Issue 78

D. D. Joshi et alii, Fracture and Structural Integrity, 78 (2026) 315-345; DOI: 10.3221/IGF-ESIS.78-19

controlled manner. The authors found that, the proposed strengthening scheme effectively enhanced load resistance, stiffness and energy absorption capacity of specimens. A combined strengthening scheme consisting of ECC and BFRP was found to be effective for progressive collapse resistance with a 31.3% increase in ultimate load-carrying capacity. The authors recommended the use of ECC at beam bottom, together with combined BFRP and steel rebars to improve progressive collapse performance and overall structural robustness. Further, Qin et al. [24] experimentally investigated the effect of near-surface-mounted GFRP bars and ECC strengthening on progressive collapse response of RC beam-slab system under corner column removal scenario. Based on the experimental findings, the formula was derived to estimate theoretical peak capacity of beam-slab system under column removal scenario using principle of virtual work and yield line theory. Experiments were conducted under quasi-static loading condition applied at the location of removed corner column. Study results revealed that, the proposed strengthening method effectively enhanced load resistance of the beam-slab system under progressive collapse scenario. Furthermore, higher peak capacity was observed for NSM strengthening than for an equivalent EBR strengthening configuration. The provision of L-shaped edge beam was more effective under corner column removal scenario and enhanced the progressive collapse resistance of beam-slab system by 52% to 65% as compared to the flat slab system. An innovative strengthening approach of using high-performance ferrocement laminate combined with bonded steel plates (HPFL-BSP) to enhance the progressive collapse resistance of RC structures was adopted by Huang et al. [25]. Experimental investigations were carried out on three one-third (1/3) scale beam-slab sub-assemblage specimens under a corner column removal scenario. In addition to the control specimen, one specimen was strengthened at the beam level, while another was strengthened at the slab level. A vertical load was applied at the location of the removed corner column using a hydraulic jack. The results demonstrated that the proposed strengthening schemes significantly improved the overall performance of the specimens in terms of load carrying-capacity, dynamic resistance, ductility and energy dissipation. The peak load-carrying capacity was enhanced by 15.60% to 29.40% in strengthened specimens compared to the control specimen. It was also observed that slab strengthening provided higher progressive collapse resistance, than beam strengthening. The authors further developed a theoretical model to predict load resistance at different stages for both control and strengthened specimens. In addition, finite element models were developed and effects of various parameters including different HPFL BSP strengthening schemes, reinforcement damage, boundary conditions and beam-slab interaction on progressive collapse resistance were investigated by Huang et al. [26]. Huang et al. [27] studied the behaviour of a three-dimensional (3D) RC frame comprising a one-bay x two-bay, two-stories, under column removal scenario through experimental and numerical studies. High-performance ferrocement laminate and bonded steel plates were used as strengthening measure to enhance progressive collapse resistance. Experimental studies were conducted on two one-third (1/3) scale test specimens. The experimental results were compared with numerical analysis and additional parametric studies were also carried out to understand the effect of steel-strand quantity and the influence of strengthening location on progressive collapse resistance. The results showed that proposed strengthening scheme improved initial stiffness and bearing capacity of frames under column removal scenario until the fracture of steel strands. External cable systems Elkoly and El-Ariss [28] proposed the use of external fiber-reinforced plastic (FRP) cables at anchorage and deviator/saddle locations, to mitigate progressive collapse in continuous beams subjected to an interior column removal scenario. The effectiveness of the proposed technique was evaluated through numerical investigations. A push-down analysis was performed to simulate the column loss condition. The study included key parameters such as beam cable types, cross sectional shape, location of deviators/saddle points, cross-sectional area and cable profile within the numerical model. The results indicated that the incorporation of FRP cables enhanced the load-carrying capacity and energy dissipation of the beam at large vertical deformations during the column removal case. However, the authors also recommended performing experimental studies to validate the effectiveness of the proposed external unbonded FRP cable system for progressive collapse mitigation. Liu et al. [29] investigated the use of hanging CFRP strip cables with end anchorages, for retrofitting of reinforced concrete (RC) frames under column removal scenario. Experimental studies were conducted on one-half (1/2) scale specimens of a three-storey, three-bay by two-bay RC frame subjected to the sudden removal of two ground storey columns. Column removal was accomplished using projectile impact generated by a compressed hydrogen gas gun. The experimental results demonstrated that CFRP strip cables effectively reduced the risk of total collapse of the RC frame under simultaneous removal of two columns. Furthermore, the authors proposed a simplified method for estimating the average strain in CFRP strip cables, along with a resisting mechanism to predict the ultimate load-carrying capacity of beams, slabs and CFRP strip cables.

321