Optimization methods tailored for practical engineering applications continue to evolve in order to realize lightweight single-layer reticulated shell structures and maximize node stiffness. This paper takes the minimum amount of steel as the objective function, and divides the rod types into three groups and three corresponding one-to-one optimization schemes. Considering the stress and stiffness of the rod and the displacement and stability constraints of the whole structure, the equal step search method combined with the criterion method is used to optimize the rod size. Then the multi-scale calculation model based on the multi-point constraint method is established. Through calculation and analysis, the boundary load condition of the target node is obtained as the boundary condition of node optimization. Finally, the variable density method is used to optimize the topology of the node domain, and the minimum member size is included in the constraint conditions to obtain the optimized node form that is conducive to additive manufacturing. The research shows that reasonable cross-section value and grouping of members can effectively reduce the steel consumption without compromising the overall stability performance. The amount of steel used in the three optimization plans was reduced by 12%, 23%, and 28%, respectively, compared to before the optimization. The multi-scale model not only takes into account the calculation accuracy, but also can effectively simulate the stress conditions in the node domain. The development of topology optimization and additive manufacturing technology broadens the space for optimization design, and provides new ideas for advanced design to integrate intelligent manufacturing.

Auxetic materials and structures exhibit high energy absorption, vibration damping, and fracture toughness at the macroscopic level. Lightweight designs and perforated structures in buckling-restrained braces (BRBs) have garnered significant attention. However, existing auxetic cellular configurations remain relatively simplistic, with particularly limited options capable of synergizing with BRBs to achieve combined energy dissipation and seismic mitigation performance. This study introduces a novel composite auxetic cellular unit with a honeycomb structure of negative Poisson’s ratio and corresponding design method. The cellular unit is combined with a BRB to develop a new composite auxetic perforated BRB (NPR-BRB). Experimental and numerical simulation methods are used to investigate the effects of two core plate materials (Q235B and LY160), the reentrant angle, and the cross-sectional weakening rate of the composite honeycombs on the NPR-BRB’s performance under cyclic loading. In this study, four BRB specimens were fabricated, and the experimental results reveal that the fracture surface morphology (cup- and shell-shaped) depends on the deformation mechanism. One of the NPR-BRBs demonstrates stable hysteretic behavior, with an equivalent viscous damping ratio of 0.469 and a cumulative plastic strain of 219.7. Numerical simulations indicate that the LY160 BRB exhibits higher deformation capacity and energy dissipation, reducing stress concentration. The concavity angle has a negligible influence on performance. An increase in the cross-sectional weakening rate is correlated with a reduction in bearing capacity, hysteresis loop area, and compression–tension asymmetry, and an increase followed by a decrease in equivalent viscous damping ratio and cumulative plastic strain. The novel hybrid auxetic cellular units may enhance the energy dissipation performance of BRBs.