Impact performance of GFRP-reinforced seawater sea sand concrete slabs: Influence of span-to-depth ratio

The impact response of reinforced concrete (RC) structures is governed by not only the local stiffness but also the global stiffness. Among the key factors influencing the global stiffness, the span-to-depth ratio plays a crucial role. However, most existing studies on the impact behavior of structures reinforced with fibre-reinforced polymer (FRP) have yet to clarify its effect. Notably, no research to date has explored the impact response of seawater sea-sand concrete (SSC) slabs reinforced with glass FRP bars (GFRP-SSC). This study experimentally investigates the effect of the span-to-depth ratio on the flexural response of one-way GFRP-SSC slabs under impact loading. This study also proposes a spring-mass model for the impact force and deflection and derives a dynamic amplification factor for GFRP-SSC slabs. The results show that the span-to-depth ratios significantly influenced the impact behaviour of GFRP-SSC slabs. An increase in span length enlarged the circumference crack region while reduced severity of cracks. Interestingly, longer-span slabs (with lower global stiffness) exhibited higher impact forces (up to 25.2 %), yet also have much larger deflection (up to 2.69 times) and longer response durations compared to shorter-span slabs. Incorporating fiber reinforcement both slightly improved the slabs’ impact force and reduced deflection, while also contributing to better crack control. Compared with conventional RC slabs, GFRP-SSC slabs exhibited overall similar flexural response and impact force, but experienced greater deflection. The derived dynamic amplification factor for bending moment of the GFRP-SSC slabs is 3.24. The proposed spring-mass model well predicts the time histories of the impact force and deflection of the GFRP-SSC slab with close agreement to the experimental results. • First study on FRP-reinforced sea sand-sea water concrete slabs under impact. • Stress wave propagation and negative reaction force in reinforced slabs. • Spring-mass model for sea sand-sea water concrete slabs under impact. • Dynamic amplification factor for moment of concrete slabs.