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Recent earthquakes have highlighted the vulnerability of reinforced concrete (RC) frames with masonry infill walls, particularly in developing countries, where such structural systems often experience severe damage and significant economic and human losses. Although masonry infills can considerably enhance the initial stiffness and lateral load capacity of RC frames, inadequate detailing may lead to brittle failure mechanisms and unsatisfactory seismic performance. This study presents an experimental investigation into the seismic response of RC frames with hollow clay block infills subjected to both in-plane (IP) and out-of-plane (OOP) loading. A strengthening technique employing alkali-resistant (AR) glass fiber strips embedded in a thin cementitious mortar overlay was evaluated. Five half-scale, single-bay, single-storey RC frame specimens were constructed and tested: one bare frame, two infilled frames subjected to in-plane cyclic loading (unstrengthened and strengthened), and two comparable infilled frames subjected to monotonic out-of-plane loading. The experimental results demonstrate that the presence of masonry infills significantly increases the initial stiffness and lateral load capacity of RC frames. Furthermore, the proposed strengthening system enhances structural performance, particularly under out-of-plane loading conditions. Compared with the unstrengthened specimens, the strengthened frames exhibited increases of up to 38% in-plane lateral load capacity and more than 170% in out-of-plane load capacity. Within the limitations of the experimental program, the findings indicate that the proposed AR glass fiber–based strengthening technique represents a practical and efficient solution for improving the seismic performance of masonry-infilled RC frames under both in-plane and out-of-plane loading.
Ostad et al. (Wed,) studied this question.