This study proposes a high-strength bottom-bar interlocking and anchorage precast beam–column joint (HSRU-PBCJ), which utilizes high-strength longitudinal reinforcement combined with U-shaped anchorage at the beam bottom. Low-cycle reversed loading tests were conducted on two precast specimens and one cast-in-place specimen to evaluate their seismic performance. Based on these results, parametric analyses were conducted through numerical simulations to investigate the effects of axial compression ratio, concrete strength, beam-end longitudinal reinforcement strength, and beam-end longitudinal reinforcement ratio on the seismic performance. The results indicate that the proposed joint exhibits stable and full hysteresis loops, cumulative energy dissipation comparable to that of the cast-in-place joint, and a 23.94–26.39% increase in equivalent viscous damping after yielding, achieving a displacement ductility coefficient of 4.14, which confirms its substantially improved seismic performance. The parametric study shows that maintaining a moderate axial compression ratio (≤0.6) enhances both load-bearing capacity and energy dissipation, whereas excessive values result in strength reduction. Increasing the beam-end longitudinal reinforcement strength significantly improves load-bearing capacity but may reduce energy dissipation. In addition, improving concrete strength and appropriately increasing the reinforcement ratio can further enhance both load-bearing capacity and energy dissipation, although a balance between seismic performance and economic considerations is recommended.

This study addresses the complexity and high cost associated with traditional temporary formwork in post-cast strips. An innovative use of fish-scale mesh as a permanent interface material is proposed. This material serves as both construction framework and a connector during the service phase. The study investigates the enhancement mechanism of fish-scale mesh on the interfacial bond between new and old concrete. A multi-parameter experimental framework combined with full-field strain measurement was employed. Three specimen types with varying hole heights and numbers were designed and fabricated. Macro-mechanical properties were evaluated through double-shear and splitting-tensile tests. The interfacial strain field was quantified with high precision and visual clarity using Digital Image-Correlation (DIC) technology. Results show that introducing fish-scale mesh alters the interface failure mode. In mesh-free specimens, failure occurs through brittle interfacial delamination. With fish-scale mesh, failure transitions to ductile rupture within the concrete body. The number of holes has the greatest effect on shear strength, followed by hole height. Among all configurations, the fish-scale mesh with a hole height of 6 mm and 30 holes demonstrated the best performance. The shear strength and splitting strength increase by about 32% and 13%, respectively, compared to mesh-free specimens. Based on experimental results and theoretical derivation, a shear-bearing capacity formula for the fish-scale mesh interface is proposed. This model innovatively incorporates the shear key area of the fish-scale mesh, along with weakening and disturbance coefficients derived from experimental data. The theoretical model was validated against experimental results, showing a good agreement and supporting the use of fish-scale mesh as a permanent interface material.

Densely distributed small holes significantly affect the mechanical behavior and fracture characteristics of rock masses. In this study, the two-dimensional particle flow code was employed to establish a series of numerical models of dolomitic limestone, with the number of small circular holes increasing according to the sequence (2n − 1)² (n = 1–6). Comparative models with equivalent area and variable spacing were additionally designed to explore their regulatory effects. The strength, crack evolution, and contact force chain distribution of each model were systematically analyzed. The results reveal that the number of small holes exhibits an approximately linear negative correlation with the rock strength. The number of holes dominates the crack initiation location and propagation path. The crack initiation stress gradually decreases with increasing hole number, while the ratio of crack initiation stress to peak stress exhibits a V-shaped trend. As the hole number increases, the distribution of compressive force chains shifts from the sides of holes to the vertical strips between holes, and tensile force chains become significantly enhanced in the areas above and below the holes. Hole spacing and equivalent area exert only local modulating effects; the number and spatial arrangement of holes remain the dominant controls on strength deterioration and fracture evolution. These findings offer a theoretical foundation for stability assessment in rock masses characterized by densely distributed hole defects.