In this study, the performance of precast concrete segmental bridge columns (PCSBCs) against truck impacts was numerically investigated and compared with a corresponding conventional monolithic column (CMC). The numerical results have shown that although the impact force time histories of the two columns were quite similar under the same loading conditions, the PCSBC showed a better performance in terms of the induced bending moment and shear force by high impact force due to shear slippage and joint rocking between concrete segments. Also, the damage and failure of PCSBCs were localized at the two bottommost segments due to compression damage and/or combined flexural and shear failure of the concrete segment, whereas failure of the CMC distributed widely with flexural cracks, shear cracks, and punching shear at multiple sections. Furthermore, the base segment, which was found to absorb about 80% of the total absorbed energy of the PCSBC, played a crucial role in controlling the failure of the PCSBC. An analytical method to estimate the bending moment required to open the segment joint and the ultimate bending moment was also developed with consideration of the dynamic increase factor and the increase in axial force associated with stress wave propagation in the column induced by impact load.
Precast segmental concrete beams (PSBs) prestressed with external tendons have become increasingly popular. This type of structure takes advantage of both the segmental construction method and the external prestressing technique. However, corrosion of steel tendons is still a great concern, which might increase the lifecycle costs of the structure. This study presents an experimental investigation into the use of carbon fiber–reinforced polymer (CFRP) tendons as an alternative to steel tendons for segmental concrete beams to mitigate the corrosion problems. To the best of the authors' knowledge, this is the first study using CFRP tendons to externally prestress segmental concrete beams. Four large-scale, T-shaped segmental concrete beams with different types of joints and tendon materials (steel/CFRP tendons) were built and cyclically tested under four-point loading. The test results show that CFRP tendons can replace steel tendons in segmental concrete beams as an external prestressing material. All the tested beams exhibited excellent performance regarding load-carrying capacity and ductility. The type of joint had an insignificant effect on the overall flexural behavior of the beams. After the joints opened, the beams with epoxy-coated joints behaved similarly to the beams with dry joints. The beams with CFRP tendons exhibited nonlinear behavior after the opening of joints; however, the level of nonlinearity was much less than that of the beams with steel tendons. Steel tendons achieved very high stresses at the ultimate stage, which were approximately 94% of their ultimate tensile strength. However, CFRP tendons ruptured at quite low stresses, which were approximately 78% of their nominal breaking strength on average. Finally, all the existing models examined in this study predict the tendon stress and the ultimate load of the beams with steel tendons well, but they encounter large scatter for the prediction of the tendons' stress and strength of the beams with CFRP tendons.
Masonry walls are known for their limited impact resistance, even when retrofitted with CFRP (carbon fibre-reinforced polymer) and nanomaterials. This paper presents the findings of an experimental study using split Hopkinson pressure bar (SHPB) tests aimed at exploring the potential application of auxetics textile reinforced mortar (TRM) composites in impact protection. This study will provide the initial understanding of the composite as a structural reinforcement solution for masonry walls. Key findings reveal that the peak strength increases with rising strain rates, highlighting significant strain rate sensitivity in TRMs with auxetic (AX) and carbon fabric (CF) reinforcements. AX samples exhibit better energy absorption as compared to the reference plain mortar (PM) samples, particularly at higher strain rates, surpassing CF samples beyond 150 s−1. Moreover, the insertion of auxetic and carbon fabrics eliminates crack development and mitigates the severity of sample failure. The negative Poison ratio effect of auxetic fabrics significantly enhances the lateral confinement, ultimately improving the dynamic performance of AX samples compared to CF samples. These findings underscore the potential of auxetic materials in enhancing dynamic performance, particularly under high strain rates, with clear implications for engineering applications, including in masonry buildings.
A technique called "circularization" [where segmental, circular, concrete covers made of different concrete strengths (40 MPa, 80 MPa and 100 MPa)] was used to change a square column to a circular column. The behavior of the strengthened specimens under different loading conditions [including concentric loading, eccentric loading (25 mm and 50 mm) and flexural bending] was investigated. The experimental results demonstrate that using high-strength concrete (HSC) for the additional covers to strengthen existing square reinforced concrete (RC) columns provides higher load-carrying capacity than covers made of normal strength concrete. The highest capacity of the strengthened columns was four times higher than that of the corresponding reference column under concentric loading. Theoretical interaction diagrams were established and showed a good agreement with the experimental results.
