Size and geometry effects on compressive failure of laminated bamboo: a combined experimental and multi-model theoretical approach

Laminated bamboo (LB) represents a promising sustainable construction material, inheriting bamboo’s high strength, lightweight properties, and good ductility. However, the dimensional stability of mechanical performance—specifically size effects—remains a critical design challenge requiring systematic investigation. This study investigates the compression behavior of LB with tests of four specimen groups spanning volumes from 62,500 to 4,000,000 mm³ (25 × 25 × 100 mm to 100 × 100 × 400 mm). The research objectives encompass (i) characterizing compression behavior and failure mechanisms across different specimen scales, (ii) quantifying geometric and volumetric size effects on mechanical properties, (iii) evaluating theoretical frameworks for size effect prediction, (iv) developing progressive modeling approaches incorporating material heterogeneity, and (v) establishing design parameters for practical applications. Results demonstrate modest proportional size effects (1.60% strength reduction, 8.62% modulus reduction for 4× proportional scaling) but significant geometric optimization benefits, with cubic specimens achieving 15.78% higher strength and 25.11% greater modulus than equivalent-volume prismatic specimens. All specimens exhibited interfacial delamination failure with size-dependent crack propagation patterns. Theoretical analysis incorporates Weibull statistics, Bažant’s fracture mechanics, and Carpinteri’s fractal theory, with fracture energy modeling performing optimally. Three progressive modeling approaches achieve prediction accuracies ranging from 1.17% to 0.37% errors, with density-coupled modeling providing superior performance despite minimal density variations (COV = 9.27%). The research establishes size effect factors (0.86 for strength, 0.78 for modulus) and critical dimensions (125.64–126.14 mm), addressing critical gaps in LB size-dependent behavior. These parameters enable the development of reliable design methodologies for large-scale sustainable construction.