Size influence of laminated bamboo bending mechanical properties with the consideration of density

Laminated bamboo (LB), as a novel green composite material with a high strength-to-weight ratio, has attracted growing attention. However, there is a gap in understanding how size influences the bending properties of LB, specifically modulus of rupture (MOR) and modulus of elasticity (MOE). To address this, seven groups of LB specimens (n = 20 per group, 140 total) with dimensions ranging from 25 × 25 × 400 mm to 100 × 100 × 1450 mm were tested to investigate the effects of single length, span, width, sectional area, and volume on failure modes and basic properties, including the consideration of density (0.60–0.70 g/cm³). The results indicate that width exerts less influence compared to single length and span. When specimens are proportionally enlarged by 2–4 times, MOR and MOE decrease to 82.87 %–65.90 % and 94.11 %–80.56 % of their original values, respectively. Density plays a critical role in modulating the relationship between MOR, MOE, and size-effects. Three theoretical models (Weibull, Bažant, and Carpinteri) were evaluated. Consequently, size-effect models were developed to determine the size factors for MOR and MOE as 0.79 and 0.88, respectively. This research will serve as a reference base for defining the resistance partial factor and design values as well as limiting the size of basic bending performance specimens.