Issue 78

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

shear walls, as well as their hysteretic response and observed failure mode. Specimens with relatively short embedment lengths exhibited early interface slip accompanied by a reduction in lateral strength. Longer embedment lengths led to a shift toward flexure-dominated behavior and better cyclic performance. An embedment length of 20Ø produced a balanced combination of strength, stiffness-retention, and cyclic stability. K EYWORDS . Reinforced concrete shear walls, Implanted vertical rebars, Cycle loading, Anchorage length, Stiffness degradation, Bond effect.

I NTRODUCTION

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einforced concrete (RC) buildings in regions exposed to earthquakes or strong winds depend strongly on their lateral load resisting systems to maintain sufficient stiffness, strength, and deformation capacity. From past seismic events, older RC buildings, especially those designed before the widespread adoption of modern seismic codes, are particularly exposed to severe damage when subjected to lateral forces exceeding their original design assumptions. These exposures are regular due to non-ductile detailing and insufficient confinement in reinforced concrete shear walls, which can lead to brittle failure modes such as diagonal tension cracking, sliding shear, or compression failure [1]. RC shear walls are known for resisting lateral loads due to their stiffness, their ability to dissipate energy, and their ability to control inter-story drift. If they are well designed, these walls can really limit earthquake damage and help in building stability during an earthquake. However, many existing structures still depend on shear walls designed under outdated seismic requirements which did not include today’s ductility and capacity design requirements. As a result, deficiencies such as poor confinement, inadequate anchorage, and improper reinforcement detailing remain common in older buildings [1-2]. Over the last decade, the assessment and rehabilitation of aging RC buildings have gained increased attention, not only because of the repeated occurrence of damaging earthquakes, but also due to the economic impracticality of replacing large segments of the existing building stock. A wide variety of rehabilitation methods has been explored, including RC jacketing, steel plate shear walls, FRP-based strengthening, and braced-frame systems [3]. In addition to seismic assessment and retrofit strategies, recent studies have highlighted the importance of code-compliant design and optimization of reinforced concrete structural systems according to modern international provisions. Furthermore, advanced damage-detection techniques for RC structures subjected to earthquake excitation have been developed to improve structural assessment and post-earthquake evaluation [4-5]. New shear walls can be positioned to reduce torsional irregularities while providing a direct and strong load path to the foundation. However, the effectiveness of this method depends heavily on the reliability of the connection between the new wall and the existing structure; particularly at the wall-foundation interface. Insufficient force transfer at this interface may result in excessive slip, premature separation, and rapid degradation of stiffness under cyclic loading [1]. Studies on bond behavior between reinforcing steel and concrete consistently show that bond strength and bond–slip response are governed by interacting material, geometric, and damage-related parameters. Yalciner et al. [6] showed that corrosion-induced bond degradation depends strongly on concrete cover, compressive strength, and crack development, with higher-strength concrete exhibiting more brittle losses. Bashir et al. [7] and Shen et al. [8] further emphasized the nonlinear, multi-parameter nature of bond-slip behaviour and the need for refined predictive models beyond simplified empirical expressions. Gambarova and Rosati [9] declared that splitting cracks reduce peak strength and bond stiffness, while the capacity could be partially restored by confinement. In the broader structural context, Gkournelos et al. [10] and Basereh et al. [11] linked crack and bond damage control to improved seismic retrofit performance and reparability. Experimental studies emphasized the effect of embedment conditions, recycled aggregates, and testing setup on the bond performance and predictive reliability. When post-installed bars are bonded using suitable adhesive systems, they can approach performance and hysteretic behavior comparable to cast-in-place reinforcement by showing sufficient ductility, stable cyclic response, and reliable load-displacement behavior under both monotonic and cyclic loading [12-14]. As a result of these findings, modern structural standards - including ASCE 41-23 [15] and updated international seismic design provisions, now allow the use of implanted reinforcement (chemically post-installed reinforcement) for structural applications in seismic zones, provided that the adhesive systems and development lengths meet qualification and

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