.25 ϕ for hole diameter showed the best result for bonding the steel bar with concrete, especially in specimens with diameter 18 mm. Excessively small hole diameter might restrict adhesive penetration, producing weak interfacial zone. It can be concluded from the overall results that moderate hole diameters combined with high-quality adhesives produce the most efficient load transfer characteristics. These results go well with the anchor system optimization studies carried out by Shen et al. [8], and the results reported in [1,6]. Based on these results, CMB adhesive combined with a 1.25 ϕ hole diameter that provided the most reliable performance was adopted in the construction of the shear wall specimens.

Figure 10: Effect of Hole diameter on bond stress per unit length.

Figure 9: Effect of Bond Material .

S HEAR WALLS TEST RESULTS

T

he optimal configuration of the bond material and the hole diameter that resulted from the pull-out tests was adopted consistently in all shear wall specimens tested in the present study. All tested specimens shared identical dimensions, reinforcement layouts, concrete strength, and loading protocol; thus, the behavior observed in the cyclic tests can be attributed primarily to the anchorage length rather than deficiencies in the bonding quality itself. The experimental testing program began with the control shear wall (C.S.W.), which was tested first to establish a reference benchmark for lateral load-carrying capacity and governing failure mode. The lateral load-top displacement responses of all tested specimens are presented in Fig. 11, illustrating the evolution of stiffness, strength, and post-peak behavior under cyclic loading. In addition, the envelope (backbone) curves of all specimens are compared in Fig. 12 to facilitate a direct assessment of strength, deformation capacity, and global response characteristics. Test results for all four specimens are summarized in Tab. 3, which reports the lateral load and corresponding top displacement at key response stages, including first concrete cracking, peak lateral resistance, and the onset of significant strength degradation. A significant loss of lateral strength was observed as a reduction of 20% from the peak lateral load.

First crack

Peak load

Strength loss

Implanted length

Specimen

F (kN) 209.55 53.004

Δ top (mm)

F (kN) 236.38

Δ top (mm)

F (kN) 194.12

Δ top (mm)

C.S.W

55 Ø 10 Ø 15 Ø 20 Ø

27.11 25.04 24.34

30.86 30.45 30.31 30.62

36.08

S.W.I1 S.W.I2 S.W.I3

62.57

42.59 89.36

41.8

87.47

105.08 149.28

40.97

124.55 38.08 Table 3: Experimental response parameters of shear wall specimens at first cracking, peak load, and strength degradation. 26.097 118.01

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