# The Stability of New Single-Layer Combined Lattice Shell Based on Aluminum Alloy Honeycomb Panels
## 2 Experimental Study on Stability of NSCLS  
### The Design and Fabrication of the Test Model  
To study how a honeycomb panel enhances the stable bearing capacity of a lattice shell structure, in this paper, the authors designed six single-layer aluminum alloy lattice shell models. Among the six models, three were lattice shells without honeycomb panels providing reinforcement (A\({}_{1}\), A\({}_{2}\), and A\({}_{3}\)), and the other three were lattice shell models with reinforcement (B\({}_{1}\), B\({}_{2}\), and B\({}_{3}\)). Figure 2a-d show the configurations of the models. The model plane was a regular hexagon. The diameter was 1400 mm, and the vector height was 250 mm (as shown in Figure 2g,h). The models were made by assembling 90 bars, 37 nodes, and 54 triangular plates together. The bars were square aluminum alloy tubes. The side length was 20 mm, and the wall thickness was 2 mm. The bars were connected by circular disc node connectors 72 mm in diameter.  
To guarantee the processing accuracy of the test model, the holes on each aluminum alloy bar were precision drilled using wire cutting technology. At the upper and lower surfaces of the rods, four screw holes of 2.5 mm in diameter were machined on each surface to connect the nodal plates. To prevent the rods from colliding during assembly, the ends of the rods were cut off. Because the scale of the test model was limited by the loading equipment, the thickness of the aluminum alloy honeycomb panel was only approximately 3 mm if the components of the test model were designed at full scale. The existing processing technology was not yet able to produce such thin aluminum alloy honeycomb panels. We decided to use 1-mm-thick aluminum alloy plates in place of the honeycomb panel. Because the aluminum alloy plate and the nodal plate were placed in the same positions for nodal attachment, to accommodate the nodal plate, the corners of the aluminum plate were rounded using laser cutting equipment. The circular gussets of the connecting rods were spherical disks with a certain curvature that were stamped using a specialized mold. A total of 24 pre-machined threaded holes (their diameters were same as those of the holes at the end of the rod) were drilled on each joint plate (Figure 2e). The bolt holes at the ends of the rod were aligned with the holes in the gusset plate and tightly fit with high-strength bolts. In the model with integrated aluminum alloy plates, because the cross section of the square aluminum alloy tube was too small, the aluminum plate and  
Figure 2: Overview of the test model: (**a,b**) Lattice shell model without aluminum plate (A\({}_{1}\), A\({}_{2}\), and A\({}_{3}\)); (**c,d**) Combined lattice shell model (B1, B2, and B3); (**e**) Node in the middle; (**f**) Supporting node; (**g**) Plan view of the model; and, (**h**) Side view of the model.  
the bar could not be bolted (the minimum margin requirements were not met) or welded (the thin aluminum plate was prone to burning through). Therefore, they were connected using a high-strength structural adhesive. The model was supported by fixed supports that were slotted into a computer numerical control (CNC) machine. The dimensions of the three slots were measured repeatedly. It was ensured that the actual projected length and width of the aluminum alloy square tube in the lattice model were the same, and then, the bars were placed in the slot. In this way, the rod's linear and angular displacements (Figure 2f) were well constrained. To study the influence of geometric imperfections of nodes on the bearing capacity of each model, geometric imperfections were introduced into two models (A\({}_{2}\) and B\({}_{2}\)). The method was to reduce the Z coordinate of the top of the model by 5.6 mm (i.e., 1/250 of the lattice shell's span).