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This study presents an experimental investigation of the fire response of six columns strengthened with polyparaphenylene benzobisoxazole (PBO) FRCM system, and tested in a large-scale furnace following ASTM E119 standards. The parameters investigated included the number of PBO-FRCM layers and the presence of a fireproofing insulation layer. Test results highlighted the effectiveness of PBO-FRCM in insulating the column, with the strengthened column showing a substantial 31.9% reduction in temperature readings at the concrete surface compared to its unstrengthened counterpart. Furthermore, the presence of Sikacrete 213F fireproofing system reduced temperature readings within the column's section by an average of 65%. Based on the experimental results, a parametric numerical study were developed and verified using ABAQUS software. The parameters studied included the number of PBO-FRCM layers (0, 1, and 2 layers), the presence of a 30 mm thick insulation layer, and the axial preloading taken as 40, 60, and 75% of the ultimate column's capacity. The model accurately predicted the temperature readings across the columns. Strengthening the columns with PBO-FRCM significantly increased their resistance during fire, doubling fire-resistance duration with one layer. Adding fireproof insulation led to significant increase in load resistance duration. The percentage drop in temperature after 1 hour of fire exposure was around 70% at the FRCM surface for the insulated column strengthened with one layer of FRCM. Higher preload percentages reduced both the fire-resistance duration and ductility of the columns. For the group of columns strengthened with one layer, increasing the preloading percentage to 60% and 75% resulted in decreases in the fire-resistance duration of 35% and 73%, respectively.

For the past decade, researchers have been experimenting with the use of Demolished Concrete Lumps (DCLs) in structural members, as it has been proven to be a promising method to recycle concrete in different field applications. Although there have been several studies on incorporating DCLs in Concrete Filled Steel Tube (CFST) members, there are no studies that evaluate its effect on the flexural performance of CFST beams. Therefore, this paper focuses on studying the flexural behavior of CFST beams with DCLs, where the DCLs are inserted at the center of the cross-section. In total, fourteen circular CFST and two circular Steel Tube (ST) specimens were tested under bending using a four-point loading setup. The specimens are categorized into two different steel tube sections, where two circular sections of D/t = 55 (C1) and D/t = 45 (C2) were considered. The CFST specimens within each steel tube category differ in DCLs particle sizes and DCLs inner occupation area. CFST beams filled completely with normal concrete were also tested as control specimens. In addition, two CFST specimens from the steel section C2 were left partially hollow at the center to study the contribution of DCLs to the overall flexural performance. The results were very promising as the flexural behavior of DCL CFST specimens was very similar to the control CFST specimens. The DCLs’ particle sizes and the inner occupation area had minimal effect on the ductility, stiffness, yielding capacity, and ultimate capacity of the CFST specimens. The maximum percentage reduction in the flexural capacity between DCL CFST and control specimens were less than 2% for both sections whereas the percentage gain was up to 7%. Furthermore, the obtained flexural capacities were compared with nominal predictions from different design codes and models. All codes underestimated the capacities of all CFST specimens, with Han's model being the most conservative, followed by EC4, BS-5400–5, and AISC-LRFD, respectively.

This research investigates the flexural behavior and serviceability performance of basalt fiber-reinforced polymer (BFRP) reinforced concrete (RC) beams cast with normal- and high-strength concretes (NSC and HSC). Carbon FRP (CFRP) and steel-reinforced concrete beams were also included for comparison purposes. Four-point bending tests were performed on a total of 14 slender beams with dimensions of 180 mm × 230 mm × 2200 mm. The main aim was to examine the improvement in the performance of BFRP RC beams using HSC and to assess its compatibility with the recommendations and guidelines of the ACI440 Code. The test results were reported and discussed in terms of flexural capacity, deflection, crack width, reinforcement and concrete strains, and failure modes. The results revealed that the flexural capacities of BFRP beams were slightly underestimated by ACI440.1R-15 while reasonable predictions were observed for the cracking moments in HSC and NSC. The use of HSC as compared to NSC enhanced the cracking and ultimate moments of all BFRP RC beams by 10% and 16%, respectively. Furthermore, the average bond-coefficient (kb) value for BFRP-RC beams was found to be 0.70 which is much lower than the conservative kb value suggested by the ACI440 guidelines for sand-coated FRP bars.

The application of fiber-reinforced polymers (FRP) bars in the building industry has grown intensively over the years, due to their numerous advantages such as corrosion resistance. However, current guidelines in design codes disregard the contribution of FRP bars in compression. The need of investigation of compressive mechanical properties of FRP bars is important, while there is a lack of experimental tests under varying dynamic and quasi-static loading rates. The present paper aims to evaluate the compressive strength and failure modes of glass and basalt fiber-reinforced polymer (GFRP and BFRP) bars. A series of quasi-static and dynamic tests were performed on different FRP bar sizes. Dynamic tests were conducted using the drop hammer procedure and different loading rates were achieved through varying the weight of mass and height of fall. Results showed that GFRP bars attained higher compressive strengths than BFRP bars for the same loading conditions. GFRP bars exhibited compressive strength in the range of 300 MPa to 600 MPa while the maximum compressive strength of BFRP bars was 470 MPa. The increase in the bar diameter resulted in an increase in the compressive strength of most FRP bars. However, Some FRP bars showed different variation in their compressive strengths at high loading rates. Finite element (FE) models were also developed to simulate the FRP bars under dynamic tests by considering the orthotopic material nature of the FRP composites. The FE models were verified with the experiments and successfully described qualitatively the trends observed during the full-scale drop-hammer tests.