PSI - Issue 78

Rawand Alnsour et al. / Procedia Structural Integrity 78 (2026) 1261–1268

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4. Future direction for retrofitting As the need for dependable and efficient seismic retrofit solutions grows, particularly for aging RC structures that no longer comply with modern seismic standards, it becomes crucial to identify strengthening methods that are not only effective and affordable but also practical for real-world application. A major weakness in many of these structures is brittle shear failure, especially in beams and joints with insufficient transverse reinforcement. This deficiency can lead to sudden and severe collapse during seismic events. A promising retrofit method involves using post-installed screw anchors as an alternative to traditional stirrups to enhance shear resistance. When properly embedded within the concrete cross-section, these anchors act as mechanical shear reinforcements by intercepting diagonal tension cracks. This technique is particularly advantageous in confined or hard-to-access areas where conventional retrofitting methods, such as concrete jacketing, FRP wrapping, or externally bonded reinforcements, may be difficult or impractical to implement. To date, a number of experimental studies have investigated the shear strength improvement achieved through such systems. In particular, (Buhler & Vilotijević, 2022) and (Buhler et al., n.d.) introduced the RELAST system, which integrates self-tapping concrete screw anchors with a two-component injectable adhesive. This system transfers shear forces through a combination of mechanical interlocking and bonding mechanisms. Laboratory tests, including four point bending experiments on RC beams, demonstrated up to a 100% increase in shear resistance under monotonic loading. These studies also explored the influence of variables such as anchor size, embedment depth, spacing, and bonded versus unbonded configurations, shown in Fig. 8. However, it is important to note that these investigations mainly addressed monotonic loading and did not thoroughly evaluate performance under cyclic conditions. Consequently, aspects such as failure modes, energy dissipation, and durability under repeated seismic loading remain insufficiently studied. Therefore, further research is needed to fully understand the seismic retrofitting potential of screw anchor systems, especially under realistic cyclic and dynamic loading scenarios. Nonetheless, the existing results offer a solid experimental basis and highlight the practicality and effectiveness of anchor-based solutions in enhancing shear strength.

Fig. 8. Installation conditions (Buhler & Vilotijević, 2022) , (Buhler et al., n.d.).

5. Life Cycle Assessment (LCA) consideration for future work In addition to mechanical performance, it is crucial that future investigations into the use of post-installed screw anchors for shear retrofitting adopt a holistic, multi-perspective approach. While structural efficiency remains important, equal attention should be given to the environmental impact of the proposed solution, both in the short and long term. In the short term, localized anchorage systems may offer significant benefits during execution, including reduced material consumption, lower energy demand, minimized construction waste, and less disruption to building operations. In the long term, the minimal invasiveness of screw anchors and their potential for disassembly can facilitate reuse and recyclability, aligning with sustainable design principles. Considering both of these dimensions, Life Cycle Assessment (LCA) emerges as a valuable tool for systematically evaluating the environmental performance