Effects of protective concrete cover and cross-section size on the mechanical properties of lightweight concrete beams: An experimental and simulation investigation

• The influence of protective cover thickness on the bending of structures was systematically studied; • The structural bending mechanism was revealed via PEEQ and fracture energy; • The steel reinforcement constraint mechanism was introduced into the discussion. Lightweight concrete (LWC) offers material advantages in floating structures due to its low density. Increasing the concrete cover thickness of LWC structures enhances their durability in marine environments, but it also affects their structural mechanical properties. This study focuses on investigating the effect of concrete cover thickness on the mechanical properties of LWC beams. A calibrated finite element model validated through four-point bending tests indicates that, with beam dimensions held constant, increasing the cover thickness reduces the cracking load (↓13.7%), peak load (↓21.2%), and post-cracking stiffness (↓38.9%). However, increasing the cover thickness by raising the beam height resulted in a 35.4% increase in cracking load and initial stiffness, with negligible impact on ultimate load-carrying capacity. The study reveals a negative correlation between fracture toughness and concrete cover thickness in LWC structures. Furthermore, from the perspective of structural plastic strain, the damage characteristics of LWC structures were analyzed, showing reduced plastic strain with increasing concrete cover thickness. The findings provide a quantitative exploration of the relationship between concrete cover thickness and the behavior of LWC structures from multiple dimensions, offering crucial theoretical support for the application of LWC structures in scenarios requiring high durability.