Compressive mechanical properties of mongolian scots pine: The influence of specimen dimensions

• Volumetric size effect coefficients determined: 0.121 (L), 0.077 (R), 0.199 (T). • Strength prediction errors of merely 1.98%-4.80% for large specimens. • Height effect (0.25) exceeds width effect on longitudinal strength. • Finite element analysis validates size-specific constitutive parameters. • Medium/large specimens provide more reliable mechanical characterization. Wood is an orthotropic material whose compressive mechanical properties exhibit significant directional dependence. This study systematically investigates the size effects on the axial compression behavior of Mongolian Scots pine (Pinus sylvestris var. mongolica) across all three principal anatomical directions. Through comprehensive testing of 96 specimens spanning dimensions from 20×20×30 mm³ to 80×80×120 mm³, we establish quantitative volumetric size-effect coefficients for longitudinal (0.121), radial (0.077), and tangential (0.199) compression using Weibull weakest-link theory. The novel application of this statistical framework across multiple material directions represents a significant advancement beyond conventional approaches that typically consider only longitudinal compression. Our multi-directional coefficients enable reliable strength predictions across specimen sizes, achieving remarkably low errors of merely 1.98%, 2.70%, and 4.80% when validated against 80×80×120 mm specimens in the L, R, and T directions, respectively—substantially improving upon existing unidirectional models. Furthermore, we decouple the geometric influences in longitudinal compression, identifying height (coefficient: 0.25) as the dominant factor over width. Finite element simulations incorporating orthotropic constitutive laws confirm that accurate compression modeling requires these size-corrected parameters. This systematic quantification provides engineers with a validated methodology for scaling mechanical properties from laboratory specimens to structural elements, offering direct implications for timber design practice and potential revisions to structural design codes.