This paper presents experimental and numerical study to investigate the flexural behaviour of strengthened RC beams using three CFRP techniques. Considered main variables were CFRP technique, amount of CFRP NSM and rope and cost/increase in strength effectiveness. Results indicate that using CFRP rope and sheet increased significantly maximum load and maximum strain of RC beams. Average increase in strength and maximum strain were 76.3% to 143.5% and 206% to 246% as the control RC beam. Moreover, RC beams strengthened with CFRP rope exhibited strength approximately similar to ones strengthened with CFRP strip. The cost/increase in strength ratio of specimens strengthened by CFRP rope is 61% higher than the ratio of specimens strengthened by CFRP NSM strip. Hence, the specimens strengthened by one layer of CFRP rope is the most economic techniques based in cost/increase in strength ratio even though it exhibited maximum load less than the specimens strengthened with two layers of CFRP rope or strip. CFRP rope was 40% lower than CFRP strip when same strengthening effect was achieved. Finally, complementary to experimental work a finite element model FEM was developed to investigate the flexural behaviour of beam. The FEA model showed somehow good agreement with the experimental results.

This experimental study presents the influence of basalt fiber on the rheological and mechanical properties and the durability behavior of self-compacting concrete (SCC). In this study, a total of five self-compacting concrete mixtures were prepared: one as a control mix and the other mixes with 0.05%, 0.1%, 0.15%, and 0.2% basalt fibers. Slump flow and V-funnel flow tests were employed to assess the influence of basalt fibers on the rheological properties of fresh self-compacting concrete (SCC). Additionally, mechanical properties, including compressive strength, splitting tensile strength, and flexural strength, were analyzed. Furthermore, the mechanical properties were assessed following exposure to elevated temperatures (400 °C and 600 °C) as well as 100 and 200 freeze-thaw (F/T) cycles. Additionally, water absorption and ultrasonic pulse velocity tests were conducted on the SCC mixes after 28 days of curing. The results revealed that the addition of fiber has a significant effect on the rheological properties of fresh SCC mixtures. As the volume of fibers increases, the reduction in rheological properties increases. Basalt fiber had no effect on the compressive strength, while the splitting and flexural strength were significantly enhanced by 33% using basalt fiber. As temperatures and freezing-thawing cycles escalated, the mechanical properties of SCC exhibited a decline. Experimental findings indicated that elevating the temperature to 600 °C resulted in a decrease of over 20% in both the tensile and compressive strengths of SCC. Moreover, the results demonstrated that the incorporation of basalt fibers substantially enhanced the mechanical properties of SCC when subjected to high temperatures and freezing-thawing cycles. In addition, water absorption increased slightly by the incorporation of basalt fiber.

Reliable material stress-strain relationship is the cornerstone of any analysis process. Unlike reinforced concrete, limited studies focused on the stress-strain behavior of confined reinforced masonry. Reinforced masonry boundary elements (RMBEs) added at the masonry shear wall ends allow placing of at least four longitudinal reinforcement bars restrained by transverse hoops and thus introducing confinement to the wall’s most stressed zone. This study presents the observed stress-strain relationship of 30 C-shaped half-scale fully grouted unreinforced and reinforced masonry boundary element specimens tested under concentric compression loading. The effect of changing hoop spacing, longitudinal reinforcement ratio, and the strength of grout on the axial stress-strain behavior of RMBE is investigated. This study quantifies and correlates the effect of these parameters on the RMBE peak stress, strain corresponding to peak, and postpeak behavior. Finally, this study investigates the capability of three existing stress-strain models in predicting the RMBE stress-strain relationship. Enhancement in both peak and postpeak stress-strain behavior were observed by decreasing the hoop spacing, increasing the longitudinal reinforcement ratio, and increasing the grout strength. The studied models overestimated the enhancement in the RMBE strength, significantly overestimated the enhancement in the RMBE strain capacity, and did not capture the postpeak stress drop. This study emphasizes the need for a new stress-strain model that can predict the RMBE response considering various confinement effects.

Purpose: This study aims to conduct an experimental study and finite element model (FEM) to investigate the flexural behavior of heat-damaged beams strengthened/repaired by hybrid fiber-reinforced polymers (HFRP).Design/methodology/approach: Two groups of beams of (150 × 250 × 1,200) mm were cast, strengthened and repaired using different configurations of HFRP and tested under four-point loadings. The first group was kept at room temperature, while the second group was exposed to a temperature of 400°C.Findings: It was found that using multiple layers of carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP) enhanced the strength more than a single layer. Also, the order of two layers of FRP showed no effect on flexural behavior of beams. Using a three-layer scheme (attaching the GFRP first and followed by two layers of CFRP) exhibited increase in ultimate load more than the scheme attached by CFRP first. Furthermore, the scheme HGC (heated beam repaired with glass and carbon, in sequence) allowed to achieve residual flexural capacity of specimen exposed to 400°C. Typical flexural failure was observed in control and heat-damaged beams, whereas the strengthened/repaired beams failed by cover separation and FRP debonding, however, specimen repaired with two layers of GFRP failed by FRP rupture. The FEM results showed good agreement with experimental results.Originality/value: Few researchers have studied the effects of HFRP on strengthening and repair of heated, damaged reinforced concrete (RC) beams. This paper investigates, both experimentally and analytically, the performance of externally strengthened and repaired RC beams, in flexure, with different FRP configurations of CFRP and GFRP.