Laminated bamboo (LB), as a novel eco-friendly composite material with a high strength-to-weight ratio, has garnered increasing interest. However, there is a gap in comprehending the impact of size on the tensile properties of LB, particularly tensile strength and modulus. In contrast with conventional materials such as concrete and wood, which have specified specimen sizes and size effect factors to address performance variances linked to size, LB lacks such standards and references. To address this, seven groups of LB specimens of varying sizes were developed and tested to examine the impact of length, thickness, and sectional area on failure mechanisms and fundamental features, including density considerations. The findings demonstrate that size does not significantly influence the failure mode. Length exerts a smaller influence than thickness. When specimens are scaled up by a factor of two, tensile strength and modulus diminish to 82.86% and 88.38% of their initial values, respectively. Density significantly influences the relationships of tensile strength, modulus, and size effects. Consequently, size effect models incorporating both specific properties and the density–property relationship were developed.

As 3D printing emerges as a transformative technology in construction, the structural performance of 3D-printed mortar (3DPM) has become a key research focus. This study conducted shear tests on reinforced specimens combining 3D-printed mortar (3DPM) and normal mortar (NM). Four different shapes of interfacial locking design (I-shaped, K-shaped, C-shaped, S-shaped) were examined, comparing reinforced (CR) and non-reinforced (NR) specimens. The investigation analyzed failure modes, crack propagation patterns, and shear transfer mechanisms at CR series specimens under direct shear loading. CR-S specimens exhibited a shear peak load value 14.0% higher than CR-K specimens, 33.2% higher than CR-C specimens, and 42.9% higher than CR-I specimens. CR-I specimens exhibited pure adhesive failure. CR-K, CR-C, and CR-S specimens showed composite failure patterns combining adhesive and shear failure mechanisms. Strain analysis revealed the maximum horizontal strain ε_xx across all specimen shapes. CR-C and CR-S specimens recorded strain values exceeding CR-I and CR-K specimens by over 50%. Reinforcement produced pronounced increases in ultimate bearing capacity for I-shaped and C-shaped specimens, achieving gains of 51.9% and 60.4%, respectively. Reinforcement substantially enhanced energy dissipation capacity. Compared with NR series specimens, the performance improvements ranked as follows: CR-C (+164.67%) > CR-S (+70.70%) > CR-I (+52.05%) > CR-K (+9.42%).

This study investigates the interlayer shear performance of 3D-printed concrete (3DPC) using direct shear tests. Three nominal layer heights, 5 mm, 10 mm, and 15 mm, were considered, and specimens were loaded parallel to the printing path (x direction) and perpendicular to the printing path (y direction). The results show that the interlayer nominal shear strength decreased with increasing layer height. When the layer height increased from 5 mm to 10 mm and then to 15 mm, the nominal shear strength decreased from 9.18 MPa to 7.01 MPa and 4.88 MPa in the x direction, and from 7.87 MPa to 5.29 MPa and 2.68 MPa in the y direction. At the same layer height, the x-direction specimens exhibited higher nominal shear strength than the corresponding y-direction specimens, with increases of approximately 17%, 33%, and 82% for the 5 mm, 10 mm, and 15 mm series, respectively. DIC analysis indicated that tensile–shear damage was the main local failure characteristic. The loading-direction effect was related to different shear-transfer paths: the L-x specimens mainly followed a “continuous filaments-mortar matrix-interlayer bonding” path, whereas the L-y specimens were more controlled by weak interlayer-edge regions and local stress concentration. The effective shear-area analysis showed that the effective bonded area decreased with increasing layer height. After area correction, the corrected shear strengths of the x-direction specimens were 9.18 MPa, 8.76 MPa, and 8.13 MPa for L-5-x, L-10-x, and L-15-x, respectively, while those of the y-direction specimens were 7.87 MPa, 6.61 MPa, and 4.47 MPa, respectively. This indicates that a larger layer height not only reduced the effective bonded area but also weakened filament compaction and bonding quality. The findings provide a mechanism-oriented basis for understanding the anisotropic interlayer shear behavior of 3DPC.