# The Stability of New Single-Layer Combined Lattice Shell Based on Aluminum Alloy Honeycomb Panels
## 5 Conclusions  
In this paper, the authors propose a new type of lightweight and high-strength aluminum alloy spatial combined lattice shell (referred to as a NSCLS). The authors analyze the structure's stability using experimental studies and a nonlinear finite element analysis. The following major conclusions are reached:  
Figure 11: The critical load for different defect sizes for the lattice shell models with different plate thicknesses: (**a**) Model with a plate thickness of 2.5 mm; (**b**) Model with a plate thickness of 3.0 mm; and, (**c**) Combined lattice shell models with different plate thicknesses.  
1. By precision processing six models using a CNC machine and accounting for the initial geometric defects in the aluminum alloy lattice shell models, the authors performed a stability comparison. The results show that the overall stiffness and stable bearing capacity of the lattice shell are remarkably improved due to the aluminum alloy reinforcing plate. Regardless of whether there are geometric defects, the steady bearing capacity of the new combined lattice shells is approximately 16% higher than that of a lattice shell with the same span and no reinforcing plate. The magnitude of the increase for the lattice shell model with no defects is higher than that of the model with defects.
2. The NSCLS is a defect-sensitive structure. The influence of geometric defects on its stable bearing capacity is very obvious. The results of comparing the lattice shell models show that the sensitivities of the two types of structures are different. The bearing capacity of the defective model with no plate is approximately 7% lower than that of the model without defects. In the combined lattice shell model, the bearing capacity of the model with defects is 12% lower than that of the model without defects.
3. The finite element analysis results of applying the random defect mode method show that the theoretical failure patterns of the experimental models are basically consistent with those that were measured in the tests. The average difference between the theoretical stable bearing capacity and the experimental value is 5.7%. The theoretical load-displacement curves are also very close to the ones that were obtained in the tests. This indicates that the random defect mode method with a truncated Gaussian distribution is reasonable and reliable. It has sufficient accuracy. It can be used in structural analysis and design in practical engineering.
4. As the lowest-order buckling mode is unable to characterize the most unfavorable distribution of defects in the new structure, the critical load obtained using the uniform defect mode is frequently not the smallest critical load. Therefore, the existing specification of defect sizes can no longer be applicable. By calculating and analyzing nearly 20,000 NSCLS, we find that after the initial geometric defect value of the combined lattice shell reaches 3/1000 of the shell's span, the stable bearing capacity decreases sharply. We recommend that the values be used as the maximum defect size for the combined lattice shell. The studies in this paper provide a theoretical basis for future design specifications for new composite lattice shell structures.  
This study was supported by the Natural Science Foundation of China under Grant No. 51578136.  
[PERSON] and [PERSON] conceived and designed the experiments; [PERSON] performed the experiments; [PERSON] and [PERSON] analyzed the data; [PERSON] and [PERSON] contributed reagents/materials/analysis tools; [PERSON] wrote the paper.  
The authors declare no conflict of interest.