Comparative analysis of the material properties of four commonly used timber species in the restoration of historical buildings in Shanxi, China

Historical timber buildings in Shanxi province, China, face significant restoration challenges due to natural degradation, extreme weather events, and restrictions on native timber harvesting, necessitating the use of alternative timber species for structural repairs. This study examines the material properties of four timber species – Chinese pine (Pinus tabuliformis Carrière), larch (Larix gmelinii var. principis-rupprechtii [Mayr] Pilger), Douglas fir (Pseudotsuga menziesii [Mirbel] Franco), and Mongolian Scots pine (Pinus sylvestris var. mongolica Litv.) – commonly used in the restoration of historical timber buildings in Shanxi. Given the structural diversity of these buildings, six loading modes were applied to assess the suitability of each species for different structural components: compression parallel to the grain, compression perpendicular to the grain in the radial direction, shear parallel to grain along the longitudinal-radial plane, shear parallel to grain along the longitudinal-tangential plane, four-point static bending, and tension. Douglas fir exhibited the highest compressive strength parallel to the grain, making it well-suited for load-bearing components, while Chinese pine demonstrated strong compressive strength perpendicular to the grain in the radial direction. Larch and Douglas fir excelled in shear resistance, and all four species exhibited high bending strengths, supporting their use in primary structural components. In contrast, Mongolian Scots pine exhibiting lower shear and bending strengths is more appropriate for non-load-bearing applications where structural demands are minimal. Positive correlations between strength, density, and dynamic modulus of elasticity suggest that density and ultrasonic testing can serve as effective non-destructive evaluation methods. These findings provide valuable insights into material selection for heritage timber restoration, promoting species-specific applications that enhance structural resilience while preserving traditional carpentry techniques.