Narrow Results

This paper presents a novel approach to enhance the energy absorption (EA) of honeycombs in the out-of-plane direction. Inspired by the Koch fractal, a fractal hexagonal honeycomb (FHH) is presented in this paper. In our study, we use Abaqus/Explicit to build a finite element model of the honeycomb, through which we conduct a series of studies on the performance of this honeycomb. Initially, we compare the mechanical properties and deformation modes of the FHH with those of a conventional hexagonal honeycomb. The results demonstrate notable improvements in crashworthiness metrics for the FHH, including a 52% increase in specific EA, a 45% enhancement in crushing load efficiency (CLE), and an 8% reduction in peak crushing force (PCF) compared to the conventional counterpart. Subsequently, this paper investigates the fractal arc honeycomb and evaluates the effect of the center angle on mechanical properties by varying its value. Furthermore, the mechanical properties of layered honeycomb and fractal honeycomb structures with different wall thicknesses are systematically examined. In the last section, we explore the theoretical analysis of the fractal-hexagonal honeycomb and find that the results of the theoretical analysis are in good agreement with those of the simulation, indicating that the experimental simulation results are reliable. Overall, the findings of this study offer valuable insights for the innovative design of hexagonal honeycomb structures, providing a reference for future advancements in this field.

The paper presents a systematic assessment of a simplified procedure to evaluate the response of unreinforced masonry walls subjected to out-of-plane seismic excitation. The nonlinear force-displacement response of a wall is idealised by means of a suitable tri-linear curve. The meaningful parameters characterising the walls and different ground motions were combined for a total of 1248 case studies. For each combination of parameters, a nonlinear SDOF dynamic time-history analysis was performed, and the results were taken as the reference for a simplified "equivalent stiffness" approach. It is shown how a suitably accurate prediction of collapse can be made by using appropriate stiffness values and elastic response spectra. Among the most relevant results for applications, it appears that initial stiffness (and therefore initial period) is not crucial in determining the occurrence of collapse. Instead, collapse depends primarily on the second and third branches of the tri-linear force-displacement relationship, i.e. on maximum strength and ultimate displacement capacity. It is shown how these latter parameters are only moderately sensitive to material mechanical parameters which are usually affected by strong uncertainty when assessing an existing building, namely the elastic modulus E and the compressive strength of masonry.

Three steel-plate composite walls were tested under reversal loads. The primary purpose of this experiment was to investigate the out-of-plane behavior of steel-plate composite walls under seismic actions, including the failure modes, hysteretic behavior, strength, and stiffness while emphasizing the effects of shear span, connection details, and thickness of the steel plates. All specimens showed some pinching effect in the hysteresis loops. Both shear failure and flexural failure occurred in the tests depending on the shear span and steel plate thickness of the specimens. All surface steel plates of the specimens remained unbuckled before yielding during the loading process, which indicated that the ratio of connector spacing to surface steel plate thickness adopted for the specimens satisfied the requirement of yielding before buckling. The test results also showed that the tie bars contributed significantly to the out-of-plane shear strength of the steel-plate composite walls.