Behaviour of seawater sea-sand reinforced concrete composite beams strengthened with C-FRCM subjected to impact loading

Seawater sea-sand reinforced concrete (SSRC) offers a sustainable solution for marine construction; however, its structural performance under impact loading remains inadequately understood. This paper examines the lateral impact behavior of SSRC composite beams strengthened with carbon fabric-reinforced cementitious matrix (C-FRCM) through a finite element (FE) modeling together with the of experimental results, where previous experimental results revealed that C-FRCM significantly enhanced crack distribution, reduced mid-span deflections, and improved energy dissipation capacity. A three-dimensional nonlinear FE model was developed using ABAQUS programme and validated against experimental results, demonstrating good consistency in impact load histories, displacement responses, and failure modes. Parametric studies were conducted to investigate the effects of various factors on the performance the composite beams, including the number of C-FRCM layers, span-to-depth ratios, impact velocities, impact masses, and impact locations. The results indicate that using two layers of C-FRCM provides the most effective strengthening, achieving over 80% energy absorption efficiency. Larger span-to-depth ratios and higher impact velocities were found to significantly increase structural deformation. Additionally, increasing the impact mass extended the impact duration and exacerbated residual deflections, while impacts closer to the supports caused more localized and severe damage despite reducing overall deformation. The study confirms the effectiveness of C-FRCM as a reliable strengthening technique to enhance the impact resistance of SSRC members. These findings offer valuable insights for the design of resilient coastal and marine structures capable of withstanding accidental impact events.